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Background The cyclic anionic lipopeptide daptomycin is used in the treatment of severe infections caused by Gram-positive pathogens, including MRSA. Daptomycin resistance, although rare, often results in treatment failure. Paradoxically, in MRSA, daptomycin resistance is usually accompanied by a concomitant decrease in β-lactam resistance in what is known as the ‘see-saw effect’. This resensitization is extensively used for the treatment of MRSA infections, by combining daptomycin and a β-lactam antibiotic, such as oxacillin. Objectives We aimed: (i) to investigate the combined effects of daptomycin and oxacillin on the lipid composition of the cellular membrane of both daptomycin-resistant and -susceptible MRSA strains; and (ii) to assess the involvement of the post-translocational protein PrsA, which plays an important role in oxacillin resistance in MRSA, in membrane lipid composition and remodelling during daptomycin resistance/β-lactam sensitization. Results The combination of microbiological and biochemical studies, with fluorescence microscopy using lipid probes, showed that the lipid composition and surface charge of the daptomycin-resistant cells exposed to daptomycin/oxacillin were dependent on antibiotic concentration and directly associated with PrsA, which influenced cardiolipin remodelling/relocation. Conclusions Our findings show that PrsA, in addition to its post-transcriptional role in the maturation of PBP 2a, is a key mediator of cell membrane remodelling connected to the see-saw effect and may have a key role in the resensitization of daptomycin-resistant strains to β-lactams, such as oxacillin.

Research Areas: Infectious Diseases ; Pharmacology & Pharmacy ABSTRACT . Coagulase-positive staphylococci (CoPS) account for most bacteria-related pyoderma in companion animals. Emergence of methicillin-resistant strains of Staphylococcus pseudintermedius (MRSP), Staphylococcus aureus (MRSA) or Staphylococcus coagulans (MRSC), often with multidrugresistant (MDR) phenotypes, is a public health concern. The study collection comprised 237 staphylococci (S. pseudintermedius (n = 155), S. aureus (n = 55) and S. coagulans (n = 27)) collected from companion animals, previously characterized regarding resistance patterns and clonal lineages. Biofilm production was detected for 51.0% (79/155), 94.6% (52/55) and 88.9% (24/27) of the S. pseudintermedius, S. aureus and S. coagulans, respectively, and was a frequent trait of the predominant S. pseudintermedius and S. aureus clonal lineages. The production of biofilm varied with NaCl supplementation of the growth media. All S. pseudintermedius and S. aureus strains carried icaADB. Kaplan–Meier survival analysis of Galleria mellonella infected with different CoPS revealed a higher virulence potential of S. aureus when compared with other CoPS. Our study highlights a high frequency of biofilm production by prevalent antimicrobial-resistant clonal lineages of CoPS associated with animal pyoderma, potentially related with a higher virulence potential and persistent or recurrent infections. info:eu-repo/semantics/publishedVersion

Chronic airways infection with methicillin-resistant Staphylococcus aureus (MRSA) is associated with worse respiratory disease cystic fibrosis (CF) patients. Ceftaroline is a cephalosporin that inhibits the penicillin-binding protein (PBP2a) uniquely produced by MRSA. We analyzed 335 S. aureus isolates from CF sputum samples collected at three US centers between 2015–2018. Molecular relationships demonstrated that high-level resistance of preceding isolates to carbapenems were associated with subsequent isolation of ceftaroline resistant CF MRSA. In vitro evolution experiments showed that pre-exposure of CF MRSA to meropenem with further selection with ceftaroline implied mutations in mecA and additional mutations in pbp1 and pbp2, targets of carbapenems; no effects were achieved by other β-lactams. An in vivo pneumonia mouse model showed the potential therapeutic efficacy of ceftaroline/meropenem combination against ceftaroline-resistant CF MRSA infections. Thus, the present findings highlight risk factors and potential therapeutic strategies offering an opportunity to both prevent and address antibiotic resistance in this patient population., Varela, Roch et al. find that resistance of preceding isolates to carbapenems is associated with the subsequent isolation of methicillin-resistant Staphylococcus aureus (MRSA) resistant to ceftaroline. Addition of meropenem reduces the cystic fibrosis MRSA’s resistance to ceftaroline in a pneumonia mouse model, suggesting a strategy to control antibiotics resistance.

