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Introduction: This study explores effects of pH and inoculum size on imipenem versus tigecycline activity against E. coli, B. fragilis and E. faecalis, both in individual and mixed cultures. Methods: MIC/MBCs (mg/L) of tigecycline and imipenem were 0.12/≥ 16 and 4/4 for E. coli, 0.12/0.5 and ≥ 16/≥ 16 for B. fragilis, and 0.12/≥ 16 and 2/≥ 16 for E. faecalis, respectively. Killing curves in supplemented Brucella broth were performed at pH 7 or 5.8, with two final inocula (≈ 105 or ≈ 107 cfu/ml) of each isolate (individual cultures) and with 1:1:1 mixed inocula. Tubes were 48 h incubated at 37 ºC in anaerobiosis. Final concentrations (estimated concentrations in colon) were 1.50 mg/L for tigecycline and 26.40 mg/L for imipenem, with antibiotic-free curves as controls. Experiments were performed in triplicate. Results: Imipenem showed inoculum effect against E.coli and B. fragilis, with reductions in initial inocula in experiments with standard inocula contrasting with increases in experiments with high inocula (both individual and mixed cultures). Against E. faecalis no inoculum effect for imipenem was observed in individual cultures, with marked reductions in initial inocula regardless inoculum size. However in mixed experiments the indirect protection of E. faecalis by the two gramnegatives resulted in bacterial regrowth. This protection was inoculum-dependant since it occurred with high but not with standard inocula. Tigecycline reduced initial inocula of the three isolates regardless culture type (individual/mixed) or experimental conditions (pH/inocula size), with lower reductions for the tolerant E. faecalis. Conclusion: Carbapenemase activity was inoculum-dependant for self-protection and indirect protection of E. faecalis., Depto. de Medicina, Fac. de Medicina, TRUE, pub

Acinetobacter baumannii is considered one of the greatest threats to public health on a global scale. This Gram-negative pathogen causes severe infections, mostly of nosocomial origin, with a high mortality rate. In recent years, the rapid increase in the emergence and spread of antibiotic resistance in A. baumannii has significantly limited the effective therapeutic options against infections caused by this bacterium. The last-line antibiotics used in the treatment of multidrug-resistant (MDR) A. baumannii are carbapenems, tigecycline and polymyxins. However, resistance to these antibiotics is steadily increasing, especially to carbapenems, leading to an extensively drug-resistant (XDR) and even pandrug-resistant (PDR) phenotype of A. baumannii. In 2021, the European Centre for Disease Prevention and Control (ECDC) reported that resistance of Acinetobacter spp. to carbapenems reached 50% or more, mostly in Southern and Eastern European countries. Although the Western Balkans is a part of this region, detailed studies on the epidemiology and antibiotic resistance of A. baumannii are mainly limited to Serbia and Croatia. In most cases, carbapenem resistance in A. baumannii is due to the production of carbapenemases, in particular b-lactamases belonging to the class D known as oxacillinases. The studies from the Western Balkan countries revealed that besides the intrinsic blaOXA-51-like gene, the most prevalent acquired oxacillinase gene was the blaOXA- 24-like followed by the blaOXA-23-like, while the blaOXA-58-like and metallo- b-lactamase blaNDM-1 genes were less common. Although significantly lower compared to carbapenem-resistant, the number of A. baumannii isolates resistant to tigecycline and colistin is on a continual rise in the Western Balkans. As worldwide, the main mechanism conferring tigecycline resistance to A. baumannii from the Western Balkans was overexpression of efflux pumps. Also, the majority of reported alternations leading to colistin resistanc

C.M.O. and J.A.E. designed the study, performed the experiments, analyzed and interpreted the results, and wrote the draft manuscript. C.M.-E. collected the samples, provided the isolates for this study, and revised and approved the final version of the manuscript. N.M. performed the experiments, D.T.L. and G.M. analyzed and interpreted the results, and A.H. revised the manuscript. B.G.Z. conceived, designed, and coordinated the study and revised and approved the final versión of the manuscript., In this study, we characterized two tigecycline-resistant Klebsiella pneumoniae isolates from dog urine samples. The isolates were genetically unrelated, belonging to sequence type 11 (ST11) and ST147, both classically related to human isolates. To the best of our knowledge, this is the first identification of tigecycline-resistant isolates from animals. We unveil here the worrisome circulation among animals of bacterial clones resistant to this last-resort antibiotic., Unión Europea (EvoTAR282004-FP7; EFFORT613754FP7), Comunidad de Madrid (2016-T1/BIO-1105), Depto. de Sanidad Animal, Fac. de Veterinaria, TRUE, pub

Although the combination of polymyxin and tigecycline is widely used in treating carbapenem-resistant bacterial infections, the benefit of this combination is still uncertain. To assess whether adding polymyxin B to the high-dose tigecycline regimen would result in better clinical outcomes than the high-dose tigecycline therapy in patients with pneumonia caused by carbapenem-resistant Klebsiella pneumoniae and Acinetobacter baumannii, we conducted a propensity score-matched cohort study in a single center between July 2019 and December 2021. Of the 162 eligible patients, 102 were included in the 1:1 matched cohort. The overall 14-day mortality in the matched cohort was 24.5%. Compared with high-dose tigecycline, the combination therapy was not associated with better clinical outcomes, and showed similar 14-day mortality (OR, 0.72, 95% CI 0.27–1.83, p = 0.486), clinical cure (OR, 1.09, 95% CI 0.48–2.54, p = 0.823), microbiological cure (OR, 0.96, 95% CI 0.39–2.53, p = 0.928) and rate of nephrotoxicity (OR 0.85, 95% CI 0.36–1.99, p = 0.712). Subgroup analyses also did not demonstrate any statistical differences. Based on these results, it is reasonable to recommend against adding polymyxin B to the high-dose tigecycline regimen in treating pneumonia caused by carbapenem-resistant K. pneumoniae and A. baumannii.

type:Article, Objectives: Tetracyclines are used in veterinary medicine for livestock. Tigecycline, a semisynthetic tetra- cycline derivative, is a last-resort antimicrobial used to treat multidrug-resistant Gram-negative bacterial infections. The prevalence of variants of the mobile tigecycline resistance gene tet (X) in livestock is in- creasing worldwide. However, the prevalence of Tet(X) among livestock in Japan is unclear. This study was conducted to clarify the prevalence of Tet(X) in pigs in Japan, focusing on isolation and molecular characterisation of plasmid-mediated tet (X)-positive Escherichia coli through retrospective analysis. Methods: We retrospectively screened for tigecycline-resistant E. coli strains isolated from pigs. The tigecycline-resistant strain and tet (X)-harbouring plasmid were characterised. Results: The IncW plasmid harbouring the tet (X) variant [previously named as tet (X6)] was detected in one E. coli isolate from pigs (0.8%; 1/120) in 2012. The tet (X) plasmid was transferable by conjugation to the E. coli ML4909 recipient strain. Some mobile genetic elements (Tn As3 and IS Vsa3 ) were observed in the region surrounding tet (X). The tet (X)-harbouring plasmid shared a conserved backbone with IncW plasmid R388, which is a broad-host-range plasmid. Conclusion: The emergence and spread of tet (X) variants in Enterobacterales poses a public-health con- cern. To the best of our knowledge, this is the first report of the emergence of an IncW plasmid har- bouring tet (X). Using tetracyclines in livestock exerts selective pressure on the tet (X) plasmid; therefore, prudent use of tetracyclines is required.

Die zunehmende Inzidenz multiresistenter Bakterien stellt eine immer größer werdende Gefahr für die öffentliche Gesundheit dar. Auch bei Tigecyclin, ein Derivat des Tetracyclins und gleichzeitig Antibiotikum der letzten Instanz, konnten bereits Resistenzen beobachtet werden. Da der Wirkungsmechanismus der beiden Antibiotika Tetracyclin und Tigecyclin durch Hemmung der Proteinbiosynthese aufgrund der Bindung an die 30S-Untereinheit des Ribosoms entsteht, führen unter anderem Mutationen ribosomaler Proteine zu Resistenzen. Vor allem Mutationen in der flexiblen Schleife des rpsJ-Gens, welches für das ribosomale Protein S10 kodiert, konnten in Tigecyclin-resistenten Isolaten nachgewiesen werden. Der genaue Mechanismus dieser Resistenz und sonstige Auswirkungen auf die Zelle wurden bisher kaum erforscht. Daher war das Ziel der Arbeit, Effekte von Mutationen in E. coli im Valin 57 der S10-Schleife auf das Wachstum, die Tetracyclin- bzw. Tigecyclin-Resistenz sowie die Ribosomenbiogenese und die Translation anhand zehn verschiedener rpsJ-Mutanten zu untersuchen. Es konnte gezeigt werden, dass die Mutation einer einzelnen Aminosäure ausreicht, um die Empfindlichkeit gegenüber Tetracyclin und Tigecyclin zu verändern, wobei ein Austausch zu einer gesteigerten Empfindlichkeit führte, wohingegen acht Mutationen zu einer verminderten Empfindlichkeit führten. Da sowohl die beiden Antibiotika als auch die S10-Schleifenregion mit der Helix h31 der 16S rRNA in Verbindung stehen, kommt es vermutlich aufgrund der Mutationen zu einer veränderten Positionierung der h31, wodurch die Bindungsaffinität des Tigecyclins beeinflusst wird. Allerdings führte keine Mutation zu einer Tigecyclin-MHK über 0,5 g/mL, um laut EUCAST als resistent eingestuft zu werden, weswegen vermutet wird, dass zusätzliche Mutationen (z.B. im rpsC-Gen) notwendig sind um eine entsprechende Resistenzfähigkeit zu erreichen. Zudem konnte gezeigt werden, dass rpsJ-Mutationen einen Einfluss auf die Ribosomenbiogenese haben

