Search

Achromobacter genus (including Achromobacter xylosoxidans, the most prevalent Achromobacter species in patients with cystic fibrosis) is poorly susceptible to most conventional antibiotics. Contribution of efflux by AxyABM, AxyXY-OprZ, and AxyEF-OprN and of target mutations were studied in clinical isolates of A. xylosoxidans and Achromobacter insuavis. Forty-one isolates longitudinally collected from 21 patients with CF were studied by whole-genome sequencing (WGS)-typing, determination of minimum inhibitory concentrations (MICs) of β-lactams, aminoglycosides, colistin, azithromycin, ciprofloxacin, chloramphenicol, and doxycycline, and expression (quantitative RT-PCR) and function (measure of the uptake of a fluorescent substrate) of efflux pumps. WGS-based typing resulted in 10 clusters comprising 2 or 3 isolates and 20 singletons. The efflux activity was high in strains with elevated MICs for amikacin or azithromycin. This work sheds a new light on the impact of efflux and target mutations in resistance of Achromobacter to several drugs.

Aminoglycosides are among the most commonly prescribed antibiotics in hospitalised Australian adults and children. A proportion of individuals with an underlying genetic predisposition to aminoglycoside‐induced hearing loss (AIHL) can develop bilateral sensorineural hearing loss that is immediate and profound after just a single standard dose of an aminoglycoside. A recent publication described the use of a rapid point‐of‐care test (POCT) in a neonatal nursery in the United Kingdom for real‐time detection of infants at risk of AIHL, in whom exposure to aminoglycosides could then be avoided. This proof of concept study should provide a catalyst for further development of similar assays that would be suitable for Australia's genetically diverse population. The barriers to mitigating the impact of AIHL on Australian children are not primarily technical, but involve a lack of data on the prevalence of the MT‐RNR1 mutations in our current neonatal and paediatric populations and intensive care nurseries. [ABSTRACT FROM AUTHOR]

Surface‐independent smart antibacterial coatings with on‐demand antibiotics release profiles have attracted increasing attention in medical instruments, antibiotics delivery platforms, and implanted devices. Although several approaches have been well documented, the facile preparation of antibacterial coatings onto universal substrates with high antibiotics loading efficiencies, tunable drug release profiles, and excellent antibacterial performances is still met with many challenges, especially related to the redundant coating material synthesis and selective substrate fabrication process. To resolve this issue, the authors report a facile and robust fabrication method towards smart antibacterial coating surfaces on various substrates via a one‐pot integration of two types of naturally occurring building blocks, aminoglycosides and protocatechualdehyde in the presence of plant enzyme horseradish peroxidase. The simultaneous dynamic imine bonds formation and enzymatic polymerization within the system during the one‐pot reaction enable the facile fabrication of diverse surface‐independent smart antibacterial coatings, which can demonstrate several promising features including high drug loading and dynamic (i.e., pH‐responsive) properties, tunable and on‐demand antibiotics release behaviors, and efficient antibacterial activities both in vitro and in vivo. This work may offer new opportunities towards the robust and universal antibacterial coating materials by the bioinspired integration of all natural building blocks. [ABSTRACT FROM AUTHOR]

Infective endocarditis (IE) in neonates is associated with high mortality and incidence has been increasing over the past two decades. The majority of very low birth weight infants will be treated with at least one nephrotoxic medication during their hospital course. Over one-quarter of very low birth weight neonates exposed to gentamicin may develop acute kidney injury (AKI); this is particularly worrisome as AKI is an independent factor associated with increased neonatal mortality and increased length of stay. AKI during periods of neonatal nephrogenesis, which continues until 34-36 weeks postmenstrual age, may also have serious effects on the long-term nephron development which subsequently puts infants at risk of chronic kidney disease. Extended interval (EI) aminoglycoside (AMG) dosing has been used for decades in adult populations and has proven to reduce AKI while being at least as effective as traditional dosing, although there is limited published research for using an EI AMG in endocarditis in adults or pediatric patients. We describe an extremely low birth weight neonate, born preterm at 24 weeks gestation treated for Klebsiella pneumoniae IE that required AMG therapy who also had concurrent AKI. We utilized EI AMG combination therapy for treatment of Klebsiella pneumoniae endocarditis with good outcome and encourage others to report their experiences to improve our knowledge of EI AMG in this population. [ABSTRACT FROM AUTHOR]

It is well known that loss of aerobic respiration in Gram-negative bacteria can diminish the efficacy of a variety of bactericidal antibiotics, which has lead to subsequent demonstrations that the formation of reactive oxygen species (ROS) and the proton motive force (PMF) can both play a role in antibiotic toxicity. The susceptibility of Gram-negative bacteria to aminoglycoside antibiotics, particularly gentamicin, has previously been linked to both the production of ROS and the rate of antibiotic uptake that is mediated by the PMF, although the relative contributions of ROS and PMF to aminoglycoside toxicity has remained poorly understood. Herein, gentamicin was shown to elicit a very modest increase in ROS levels in an aerobically grown Escherichia coli clinical isolate. The well-characterised uncoupler 2,4-dinitrophenol (DNP) was used to disrupt the PMF, which resulted in a significant decrease in gentamicin lethality towards E. coli. DNP did not significantly alter respiratory oxygen consumption, supporting the hypothesis that this uncoupler does not increase ROS production via elevated respiratory oxidase activity. These observations support the hypothesis that maintenance of PMF rather than induction of ROS production underpins the mechanism for how the respiratory chain potentiates the toxicity of aminoglycosides. This was further supported by the demonstration that the uncoupler DNP elicits a dramatic decrease in gentamicin lethality under anaerobic conditions. Together, these data strongly suggest that maintenance of the PMF is the dominant mechanism for the respiratory chain in potentiating the toxic effects of aminoglycosides. [ABSTRACT FROM AUTHOR]

Objective(s): In this study, it is aimed to investigate the potential protective effect of caffeic acid phenethyl ester (CAPE) on ototoxicity caused by gentamicin in a rat model. Materials and Methods: Thirty Wistar albino rats were divided into 3 groups. Group I was selected as the control group. Gentamicin was administered intraperitoneally in group II, gentamicin and CAPE in group III. Audiological assessment was performed by the distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) measurements before and after treatment of each group. At the end of the study all rats were decapitated, cochlea was removed and electron microscopic examination was performed. Results:: In group II post-treatment DPOAE levels were found to be lower than pretreatment DPOAE levels (P<0.05). However, in group III, there is no significant difference between pre- and posttreatment DPOAE levels (P>0.05). Except for Group I, ABR thresholds increased after the procedure and this increase was statistically significant (P<0.0001). According to histological examination by transmission electron microscopy, CAPE has a cellular protective effect against gentamicin ototoxicity. Conclusion: CAPE may ameliorate hearing deterioration caused by gentamicin ototoxicity and protect the cochlear cells from apoptosis due to the strong antioxidant effect. [ABSTRACT FROM AUTHOR]

Background and purpose: Aminoglycosides (AG) such as Amikacin that are widely used to prevent and treat infections in neonates have nephrotoxic effects. The aim of this study was to evaluate the role of urinary index to Glomerular filtration rate (GFR) in diagnosis of tubular renal injury following administration of Amikacin in neonates admitted to neonatal intensive care unit (NICU). Materials and methods: In this descriptive cross-sectional study, 45 neonates admitted to NICU with confirmed sepsis undergone treatment with Amikacin and Ampicillin and 45 neonates were treated with Ampicillin and Cefotaxime. GFR was calculated using Schwartz's formula (serum creatinine/height * 0.45) and categorized based on Fanaroff table. In both groups, BUN, Cr, and GFR were measured at days one and seven. Data analysis was performed in SPSS. Results: Two (4.4%) patients in the group treated with Amikacin and Ampicillin and one (2.2%) in the group who received Ampicillin and Cefotaxime developed acute kidney injury (AKI). GFR changes and Cr levels at day seven were not found to be significantly different between septic neonates treated with Amikacin and Ampicillin and neonates treated with other non-aminoglycosidic antibiotics (P>0.05). Conclusion: There was no difference in incidence of AKI between neonates receiving Amikacin and Ampicillin and those who received Ampicillin and Cefotaxime. Hence, AKI in these neonates requires further evaluations. [ABSTRACT FROM AUTHOR]