Staphylococcus pseudintermedius is commonly associated with colonization or infection in dogs, and was identified as a novel species within the genus Staphylococcus in 2006. Methicillin resistance emerged in S. pseudintermedius during the last decade. We describe here a genomic characterization of the first methicillin-resistant S. pseudintermedius (MRSP) recovered from a human patient in Argentina. The strain was phenotypically identified as MRSP 8510 by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and antimicrobial susceptibility testing. We assessed genetic characterization by mecA PCR, SCCmec (staphylococcal chromosomal cassette) typing, and whole-genome sequencing. MRSP 8510 was phenotypically resistant to six classes of antimicrobial agents, consistent with the genes found in its genome. We concluded that MRSP 8510 was a multidrug-resistant ST1412 isolate. This study highlights the importance of the detection and characterization of pathogens with potential risks of zoonotic transmission to humans, as they may constitute a reservoir of genes associated with antimicrobial resistance.

Extraintestinal pathogenic

Certain methicillin-resistant Staphylococcus aureus (MRSA) strains exhibit β-lactam susceptibility in vitro, ex vivo, and in vivo in the presence of NaHCO3 (NaHCO3-responsive MRSA). Here, we investigate the impact of NaHCO3 on factors required for PBP2a functionality., Certain methicillin-resistant Staphylococcus aureus (MRSA) strains exhibit β-lactam susceptibility in vitro, ex vivo, and in vivo in the presence of NaHCO3 (NaHCO3-responsive MRSA). Here, we investigate the impact of NaHCO3 on factors required for PBP2a functionality. Prototype NaHCO3-responsive and -nonresponsive MRSA strains (as defined in vitro) were assessed for the impact of NaHCO3 on the expression of genes involved in PBP2a production-maturation pathways (mecA, blaZ, pbp4, vraSR, prsA, sigB, and floA), membrane PBP2a and PrsA protein content, and membrane carotenoid content. Following NaHCO3 exposure in NaHCO3-responsive (versus nonresponsive) MRSA, there was significantly reduced expression of (i) mecA and blaZ, (ii) the vraSR-prsA gene axis, and (iii) pbp4. Carotenoid production was reduced while floA expression was increased by NaHCO3 exposure in all MRSA strains. This work underscores the distinct regulatory impact of NaHCO3 on a cadre of genes encoding factors required for the maintenance of the MRSA phenotype through PBP2a functionality and maturation.

Background Chronic obstructive pulmonary disease patients have been shown in orthopedic literature to have poorer outcomes and higher rates of complications from surgery. In this retrospective review, medical complications, length of stay, and costs were obtained to explore the effects of chronic obstructive pulmonary disease on patients undergoing primary total shoulder arthroplasty. Methods Total shoulder arthroplasty cases from January 2005 to March 2014 were queried and analyzed from a nationwide database. Study patients were matched 1:5 to controls by age, sex, and medical comorbidities associated with chronic obstructive pulmonary disease. In-hospital length of stay, 90-day medical complications, day of surgery, and total global 90-day episode of care costs were obtained for comparison. Results Chronic obstructive pulmonary disease patients were found to have higher incidence and odds (53.91 vs. 11.95%; OR: 3.58, 95%CI: 3.18–3.92, p Discussion Chronic obstructive pulmonary disease patients undergoing primary total shoulder arthroplasty have higher rates of medical complications, in-hospital length of stay, and costs of care. This represents an important factor that will allow orthopedic surgeons to adequately manage expectations and educate chronic obstructive pulmonary disease patients of the potential complications which may occur following total shoulder arthroplasty.