Crimean-Congo hemorrhagic fever virus (CCHFV) belongs to the genus Orthonairovirus and is the causative agent of a viral hemorrhagic disease with a case fatality rate of 30%. However, limited studies have been conducted to explore antiviral compounds specific to CCHFV. In this study, we developed a minigenome system of orthonairoviruses, CCHFV and Hazara virus to analyze viral replication and screened an FDA-approved compound library. The transfection of the minigenome components induced marked increase in luciferase expression, indicating the sufficient replication and translation of reporter RNA. Compound library screening identified 14 candidate compounds that significantly decreased luciferase activity. Some of the compounds also inhibited the replication of the infectious Hazara virus. The mechanism of inhibition by tigecycline was further analyzed, and a decrease in the interaction between the viral N protein and RNA by tigecycline was observed. This work provides a basis for validation using animal models and the design of chemical derivatives with stronger activity in future studies on the development of an antiviral against CCHFV., identifier:Antiviral Research, 200, art. no. 105276; 2022

Mitochondria are involved in the development and acquisition of a malignant phenotype in hematological cancers. Recently, their role in the pathogenesis of multiple myeloma (MM) has been suggested to be therapeutically explored. MYC is a master regulator of b-cell malignancies such as multiple myeloma, and its activation is known to deregulate mitochondrial function. We investigated the impact of mitochondrial activity on the distinct entities of the disease and tested the efficacy of the mitochondrial inhibitor, tigecycline, to overcome MM proliferation. COXII expression, COX activity, mitochondrial mass, and mitochondrial membrane potential demonstrated a progressive increase of mitochondrial features as the disease progresses. In vitro and in vivo therapeutic targeting using the mitochondrial inhibitor tigecycline showed promising efficacy and cytotoxicity in monotherapy and combination with the MM frontline treatment bortezomib. Overall, our findings demonstrate how mitochondrial activity emerges in MM transformation and disease progression and the efficacy of therapies targeting these novel vulnerabilities., Instituto de Salud Carlos III (ISCIII)/ MINECO/ FEDER, CRIS contra el Cancer Foundation, AECC, Comunidad de Madrid, Sección Deptal. de Bioquímica y Biología Molecular (Farmacia), Depto. de Medicina, Fac. de Farmacia, Fac. de Medicina, TRUE, pub

The aim of this study was to investigate the presence of colistin- and/or tigecycline-resistant Klebsiella spp. in influents from four wastewater treatment plants (WWTPs), which partly reflect the gut microbiome of human populations. Colistin- and tigecycline-resistant Klebsiella pneumoniae isolates (K30/ST29) were detected four times from the WWTP A during a period of 3 months. Disruptions of the mgrB and ramR genes by ISEc68 and ISKpn21, respectively, were identified in those four isolates. They also shared the IncL/M 86,197-bp plasmids carrying a bla(CTX-M-3) and Tn1548-associated armA [IS26-IntI1-dfrA12-gucF-aadA2-qacE Delta 1-sul1-ISCR1-ISEc28-armA-ISEc29-msr(E)-mph(E)-IS26]. Those isolates formed a distinct cluster within wgMLST clusters of ST29 K30 public reference strains of human origin and were unique due to harboring of Tn21-like mercury resistance operon transposons in addition to silver, copper, and arsenic resistance determinants. Five K. pneumoniae strains with different STs and 1 Klebsiella quasipneumoniae strain, exhibiting colistin resistance, were detected in WWTPs B, C, and D. For these isolates, disruptions of mgrB by ISEc68 (three isolates) or ISEcl1 (one isolate), insertion of IS2 in the mgrB promoter region (one isolate), and inactivation of MgrB by a nonsense mutation (one isolate) were identified. Close monitoring of these mcr-negative colistin- and/or tigecycline-resistant bacteria in wastewater influents is imperative to avoid further limiting of treatment options., Article, Microbial Drug Resistance 27(10) : 1433-1442(2021)

The aim of this study was to investigate the presence of colistin- and/or tigecycline-resistant Klebsiella spp. in influents from four wastewater treatment plants (WWTPs), which partly reflect the gut microbiome of human populations. Colistin- and tigecycline-resistant Klebsiella pneumoniae isolates (K30/ST29) were detected four times from the WWTP A during a period of 3 months. Disruptions of the mgrB and ramR genes by ISEc68 and ISKpn21, respectively, were identified in those four isolates. They also shared the IncL/M 86,197-bp plasmids carrying a bla(CTX-M-3) and Tn1548-associated armA [IS26-IntI1-dfrA12-gucF-aadA2-qacE Delta 1-sul1-ISCR1-ISEc28-armA-ISEc29-msr(E)-mph(E)-IS26]. Those isolates formed a distinct cluster within wgMLST clusters of ST29 K30 public reference strains of human origin and were unique due to harboring of Tn21-like mercury resistance operon transposons in addition to silver, copper, and arsenic resistance determinants. Five K. pneumoniae strains with different STs and 1 Klebsiella quasipneumoniae strain, exhibiting colistin resistance, were detected in WWTPs B, C, and D. For these isolates, disruptions of mgrB by ISEc68 (three isolates) or ISEcl1 (one isolate), insertion of IS2 in the mgrB promoter region (one isolate), and inactivation of MgrB by a nonsense mutation (one isolate) were identified. Close monitoring of these mcr-negative colistin- and/or tigecycline-resistant bacteria in wastewater influents is imperative to avoid further limiting of treatment options., Article, Microbial Drug Resistance 27(10) : 1433-1442(2021)

Objective: Acinetobacter baumannii species cause nosocomial infections and can subsequently develop multidrug resistance (MDR). The objective of this study was to evaluate the susceptibility of A. baumannii to a novel combination of colistin and tigecycline, which may provide a faster and more efficacious treatment via a synergistic effect. Methods: We included 50 MDR A. baumannii samples that were isolated in our clinics between 2009 and 2014. We used broth microdilution (BMD) and the E-test to evaluate the effects of colistin and tigecycline, and the E-test to assess the interaction of the colistin-tigecycline combination. The interaction between the two antibiotics was evaluated using the fractional inhibition concentration (FIC) index and was classified as follows: FIC = 1.0.5, synergistic; 0.5 FIC 1, partially synergistic; FIC=1, additive; 1 FIC 4, indifferent; and FIC >= 4, antagonistic. Results: No tigecycline and colistin resistance was determined by BMD or E-test. The interaction between colistin and tigecycline, when used in combination, was 2% synergistic, 6% additive, 88% indifferent, and 4% antagonistic. Conclusion: Although combination therapy is suggested for MDR A. baumannii infections, our results suggest that the synergistic effect of the colistin-tigecycline combination is insufficient to make it an optimal treatment choice.

Objective: Acinetobacter baumannii species cause nosocomial infections and can subsequently develop multidrug resistance (MDR). The objective of this study was to evaluate the susceptibility of A. baumannii to a novel combination of colistin and tigecycline, which may provide a faster and more efficacious treatment via a synergistic effect. Methods: We included 50 MDR A. baumannii samples that were isolated in our clinics between 2009 and 2014. We used broth microdilution (BMD) and the E-test to evaluate the effects of colistin and tigecycline, and the E-test to assess the interaction of the colistin-tigecycline combination. The interaction between the two antibiotics was evaluated using the fractional inhibition concentration (FIC) index and was classified as follows: FIC = 1.0.5, synergistic; 0.5 FIC 1, partially synergistic; FIC=1, additive; 1 FIC 4, indifferent; and FIC >= 4, antagonistic. Results: No tigecycline and colistin resistance was determined by BMD or E-test. The interaction between colistin and tigecycline, when used in combination, was 2% synergistic, 6% additive, 88% indifferent, and 4% antagonistic. Conclusion: Although combination therapy is suggested for MDR A. baumannii infections, our results suggest that the synergistic effect of the colistin-tigecycline combination is insufficient to make it an optimal treatment choice.