Copyright of Diyala Journal for Pure Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multidrug-resistant bacteria from different sources have been steadily emerging, and an increasing number of resistance mechanisms are being uncovered. In this work, we characterized a novel resistance gene named aac(2′)-If from an isolate of a novel Providencia species, Providencia wenzhouensis R33 (CCTCC AB 2021339). Susceptibility testing and enzyme kinetic parameter analysis were conducted to determine the function of the aminoglycoside 2′- N -acetyltransferase. Whole-genome sequencing and comparative genomic analysis were performed to elucidate the molecular characteristics of the genome and the genetic context of the resistance gene-related sequences. Among the functionally characterized resistance genes, AAC(2′)-If shares the highest amino acid sequence identity of 70.79% with AAC(2′)-Ia. AAC(2′)-If confers resistance to several aminoglycoside antibiotics, showing the highest resistance activity against ribostamycin and neomycin. The recombinant strain harboring aac(2′)-If (pUCP20- aac(2′)-If /DH5α) showed 256- and 128-fold increases in the minimum inhibitory concentration (MIC) levels to ribostamycin and neomycin, respectively, compared with those of the control strains (DH5α and pUCP20/DH5α). The results of the kinetic analysis of AAC(2′)-If were consistent with the MIC results of the cloned aac(2′)-If with the highest catalytic efficiency for ribostamycin (k cat /K m ratio = [3.72 ± 0.52] × 104 M–1⋅s–1). Whole-genome sequencing demonstrated that the aac(2′)-If gene was located on the chromosome with a relatively unique genetic environment. Identification of a novel aminoglycoside resistance gene in a strain of a novel Providencia species will help us find ways to elucidate the complexity of resistance mechanisms in the microbial population. [ABSTRACT FROM AUTHOR]

To determine the appropriateness of empiric antibiotic therapy and the possible benefit of adding short-course gentamicin in septic shock patients with abdominal, urogenital, or an unknown focus. Secondary objectives were the effect of gentamicin addition on shock reversal and the incidence of a fungal infection. Microbiological cultures, antibiotic treatment, and antibiotic resistance patterns of the cultured microorganisms were recorded during the first 5 days of admission. Inappropriate antibiotic therapy was defined as a prescription within the first 24 h that did not cover cultured bacteria during the first 5 days of admission and was determined in the overall group and in patients receiving adjunctive gentamicin (combination therapy) versus patients receiving monotherapy. Binomial logistic regression analysis was used to investigate the association of gentamicin addition with shock reversal. Of 203 septic shock patients, with abdominal (n = 143), urogenital (n = 27) or unknown (n = 33) focus, 115 patients received monotherapy, and 88 patients received combination therapy. Inappropriate therapy occurred in 29 patients (14%), more frequently in monotherapy (17%) versus combination therapy (10%). Combination therapy would have been effective in 55% of patients with inappropriate monotherapy. We found no association between gentamicin addition and shock reversal (p =.223). A fungal infection was present in 22 patients (11%). Inappropriate empirical antibiotic therapy occurs in 17% of septic shock patients receiving monotherapy. In 55% of these patients, additional gentamicin would have resulted in appropriate therapy. When clinical course is unfavourable, lowering the threshold for administering adjunctive aminoglycoside and antifungal therapy should be considered. [ABSTRACT FROM AUTHOR]

Enterococcus spp. are remarkable multidrug resistant (MDR) bacteria that are causing serious healthcare-associated infections. The current study investigated the frequency of Enterococcus spp., antimicrobial susceptibility, biofilm formation and the presence of some plasmid-mediated virulence characters and antimicrobial resistance determinants in enterococcal isolates from Egyptian hospitals in Cairo. Enterococcus bacterial isolates were recovered from different clinical specimens and identified using biochemical testing and KB005A HiStrep™ identification kit. Kirby-Bauer disc diffusion method and/or broth microdilution method were used to determine the antimicrobial susceptibility patterns. Phenotypic assays were performed to study biofilm formation and cytolysin and gelatinase production. PCR assays targeting the plasmid-carried genes aac(6’)-aph(2’), aph(3)-IIIa, vanA, agg and cylA were performed. In this study, 50 isolates of diverse Enterococcus spp. were identified with E. faecium was the most frequently isolated one. High resistance profiles were determined against tested antimicrobials and all isolates were MDR. Moderate biofilm formation was detected in 20% of isolates, 18% showed complete blood hemolysis and 12% produced gelatinase. All isolates carried the tested aminoglycosides resistance genes, while vanA was found only in 4 isolates (8%). The virulence genes agg and cylA were detected in 4% and 32% of isolates, respectively. In conclusion, E. faecium was the most prevalent species. The entire isolates set were MDR and the plasmid-carried aminoglycoside resistance genes were extensively disseminated among MDR isolates. Thus, regular surveillance studies, from the area of study or other geographical regions in Egypt, and strict infection control measures are required to monitor the emerging MDR enterococci.

Abstract Background This study aimed to identify ten different 16S rRNA methyltransferase genes (rmtA, rmtB, rmtC, rmtD, armA, rmtF, npmA, rmtH, rmtE and rmtG) and their coexisting ESBL and carbapenemase with the emergence of three E.coli clones within a single study centre. Methods A total of 329 non-duplicate E.coli isolates were studied to detect the presence of 16S rRNA methyltransferases along with β-lactamases (TEM, SHV, OXA, VEB, GES, PER,CTX-M types, NDM, OXA-48,VIM, IMP and KPC) using PCR assay. Horizontal transferability were validated by transformation and conjugation analysis. Plasmid incompatibility typing and MLST analysis was also performed. Results A total of 117 isolates were found to be resistant to at least one of the aminoglycoside antibiotics. It was observed that 77 (65.8%) were positive for 16S rRNA methyltransferases. Among them thirty nine isolates were found to harbour only bla CTX-M-15, whereas combination of genes were observed in three isolates (bla VEB+ bla CTX-M-15 in 2 isolates and bla PER + bla CTX-M-15 in 1 isolate). bla NDM and bla OXA-48 like genes were found in 23 and 9 isolates, respectively. All the resistance genes were conjugatively transferable, and incompatibility typing showed multiple 16S rRNA methyltransferase genes were originated from a single Inc. I1 group. MLST analysis detected 3 clones of E.coliST4410, ST1341 and ST3906. Conclusion The present study identified emergence of three clones of E.coli, resistant to aminoglycoside -cephalosporin- carbapenem. This warrants immediate measures to trace their transmission dynamics in order to slow down their spread in clinical setting.

The antimicrobial resistance rate in bacteria has increased over the last several decades. The transfer of antimicrobial resistant determinants on mobile genetic elements could cause the accelerated emergence and spread of multidrug resistant bacteria. This study investigated the aminoglycoside resistance determinants transferred by mobile genetic elements in a total of 33 aminoglycoside non-susceptible E. coli isolated from clinical specimens in Chungcheong province. 16S ribosomal RNA methyl-transferases (RMTases) and aminoglycoside-modifying enzyme (AME) genes were detected via PCR and DNA sequencing. The most common AME genes were aac(3′)-II gene (54.5%), followed by aph(3′)-Ia (18.2%) and aac(6′)-Ib (15.2%). None of the evaluated RMTase genes were detected in the 33 isolates. Seventeen of the 18 isolates harboring aac(3′)-II gene were resistant to gentamicin, and 16 of them were resistant to tobramycin. The 5 isolates harboring aac(6′)-Ib gene were all resistant to tobramycin. In this study, we confirmed that one of the important mechanisms of aminoglycoside resistance in E. coli isolated from human is the acquisition of AME genes. Continuing investigations of antimicrobial resistant determinants in bacteria isolated from human may be required to prevent dissemination of antimicrobial resistant bacteria.

Purpose: Although the current widespread use of amikacin is in intra-abdominal sepsis treatment, its pharmacokinetic changes in the present setting are not yet well known. This study was aimed to evaluate the amikacin pharmacokinetic profile in critically ill patients with intraabdominal sepsis compared to pneumosepsis. Methods: Adult septic patients received amikacin therapy were studied. Patients with intraabdominal sepsis were enrolled in group 1 (n=16), and patients with pneumosepsis were enrolled in group 2 (n=13). The amikacin serum concentrations were evaluated in the first, second, fourth and sixth hours after initiating 30-minute infusion. The pharmacokinetic parameters were calculated for each patient. Results: There was no significant difference in the volume of distribution between the two groups (0.33±0.08 vs. 0.28±0.10 L/kg, P=0.193). The amikacin clearance was significantly lower in group 1 compared to group 2 (58.5±21.7 vs. 83.9±37.0 mL/min, P=0.029). There was no significant correlation between amikacin clearance and creatinine clearance estimated by Cockcroft-Gault formula in all patients (P=0.206). The half-life was significantly longer in group 1 compared to group 2 (5.3±2.8 vs. 3.4±3.2 hours, P=0.015). Conclusion: Pathophysiologic changes following intra-abdominal sepsis can affect amikacin pharmacokinetics behavior. The clearance and half-life may change, but the alteration of the volume of distribution is not significantly different in comparison with pneumosepsis. Further studies are required to evaluate the pharmacokinetic variables of amikacin in critically ill patients with intra-abdominal sepsis.