Systemic capillary leak syndrome (SCLS) is a very rare and lethal disease characterized by hemoconcentration and hypoalbuminemia caused by reversible plasma extravasation. The underlying cause for SCLS remains largely unknown and acute treatment has remained mainly supportive. Prophylaxis with intravenous immunoglobulin (IVIG) has been shown to successfully prevent further episodes in affected patients. We reported a case of SCLS in a patient who presented to our hospital with COVID-19 and developed profound shock.

Staphyloxanthin (STX) is a saccharolipid derived from a carotenoid in Staphylococcus aureus involved in oxidative-stress tolerance and antimicrobial peptide resistance. STX influences the biophysical properties of the bacterial membrane and has been associated to the formation of lipid domains in the regulation of methicillin-resistance. In this work, a targeted metabolomics and biophysical characterization study was carried out to investigate the biosynthetic pathways of carotenoids, and their impact on the membrane biophysical properties. Five different S. aureus strains were investigated, including three wild-type strains containing the crtM gene related to STX biosynthesis, a crtM-deletion mutant, and a crtMN plasmid-complemented variant. LC-DAD-MS/MS analysis of extracts allowed the identification of 34 metabolites related to carotenogenesis in S. aureus at different growth phases (8, 24 and 48 h), showing the progression of these metabolites as the bacteria advances into the stationary phase. For the first time, 22 members of a large family of carotenoids were identified, including STX and STX-homologues, as well as Dehydro-STX and Dehydro-STX-homologues. Moreover, thermotropic behavior of the CH2 stretch of lipid acyl chains in live cells by FTIR, show that the presence of STX increases acyl chain order at the bacterial growth temperature. Indeed, the cooperative melting event of the bacterial membrane, which occurs around 15 °C in the native strains, shifts with increased carotenoid content. These results show the diversity biosynthetic of carotenoids in S. aureus, and their influence on membrane biophysical properties., This research was funded by the Faculty of Sciences, Universidad de los Andes (INV-2018-48-1338 and INV-2019-86-1843). The Colombian Ministerio de Ciencia, Tecnología e Innovación (MinCiencias) for the Doctoral Fellowship No. 785 (Call 2017) to Gerson-Dirceu López, the support to No. 80740-532-2019 project, and the Grant No. 120480763040. Also, Ministerio de Ciencia y Universidades from Spain, funded the AGL2017-89417-R project.