Objectives: To characterize the clonal spread of carbapenem-resistant Klebsiella pneumoniae and Escherichia coli isolates between different healthcare institutions in Catalonia, Spain. Methods: Antimicrobial susceptibility was tested by disc diffusion. MICs were determined by gradient diffusion or broth microdilution. Carbapenemase production was confirmed by Lateral flow. PCR and Sanger sequencing were used to identify the allelic variants of resistance genes. Clonality studies were performed by PFGE and MLST. Plasmid typing, conjugation assays, S1-PFGE plus Southern blotting and MinION Oxford Nanopore sequencing were used to characterize resistance plasmids. Results: Twenty-nine carbapenem-resistant isolates recovered from three healthcare institutions between January and November 2016 were included: 14 K. pneumoniae isolates from a tertiary hospital in the south of Catalonia (hospital A); 2 K. pneumoniae isolates from a nearby healthcare centre; and 12 K. pneumoniae isolates and 1 E. coli isolate from a tertiary hospital in Barcelona (hospital B). The majority of isolates were resistant to all antimicrobial agents, except colistin, and all were NDM producers. PFGE identified a major K. pneumoniae clone (n = 27) belonging to ST147 and co-producing NDM-1 and CTX-M-15, with a few isolates also harbouring bla(OXA-48). Two sporadic isolates of K. pneumoniae ST307 and E. coli ST167 producing NDM-7 were also identified. bla(OXA-48). was carried in two related IncR plasmid populations and bla(NDM)(-1) in a conjugative 50 kb IncX3 plasmid. Conclusions: We report the inter-hospital dissemination of XDR high-risk clones of K. pneumoniae and E. coli associated with the carriage of small, transferable plasmids harbouring bla(NDM) genes.

Study designA controlled, interventional animal study.ObjectiveSpinal implant infection (SII) is a devastating complication. The objective of this study was to evaluate the efficacy of a novel implant coating that has both a passive antibiotic elution and an active-release mechanism triggered in the presence of bacteria, using an in vivo mouse model of SII.Summary of background dataCurrent methods to minimize the frequency of SII include local antibiotic therapy (vancomycin powder), betadine irrigation, silver nanoparticles, and passive release from antibiotic-loaded poly(methyl methacrylate) cement beads, all of which have notable weaknesses. A novel implant coating has been developed to address some of these limitations but has not been tested in the environment of a SII.MethodsA biodegradable coating using branched poly(ethylene glycol)-poly(propylene sulfide) (PEG-PPS) polymer was designed to deliver antibiotics. The in vivo performance of this coating was tested in the delivery of either vancomycin or tigecycline in a previously established mouse model of SII. Noninvasive bioluminescence imaging was used to quantify the bacterial burden, and implant sonication was used to determine bacterial colony-forming units (CFUs) from the implant and surrounding bone and soft tissue.ResultsThe PEG-PPS-vancomycin coating significantly lowered the infection burden from postoperative day 3 onwards (P < 0.05), whereas PEG-PPS-tigecycline only decreased the infection on postoperative day 5 to 10 (P < 0.05). CFUs were lower on PEG-PPS-vancomycin pins than PEG-PPS-tigecycline and PEG-PPS pins alone on both the implants (2.4 × 10, 8.5 × 10, and 1.0 × 10 CFUs, respectively) and surrounding bone and soft tissue (1.3 × 10, 4.8 × 10, and 5.4 × 10 CFUs, respectively) (P < 0.05).ConclusionThe biodegradable PEG-PPS coating demonstrates promise in decreasing bacterial burden and preventing SII. The vancomycin coating outperformed the tigecycline coating in this model compared to

bstract: Concomitant use of two or more drugs in therapy is becoming a more frequent phenomenon and clinically relevant drug–drug interactions at the level of binding to human serum albumin (HSA) are more often. The influence of fluoroquinolones–sparfloxacin, levofloxacin, and ciprofloxacin, on the interaction between tigecycline and HSA, was investigated in vitro by means of fluorescence and absorption spectroscopy. The results of UV–Vis and fluorescence spectroscopy showed that the fluorescence quenching of HSA was a result of the formation of new complexes through a static quenching process. The binding constants (Ka) and the number of binding sites (n) of all systems were calculated. The presence of sparfloxacin and ciprofloxacin increases and that of levofloxacin slightly decreases the binding constant of the HSA–tigecycline system. Competitive binding studies in the presence of site-specific markers showed that tigecycline was not significantly displaced by ibuprofen, but warfarin showed a significant displacement of tigecycline. These results suggest that the competitive binding of tigecycline and warfarin to HSA exists. The results confirm that the binding site of tigecycline is mainly located in Sudlow’s site I (subdomain IIA) of HSA. Graphic abstract: [Figure not available: see fulltext.

The objective was to detect resistance against fosfomycin (FOS), colistin (COL) and tigecycline (TGC) in enterobacteria recovered from surface and deep water sources in the province of Chaco (Argentina). Isolations from water samples from rivers, lagoons and wells were included. Resistance profiles were studied by disk diffusion and broth dilution. A total of 70 water samples were analyzed (40 from a surface origin and 30 from the underground). 106 enterobacteria isolates were obtained (68 from the superficial sources and 38 from the underground ones). In surface waters 10 isolates (14.7%) were resistant to some of the antimicrobials studied while in groundwater, 3 (7.9%) isolates were resistant. It made a total of FOS (8), TGC (1), COL (1), FOS+TGC (2) y FOS+COL (1). This is the first study carried out in our country that focusses on the detection of enterobacteria resistant to FOS, COL and TGC in aquatic environments. Although the amount of resistant isolation found is relatively low, its mere presence should alert about the possible passage of this type of bacteria from the environment to humans, considering water as a reservoir and means of transmission., El objetivo fue detectar la resistencia frente a fosfomicina (FOS), colistina (COL) y tigeciclina (TGC) en enterobacterias recuperadas de fuentes superficiales y profundas de agua del Chaco (Argentina). Se incluyeron aislamientos provenientes de muestras de agua de ríos, lagunas y pozos. Se analizaron 70 muestras de agua (40 de origen superficial y 30 subterráneas). Se obtuvieron 106 aislamientos de enterobacterias (68 en fuentes superficiales y 38 en fuentes subterráneas). En aguas superficiales se encontraron 10 (14,7%) aislamientos resistentes a alguno de los antimicrobianos estudiados mientras que en aguas subterráneas resultaron resistentes 3 (7,9%) aislamientos; en total: FOS (8), TGC (1), COL (1), FOS+TGC (2) y FOS+COL (1). El presente es el primer trabajo realizado en nuestro país cuyo foco es la detección de enterobacterias resistentes a FOS, COL y TGC en ambientes acuáticos. El número de aislamientos resistentes encontrados es bajo pero su sola presencia debe alertar sobre el posible pasaje de este tipo de bacterias desde el ambiente al hombre, considerando al agua como un reservorio y medio de transmisión.

Study designA controlled, interventional animal study.ObjectiveSpinal implant infection (SII) is a devastating complication. The objective of this study was to evaluate the efficacy of a novel implant coating that has both a passive antibiotic elution and an active-release mechanism triggered in the presence of bacteria, using an in vivo mouse model of SII.Summary of background dataCurrent methods to minimize the frequency of SII include local antibiotic therapy (vancomycin powder), betadine irrigation, silver nanoparticles, and passive release from antibiotic-loaded poly(methyl methacrylate) cement beads, all of which have notable weaknesses. A novel implant coating has been developed to address some of these limitations but has not been tested in the environment of a SII.MethodsA biodegradable coating using branched poly(ethylene glycol)-poly(propylene sulfide) (PEG-PPS) polymer was designed to deliver antibiotics. The in vivo performance of this coating was tested in the delivery of either vancomycin or tigecycline in a previously established mouse model of SII. Noninvasive bioluminescence imaging was used to quantify the bacterial burden, and implant sonication was used to determine bacterial colony-forming units (CFUs) from the implant and surrounding bone and soft tissue.ResultsThe PEG-PPS-vancomycin coating significantly lowered the infection burden from postoperative day 3 onwards (P < 0.05), whereas PEG-PPS-tigecycline only decreased the infection on postoperative day 5 to 10 (P < 0.05). CFUs were lower on PEG-PPS-vancomycin pins than PEG-PPS-tigecycline and PEG-PPS pins alone on both the implants (2.4 × 10, 8.5 × 10, and 1.0 × 10 CFUs, respectively) and surrounding bone and soft tissue (1.3 × 10, 4.8 × 10, and 5.4 × 10 CFUs, respectively) (P < 0.05).ConclusionThe biodegradable PEG-PPS coating demonstrates promise in decreasing bacterial burden and preventing SII. The vancomycin coating outperformed the tigecycline coating in this model compared to

Intrinsic protein properties that may not be apparent by only examining three-dimensional structures can be revealed by careful analysis of mutant protein variants. Deep mutational scanning is a technique that allows the functional analysis of millions of protein variants in a single experiment. To enable this high-throughput technique, the mutant genotype of protein variants must be coupled to a selectable function. This chapter outlines how artificial genetic circuits in the yeast Saccharomyces cerevisiae can maintain the genotype-phenotype link, thus enabling the general application of this approach. To do this, we describe how to engineer genetic selections in yeast, methods to construct mutant libraries, and how to analyze sequencing data. We investigate the structure-function relationships of the antimicrobial resistance protein TetX to illustrate this process. In doing so, we demonstrate that deep mutational scanning is a powerful method to dissect the importance of individual residues for the inactivation of antibiotic analogues, with consequences for the rational design of new drugs to combat antimicrobial resistance.