Abstract Background Oomycetes are pathogens of mammals, fish, insects and plants, and the potato late blight agent Phytophthora infestans and the oil palm and cocoa infecting pathogen Phytophthora palmivora cause economically impacting diseases on a wide range of crop plants. Increasing genomic and transcriptomic resources and recent advances in oomycete biology demand new strategies for genetic modification of oomycetes. Most oomycete transformation procedures rely on geneticin-based selection of transgenic strains. Results We established N-acetyltransferase AAC(3)-I as a gentamicin-based selectable marker for oomycete transformation without interference with existing geneticin resistance. Strains carrying gentamicin resistance are fully infectious in plants. We further demonstrate the usefulness of this new antibiotic selection to super-transform well-characterized, already fluorescently-labelled P. palmivora strains and provide a comprehensive protocol for maintenance and zoospore electro-transformation of Phytophthora strains to aid in plant-pathogen research. Conclusions N-acetyltransferase AAC(3)-I is functional in Phytophthora oomycetes. In addition, the substrate specificity of the AAC(3)-I enzyme allows for re-transformation of geneticin-resistant strains. Our findings and resources widen the possibilities to study oomycete cell biology and plant-oomycete interactions.

Multidrug-resistant bacteria from different sources have been steadily emerging, and an increasing number of resistance mechanisms are being uncovered. In this work, we characterized a novel resistance gene named aac(2′)-If from an isolate of a novel Providencia species, Providencia wenzhouensis R33 (CCTCC AB 2021339). Susceptibility testing and enzyme kinetic parameter analysis were conducted to determine the function of the aminoglycoside 2′-N-acetyltransferase. Whole-genome sequencing and comparative genomic analysis were performed to elucidate the molecular characteristics of the genome and the genetic context of the resistance gene-related sequences. Among the functionally characterized resistance genes, AAC(2′)-If shares the highest amino acid sequence identity of 70.79% with AAC(2′)-Ia. AAC(2′)-If confers resistance to several aminoglycoside antibiotics, showing the highest resistance activity against ribostamycin and neomycin. The recombinant strain harboring aac(2′)-If (pUCP20-aac(2′)-If/DH5α) showed 256- and 128-fold increases in the minimum inhibitory concentration (MIC) levels to ribostamycin and neomycin, respectively, compared with those of the control strains (DH5α and pUCP20/DH5α). The results of the kinetic analysis of AAC(2′)-If were consistent with the MIC results of the cloned aac(2′)-If with the highest catalytic efficiency for ribostamycin (kcat/Km ratio = [3.72 ± 0.52] × 104 M–1⋅s–1). Whole-genome sequencing demonstrated that the aac(2′)-If gene was located on the chromosome with a relatively unique genetic environment. Identification of a novel aminoglycoside resistance gene in a strain of a novel Providencia species will help us find ways to elucidate the complexity of resistance mechanisms in the microbial population.

Chemical modification of old drugs is an important way to obtain new ones, and it has been widely used in developing new aminoglycoside antibiotics. However, many of the previous modifying strategies seem arbitrary for their lack of support from structural biological detail. In this paper, based on the structural information of aminoglycoside and its drug target, we firstly analyzed the reason that some 2′-N-acetylated products of aminoglycosides caused by aminoglycoside-modifying enzyme AAC(2′) can partially retain activity, and then we designed, synthesized, and evaluated a series of 2′-modified kanamycin A derivatives. Bioassay results showed our modifying strategy was feasible. Our study provided valuable structure–activity relationship information, which would help researchers to develop new aminoglycoside antibiotics more effectively.

N‐Acetyl groups are abundant functional groups found in a variety of biomolecules including aminosugars. N‐Acetyl groups are chemically stable and harsh conditions are often needed to remove them. Herein, we report a mild and efficient protocol to remove N‐acetyl groups in the presence of esters and carbamates and functionalize the resulting amine in a one‐pot manner. [ABSTRACT FROM AUTHOR]

We aimed to determine the incidence of acute kidney injury (AKI) and longitudinal changes in SCr levels and urinary biomarkers associated with AKI and aminoglycoside (AG) medication during the first week of life of late preterm infants. Urine biomarkers and SCr were measured in thirty late preterm infants on days one, two, five, and seven postnatal. Urine biomarkers included neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1 (MCP-1), epidermal growth factor (EGF), Tamm–Horsfall glycoprotein (THP), and liver fatty-acid-binding protein (L-FABP). Gestational age was positively correlated with SCr levels at birth, but inversely correlated with SCr levels at day five and day seven. Eighteen (60%) infants had stage 1 AKI, and twenty (67%) infants were treated with AGs. Infants with AKI had lower gestational age and lower birth weight than those without AKI. Urinary biomarkers adjusted according to uCr levels in infants with AKI were not statistically different from those in infants without AKI. There were no significant differences in incidence of AKI, and SCr levels during and after cessation of AG treatment. The uMCP-1/Cr ratio at days five and seven was higher in infants treated with AG than in non-treated infants. [ABSTRACT FROM AUTHOR]

Background: Bacterial superinfections associated with COVID-19 are common in ventilated ICU patients and impact morbidity and lethality. However, the contribution of antimicrobial resistance to the manifestation of bacterial infections in these patients has yet to be elucidated. Methods: We collected 70 Gram-negative bacterial strains, isolated from the lower respiratory tract of ventilated COVID-19 patients in Zurich, Switzerland between March and May 2020. Species identification was performed using MALDI-TOF; antibiotic susceptibility profiles were determined by EUCAST disk diffusion and CLSI broth microdilution assays. Selected Pseudomonas aeruginosa isolates were analyzed by whole-genome sequencing. Results: Pseudomonas aeruginosa (46%) and Enterobacterales (36%) comprised the two largest etiologic groups. Drug resistance in P. aeruginosa isolates was high for piperacillin/tazobactam (65.6%), cefepime (56.3%), ceftazidime (46.9%) and meropenem (50.0%). Enterobacterales isolates showed slightly lower levels of resistance to piperacillin/tazobactam (32%), ceftriaxone (32%), and ceftazidime (36%). All P. aeruginosa isolates and 96% of Enterobacterales isolates were susceptible to aminoglycosides, with apramycin found to provide best-in-class coverage. Genotypic analysis of consecutive P. aeruginosa isolates in one patient revealed a frameshift mutation in the transcriptional regulator nalC that coincided with a phenotypic shift in susceptibility to β-lactams and quinolones. Conclusions: Considerable levels of antimicrobial resistance may have contributed to the manifestation of bacterial superinfections in ventilated COVID-19 patients, and may in some cases mandate consecutive adaptation of antibiotic therapy. High susceptibility to amikacin and apramycin suggests that aminoglycosides may remain an effective second-line treatment of ventilator-associated bacterial pneumonia, provided efficacious drug exposure in lungs can be achieved. [ABSTRACT FROM AUTHOR]