BackgroundElectrocardiographic (EKG) abnormalities are described in 25-75% Systemic Sclerosis (SSc) patients and they are associated with other systemic manifestations1 as well as with a worse prognosis.2 There is an increasing need for clinical and laboratory biomarkers to ameliorate the diagnostic approaches to patients with EKG abnormalities.3In the last decade, many studies focused on the components of the interleukin (IL)-33/ST2 axis. Under physiological conditions, IL-33 is released by apoptotic cardiac cells, promoting a protective mechanism of cell survival, thanks to the binding with its transmembrane receptor ST2.4 During pathological cardiovascular events, an abnormal secretion of the IL-33 soluble receptor (sST2) by Th2 cells occurs. It binds IL-33 not allowing the physiological mechanism driven by the IL-33/ST2 binding previously described.4 For these reasons, sST2 has been proposed as a biomarker of cardiac injury in a variety of diseases.5ObjectivesAim of this study was to analyse clinical and demographical parameters in a group of SSc patients, trying to define any possible feature associated with EKG abnormalities. Furthermore, the role of IL-33/ST2 axis components as biomarkers of cardiac injury in patients with SSc-related EKG abnormalities was evaluated, also assessing the possible correlation with serum concentration of NT-pro-BNP, a well-known cardiac injury biomarker in SSc.MethodsData from 277 SSc patients, fulfilling the 2013 ACR/EULAR classification criteria,6 attending our Scleroderma Clinic were retrospectively analysed. We selected patients with EKG trace and a blood sample available, collected after the SSc diagnosis. The sera levels of sST2 (ELISA Kit, Abcam), IL-33 (ELISA kit, RayBiotech) and NT-pro-BNP (ELISA Kit, Abcam) were measured. Patients with a history of heart diseases occurring before the diagnosis of SSc or features of secondary cardiac involvement (pulmonary arterial hypertension, severe interstitial lung disease or renal disease) were excluded.ResultsForty-six SSc patients showed significant EKG abnormalities (rhythm and conduction disorders). Thirty-one SSc patients without pathologic finding at EKG traces were recruited as the control group.From the analysis of the clinical characteristic of the disease at the moment of serum collection, patients with EKG anomalies have more frequently both a diffuse form of disease (n°-%: 23-50 vs 7-23; p 0.01), with a mean value of mRSS higher than controls (11±9 vs 6±6; p 0.01), and a scleroderma “late” pattern at the nailfold capillaroscopy (n°-% 23-50 vs 6-19; p 0.027).Significantly higher median values of serum levels of sST2 in SSc patients with EKG disorders compared to the control group (4289pg/mL, IQR 2383 vs 2560 pg/mL, IQR 1455; p 0.0002) were detected, while opposite results were found analyzing serum levels of IL-33 (2.89 pg/mL IQR 101 vs 9 pg/mL IQR 277; p 0.032) (Graph 1). Serum NT-pro-BNP median values were significantly higher in the group of patients with EKG abnormalities than in the control group (149 pg/mL, IQR 354 vs 26 pg/mL, IQR 62; p 0.0007). These values correlated with sST2 serum levels (rho Spearman correlation 0.37; p 0.0006).ConclusionSSc patients with EKG abnormalities showed an increased skin and vascular involvement with respect to the control group. These associations could help clinicians in clinically stratifying SSc patients at risk of EKG abnormalities. To our knowledge, this is the first report evaluating the serum concentration of sST2 in SSc patients. Based on these results, we can speculate on the role of this molecule as potential biomarkers of early cardiac injury during SSc, although further studies involving a larger cohort of patients are needed.References[1]Vacca et al. Rheumatol 2014[2]Tyndall et al. Ann Rheum Dis 2010[3]Muresan et al. Clin Rheumatol 2018[4]Vianello et al. Int J Biochem Cell Biol 2019[5]Dudek et al. Adv Clin Exp Med 2020[6]van den Hoogen et al. Arthritis Rheum 2013Figure 1:Graph 1. Serum sST2 (a) and IL-33 (b) concentrations in patients with EKG abnormalities (EKG+) vs control group (EKG)Disclosure of InterestsNone declared.

Staphyloxanthin (STX) is a saccharolipid derived from a carotenoid in Staphylococcus aureus involved in oxidative-stress tolerance and antimicrobial peptide resistance. In this work, a targeted metabolomics and biophysical study was carried out on native and knock-out S. aureus strains to investigate the biosynthetic pathways of STX and related carotenoids. Identification of 34 metabolites at different growth phases (8, 24 and 48h), reveal shifts of carotenoid populations during progression towards stationary phase. Six of the carotenoids in the STX biosynthetic pathway and three menaquinones (Vitamin K2) were identified in the same chromatogram. Furthermore, other STX homologues with varying acyl chain structures reported herein for the first time, which reveal the extensive enzymatic activity of CrtO/CrtN. Fourier Transform infrared spectroscopy show that STX increases acyl chain order and shifts the cooperative melting of the membrane indicating a more rigid lipid bilayer. This study shows the diversity of carotenoids in S. aureus, and their influence on membrane biophysical properties.