The objective was to detect resistance against fosfomycin (FOS), colistin (COL) and tigecycline (TGC) in enterobacteria recovered from surface and deep water sources in the province of Chaco (Argentina). Isolations from water samples from rivers, lagoons and wells were included. Resistance profiles were studied by disk diffusion and broth dilution. A total of 70 water samples were analyzed (40 from a surface origin and 30 from the underground). 106 enterobacteria isolates were obtained (68 from the superficial sources and 38 from the underground ones). In surface waters 10 isolates (14.7%) were resistant to some of the antimicrobials studied while in groundwater, 3 (7.9%) isolates were resistant. It made a total of FOS (8), TGC (1), COL (1), FOS+TGC (2) y FOS+COL (1). This is the first study carried out in our country that focusses on the detection of enterobacteria resistant to FOS, COL and TGC in aquatic environments. Although the amount of resistant isolation found is relatively low, its mere presence should alert about the possible passage of this type of bacteria from the environment to humans, considering water as a reservoir and means of transmission., El objetivo fue detectar la resistencia frente a fosfomicina (FOS), colistina (COL) y tigeciclina (TGC) en enterobacterias recuperadas de fuentes superficiales y profundas de agua del Chaco (Argentina). Se incluyeron aislamientos provenientes de muestras de agua de ríos, lagunas y pozos. Se analizaron 70 muestras de agua (40 de origen superficial y 30 subterráneas). Se obtuvieron 106 aislamientos de enterobacterias (68 en fuentes superficiales y 38 en fuentes subterráneas). En aguas superficiales se encontraron 10 (14,7%) aislamientos resistentes a alguno de los antimicrobianos estudiados mientras que en aguas subterráneas resultaron resistentes 3 (7,9%) aislamientos; en total: FOS (8), TGC (1), COL (1), FOS+TGC (2) y FOS+COL (1). El presente es el primer trabajo realizado en nuestro país cuyo foco es la detección de enterobacterias resistentes a FOS, COL y TGC en ambientes acuáticos. El número de aislamientos resistentes encontrados es bajo pero su sola presencia debe alertar sobre el posible pasaje de este tipo de bacterias desde el ambiente al hombre, considerando al agua como un reservorio y medio de transmisión.

Recurrent somatic mutations in ETNK1 (Ethanolamine-Kinase-1) were identified in several myeloid malignancies and are responsible for a reduced enzymatic activity. Here, we demonstrate in primary leukemic cells and in cell lines that mutated ETNK1 causes a significant increase in mitochondrial activity, ROS production, and Histone H2AX phosphorylation, ultimately driving the increased accumulation of new mutations. We also show that phosphoethanolamine, the metabolic product of ETNK1, negatively controls mitochondrial activity through a direct competition with succinate at mitochondrial complex II. Hence, reduced intracellular phosphoethanolamine causes mitochondria hyperactivation, ROS production, and DNA damage. Treatment with phosphoethanolamine is able to counteract complex II hyperactivation and to restore a normal phenotype.

It is generally accepted that antibiotic-resistant mutants are selected in a range of concentrations ranging from the minimum inhibitory concentration (MIC) to the mutant preventive concentration. More recently, it has been found that antibiotic-resistant mutants can also be selected at concentrations below MIC, which expands the conditions where this selection may occur. Using experimental evolution approaches followed by whole-genome sequencing, the current study compares the evolutionary trajectories of Pseudomonas aeruginosa in the presence of tobramycin or tigecycline at lethal and sublethal concentrations. Mutants were selected at sublethal concentrations of tigecycline (1/10 and 1/50 MIC), whereas no mutants were selected in the case of tobramycin, indicating that the width of sub-MIC selective windows is antibiotic-specific. In addition, the patterns of evolution towards tigecycline resistance depend on selection strength. Sublethal concentrations of tigecycline select mutants with lower tigecycline MICs and higher MICs to other antibiotics belonging to different structural families than mutants selected under lethal concentrations. This indicates that the strength of the cross-resistance phenotype associated with tigecycline resistance is decoupled from selection strength. Accurate information on the sublethal selection window for each antibiotic of clinical value, including the phenotypes of cross-resistance of mutants selected at each antibiotic concentration, is needed to understand the role of ecosystems polluted with different antibiotic concentrations in the selection of antibiotic resistance. Integration of this information into clinical and environmental safety controls may help to tackle the problem of antibiotic resistance.

Background: In critically ill patients, the use of high tigecycline dosages (HD TGC) (200 mg/day) has been recently increasing but few pharmacokinetic/pharmacodynamic (PK/PD) data are available. We designed a prospective observational study to describe the pharmacokinetic/pharmacodynamic (PK/PD) profile of HD TGC in a cohort of critically ill patients with severe infections. Results: This was a single centre, prospective, observational study that was conducted in the 20-bed mixed ICU of a 1500-bed teaching hospital in Rome, Italy. In all patients admitted to the ICU between 2015 and 2018, who received TGC (200 mg loading dose, then 100 mg q12) for the treatment of documented infections, serial blood samples were collected to measure steady-state TGC concentrations. Moreover, epithelial lining fluid (ELF) concentrations were determined in patients with nosocomial pneumonia. Amongst the 32 non-obese patients included, 11 had a treatment failure, whilst the other 21 subjects successfully eradicated the infection. There were no between-group differences in terms of demographic aspects and main comorbidities. In nosocomial pneumonia, for a target AUC0-24/MIC of 4.5, 75% of the patients would be successfully treated in presence of 0.5 mcg/mL MIC value and all the patients obtained the PK target with MIC ≤ 0.12 mcg/mL. In intra-abdominal infections (IAI), for a target AUC0-24/MIC of 6.96, at least 50% of the patients would be adequately treated against bacteria with MIC ≤ 0.5 mcg/mL. Finally, in skin and soft-tissue infections (SSTI), for a target AUC0-24/MIC of 17.9 only 25% of the patients obtained the PK target at MIC values of 0.5 mcg/mL and less than 10% were adequately treated against germs with MIC value ≥ 1 mcg/mL. HD TGC showed a relevant pulmonary penetration with a median and IQR ELF/plasma ratio (%) of 152.9 [73.5–386.8]. Conclusions: The use of HD TGC is associated with satisfactory plasmatic and pulmonary concentrations for the treatment of sev

Introduction:Treatment of open fractures routinely involves multiple surgeries and delayed definitive fracture fixation because of concern for infection. If implants were made less susceptible to infection, a one-stage procedure with intramedullary nailing would be more feasible, which would reduce morbidity and improve outcomes. Methods:In this study, a novel open fracture mouse model was developed using Staphylococcus aureus (S. aureus) and single-stage intramedullary fixation. The model was used to evaluate whether implants coated with a novel "smart" polymer coating containing vancomycin or tigecycline would be colonized by bacteria in an open fracture model infected with S. aureus. In vivo bioluminescence, ex vivo CFUs, and X-ray images were evaluated over a 42-day postoperative period. Results:We found evidence of a markedly decreased bacterial burden with the local release of vancomycin and tigecycline from the PEG-PPS polymer compared to polymer alone. Vancomycin was released in a controlled fashion and maintained local drug concentrations above the minimum inhibition concentration for S. aureus for greater than 7 days postoperatively. Bacteria were reduced 139-fold from implants containing vancomycin and undetected from the bone and soft tissue. Tigecycline coatings led to a 5991-fold reduction in bacteria isolated from bone and soft tissue and 15-fold reduction on the implants compared to polymer alone. Antibiotic coatings also prevented osteomyelitis and implant loosening as observed on X-ray. Conclusion:Vancomycin and tigecycline can be encapsulated in a polymer coating and released over time to maintain therapeutic levels during the perioperative period. Our results suggest that antibiotic coatings can be used to prevent implant infection and osteomyelitis in the setting of open fracture. This novel open fracture mouse model can be used as a powerful in vivo preclinical tool to evaluate and optimize the treatment of open fractures before further studies