Aminoglycosides are a family of naturally isolated or chemically semi‐synthesized antibiotics consisting of aminocyclitols with several amino and saccharide units. The unique molecule structures render aminoglycosides promising building blocks with high reactivity to perform various non‐covalent and covalent reactions, and they are further employed to rationally fabricate versatile materials, such as hydrogels, amphiphiles, hyperbranched polymers, biointerfaces, and nanoparticles. Despite aminoglycosides are widely used in clinics to treat bacterial infections, almost all the efforts are focused on molecular modifications to reduce their toxicities and overcome antibiotic resistance, while their actions as building blocks to construct biomaterials are scarcely discussed. In this feature article, the current progress on the rational design, emergent properties, and promising biological applications of aminoglycoside‐based biomaterials are summarized. It is believed that this paper may provide guidance to develop new biomaterials using natural functional molecules as building blocks, and start a new life of aminoglycosides from the view of materials science. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa causes chronic infections, such as cystic fibrosis, endocarditis, bacteremia, and sepsis, which are life-threatening and difficult to treat. The lack of antibiotic response in P. aeruginosa is due to adaptive resistance mechanism, which prevents the entry of antibiotics into the cytosol of the cell to achieve tolerance. Among the different groups of antibiotics, aminoglycosides are used as a parenteral antibiotic for the treatment of P. aeruginosa. This study aimed to determine the kinetics of antibiotic tolerance and gene expression changes in P. aeruginosa exposed to amikacin, gentamicin, and tobramycin. These antibiotics were exposed to P. aeruginosa at their MICs and the experimental setup was monitored for 72 h, followed by the measurement of optical density every 12 h. The growth of P. aeruginosa in the MICs of antibiotics represented the kinetics of antibiotic tolerance in amikacin, gentamicin, and tobramycin. The transcriptomic profile of antibiotic exposed P. aeruginosa PA14 was taken from the Gene Expression Omnibus (GEO), NCBI as microarray datasets. The gene expressions of two datasets were compared by test versus control. Tobramycin-exposed P. aeruginosa failed to develop tolerance in MICs of 0.5 μg/mL, 1 μg/mL, and 1.5 μg/mL, whereas amikacin- and gentamicin-treated P. aeruginosa developed tolerance. This illustrated the superior in vitro response of tobramycin over gentamicin and amikacin. Further, in silico transcriptomic analysis of tobramycin-treated P. aeruginosa resulted in differentially expressed genes (DEGs), enriched in 16s rRNA methyltransferase E, B, and L, alginate biosynthesis genes, and several proteins of the type II secretion system (T2SS) and type III secretion system (T3SS). The regulation of mucA in alginate biosynthesis, and gidB in RNA methyltransferases, suggested an increased antibiotic response and a low probability of developing resistance during tobramycin treatment. The use of tobramycin as a parenteral antibiotic with its synergistic combination might combat P. aeruginosa with increased response. [ABSTRACT FROM AUTHOR]

Due to potential antimicrobial application of chitosan nanoparticles (CNPs), alone or in combination with other natural or artificial compounds, we describe the preparation, characterization, and potent antimicrobial activity of kanamycin (KAN) and gentamicin (GM) that were chemically loaded to glucose-conjugated chitosan nanoparticles (g-CNPs). Successfully prepared CNPs, g-CNPs, and encapsulated drugs into g-CNPs backbones were evaluated by Fourier-transform infrared spectroscopy (FT-IR). Surface topology of CNPs was evaluated by X-ray diffraction pattern (XRD). Particle size and morphology of CNPs and drug-loaded nanoparticles were confirmed using transmission electron microscopy (TEM) and scanning electron microscope (SEM). Antibacterial potential of aminoglycoside loaded to g-CNPs was evaluated using minimum inhibitory concentration (MIC), as well as dynamic curves in the exposed strain to the nanoparticles were also investigated and result showed the appropriate antimicrobial activity against clinical strain of Klebsiella pneumonia. The used concentrations of 32 to 64 μg mL−1 of each KAN—g-CNPs and GM—g-CNPs showed bacteriostatic effect as well as entirely inhibitory impact on bacterial growth, respectively. In well diffusion assay, drugs loaded g-CNPs showed more antimicrobial activity with zone of inhibition (ZOI) 26.00 and 28.00 mm, compare to free nanoparticles and antimicrobial drugs with ZOI 21.00 and 10.00 mm, respectively. Furthermore, antibiofilm activity of KAN and GM loaded g-CNPs was studied using crystal violet assay and results indicated that there was a direct correlation with concentration of nanoparticles as well as anti-biofilm activity. The cell membrane integrity in the presence of KAN and GM loaded g-CNPs were evaluated and result indicated that there was an amount of released nucleic acids and proteins in environment. The inhibitory effect of KAN—g-CNPs and GM—g-CNPs on bacterial efflux pump (EP) was evaluated and result showed that all strains were sensitive to moderate concentration of nanoparticles and high sensitive to concentration of 0.5 and 0.8 μg mL−1 of ethidium bromide (EtBr) and 64 to 128 μg mL−1 of KAN—g-CNPs and GM—g-CNPs. The results clearly demonstrated that there was an inhibitory effect of the drugs loaded g-CNPs on efflux pump performances. Therefore, it can be assumed that this uniquely designed structure (KAN—g-CNPs and GM—g-CNPs) can serve as a potent next-generation antimicrobial compounds, but further studies should be performed on antimicrobial activity, in particular the mechanism of nanoparticles effect on bacterial cells. [ABSTRACT FROM AUTHOR]

The objectives of the study were to evaluate the relationship between gentamicin (GEN) and hearing loss using the Food and Drug Administration Adverse Event Reporting system (FAERS) database and elucidate the potential toxicological mechanism of GEN-induced hearing loss through a drug–gene network analysis.Using the preferred terms and standardized queries from the Medical Dictionary for Regulatory Activities, we calculated the reporting odds ratios (RORs). We extracted GEN-associated genes (seed genes) and analyzed drug−gene interactions using the ClueGO plug-in in the Cytoscape software and the DIseAse MOdule Detection (DIAMOnD) algorithm.The lower limit of the 95% confidence interval (CI) of the ROR for aminoglycosides (AG) antibacterials was over 1, and the ROR was 5.5 (5.1–6.0). We retrieved 17 seed genes related to GEN from the PharmGKB and Drug Gene Interaction databases. In total, 1018 human genes interacting with GEN were investigated using ClueGO. Through Molecular Complex Detection (MCODE) analysis, we identified 17 local gene clusters. The nodes and edges of the highest-ranked local gene cluster named “Cluster 1” were 30 and 433, respectively. According to the ClueGO analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG), Cluster 1 genes were highly enriched in “oxidative phosphorylation.” According to the ClueGO analysis using ClinVar, Cluster 1 genes were highly enriched in “mitochondrial diseases,” “mitochondrial complex I deficiency,” “hereditary hearing loss and deafness,” and “Leigh syndrome.” We identified 60 GEN-associated genes using the DIAMOnD algorithm. Several GEN-associated genes in the DIAMOnD algorithm were highly enriched in “PI3K-Akt signaling pathway,” “Ras signaling pathway,” “focal adhesion,” “MAPK signaling pathway,” “regulation of actin cytoskeleton,” “oxidative phosphorylation,” and “ECM-receptor interaction.”Our analysis demonstrated an association between several AGs and hearing loss using the FAERS database. Drug−gene network analysis demonstrated that GEN may be associated with oxidative phosphorylation-associated genes and integrin genes, which may be associated with hearing loss.

Septic arthritis causes significant morbidity and mortality in veterinary and human clinical practice and is increasingly complicated by multidrug-resistant infections. Intra-articular (IA) antibiotic administration achieves high local drug concentrations but is considered off-label usage, and appropriate doses have not been defined. Using an equine joint model, we investigated the effects of amikacin injected at three different doses (500, 125, and 31.25 mg) on the immune and cartilage responses in tibiotarsal joints. Synovial fluid (SF) was sampled at multiple time points over 24 h, the cell counts determined, and amikacin concentrations measured by liquid chromatography-mass spectrometry. Cytokine concentrations and collagen degradation products in SF were measured by ELISA and multiplex immunoassays. The mean amikacin concentrations in SF were greater than or equal to the minimum inhibitory concentration (MIC) (0.004 mg/ml) for most common equine joint pathogens at all time points tested to 24 h for all three amikacin doses evaluated. The inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) increased significantly in SF in the highest amikacin dose group, despite the fact that increases in SF cell counts were not observed. Similarly, the biomarkers of cartilage type II collagen cleavage (C2C and C12C) were increased in SF following amikacin injection. Mechanistically, we further demonstrated using in vitro studies that chondrocytes and synoviocytes killed by exposure to amikacin underwent apoptotic cell death and were phagocytosed by macrophages in a non-inflammatory process resembling efferocytosis. Neutrophils and T cells were susceptible to amikacin cytotoxicity at clinically relevant doses, which may result in blunting of cellular inflammatory responses in SF and account for the lack of increase in total nucleated cell counts following amikacin injection. In summary, decisions on whether to inject cytotoxic antibiotics such as aminoglycosides intra-articularly and what doses to use should take into account the potential harm that antibiotics may cause and consider lower doses than those previously reported in equine practice.