The predominance of Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae was caused by the spread of ST258 clone. In Latin America, KPC was reported in 2006, with the isolation of genetically unrelated K. pneumoniae in Colombia. Since then, the expansion of blaKPC in either K. pneumoniae ST258 or other Enterobacteriaceae (ETB) species was increasingly reported. In this study, we characterized 89 KPC producing Escherichia coli, Klebsiella oxytoca, Serratia marcescens, and Citrobacter freundii that were received between 2010 and 2014. The results revealed that all isolates harbored blaKPC-2. Moreover, the dissemination of KPC by non-K. pneumoniae was mainly caused by the dispersion of ETB mostly genetically unrelated. E. coli is a community pathogen that may serve as the vehicle for the spread of KPC into community settings. Recently, KPC was detected in E. coli ST131, an international epidemic and multidrug-resistant clone. We found that 5/29 KPC-producing E. coli belonged to ST131 and four were blaCTXM-15 producers. The detection of blaKPC in ST131 should be closely monitored to prevent further dissemination. The blaKPC isgenerally located within Tn4401 transposon capable of mobilization through transposition found in plasmids in ST258. Less is known about the diversity of blaKPC genetic elements that disseminate horizontally among other species of ETB. We found that 16/29 E. coli and 2/18 S. marcescens harbored blaKPC-2 in Tn4401a. In 71 isolates, blaKPC-2 was located amidst diverse Tn3-derived genetic elements bearing non-Tn4401 structure. Further studies on the plasmids that encode blaKPC-2 in these clinical isolates may provide additional insight into its transmission mechanisms. Fil: de Belder, Denise Gisele. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Lucero, Celeste. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Rapoport, Melina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Rosato, Adriana. Houston Methodist Research Institute; Estados Unidos Fil: Faccone, Diego Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Petroni, Alejandro. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Pasteran, Fernando. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Albornoz, Ezequiel Pablo. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Corso, Alejandra. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina Fil: Gómez, Sonia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina

Staphylococcus pseudintermedius is an important pathogen responsible for infections in dogs and in humans. The emergence and dissemination of methicillin-resistant S. pseudintermedius (MRSP) and the multidrug resistance frequently seen in this species make difficult the treatment of these pathogens. The cefoxitin disk is widely used as a marker of methicillin resistance mediated by the mecA gene in Staphylococcus aureus and other staphylococcal species, however, it is not useful to detect β-lactam resistance of MRSP in clinical microbiology laboratories. The purpose of this study was to elucidate the molecular bases of the dissociated phenotype between oxacillin and cefoxitin antibiotics. By using a combinatorial approach that included the Penicillin-Binding Proteins’ (PBP) profile, their affinity for different β-lactam antibiotics and the analyses of PBPs’ sequence, we provide evidence that PBP4 showed still affinity for its target cefoxitin, impairing its phenotypic resistant detection in MRSP. Together, these findings provide evidence that S. pseudintermedius PBP4 is directly associated with the dissociated oxacillin and cefoxitin phenotype.

Background Tedizolid is a protein synthesis inhibitor in clinical use for the treatment of Gram-positive infections. Pulmonary MRSA infections are a growing problem in patients with cystic fibrosis (CF) and the efficacy of tedizolid-based therapy in CF pulmonary infections is unknown. Objectives To evaluate the in vitro and in vivo activity of tedizolid and predict the likelihood of tedizolid resistance selection in CF-background Staphylococcus aureus strains. Methods A collection of 330 S. aureus strains (from adult and paediatric patients), either of normal or small colony variant (SCV) phenotypes, gathered at three CF centres in the USA was used. Tedizolid activity was assessed by broth microdilution, Etest and time–kill analysis. In vivo tedizolid efficacy was tested in a murine pneumonia model. Tedizolid in vitro mutants were obtained by 40 days of exposure and progressive passages. Whole genome sequencing of clinical S. aureus strains with reduced susceptibility to tedizolid was performed. Results MRSA strain MIC90s were tedizolid 0.12–0.25 mg/L and linezolid 1–2 mg/L; for MSSA strains, MIC90s were tedizolid 0.12 mg/L and linezolid 1–2 mg/L. Two strains, WIS 441 and Seattle 106, with tedizolid MICs of 2 mg/L and 1 mg/L, respectively, had MICs above the FDA tedizolid breakpoint (0.5 mg/L). Tedizolid at free serum concentrations exhibited a bacteriostatic effect. Mean bacterial burdens in lungs (log10 cfu/g) for WIS 423-infected mice were: control, 11.2±0.5; tedizolid-treated (10 mg/kg), 3.40±1.87; linezolid-treated (40 mg/kg), 4.51±2.1; and vancomycin-treated (30 mg/kg), 5.21±1.93. For WIS 441-infected mice the (log10 cfu/g) values were: control, 9.66±0.8; tedizolid-treated, 3.18±1.35; linezolid-treated 5.94±2.19; and vancomycin-treated, 4.35±1.7. Conclusions These results suggest that tedizolid represents a promising therapeutic option for the treatment of CF-associated MRSA/MSSA infections, having potent in vivo activity and low resistance potential.