IntroductionTreatment of open fractures routinely involves multiple surgeries and delayed definitive fracture fixation because of concern for infection. If implants were made less susceptible to infection, a one-stage procedure with intramedullary nailing would be more feasible, which would reduce morbidity and improve outcomes.MethodsIn this study, a novel open fracture mouse model was developed using Staphylococcus aureus (S. aureus) and single-stage intramedullary fixation. The model was used to evaluate whether implants coated with a novel "smart" polymer coating containing vancomycin or tigecycline would be colonized by bacteria in an open fracture model infected with S. aureus. In vivo bioluminescence, ex vivo CFUs, and X-ray images were evaluated over a 42-day postoperative period.ResultsWe found evidence of a markedly decreased bacterial burden with the local release of vancomycin and tigecycline from the PEG-PPS polymer compared to polymer alone. Vancomycin was released in a controlled fashion and maintained local drug concentrations above the minimum inhibition concentration for S. aureus for greater than 7 days postoperatively. Bacteria were reduced 139-fold from implants containing vancomycin and undetected from the bone and soft tissue. Tigecycline coatings led to a 5991-fold reduction in bacteria isolated from bone and soft tissue and 15-fold reduction on the implants compared to polymer alone. Antibiotic coatings also prevented osteomyelitis and implant loosening as observed on X-ray.ConclusionVancomycin and tigecycline can be encapsulated in a polymer coating and released over time to maintain therapeutic levels during the perioperative period. Our results suggest that antibiotic coatings can be used to prevent implant infection and osteomyelitis in the setting of open fracture. This novel open fracture mouse model can be used as a powerful in vivo preclinical tool to evaluate and optimize the treatment of open fractures before further studies in hum

U ovoj doktorskoj disertaciji je ispitivano vezivanje tigeciklina za humani serumski albumin i interakcije tigeciklina sa specifičnim markerima vezujućih mesta (varfarinom i ibuprofenom), jonima metala (Ca2+, Cu2+ i Fe3+) i fluorohinolonima (sparfloksacinom, levofloksacinom i ciprofloksacinom) koje se javljaju na nivou vezivanja za humani serumski albumin. Sve interakcije su ispitivane u simuliranim fiziološkim uslovima in vitro. Korišćene su spektroskopske metode (fluorescentna i apsorpciona spektroskopija) i AutoDock analiza. Gašenje fluorescencije aktivnog centra humanog serumskog albumina (HSA) tigeciklinom (TGC) je posledica formiranja HSA-TGC kompleksa, što ukazuje da je mehanizam gašenja fluorescencije statički proces. Konstante vezivanja (Ka) HSATGC sistema su bile 1,8 × 104; 4,0 × 105 i 4,5 × 106 L/mol na 298, 303 i 308 K, a broj vezujućih mesta (n) je izračunat na oko 1, što ukazuje da HSA i TGC formiraju komplekse u molskom odnosu približno 1:1. Prema van’t Hofovoj jednačini, vrednosti promene entalpije (ΔH0) i promene entropije (ΔS0) su bile 423,2 kJ/mol i 1502,3 J/mol·K, što ukazuje da tipične hidrofobne interakcije igraju najvažniju ulogu u reakciji vezivanja i stabilizaciji HSA-TGC kompleksa. Rastojanje vezivanja (r) između donora (HSA) i akceptora (TGC) je izračunato da iznosi 3,63 nm prema Forsterovoj teoriji rezonantnog energetskog transfera. Glavno vezujuće mesto za tigeciklin je mesto I smešteno u hidrofobnoj šupljini subdomena IIA. Mesto I je imalo prednost nad mestom II. Joni metala (Ca2+, Cu2+ i Fe3+) su indukovali povećanje afiniteta tigeciklina za humani serumski albumin. Tigeciklin je doveo do smanjenja afiniteta fluorohinolona (SPF, LVF i CPF) za humani serumski albumin. Ova doktorska disertacija treba da pruži bolje razumevanje vezivanja tigeciklina za humani serumski albumin i poboljša njegovu primenu u kliničkoj praksi. Rezultati ove doktorske disertcije mogu biti od velikog značaja za dalji razvoj prirodnih nauka, kliničke farmakologij, In this doctoral thesis the binding of tigecycline for human serum albumin and interactions of tigecycline with specific markers of binding sites (warfarin and ibuprofen), metal ions (Ca2+, Cu2+ and Fe3+) and fluoroquinolones (sparfoxacin, levofloxacin and ciprofloxacin) which occur at the level of binding for human serum albumin were investigated. All interactions were studied in simulated physiological conditions in vitro. The spectroscopic methods (fluorescence and absorption spectroscopy) and AutoDock analysis were used. Fluorescence quenching of the active center of human serum albumin (HSA) by tigecycline (TGC) is due to the formation of HSA-TGC complex, indicating that the mechanism of fluorescence quenching is a static process. The binding constants (Kа) of HSA-TGC system were 1.8 × 104, 4.0 × 105 and 4.5 × 106 L/mol at 298, 303 and 308 K, and the number of binding sites (n) was calculated at about 1, indicating that HSA and TGC formed complexes in a molar ratio of approximately 1:1. According to the van't Hof equation, the values of the enthalpy change (ΔH0) and the entropy change (ΔS0) were 423.2 kJ/mol and 1502.3 J/mol·K, indicating that typical hydrophobic interactions play a major role in the binding reaction and stabilization of HSA-TGC complex. The binding distance (r) between the donor (HSA) and the acceptor (TGC) was calculated to be 3.63 nm according to Förster resonance energy transfer theory. The major binding site for tigecycline is the site I located in the hydrophobic cavity of subdomain IIA. Тhe site I had an advantage over site II. Metal ions (Ca2+, Cu2+ and Fe3+) induced an increase in the affinity of tigecycline for human serum albumin. Tigecycline has led to a decrease in the affinity of fluoroquinolones (SPF, LVF and CPF) for human serum albumin. This doctoral thesis should provide a better understanding of the binding of tigecycline for human serum albumin and improve its application in clinical practice. The results of this doctoral th

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infections are difficult to treat since common therapeutic options including ampicillin and glycopeptides often fail. In vitro, most VRE remain susceptible to last-resort antibiotics such as linezolid, tigecycline and daptomycin. However, neither tigecycline nor linezolid act in a bactericidal manner, and daptomycin has proven activity only at high dosages licensed for treating enterococcal endocarditis. Despite these pharmacological and therapeutic limitations, reports on resistance to these last-resort drugs in VRE, and enterococci in general, have increased in recent years. In this review, we briefly recapitulate the current knowledge on the mode of action as well as the known and novel mechanisms of resistance and describe surveillance data on resistance to linezolid, tigecycline and daptomycin in enterococci. In addition, we also suggest a common nomenclature for designating enterococci and VRE with resistances to these important last-resort antibiotics.

[Objective] We aimed to compare the outcomes of patients with C.difficile infection (CDI) treated either with tigecycline associated with vancomycin, or with vancomycin alone., [Methods] This single-centre retrospective cohort study included all adults hospitalized from September 2014 through August 2015 for symptomatic, incident CDI confirmed by polymerase chain reaction for C. difficile toxin in stools. The primary outcome was the rate of favourable outcome, defined as a composite of clinical response (resolution of symptoms without need for additional CDI therapy) and achieving discharge without CDI-related surgery or intensive care; a secondary outcome was CDI recurrence. We constructed a non-parsimonious logistic regression model to calculate a propensity score (PS) for those receiving tigecycline., [Results] In all, 266 patients were included: 62 patients received both vancomycin and tigecycline, and 204 patients received vancomycin alone. The patients from the two groups were similar regarding demographics and comorbidities but patients in the tigecycline group had a more severe CDI. A favourable outcome in the tigecycline group versus the vancomycin group was found in 50/62 (81%) versus 193/204 (95%). We matched patients receiving tigecycline or not according to the PS and 86 patients (43 pairs) could be matched. The OR for favourable outcome with tigecycline in the matched analysis was 0.92 (95% CI 0.60–1.44; p 0.74). The rate of CDI recurrences was 8/62 (13%) in the tigecycline group versus 39/204 (19%) in the vancomycin group (p 0.2)., [Conclusion] Adding tigecycline to CDI standard therapy did not increase the clinical cure nor reduce the rate of CDI recurrences.

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infections are difficult to treat since common therapeutic options including ampicillin and glycopeptides often fail. In vitro, most VRE remain susceptible to last-resort antibiotics such as linezolid, tigecycline and daptomycin. However, neither tigecycline nor linezolid act in a bactericidal manner, and daptomycin has proven activity only at high dosages licensed for treating enterococcal endocarditis. Despite these pharmacological and therapeutic limitations, reports on resistance to these last-resort drugs in VRE, and enterococci in general, have increased in recent years. In this review, we briefly recapitulate the current knowledge on the mode of action as well as the known and novel mechanisms of resistance and describe surveillance data on resistance to linezolid, tigecycline and daptomycin in enterococci. In addition, we also suggest a common nomenclature for designating enterococci and VRE with resistances to these important last-resort antibiotics.