Kanamycin is a widely used selection agent in dicot-plant genetic transformation systems. In monocots, however, it does not seem to be effective as it has no or minimal effect on the normal growth of non-transformed plants. Kanamycin was previously demonstrated to bleach the pigments of the non-transgenic plants. This may yield the idea that kanamycin can be used as an effective screening marker rather than a selectable marker in monocots. Copyright (c) 2021 Malik Nawaz Shuja, Hasan Riaz, Muhsin Jamal, Muhammad Imran

The spread of multidrug-resistance in Gram-negative bacterial pathogens presents a major clinical challenge, and new approaches are required to combat these organisms. Nitric oxide (NO) is a well-known antimicrobial that is produced by the immune system in response to infection, and numerous studies have demonstrated that NO is a respiratory inhibitor with both bacteriostatic and bactericidal properties. However, given that loss of aerobic respiratory complexes is known to diminish antibiotic efficacy, it was hypothesised that the potent respiratory inhibitor NO would elicit similar effects. Indeed, the current work demonstrates that pre-exposure to NO-releasers elicits a > tenfold increase in IC50 for gentamicin against pathogenic E. coli (i.e. a huge decrease in lethality). It was therefore hypothesised that hyper-sensitivity to NO may have arisen in bacterial pathogens and that this trait could promote the acquisition of antibiotic-resistance mechanisms through enabling cells to persist in the presence of toxic levels of antibiotic. To test this hypothesis, genomics and microbiological approaches were used to screen a collection of E. coli clinical isolates for antibiotic susceptibility and NO tolerance, although the data did not support a correlation between increased carriage of antibiotic resistance genes and NO tolerance. However, the current work has important implications for how antibiotic susceptibility might be measured in future (i.e. ± NO) and underlines the evolutionary advantage for bacterial pathogens to maintain tolerance to toxic levels of NO. [ABSTRACT FROM AUTHOR]

Objectives: Characterisation of resistance phenotype and genotype is crucial to understanding the burden and transmission of antimicrobial resistance (AMR). This study aims to determine the spectrum of AMR and associated genes encoding aminoglycoside, macrolide and β-lactam classes of antimicrobials in bacteria isolated from hospitalised patients in Bangladesh.Methods: 430 bacterial isolates from patients with respiratory, intestinal, wound infections and typhoid fever, presenting to clinical care from 2015 to 2019, were examined. They included Escherichia coli (n = 85); Staphylococcus aureus (n = 84); Salmonella typhi (n = 82); Klebsiella pneumoniae (n = 42); Streptococcus pneumoniae (n = 36); coagulase-negative staphylococci (n = 28); Enterococcus faecalis (n = 27); Pseudomonas aeruginosa (n = 26); and Acinetobacter baumannii (n = 20). Reconfirmation of these clinical isolates and antimicrobial susceptibility tests was performed. PCR amplification using resistance gene-specific primers was done, and the amplified products were confirmed by Sanger sequencing.Results: 53% of isolates were multidrug-resistant (MDR), including 97% of Escherichia coli. There was a year-wise gradual increase in MDR isolates from 2015 to 2018, and there was an almost twofold increase in the number of MDR strains isolated in 2019 (P = 0.00058). Among the 5 extended-spectrum β-lactamases investigated, CTX-M-1 was the most prevalent (63%) followed by NDM-1 (22%); Escherichia coli was the major reservoir of these genes. The ermB (55%) and aac(6')-Ib (35%) genes were the most frequently detected macrolide and aminoglycoside resistance genes, respectively.Conclusion: MDR pathogens are highly prevalent in hospital settings of Bangladesh. [ABSTRACT FROM AUTHOR]

Host-directed therapies (HDTs) could enhance the activity of traditional antibiotics. AR-12 is a promising HDT against intracellular pathogens including Salmonella enterica serovar Typhimurium, and has been shown to act through modulation of autophagy and the Akt kinase pathway. Since AR-12 does not inhibit the growth of planktonic bacteria but only works in conjunction with the infected host-cell, we hypothesized that AR-12 could enhance the activity of antibiotics in less-susceptible strains in the intracellular host environment. We found that repetitive passaging of S. typhimurium in macrophages in the absence of antibiotics led to a 4-fold reduction in their intracellular susceptibility to streptomycin (STR), but had no effect on the bacteria's sensitivity to AR-12. Moreover, when the host-passaged strains were treated with a combined therapy of AR-12 and STR, there was a significant reduction of intracellular bacterial burden compared to STR monotherapy. Additionally, co-treatment of macrophages infected with multi-drug resistant S. typhimurium with AR-12 and STR or ampicillin showed enhanced clearance of the intracellular bacteria. The drug combination did not elicit this effect on planktonic bacteria. Overall, AR-12 enhanced the clearance of less susceptible S. typhimurium in an intracellular environment. [ABSTRACT FROM AUTHOR]

Objectives: The optimal dosage regimen of gentamicin in horses is still under investigation. The objectives of this study were to determine gentamicin plasma concentrations in hospitalized horses treated with 10 mg/kg gentamicin (IV, q 24 h) and to determine whether a plasma concentration to minimum inhibitory concentration (MIC) ratio of 10:1 is reached for equine pathogens using this dose. Design: Prospective clinical observational study; retrospective study on MICs of 131 gram‐negative bacteria isolated from horses (2012–2015). Setting: University teaching hospital. Animals: Ninety‐eight horses >6 months old, treated with gentamicin for their primary disease, consecutive samples. Measurements and main results: Plasma concentrations were measured 1 hour (C1h) and 20 hours (C20h) after gentamicin administration using fluorescence polarization. Presence of systemic inflammatory response syndrome (SIRS) and azotemia was recorded, as well as the reason for antimicrobial administration (primary disease) and whether administration was prophylactic or therapeutic. The target C1h of ≥20 µg/mL gentamicin was reached in 90% of horses and was sufficient to reach a plasma concentration:MIC of 10:1 in 32 of 131 (24%) of gram‐negative aerobic bacteria. A C20h ≤ 2 µg/mL was reached in 97% horses. Therapeutic versus prophylactic administration, primary disease, azotemia, and systemic inflammatory response syndrome were not associated with a failure to reach a desired peak or trough. Conclusions: The gentamicin dose of 10 mg/kg every 24 hours should be further investigated and safety assessed because a target gentamicin plasma concentration of ≥20 µg/mL was achieved in the majority of cases. Nephrotoxic side effects were not assessed. Individual drug monitoring should be performed because clinical factors are unreliable predictors of plasma concentrations. A gentamicin target concentration of ≥40 µg/mL does not offer additional benefits compared to ≥20 µg/mL, due to the bimodal distribution of resistance in bacterial isolates. [ABSTRACT FROM AUTHOR]

• Nocardia are important human pathogens. • Resistance to amikacin was described only in Nocardia wallacei. • We describe a novel gene in N. wallacei , conferring amikacin resistance. • This gene also conferred resistance in mycobacteria, when cloned. • This is the only description of such gene in nocardia. Aminoglycoside resistance in bacteria is typically conferred by specific drug-modifying enzymes. Infrequently, such resistance is achieved through 16S ribosomal RNA methyltransferases, such as NpmA and KamB encoded by Escherichia coli and Streptoalloteichus tenebrarius , respectively. These enzymes are not widespread and have not been described in Nocardia species to date. We report the genomic mining of 18 Nocardia wallacei isolates that were found to be specifically and substantially resistant to amikacin. We identified a gene coding for a protein with very distant homology to NpmA and KamB. However, 3-D modeling revealed that the tertiary structure of these three proteins was highly similar. Cloning and expressing this gene in two susceptible bacteria Nocardia asteroides , and Mycobacterium smegmatis (another Actinobacterium) led to high-level, pan-aminoglycoside resistance in both cases. We named this gene warA (Wallacei Amikacin Resistance A). This is the first description and experimental characterization of a gene of this family in Nocardia, and the first demonstration that such activity could lead to pan-aminoglycoside resistance in Mycobacteria as well. The discovery of this novel gene has important biotechnology and clinical implications. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to assess the outcomes including morbidity and mortality of carbapenem-resistant gram-negative (CRGN) infections in pediatric critical care setting. The second aim was to investigate the impact of aminoglycosides on colistin-containing regimen in CRGN-infected pediatric critical care patients. Materials and Methods: We retrospectively evaluated medical records of 82 patients who had received colistin in combination with an aminoglycoside (CA group) or another antibiotic (CO group) at two reference pediatric intensive care units (PICUs) between February 2011 and February 2016. Results: We enrolled 82 CRGN-infected patients who were admitted to PICUs of two hospitals. The median age of the patients was 24 (25th–75th percentile; 8–78.75) months, and the median duration of hospital stay was 30 days (25th–75th percentile; 16.7–57.7). No statistical difference was observed in the variables, including microbiological response, attributable mortality, crude mortality, and the duration of achieving first negative culture (p>0.05). Clinical response was significantly more observed in the CA group (85.5% vs. 63.2; p=0.048), and attributable mortality was higher in the CO group (12.7% vs. 31.6%; p=0.055). Nephrotoxicity did not show statistical difference between groups (p=0.357), and neurotoxicity was not observed. Conclusion: Colistin-containing regimen in combination with an aminoglycoside may be an effective and safe antimicrobial agent without a significant increase in side effects.