Methicillin-resistant S. aureus continues to develop resistance to antimicrobials, including those in current clinical use as daptomycin (DAP). Resistance to DAP arises by mutations in cell membrane and cell wall genes and/or upregulation of the two-component VraSR system. However, less is known about the connection between the pathogen and virulence traits during DAP resistance development. We provide new insights into VraSR and its regulatory role for virulence factors during DAP resistance, highlighting coordinated interactions that favor the higher persistence of MRSA DAP-resistant strains in the infected host., Methicillin-resistant Staphylococcus aureus (MRSA) threatens human health in hospital and community settings. The lipopeptide antibiotic daptomycin (DAP) is a frequently used treatment option for MRSA infection. DAP exposure can cause bacterial resistance because mutations are induced in genes implicated in cell membrane and cell wall metabolism. Adaptations aimed at surviving antimicrobial pressure can affect bacterial physiology and modify in vivo aptitude and pathogenesis. In this study, clinical DAP-susceptible (DAPs) and DAP-resistant (DAPr) MRSA isolates were used to investigate associations between DAP resistance and staphylococcal virulence. We previously found that VraSR is a critical sensor of cell membrane/wall homeostasis associated with DAP acquisition during MRSA infection. The present study found that DAPr CB1634 and CB5014 MRSA strains with vraSR upregulation were less virulent than their susceptible counterparts, CB1631 and CB5013. Differential gene-transcription profile analysis revealed that DAPr CB1634 had decreased agr two-component system expression, virulence factors, and highly suppressed hemolysis activity. Functional genetic analysis performed in DAPr CB1634 strains using vraSR inactivation followed by gene complementation found that vraSR acted as a transcriptional agrA regulator. These results indicated that VraSR has a broad range of regulatory functions. VraSR also appeared to affect DAPr adherence to epithelial cells, which would affect DAPr strain colonization and survival in the host. The correlation between DAP resistance and decreased virulence was also found in the CB5013 (DAPs) and CB5014 (DAPr) pair. Taken together, these findings are the first evidence that DAP resistance and MRSA virulence are tightly connected and involve compromised expression of regulatory and virulence determinants. IMPORTANCE Methicillin-resistant S. aureus continues to develop resistance to antimicrobials, including those in current clinical use as daptomycin (DAP). Resistance to DAP arises by mutations in cell membrane and cell wall genes and/or upregulation of the two-component VraSR system. However, less is known about the connection between the pathogen and virulence traits during DAP resistance development. We provide new insights into VraSR and its regulatory role for virulence factors during DAP resistance, highlighting coordinated interactions that favor the higher persistence of MRSA DAP-resistant strains in the infected host.