Early administration of broad-spectrum antibiotics is the first goal in sepsis treatment. Besides from bacteriostatic/bactericidal effects, some antibiotics may also modify the host´s response to infection. The novel antibiotic tigecycline may exert such properties; however, this property has not been evaluated in large-animal trials. We compared tigecycline with doxycycline and placebo in relation to anti-inflammatory, circulatory and organ dysfunction effects in a sterile pig model of sepsis. Doxycycline, but not tigecycline, reduced the inflammatory response as manifested by tumor necrosis factor alpha levels in plasma. Tigecycline, however, had a stabilizing effect on the circulation not exerted by doxycycline or placebo. To achieve rapid restoration of the circulating blood volume - another major goal in sepsis treatment - fluid bolus administration of is some-times practiced. In addition to crystalloids, albumin-containing solutions are suggested. Yet, some animal-experimental data suggests that rapid bolus administration of albumin reduces albumin’s plasma-expanding effect. We compared a rapid intravenous bolus of radiolabeled albumin with a slow infusion in a sterile pig model of sepsis. Rapid bolus of administration did not reduce plasma levels of albumin following administration and did not increase the amount of albumin that left the circulation. Inadequate oxygen delivery (DO2) by the circulation to the tissues may cause increased plasma lactate, which is the most striking effect of sepsis on the metabolism. However, experimental data and clinical trials refute this link, instead, suggesting other mechanisms, including impaired oxygen extraction, mitochondrial dysfunction and accelerated aerobic glycolysis. We investigated the impact of DO2, oxygen consumption (VO2), hemodynamic parameters and inflammatory response on plasma lactate and organ dysfunction in two experimental sepsis models. In the most severe cases of shock, with DO2, there was an increase

Early administration of broad-spectrum antibiotics is the first goal in sepsis treatment. Besides from bacteriostatic/bactericidal effects, some antibiotics may also modify the host´s response to infection. The novel antibiotic tigecycline may exert such properties; however, this property has not been evaluated in large-animal trials. We compared tigecycline with doxycycline and placebo in relation to anti-inflammatory, circulatory and organ dysfunction effects in a sterile pig model of sepsis. Doxycycline, but not tigecycline, reduced the inflammatory response as manifested by tumor necrosis factor alpha levels in plasma. Tigecycline, however, had a stabilizing effect on the circulation not exerted by doxycycline or placebo. To achieve rapid restoration of the circulating blood volume - another major goal in sepsis treatment - fluid bolus administration of is some-times practiced. In addition to crystalloids, albumin-containing solutions are suggested. Yet, some animal-experimental data suggests that rapid bolus administration of albumin reduces albumin’s plasma-expanding effect. We compared a rapid intravenous bolus of radiolabeled albumin with a slow infusion in a sterile pig model of sepsis. Rapid bolus of administration did not reduce plasma levels of albumin following administration and did not increase the amount of albumin that left the circulation. Inadequate oxygen delivery (DO2) by the circulation to the tissues may cause increased plasma lactate, which is the most striking effect of sepsis on the metabolism. However, experimental data and clinical trials refute this link, instead, suggesting other mechanisms, including impaired oxygen extraction, mitochondrial dysfunction and accelerated aerobic glycolysis. We investigated the impact of DO2, oxygen consumption (VO2), hemodynamic parameters and inflammatory response on plasma lactate and organ dysfunction in two experimental sepsis models. In the most severe cases of shock, with DO2, there was an increase

Early administration of broad-spectrum antibiotics is the first goal in sepsis treatment. Besides from bacteriostatic/bactericidal effects, some antibiotics may also modify the host´s response to infection. The novel antibiotic tigecycline may exert such properties; however, this property has not been evaluated in large-animal trials. We compared tigecycline with doxycycline and placebo in relation to anti-inflammatory, circulatory and organ dysfunction effects in a sterile pig model of sepsis. Doxycycline, but not tigecycline, reduced the inflammatory response as manifested by tumor necrosis factor alpha levels in plasma. Tigecycline, however, had a stabilizing effect on the circulation not exerted by doxycycline or placebo. To achieve rapid restoration of the circulating blood volume - another major goal in sepsis treatment - fluid bolus administration of is some-times practiced. In addition to crystalloids, albumin-containing solutions are suggested. Yet, some animal-experimental data suggests that rapid bolus administration of albumin reduces albumin’s plasma-expanding effect. We compared a rapid intravenous bolus of radiolabeled albumin with a slow infusion in a sterile pig model of sepsis. Rapid bolus of administration did not reduce plasma levels of albumin following administration and did not increase the amount of albumin that left the circulation. Inadequate oxygen delivery (DO2) by the circulation to the tissues may cause increased plasma lactate, which is the most striking effect of sepsis on the metabolism. However, experimental data and clinical trials refute this link, instead, suggesting other mechanisms, including impaired oxygen extraction, mitochondrial dysfunction and accelerated aerobic glycolysis. We investigated the impact of DO2, oxygen consumption (VO2), hemodynamic parameters and inflammatory response on plasma lactate and organ dysfunction in two experimental sepsis models. In the most severe cases of shock, with DO2, there was an increase

Early administration of broad-spectrum antibiotics is the first goal in sepsis treatment. Besides from bacteriostatic/bactericidal effects, some antibiotics may also modify the host´s response to infection. The novel antibiotic tigecycline may exert such properties; however, this property has not been evaluated in large-animal trials. We compared tigecycline with doxycycline and placebo in relation to anti-inflammatory, circulatory and organ dysfunction effects in a sterile pig model of sepsis. Doxycycline, but not tigecycline, reduced the inflammatory response as manifested by tumor necrosis factor alpha levels in plasma. Tigecycline, however, had a stabilizing effect on the circulation not exerted by doxycycline or placebo. To achieve rapid restoration of the circulating blood volume - another major goal in sepsis treatment - fluid bolus administration of is some-times practiced. In addition to crystalloids, albumin-containing solutions are suggested. Yet, some animal-experimental data suggests that rapid bolus administration of albumin reduces albumin’s plasma-expanding effect. We compared a rapid intravenous bolus of radiolabeled albumin with a slow infusion in a sterile pig model of sepsis. Rapid bolus of administration did not reduce plasma levels of albumin following administration and did not increase the amount of albumin that left the circulation. Inadequate oxygen delivery (DO2) by the circulation to the tissues may cause increased plasma lactate, which is the most striking effect of sepsis on the metabolism. However, experimental data and clinical trials refute this link, instead, suggesting other mechanisms, including impaired oxygen extraction, mitochondrial dysfunction and accelerated aerobic glycolysis. We investigated the impact of DO2, oxygen consumption (VO2), hemodynamic parameters and inflammatory response on plasma lactate and organ dysfunction in two experimental sepsis models. In the most severe cases of shock, with DO2, there was an increase

Early administration of broad-spectrum antibiotics is the first goal in sepsis treatment. Besides from bacteriostatic/bactericidal effects, some antibiotics may also modify the host´s response to infection. The novel antibiotic tigecycline may exert such properties; however, this property has not been evaluated in large-animal trials. We compared tigecycline with doxycycline and placebo in relation to anti-inflammatory, circulatory and organ dysfunction effects in a sterile pig model of sepsis. Doxycycline, but not tigecycline, reduced the inflammatory response as manifested by tumor necrosis factor alpha levels in plasma. Tigecycline, however, had a stabilizing effect on the circulation not exerted by doxycycline or placebo. To achieve rapid restoration of the circulating blood volume - another major goal in sepsis treatment - fluid bolus administration of is some-times practiced. In addition to crystalloids, albumin-containing solutions are suggested. Yet, some animal-experimental data suggests that rapid bolus administration of albumin reduces albumin’s plasma-expanding effect. We compared a rapid intravenous bolus of radiolabeled albumin with a slow infusion in a sterile pig model of sepsis. Rapid bolus of administration did not reduce plasma levels of albumin following administration and did not increase the amount of albumin that left the circulation. Inadequate oxygen delivery (DO2) by the circulation to the tissues may cause increased plasma lactate, which is the most striking effect of sepsis on the metabolism. However, experimental data and clinical trials refute this link, instead, suggesting other mechanisms, including impaired oxygen extraction, mitochondrial dysfunction and accelerated aerobic glycolysis. We investigated the impact of DO2, oxygen consumption (VO2), hemodynamic parameters and inflammatory response on plasma lactate and organ dysfunction in two experimental sepsis models. In the most severe cases of shock, with DO2, there was an increase

The authors report on the first case of the intraventricular administration of tigecycline described in the Western literature. A 22-year-old man developed cerebrospinal fluid infection from an extremely drug-resistant strain of Acinetobacter baumannii as a complication of endoscopic transsphenoidal surgery for the removal of a giant pituitary adenoma. The patient was safely and successfully treated with the prolonged intraventricular administration of tigecycline. Here, the authors provide the schedule details that can be invaluable in treating meningitis from extremely drug-resistant bacterial strains. Intraventricular tigecycline can be a valuable tool against multidrug-resistant central nervous system infections.