Abstract Introduction CARE was a Phase 3, randomized study evaluating the efficacy and safety of plazomicin-based combination therapy compared with colistin-based combination therapy for the treatment of patients with bloodstream infections or hospital-acquired/ventilator-associated pneumonia due to carbapenem-resistant Enterobacteriaceae (CRE). Adjunctive therapies included either tigecycline or meropenem. We sought to understand the contribution of tigecycline and meropenem to plazomicin-treated-patient outcomes by determining their observed pharmacodynamic exposures against baseline pathogens. Methods Blood samples collected for plazomicin therapeutic monitoring were assayed for tigecycline and meropenem concentrations. Population pharmacokinetic models were constructed for each antibiotic. Using the individual Bayesian posterior or a covariate-based model, concentration time profiles were simulated to estimate the pharmacodynamic exposures for each patient. Pharmacodynamic thresholds for plazomicin, tigecycline, and meropenem were a total area under the curve to minimum inhibitory concentration ratio (AUC/MIC) ≥ 85, free (f) AUC/MIC ≥ 0.9, and free time above the MIC (fT > MIC) of ≥ 40%, respectively. Results Fifteen plazomicin-treated patients were included (12 received tigecycline, 4 received meropenem, 1 received both). Microbiological response was observed in 13 (86.7%) and clinical efficacy was achieved in 11 (73.3%). Plazomicin achieved its pharmacodynamic target in all 15 patients. Meropenem fT > MIC was 0% in all 4 patients, and tigecycline fAUC/MIC was ≥ 0.9 in 9 (75%) patients. Overall, 6 (40%) of 15 patients had a tigecycline or meropenem exposure below the requisite thresholds. Microbiological response and clinical efficacy were observed in 100% (6/6) and 83.3% (5/6) of patients with low threshold attainment by tigecycline and meropenem dosing regimens, respectively. Conclusions Plazomicin successfully achieved its requisite pharmacodynamic exposure, and these data suggest that optimization of tigecycline and meropenem therapy was not required for the combination to achieve microbiological response and clinical efficacy against serious CRE infections. Trial Registration ClinicalTrials.gov number, NCT01970371. Funding Achaogen, Inc.

Bacterial pathogens are a major cause of infectious diseases in aquatic animals. The abuse of antibiotics in the aquatic industry has led to the proliferation of antibiotic resistance. It is therefore essential to develop more effective and safer strategies to increase the efficacy and extend the life span of the antibiotics used in aquaculture. In this study, we show that six aquaculture bacterial pathogens (i.e., Aeromonas hydrophila, Vibrio alginolyticus, Edwardsiella tarda, Streptococcus iniae, Vibrio harveyi, and Vibrio fluvialis) in the stationary phase can be rapidly killed after immersion in gentamicin- or neomycin-containing, ion-free solutions for a few minutes. Such hypoionic shock treatment enhances the bacterial uptake of gentamicin in an ATP-dependent manner. Importantly, we demonstrate, as a proof of concept, that gentamicin under hypoionic shock conditions can effectively kill A. hydrophila in vivo in a skin infection model of zebrafish (Danio rerio), completely curing the infected fish. Given that pathogenic bacteria generally adhere to the skin surface and gills of aquatic animals, our strategy is of potential significance for bacterial infection control, especially for small-scale economic fish farming and ornamental fish farming. Further, the combined treatment can be completed within 5 min with a relatively small volume of solution, thus minimizing the amount of residual antibiotics in both animals and the environment.

Summary: Sensory hair cells are prone to apoptosis caused by various drugs including aminoglycoside antibiotics. In mammals, this vulnerability results in permanent hearing loss because lost hair cells are not regenerated. Conversely, hair cells regenerate in birds, making the avian inner ear an exquisite model for studying ototoxicity and regeneration. Here, we use single-cell RNA sequencing and trajectory analysis on control and dying hair cells after aminoglycoside treatment. Interestingly, the two major subtypes of avian cochlear hair cells, tall and short hair cells, respond differently. Dying short hair cells show a noticeable transient upregulation of many more genes than tall hair cells. The most prominent gene group identified is associated with potassium ion conductances, suggesting distinct physiological differences. Moreover, the dynamic characterization of >15,000 genes expressed in tall and short avian hair cells during their apoptotic demise comprises a resource for further investigations toward mammalian hair cell protection and hair cell regeneration.

Apramycin is a clinically promising aminoglycoside antibiotic (AGA). To date, mechanisms underlying the biosynthesis and self‐resistance of apramycin remain largely unknown. Here we report that apramycin biosynthesis proceeds through unexpected phosphorylation, deacetylation, and dephosphorylation steps, in which a novel aminoglycoside phosphotransferase (AprU), a putative creatinine amidohydrolase (AprP), and an alkaline phosphatase (AprZ) are involved. Biochemical characterization revealed that AprU specifically phosphorylates 5‐OH of a pseudotrisaccharide intermediate, whose N‐7′ acetyl group is subsequently hydrolyzed by AprP. AprZ is located extracellularly where it removes the phosphate group from a pseudotetrasaccharide intermediate, leading to the maturation of apramycin. Intriguingly, 7′‐N‐acetylated and 5‐O‐phosphorylated apramycin that were accumulated in ΔaprU and ΔaprZ respectively exhibited significantly reduced antibacterial activities, implying Streptomyces tenebrarius employs C‐5 phosphorylation and N‐7′ acetylation as two strategies to avoid auto‐toxicity. Significantly, this study provides insight into the design of new generation AGAs to circumvent the emergence of drug‐resistant pathogens. [ABSTRACT FROM AUTHOR]

Bacterial pathogens are a major cause of infectious diseases in aquatic animals. The abuse of antibiotics in the aquatic industry has led to the proliferation of antibiotic resistance. It is therefore essential to develop more effective and safer strategies to increase the efficacy and extend the life span of the antibiotics used in aquaculture. In this study, we show that six aquaculture bacterial pathogens (i.e., Aeromonas hydrophila , Vibrio alginolyticus , Edwardsiella tarda , Streptococcus iniae , Vibrio harveyi , and Vibrio fluvialis) in the stationary phase can be rapidly killed after immersion in gentamicin- or neomycin-containing, ion-free solutions for a few minutes. Such hypoionic shock treatment enhances the bacterial uptake of gentamicin in an ATP-dependent manner. Importantly, we demonstrate, as a proof of concept, that gentamicin under hypoionic shock conditions can effectively kill A. hydrophila in vivo in a skin infection model of zebrafish (Danio rerio), completely curing the infected fish. Given that pathogenic bacteria generally adhere to the skin surface and gills of aquatic animals, our strategy is of potential significance for bacterial infection control, especially for small-scale economic fish farming and ornamental fish farming. Further, the combined treatment can be completed within 5 min with a relatively small volume of solution, thus minimizing the amount of residual antibiotics in both animals and the environment. [ABSTRACT FROM AUTHOR]

Background: While aminoglycosides (AG) have been used for decades, debate remains on their optimal dosing strategy. We investigated the international practices of AG usage specifically regarding dosing and therapeutic drug monitoring (TDM) in critically ill patients. We conducted a prospective, multicentre, observational, cohort study in 59 intensive-care units (ICUs) in 5 countries enrolling all ICU patients receiving AG therapy for septic shock. Results: We enrolled 931 septic ICU patients [mean ± standard deviation, age 63 ± 15 years, female 364 (39%), median (IQR) SAPS II 51 (38–65)] receiving AG as part of empirical (761, 84%) or directed (147, 16%) therapy. The AG used was amikacin in 614 (66%), gentamicin in 303 (33%), and tobramycin in 14 (1%) patients. The median (IQR) duration of therapy was 2 (1–3) days, the number of doses was 2 (1–2), the median dose was 25 ± 6, 6 ± 2, and 6 ± 2 mg/kg for amikacin, gentamicin, and tobramycin respectively, and the median dosing interval was 26 (23.5–43.5) h. TDM of Cmax and Cmin was performed in 437 (47%) and 501 (57%) patients, respectively, after the first dose with 295 (68%) patients achieving a Cmax/MIC > 8 and 353 (71%) having concentrations above Cmin recommended thresholds. The ICU mortality rate was 27% with multivariable analysis showing no correlation between AG dosing or pharmacokinetic/pharmacodynamic target attainment and clinical outcomes. Conclusion: Short courses of high AG doses are mainly used in ICU patients with septic shock, although wide variability in AG usage is reported. We could show no correlation between PK/PD target attainment and clinical outcome. Efforts to optimize the first AG dose remain necessary. Trial registration Clinical Trials, NCT02850029, registered on 29th July 2016, retrospectively registered, https://www.clinicaltrials.gov [ABSTRACT FROM AUTHOR]