Methicillin-resistant Staphylococcus aureus (MRSA) threatens human health in hospital and community settings. The lipopeptide antibiotic daptomycin (DAP) is a frequently used treatment option for MRSA infection. DAP exposure can cause bacterial resistance because mutations are induced in genes implicated in cell membrane and cell wall metabolism. Adaptations aimed at surviving antimicrobial pressure can affect bacterial physiology and modify in vivo aptitude and pathogenesis. In this study, clinical DAP-susceptible (DAPs) and DAP-resistant (DAPr) MRSA isolates were used to investigate associations between DAP resistance and staphylococcal virulence. We previously found that VraSR is a critical sensor of cell membrane/wall homeostasis associated with DAP acquisition during MRSA infection. The present study found that DAPr CB1634 and CB5014 MRSA strains with vraSR upregulation were less virulent than their susceptible counterparts, CB1631 and CB5013. Differential gene-transcription profile analysis revealed that DAPr CB1634 had decreased agr two-component system expression, virulence factors, and highly suppressed hemolysis activity. Functional genetic analysis performed in DAPr CB1634 strains using vraSR inactivation followed by gene complementation found that vraSR acted as a transcriptional agrA regulator. These results indicated that VraSR has a broad range of regulatory functions. VraSR also appeared to affect DAPr adherence to epithelial cells, which would affect DAPr strain colonization and survival in the host. The correlation between DAP resistance and decreased virulence was also found in the CB5013 (DAPs) and CB5014 (DAPr) pair. Taken together, these findings are the first evidence that DAP resistance and MRSA virulence are tightly connected and involve compromised expression of regulatory and virulence determinants. IMPORTANCE Methicillin-resistant S. aureus continues to develop resistance to antimicrobials, including those in current clinical use as daptomycin (DAP). Resistance to DAP arises by mutations in cell membrane and cell wall genes and/or upregulation of the two-component VraSR system. However, less is known about the connection between the pathogen and virulence traits during DAP resistance development. We provide new insights into VraSR and its regulatory role for virulence factors during DAP resistance, highlighting coordinated interactions that favor the higher persistence of MRSA DAP-resistant strains in the infected host.

Neonicotinoids are effective insecticides used on many important arable and horticultural crops. They are nicotinic acetylcholine receptor agonists which disrupt the function of insect neurons and cause paralysis and death. In addition to direct mortality, there are numerous sublethal effects of low doses of neonicotinoids on bees. We hypothesize that some of these large array of effects could be a consequence of epigenetic changes in bees induced by neonicotinoids. We compared whole methylome (BS-seq) and RNA-seq libraries of the brains of buff-tailed bumblebee Bombus terrestris workers exposed to field-realistic doses of the neonicotinoid imidacloprid to libraries from control workers. We found numerous genes which show differential expression between neonicotinoid-treated bees and control bees, but no differentially methylated cytosines in any context. We found CpG methylation to be focused mainly in exons and associated with highly expressed genes. We discuss the implications of our results for future legislation.

Purpose: Studies have shown the prevalence of iron deficiency anemia (IDA) increasing worldwide, and currently the literature is limited on the impact of IDA on outcomes following revision total hip arthroplasty (RTHA). Therefore, the purpose of this study was to determine whether IDA patients undergoing RTHA have longer: 1) in-hospital lengths of stay (LOS); 2) medical complications; and 3) costs of care. Materials and Methods: A retrospective query of a nationwide administrative claims database was performed. Using Boolean command operations, the study group consisted of all patients in the database undergoing RTHA with IDA; whereas, patients without IDA served as controls. To reduce the effects of confounding, study group patients were matched to controls in a 1:5 ratio by age, sex, and medical comorbidities yielding 92,948 patients with (n=15,508) and without (n=77,440) IDA undergoing revision THA. A P-value less than 0.001 was considered statistically significant. Results: IDA patients were found to have significantly longer in-hospital LOS (5 days vs. 4 days, P

Klebsiella pneumoniae strains producing K. pneumoniae carbapenemase (KPC) cause serious infections in debilitated and immunocompromised patients and are associated with prolonged hospital stays and increased mortality rates. Daptomycin is a lipopeptide used against Staphylococcus aureus infection and considered inactive against Gram-negative bacteria. We investigated the effectiveness of a daptomycin-meropenem combination by synergy kill curve and a pharmacokinetic/pharmacodynamic model. The combination may represent a novel therapeutic strategy against infections caused by KPC-producing K. pneumoniae strains.