Acute myeloid leukemia (AML) cells meet the higher energy, metabolic, and signaling demands of the cell by increasing mitochondrial biogenesis and mitochondrial protein translation. Blocking mitochondrial protein synthesis through genetic and chemical approaches kills human AML cells at all stages of development in vitro and in vivo. Tigecycline is an antimicrobial that we found inhibits mitochondrial protein synthesis in AML cells. Therefore, we conducted a phase 1 dose-escalation study of tigecycline administered intravenously daily 5 of 7 days for 2 weeks to patients with AML. A total of 27 adult patients with relapsed and refractory AML were enrolled in this study with 42 cycles being administered over seven dose levels (50-350 mg/day). Two patients experienced DLTs related to tigecycline at the 350 mg/day level resulting in a maximal tolerated dose of tigecycline of 300 mg as a once daily infusion. Pharmacokinetic experiments showed that tigecycline had a markedly shorter half-life in these patients than reported for noncancer patients. No significant pharmacodynamic changes or clinical responses were observed. Thus, we have defined the safety of once daily tigecycline in patients with refractory AML. Future studies should focus on schedules of the drug that permit more sustained target inhibition.

BackgroundPostoperative infection is a devastating complication following arthroplasty. The goals of this study were to introduce a "smart" implant coating that combines passive elution of antibiotic with an active-release mechanism that "targets" bacteria, and to use an established in vivo mouse model of post-arthroplasty infection to longitudinally evaluate the efficacy of this polymer implant coating in decreasing bacterial burden.MethodsA novel, biodegradable coating using branched poly(ethylene glycol)-poly(propylene sulfide) (PEG-PPS) polymer was designed to deliver antibiotics both passively and actively. In vitro-release kinetics were studied using high-performance liquid chromatography (HPLC) quantification in conditions representing both the physiologic environment and the more oxidative, hyperinflammatory environment of periprosthetic infection. The in vivo efficacy of the PEG-PPS coating delivering vancomycin and tigecycline was tested using an established mouse model of post-arthroplasty infection. Noninvasive bioluminescence imaging was used to quantify the bacterial burden; radiography, to assess osseointegration and bone resorption; and implant sonication, for colony counts.ResultsIn vitro-release kinetics confirmed passive elution above the minimum inhibitory concentration (MIC). A rapid release of antibiotic was noted when challenged with an oxidative environment (p < 0.05), confirming a "smart" active-release mechanism. The PEG-PPS coating with tigecycline significantly lowered the infection burden on all days, whereas PEG-PPS-vancomycin decreased infection on postoperative day (POD) 1, 3, 5, and 7 (p < 0.05). A mean of 0, 9, and 2.6 × 10(2) colony-forming units (CFUs) grew on culture from the implants treated with tigecycline, vancomycin, and PEG-PPS alone, respectively, and a mean of 1.2 × 10(2), 4.3 × 10(3), and 5.9 × 10(4) CFUs, respectively, on culture of the surrounding tissue (p < 0.05).ConclusionsThe PEG-PPS coating provides a pro

The incidence of Clostridium difficile infection (CDI) continues to rise, whilst treatment remains problematic due to recurrent, refractory and potentially severe nature of disease. The treatment of C. difficile is a challenge for community and hospital-based clinicians. With the advent of an expanding therapeutic arsenal against C. difficile since the last published Australasian guidelines, an update on CDI treatment recommendations for Australasian clinicians was required. On behalf of the Australasian Society of Infectious Diseases, we present the updated guidelines for the management of CDI in adults and children.Copyright © 2016 Royal Australasian College of Physicians.

The incidence of Clostridium difficile infection (CDI) continues to rise, whilst treatment remains problematic due to recurrent, refractory and potentially severe nature of disease. The treatment of C. difficile is a challenge for community and hospital-based clinicians. With the advent of an expanding therapeutic arsenal against C. difficile since the last published Australasian guidelines, an update on CDI treatment recommendations for Australasian clinicians was required. On behalf of the Australasian Society of Infectious Diseases, we present the updated guidelines for the management of CDI in adults and children.Copyright © 2016 Royal Australasian College of Physicians.

BackgroundPostoperative infection is a devastating complication following arthroplasty. The goals of this study were to introduce a "smart" implant coating that combines passive elution of antibiotic with an active-release mechanism that "targets" bacteria, and to use an established in vivo mouse model of post-arthroplasty infection to longitudinally evaluate the efficacy of this polymer implant coating in decreasing bacterial burden.MethodsA novel, biodegradable coating using branched poly(ethylene glycol)-poly(propylene sulfide) (PEG-PPS) polymer was designed to deliver antibiotics both passively and actively. In vitro-release kinetics were studied using high-performance liquid chromatography (HPLC) quantification in conditions representing both the physiologic environment and the more oxidative, hyperinflammatory environment of periprosthetic infection. The in vivo efficacy of the PEG-PPS coating delivering vancomycin and tigecycline was tested using an established mouse model of post-arthroplasty infection. Noninvasive bioluminescence imaging was used to quantify the bacterial burden; radiography, to assess osseointegration and bone resorption; and implant sonication, for colony counts.ResultsIn vitro-release kinetics confirmed passive elution above the minimum inhibitory concentration (MIC). A rapid release of antibiotic was noted when challenged with an oxidative environment (p < 0.05), confirming a "smart" active-release mechanism. The PEG-PPS coating with tigecycline significantly lowered the infection burden on all days, whereas PEG-PPS-vancomycin decreased infection on postoperative day (POD) 1, 3, 5, and 7 (p < 0.05). A mean of 0, 9, and 2.6 × 10(2) colony-forming units (CFUs) grew on culture from the implants treated with tigecycline, vancomycin, and PEG-PPS alone, respectively, and a mean of 1.2 × 10(2), 4.3 × 10(3), and 5.9 × 10(4) CFUs, respectively, on culture of the surrounding tissue (p < 0.05).ConclusionsThe PEG-PPS coating provides a pro

Given the rapidly changing landscape of antimicrobial resistance, continuous monitoring of antimicrobial susceptibility in clinically relevant bacterial isolates plays an important role in the management of infectious diseases. The Tigecycline Evaluation and Surveillance Trial (TEST) is an ongoing worldwide surveillance programme monitoring the in vitro activity of tigecycline and a panel of representative comparator antibiotics. We report longitudinal susceptibility data on a large set of isolates (n=36,044) from clinically significant bacterial species collected in 25 microbiological laboratories from 2006 to 2014. Trends include a strong increase of carbapenem and levofloxacin resistance in Acinetobacter spp., and smaller increasing rates of ESBL-producing Escherichia coli and vancomycin-resistant enterococci. Across the reporting period, the tigecycline minimum inhibitory concentrations (MICs) at which 50% and 90% of isolates were inhibited remained stable and susceptibility rates were consistently high (93-100%) for all bacterial species.

Acute myeloid leukemia (AML) cells meet the higher energy, metabolic, and signaling demands of the cell by increasing mitochondrial biogenesis and mitochondrial protein translation. Blocking mitochondrial protein synthesis through genetic and chemical approaches kills human AML cells at all stages of development in vitro and in vivo. Tigecycline is an antimicrobial that we found inhibits mitochondrial protein synthesis in AML cells. Therefore, we conducted a phase 1 dose-escalation study of tigecycline administered intravenously daily 5 of 7 days for 2 weeks to patients with AML. A total of 27 adult patients with relapsed and refractory AML were enrolled in this study with 42 cycles being administered over seven dose levels (50-350 mg/day). Two patients experienced DLTs related to tigecycline at the 350 mg/day level resulting in a maximal tolerated dose of tigecycline of 300 mg as a once daily infusion. Pharmacokinetic experiments showed that tigecycline had a markedly shorter half-life in these patients than reported for noncancer patients. No significant pharmacodynamic changes or clinical responses were observed. Thus, we have defined the safety of once daily tigecycline in patients with refractory AML. Future studies should focus on schedules of the drug that permit more sustained target inhibition.