• Ebselen can prevent tobramycin-induced hair cell loss in vitro cochlear cultures. • 14-day tobramycin treatment in vivo leads to fluctuating hearing loss by ABR. • Mice treated with ebselen showed less tobramycin-induced hearing loss by ABR. • Modified cochleotoxic change criteria may allow translation to human studies. • Tobramycin-induced hearing loss is not associated with significant hair cell loss. Cystic fibrosis patients are often adminstered tobramycin to treat pulmonary infections. Unfortunately, a common side effect is hearing loss, which can fluctuate. Ebselen has known anti-inflammatory properties and could reduce the incidence and severity of tobramycin-induced hearing loss. In vitro : neonatal cochlear cultures were treated with tobramycin or cotreated with tobramycin and ebselen for 3 days. In vivo : adult mice were injected with tobramycin or tobramycin and ebselen for 14 days. ABRs were collected in a repeated measures design until 56 days after treatments. ABR threshold shifts were analyzed and a novel cochleotoxic criteria applied to determine the incidence of ototoxicity. Cochlear immunohistology was analyzed for IHC and OHC loss. Tobramycin leads to significant IHC and OHC loss in cochlear explant cultures. Ebselen co-treatment at 1:20 concentrations resulted in significant otoprotection. Tobramycin leads to significant ABR threshold shifts that are ameliorated by ebselen co-treatment. Hearing loss did not correlate with significant IHC or OHC loss. This mouse model of tobramycin-induced ototoxicity is clinically relevant in that it results in an incidence and severity of hearing loss recently documented in clinic. The in vitro experiments show that tobramycin kills hair cells and that ebselen co-treatment can attenuate this ototoxicity. The in vivo model shows tobramycin-induced hearing loss is ameliorated by ebselen co-treatment, but this is not explained by concomitant hair cell loss. These preclinical data support the testing of ebselen in CF patients receiving tobramycin treatment. [ABSTRACT FROM AUTHOR]

• We found a greater than expected incidence of ototoxicity after a single course of tobramycin in patients with cystic fibrosis. • A heterogeneous ototoxic effect including unilateral, bilateral, and asymmetric changes were observed four weeks after treatment ended. • We observed multiple auditory deficits including decrease in word recognition. • Worsening or changes in tinnitus and vertigo were less pronounced than hearing loss. • These effects were seen independent of age, prior aminoglycoside use, or duration of tobramycin treatment. Aminoglycosides are commonly used to treat infections in CF patients and are highly ototoxic. The incidence of tobramycin-induced hearing loss, tinnitus, vertigo or dizziness (ototoxicity) varies widely from 0 to 56% secondary to variation in patient enrollment, dosing, audiometry, and ototoxic criteria. The aim of this study is to determine the incidence of ototoxicity after one course of once-daily IV tobramycin in CF patients. Adult CF patients with acute pulmonary exacerbations were enrolled on IV tobramycin (10 mg/kg/d, ≥10 days). Pure-tone audiometry was performed for standard and extended high frequencies in the sensitive range for ototoxicity (SRO). American-Speech-Language-Hearing-Association cochleotoxicity criteria were applied. Distortion product otoacoustic emissions (DPOAE) and the words-in-noise-test (WINT) were assessed. Tinnitus Functional Index (TFI) and Vertigo Symptoms Scale (VSS) were used. Eighteen CF patients, mean age 31.1 (18–59), were enrolled. The incidence of cochleotoxic change from baseline at 2 and 4 weeks post-treatment was 89% and 93%. For DPOAE, a measure of outer hair-cell function, the incidence of ≥5 dB decrease was 82% and 80%. For WINT, a measure of word recognition, the incidence of ≥10% decrease was 17% and 40%. For TFI, the incidence of ≥10pt increase was 12% and 8%, and for VSS, the incidence of ≥6pt increase was 0% and 8%. One course of IV tobramycin was sufficient to cause hearing loss and other ototoxic symptoms four weeks after treatment ended. Audiometric measures were more sensitive to ototoxic change than TFI & VSS. Age and duration of tobramycin treatment were not obvious factors for predicting ototoxicity. [ABSTRACT FROM AUTHOR]

Aminoglycoside antibiotics treat respiratory infections in cystic fibrosis (CF). An aminoglycoside induced ototoxicity algorithm (AIOA) was implemented to assess ototoxicity among people with CF treated with intravenous and/or inhaled aminoglycosides. Prior to AIOA implementation, 14 of 52 patients (27%) treated with intravenous aminoglycosides had an audiogram. In the 24 months post AIOA implementation, 43 of 44 patients (98%) treated with intravenous aminoglycosides had an audiogram, with 27 (63%) demonstrating abnormalities. Prior to AIOA development, 18 of 70 patients (26%) who received at least two courses of inhaled aminoglycosides had an audiogram. Post AIOA implementation, 33 patients qualified for an audiogram after receiving inhaled aminoglycosides. Of these, 19 (58%) had an audiogram and 10 (53%) had abnormalities. Overall, we identified 46 (61%) people with CF with hearing abnormalities compared to 2.4% in the CF Foundation Patient Registry. This suggests an urgent need for CF programs to implement AIOAs. [ABSTRACT FROM AUTHOR]

Aims: Bayesian forecasting software can assist in guiding therapeutic drug monitoring (TDM)‐based dose adjustments for amikacin to achieve therapeutic targets. This study aimed to evaluate amikacin prescribing and TDM practices, and to determine the suitability of the amikacin model incorporated into the DoseMeRx® software as a replacement for the previously available software (Abbottbase®). Methods: Patient demographics, pathology, amikacin dosing history, amikacin concentrations and Abbottbase® predicted TDM targets (area under the curve up to 24 hours, maximum concentration and trough concentration) were collected for adults receiving intravenous amikacin (2012–2017). Concordance with the Australian Therapeutic Guidelines was assessed. Observed and predicted amikacin concentrations were compared to determine the predictive performance (bias and precision) of DoseMeRx®. Amikacin TDM targets were predicted by DoseMeRx® and compared to those predicted by Abbottbase®. Results: Overall, guideline compliance for 63 courses of amikacin in 47 patients was suboptimal. Doses were often lower than recommended. For therapy >48 h, TDM sample collection timing was commonly discordant with recommendations, therapeutic target attainment low and 34% of dose adjustments inappropriate. DoseMeRx® under‐predicted amikacin concentrations by 0.9 mg/L (95% confidence interval [CI] –1.4 to −0.5) compared with observed concentrations. However, maximum concentration values (n = 19) were unbiased (−1.7 mg/L 95%CI –5.8 to 0.8) and precise (8.6% 95%CI 5.4–18.1). Predicted trough concentration values (n = 7) were, at most, 1 mg/L higher than observed. Amikacin area under the curve values estimated using Abbottbase® (181 mg h/L 95%CI 161–202) and DoseMeRx® (176 mg h/L 95%CI 152–199) were similar (P =.59). Conclusion: Amikacin dosing and TDM practice was suboptimal compared with guidelines. The model implemented by DoseMeRx® is satisfactory to guide amikacin dosing. [ABSTRACT FROM AUTHOR]

Kanamycin A is an aminoglycoside antibiotic isolated from Streptomyces kanamyceticus and used against a wide spectrum of bacteria, including Mycobacterium tuberculosis. Biosynthesis of kanamycin involves an oxidative deamination step catalyzed by kanamycin B dioxygenase (KanJ), thereby the C2' position of kanamycin B is transformed into a keto group upon release of ammonia. Here, we present for the first time, structural models of KanJ with several ligands, which along with the results of ITC binding assays and HPLC activity tests explain substrate specificity of the enzyme. The large size of the binding pocket suggests that KanJ can accept a broad range of substrates, which was confirmed by activity tests. Specificity of the enzyme with respect to its substrate is determined by the hydrogen bond interactions between the methylamino group of the antibiotic and highly conserved Asp134 and Cys150 as well as between hydroxyl groups of the substrate and Asn120 and Gln80. Upon antibiotic binding, the C terminus loop is significantly rearranged and Gln80 and Asn120, which are directly involved in substrate recognition, change their conformations. Based on reaction energy profiles obtained by density functional theory (DFT) simulations, we propose a mechanism of ketone formation involving the reactive FeIV = O and proceeding either via OH rebound, which yields a hemiaminal intermediate or by abstraction of two hydrogen atoms, which leads to an imine species. At acidic pH, the latter involves a lower barrier than the OH rebound, whereas at basic pH, the barrier leading to an imine vanishes completely. Databases: Structural data are available in PDB database under the accession numbers: 6S0R, 6S0T, 6S0U, 6S0W, 6S0V, 6S0S. Diffraction images are available at the Integrated Resource for Reproducibility in Macromolecular Crystallography at http://proteindiffraction.org under DOIs: 10.18430/m36s0t, 10.18430/m36s0u, 10.18430/m36s0r, 10.18430/m36s0s, 10.18430/m36s0v, 10.18430/m36s0w. A data set collection of computational results is available in the Mendeley Data database under DOI: 10.17632/sbyzssjmp3.1 and in the ioChem‐BD database under DOI: 10.19061/iochem‐bd‐4‐18. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance is one of the biggest threats to public health systems worldwide, and aminoglycosides are key drugs for treating drug-resistant infections. Because of the nephrotoxicity of aminoglycosides, therapeutic drug monitoring is recommended, but few studies of the target trough concentration (Cmin) have been reported. To address the problem, we performed a meta-analysis to confirm the target Cmin of aminoglycosides for minimizing the risk of nephrotoxicity. We conducted a literature search using MEDLINE, the Cochrane Library, and Ichushi-Web. In the meta-analysis, nephrotoxicity was compared between the Cmin ≥2 mg/L and Cmin <2 mg/L groups for gentamicin and between the Cmin ≥10 mg/L and Cmin <10 mg/L groups for amikacin. No randomized controlled trials were reported for any of the drugs. Five observational studies involving 615 patients were reported for gentamicin, and two observational studies involving 159 patients were identified for amikacin. For gentamicin, Cmin <2 mg/L was linked to a significantly lower rate of nephrotoxicity than Cmin ≥2 mg/L (odds ratio [OR] = 0.22, 95% confidence interval [CI] = 0.12–0.40). For amikacin, Cmin <10 mg/L was associated with a significantly lower rate of nephrotoxicity than Cmin ≥10 mg/L (OR = 0.05, 95% CI = 0.01–0.21). Although further well-controlled studies with a low risk of bias are needed, the current meta-analysis demonstrated that Cmin <2 mg/L and Cmin <10 mg/L may reduce the risk of nephrotoxicity linked to gentamicin and amikacin, respectively. [ABSTRACT FROM AUTHOR]

Short-course aminoglycosides as adjunctive empirical therapy to β-lactams in patients with a clinical suspicion of sepsis are used to broaden antibiotic susceptibility coverage and to enhance bacterial killing. We quantified the impact of this approach on 30-day mortality in a subset of sepsis patients with a Gram-negative bloodstream infection. From a prospective cohort study conducted in seven hospitals in the Netherlands between June 2013 and November 2015, we selected all patients with Gram-negative bloodstream infection (GN-BSI). Short-course aminoglycoside therapy was defined as tobramycin, gentamicin or amikacin initiated within a 48-hour time window around blood-culture obtainment, and prescribed for a maximum of 2 days. The outcome of interest was 30-day all-cause mortality. Confounders were selected a priori for adjustment using a propensity score analysis with inverse probability weighting. A total of 626 individuals with GN-BSI who received β-lactams were included; 156 (24.9%) also received aminoglycosides for a median of 1 day. Patients receiving aminoglycosides more often had septic shock (31/156, 19.9% versus 34/470, 7.2%) and had an eight-fold lower risk of inappropriate treatment (3/156, 1.9% versus 69/470, 14.7%). Thirty-day mortality was 17.3% (27/156) and 13.6% (64/470) for patients receiving and not receiving aminoglycosides, respectively; yielding crude and adjusted odds ratios for 30-day mortality for patients treated with aminoglycosides of 1.33 (95% CI 0.80–2.15) and 1.57 (0.84–2.93), respectively. Short-course adjunctive aminoglycoside treatment as part of empirical therapy with β-lactam antibiotics in patients with GN-BSI did not result in improved outcomes, despite better antibiotic coverage of pathogens. [ABSTRACT FROM AUTHOR]

Introduction: Drug-induced nephrotoxicity is a condition in which kidney injury occurs directly or indirectly by medication which is the third most common cause of acute kidney injury. Drugs can cause approximately 20% of nephrotoxicity. Aminoglycosides are natural or synthetic antibiotics discovered in 1944. Their effectiveness in multidrug resistant Gram-negative pathogens and satistying bactericidal activity make them a useful class of antibiotics across various aerobic gram-negative organisms. Ototoxicity, nephrotoxicity and rarely peripheral neuropathy, encephalopathy, neuromuscular and autonomic transmission blockade have been identified as some side effects of this class. Cinnamaldehyde is a natural compound with a wide range of biological activities such as antimicrobial, anti-oxidant, anti-tumor, and anti-inflammatory effects. The protective effects of cinnamaldehyde have been investigated in a few studies. There is evidence which shows that cinnamaldehyde has some renoprotective effects and it contains antioxidant properties. In this study, the effect of cinnamaldehyde on nephrotoxicity induced by gentamicin was evaluated. Methods and Materials: In this study, 24 Wistar rats were divided into four groups (n=6). Group 1: control group (received only normal saline injections), Group 2: injected with gentamicin (100 mg/kg for the last ten days, i.p.), Group 3: injected with cinnamaldehyde (30 mg/kg, ip for 30 days), Group 4: was given cinnamaldehyde (alone for 30 days) and then injected with GM (for 10 days). Urea, creatinine, and superoxide dismutase (SOD) in serum were analyzed. Results: Increased level of serum urea, creatinine, and decreased level of SOD was observed in the group that received gentamicin. Increasing serum urea and creatinine (p<0.05) have been significantly prevented by coadministration of cinnamaldehyde and gentamicin; a significant increase in the serum activity of superoxide dismutase was observed as compared to the gentamicin group (p<0.05). Conclusion: The results revealed that gentamicin-induced biochemical alterations in the kidney were decreased significantly by cinnamaldehyde. [ABSTRACT FROM AUTHOR]

Campylobacter jejuni is a foodborne pathogen causing bacterial gastroenteritis, with the highest incidence reported in Europe. The prevalence of antibiotic resistance in C. jejuni, as well as in many other bacterial pathogens, has increased over the last few years. In this report, we describe the presence of a plasmid in a multi-drug-resistant C. jejuni strain isolated from a gastroenteritis patient. Mating experiments demonstrated the transference of this genetic element (pCjH01) among C. jejuni by plasmid conjugation. The pCjH01 plasmid was sequenced and assembled, revealing high similarity (97% identity) with pTet, a described tetracycline resistance encoding plasmid. pCjH01 (47.7 kb) is a mosaic plasmid composed of a pTet backbone that has acquired two discrete DNA regions. Remarkably, one of the acquired sequences carried an undescribed variant of the aadE-sat4-aphA-3 gene cluster, providing resistance to at least kanamycin and gentamycin. Aside from the antibiotic resistance genes, the cluster also carries genes coding for putative regulators, such as a sigma factor of the RNA polymerase and an antisigma factor. Homology searches suggest that Campylobacter exchanges genetic material with distant G-positive bacterial genera.

To explore a possible recessive selective marker for future DNA-free genome editing by direct delivery of a CRISPR/Cas9-single guide RNA (sgRNA) ribonucleoprotein complex, we knocked out homologs of the ArabidopsisMulti-Antibiotic Resistance 1 (MAR1)/RTS3 gene, mutations of which confer aminoglycoside resistance, in tobacco plants by an efficient Agrobacterium-mediated gene transfer. A Cas9 gene was introduced into Nicotiana tabacum and Nicotiana sylvestris together with an sgRNA gene for one of three different target sequences designed to perfectly match sequences in both S- and T-genome copies of N. tabacumMAR1 homologs (NtMAR1hs). All three sgRNAs directed the introduction of InDels into NtMAR1hs, as demonstrated by CAPS and amplicon sequencing analyses, albeit with varying efficiency. Leaves of regenerated transformant shoots were evaluated for aminoglycoside resistance on shoot-induction media containing different aminoglycoside antibiotics. All transformants tested were as sensitive to those antibiotics as non-transformed control plants, regardless of the mutation rates in NtMAR1hs. The NtMAR1hs–knockout seedlings of the T1 generation showed limited aminoglycoside resistance but failed to form shoots when cultured on shoot-induction media containing kanamycin. The results suggest that, like Arabidopsis MAR1, NtMAR1hs have a role in plants’ sensitivity to aminoglycoside antibiotics, and that tobacco has some additional functional homologs.

Copyright of Van Tip Dergisi is the property of Yuzuncu Yil University, Faculty of Medicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)