BackgroundPostoperative infection is a devastating complication following arthroplasty. The goals of this study were to introduce a "smart" implant coating that combines passive elution of antibiotic with an active-release mechanism that "targets" bacteria, and to use an established in vivo mouse model of post-arthroplasty infection to longitudinally evaluate the efficacy of this polymer implant coating in decreasing bacterial burden.MethodsA novel, biodegradable coating using branched poly(ethylene glycol)-poly(propylene sulfide) (PEG-PPS) polymer was designed to deliver antibiotics both passively and actively. In vitro-release kinetics were studied using high-performance liquid chromatography (HPLC) quantification in conditions representing both the physiologic environment and the more oxidative, hyperinflammatory environment of periprosthetic infection. The in vivo efficacy of the PEG-PPS coating delivering vancomycin and tigecycline was tested using an established mouse model of post-arthroplasty infection. Noninvasive bioluminescence imaging was used to quantify the bacterial burden; radiography, to assess osseointegration and bone resorption; and implant sonication, for colony counts.ResultsIn vitro-release kinetics confirmed passive elution above the minimum inhibitory concentration (MIC). A rapid release of antibiotic was noted when challenged with an oxidative environment (p < 0.05), confirming a "smart" active-release mechanism. The PEG-PPS coating with tigecycline significantly lowered the infection burden on all days, whereas PEG-PPS-vancomycin decreased infection on postoperative day (POD) 1, 3, 5, and 7 (p < 0.05). A mean of 0, 9, and 2.6 × 10(2) colony-forming units (CFUs) grew on culture from the implants treated with tigecycline, vancomycin, and PEG-PPS alone, respectively, and a mean of 1.2 × 10(2), 4.3 × 10(3), and 5.9 × 10(4) CFUs, respectively, on culture of the surrounding tissue (p < 0.05).ConclusionsThe PEG-PPS coating provides a pro

Despite ubiquitous activation in human cancer, essential downstream effector pathways of the MYC transcription factor have been difficult to define and target. Using a structure/function-based approach, we identified the mitochondrial RNA polymerase (POLRMT) locus as a critical downstream target of MYC. The multifunctional POLRMT enzyme controls mitochondrial gene expression, a process required both for mitochondrial function and mitochondrial biogenesis. We further demonstrate that inhibition of this newly defined MYC effector pathway causes robust and selective tumor cell apoptosis, via an acute, checkpoint-like mechanism linked to aberrant electron transport chain complex assembly and mitochondrial reactive oxygen species (ROS) production. Fortuitously, MYC-dependent tumor cell death can be induced by inhibiting the mitochondrial gene expression pathway using a variety of strategies, including treatment with FDA-approved antibiotics. In vivo studies using a mouse model of Burkitt's Lymphoma provide pre-clinical evidence that these antibiotics can successfully block progression of MYC-dependent tumors.

Antibiotic resistance is an ongoing global medical crisis and we are in great need of new antibacterial agents to combat rapidly emerging resistant pathogens. Tigecycline is one of few drugs that have been introduced into medicine during the last two decades. It is a broad-spectrum third generation tetracycline that is active against multidrug-resistant bacteria that cause complicated infections. In this thesis I examined the development of tigecycline resistance in Escherichia coli and associated in vitro and in vivo fitness effects. Selections of spontaneous E. coli mutants revealed relatively high accumulation rates of changes in the multidrug efflux system AcrAB-TolC regulation network and in heptose biosynthesis and transport pathways important for lipopolysaccharide (LPS) synthesis. Both groups of mutations led to reduced susceptibility to tigecycline and slower growth compared to the wild-type bacteria. Additional in vitro fitness assays and in vivo competitions showed that LPS mutants were less fit than efflux mutants, providing a possible explanation for why up-regulation of multidrug efflux pumps is the main tigecycline resistance mechanism reported in clinical isolates. Tigecycline was designed to evade the two most common tetracycline resistance mechanisms conferred by Tet proteins, efflux and ribosomal protection. However, tigecycline is a substrate for the tetracycline modifying enzyme Tet(X). Screening of Tet protein mutant libraries showed that it is possible to select Tet mutants with minimal inhibitory concentrations of tigecycline that reach clinically relevant levels. Mutations in Tet proteins that permitted a better protection from tigecycline frequently exhibited reduced activity against earlier generations of tetracyclines, except for the Tet(X) enzyme mutants, which were better at inactivating all tested tetracyclines. This is particularly worrisome because different variants of Tet(X) have recently spread to multidrug-resistant pathogens thr

Antibiotic resistance is an ongoing global medical crisis and we are in great need of new antibacterial agents to combat rapidly emerging resistant pathogens. Tigecycline is one of few drugs that have been introduced into medicine during the last two decades. It is a broad-spectrum third generation tetracycline that is active against multidrug-resistant bacteria that cause complicated infections. In this thesis I examined the development of tigecycline resistance in Escherichia coli and associated in vitro and in vivo fitness effects. Selections of spontaneous E. coli mutants revealed relatively high accumulation rates of changes in the multidrug efflux system AcrAB-TolC regulation network and in heptose biosynthesis and transport pathways important for lipopolysaccharide (LPS) synthesis. Both groups of mutations led to reduced susceptibility to tigecycline and slower growth compared to the wild-type bacteria. Additional in vitro fitness assays and in vivo competitions showed that LPS mutants were less fit than efflux mutants, providing a possible explanation for why up-regulation of multidrug efflux pumps is the main tigecycline resistance mechanism reported in clinical isolates. Tigecycline was designed to evade the two most common tetracycline resistance mechanisms conferred by Tet proteins, efflux and ribosomal protection. However, tigecycline is a substrate for the tetracycline modifying enzyme Tet(X). Screening of Tet protein mutant libraries showed that it is possible to select Tet mutants with minimal inhibitory concentrations of tigecycline that reach clinically relevant levels. Mutations in Tet proteins that permitted a better protection from tigecycline frequently exhibited reduced activity against earlier generations of tetracyclines, except for the Tet(X) enzyme mutants, which were better at inactivating all tested tetracyclines. This is particularly worrisome because different variants of Tet(X) have recently spread to multidrug-resistant pathogens thr

Eggerthella lenta is an emerging pathogen that has been underrecognized due to historical difficulties with phenotypic identification. Until now, its pathogenicity, antimicrobial susceptibility profile, and optimal treatment have been poorly characterized. In this article, we report the largest cohort of patients with E. lenta bacteremia to date and describe in detail their clinical features, microbiologic characteristics, treatment, and outcomes. We identified 33 patients; the median age was 68 years, and there was no gender predominance. Twenty-seven patients (82%) had serious intra-abdominal pathology, often requiring a medical procedure. Of those who received antibiotics (28/33, 85%), the median duration of treatment was 21.5 days. Mortality from all causes was 6% at 7 days, 12% at 30 days, and 33% at 1 year. Of 26 isolates available for further testing, all were identified as E. lenta by both commercially available matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, and none were found to harbor a vanA or vanB gene. Of 23 isolates which underwent susceptibility testing, all were susceptible to amoxicillin-clavulanate, cefoxitin, metronidazole, piperacillin-tazobactam, ertapenem, and meropenem, 91% were susceptible to clindamycin, 74% were susceptible to moxifloxacin, and 39% were susceptible to penicillin.Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Eggerthella lenta is an emerging pathogen that has been underrecognized due to historical difficulties with phenotypic identification. Until now, its pathogenicity, antimicrobial susceptibility profile, and optimal treatment have been poorly characterized. In this article, we report the largest cohort of patients with E. lenta bacteremia to date and describe in detail their clinical features, microbiologic characteristics, treatment, and outcomes. We identified 33 patients; the median age was 68 years, and there was no gender predominance. Twenty-seven patients (82%) had serious intra-abdominal pathology, often requiring a medical procedure. Of those who received antibiotics (28/33, 85%), the median duration of treatment was 21.5 days. Mortality from all causes was 6% at 7 days, 12% at 30 days, and 33% at 1 year. Of 26 isolates available for further testing, all were identified as E. lenta by both commercially available matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, and none were found to harbor a vanA or vanB gene. Of 23 isolates which underwent susceptibility testing, all were susceptible to amoxicillin-clavulanate, cefoxitin, metronidazole, piperacillin-tazobactam, ertapenem, and meropenem, 91% were susceptible to clindamycin, 74% were susceptible to moxifloxacin, and 39% were susceptible to penicillin.Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Antibiotic resistance is an ongoing global medical crisis and we are in great need of new antibacterial agents to combat rapidly emerging resistant pathogens. Tigecycline is one of few drugs that have been introduced into medicine during the last two decades. It is a broad-spectrum third generation tetracycline that is active against multidrug-resistant bacteria that cause complicated infections. In this thesis I examined the development of tigecycline resistance in Escherichia coli and associated in vitro and in vivo fitness effects. Selections of spontaneous E. coli mutants revealed relatively high accumulation rates of changes in the multidrug efflux system AcrAB-TolC regulation network and in heptose biosynthesis and transport pathways important for lipopolysaccharide (LPS) synthesis. Both groups of mutations led to reduced susceptibility to tigecycline and slower growth compared to the wild-type bacteria. Additional in vitro fitness assays and in vivo competitions showed that LPS mutants were less fit than efflux mutants, providing a possible explanation for why up-regulation of multidrug efflux pumps is the main tigecycline resistance mechanism reported in clinical isolates. Tigecycline was designed to evade the two most common tetracycline resistance mechanisms conferred by Tet proteins, efflux and ribosomal protection. However, tigecycline is a substrate for the tetracycline modifying enzyme Tet(X). Screening of Tet protein mutant libraries showed that it is possible to select Tet mutants with minimal inhibitory concentrations of tigecycline that reach clinically relevant levels. Mutations in Tet proteins that permitted a better protection from tigecycline frequently exhibited reduced activity against earlier generations of tetracyclines, except for the Tet(X) enzyme mutants, which were better at inactivating all tested tetracyclines. This is particularly worrisome because different variants of Tet(X) have recently spread to multidrug-resistant pathogens thr