Methicillin-resistant Staphylococcus aureus (MRSA) acquisition in cystic fibrosis (CF) patients confers a worse clinical outcome with increased rate of declined lung function. Telavancin, an approved lipoglycopeptide used to treat infections due to S. aureus has a dual mode of action causing inhibition of the peptidoglycan synthesis and membrane depolarization. CF-associated MRSA infections remain an important problem with no foreseeable decline in prevalence rates. Although telavancin is currently in clinical use for complicated skin infections and hospital-acquired pneumonia, the activity against CF-associated S. aureus infections has not been investigated. In this work, we studied the activity of telavancin against CF S. aureus strains collected from diverse geographical CF centers in the USA. We found that telavancin-MIC90 was 0.06 μg/ml, 8-fold lower than ceftaroline or daptomycin and 25-fold lower than linezolid and vancomycin. We demonstrate that telavancin at serum-free concentrations has rapid bactericidal activity with a decrease of more than 3 log10 CFU/ml during the first 4 to 6 hours of treatment, performing better in this assay than vancomycin and ceftaroline, including S. aureus resistant to ceftaroline.Telavancin resistance was infrequent (0.3%), although we found that it can occur in-vitro in both CF-and non-CF S. aureus strains by progressive passages with sub-inhibitory concentrations. Genetic analysis of telavancin in-vitro mutants showed gene polymorphisms in cell wall and virulence genes, and increased survival in a Galleria mellonella infection model. Thus, we conclude that telavancin represents a promising therapeutic option for CF infections with potent in-vitro activity and low resistance potential.

Methicillin-resistant Staphylococcus aureus (MRSA) acquisition in cystic fibrosis (CF) patients confers a clinical outcome worse than that in non-CF patients with an increased rate of declined lung function. Telavancin, an approved lipoglycopeptide used to treat infections due to S. aureus, has a dual mode of action causing inhibition of peptidoglycan synthesis and membrane depolarization. MRSA infections in CF patients remain an important problem with no foreseeable decline in prevalence rates. Although telavancin is currently in clinical use for the treatment of complicated skin infections and hospital-acquired pneumonia, the activity against S. aureus infections in CF patients has not been investigated. In this work, we studied the activity of telavancin against CF patient-derived S. aureus strains collected from geographically diverse CF centers in the United States. We found that the telavancin MIC90 was 0.06 μg/ml, 8-fold lower than the ceftaroline or daptomycin MIC90 and 25-fold lower than the linezolid and vancomycin MIC90 We demonstrate that telavancin at serum free concentrations has rapid bactericidal activity, with a decrease of more than 3 log10 CFU/ml being achieved during the first 4 to 6 h of treatment, performing better in this assay than vancomycin and ceftaroline, including against S. aureus strains resistant to ceftaroline. Telavancin resistance was infrequent (0.3%), although we found that it can occur in vitro in both CF- and non-CF patient-derived S. aureus strains by progressive passages with subinhibitory concentrations. Genetic analysis of telavancin-resistant in vitro mutants showed gene polymorphisms in cell wall and virulence genes and increased survival in a Galleria mellonella infection model. Thus, we conclude that telavancin represents a promising therapeutic option for infections in CF patients with potent in vitro activity and a low resistance development potential.

This chapter will review the types of surgical drains and tubes available to the modern general and thoracic surgeon, with a brief mention of those available to the interventional radiologist. Proper drain care and management are also discussed with a focus on individual drain types and indications for use. Negative-pressure wound therapy (NPWT) is also reviewed. These modern drainage tools for managing wounds, fluid collections, abscesses, and enteric fistulae have significantly reduced the need for both initial and re-operative surgeries. This has led to decreased morbidity and mortality in the surgical population and has reduced the need for emergent interventions, thereby reducing the associated debilitating inflammatory response, unanticipated “collateral damage,” and stress to both the patient and operating surgeon.

Autonomic nervous system is involved in body weight regulation. Gastrointestinal manifestations of systemic sclerosis (SSc) can influence patients’ nutritional status and facilitate the development of protein–energy malnutrition. The aim of the study is to assess the nutritional status of SSc patients and to explore its possible correlation with autonomic dysfunction using heart rate variability (HRV). We enrolled 19 SSc subjects and 19 healthy subjects as controls. Body mass index (BMI) and body surface area (BSA) were collected and recorded in all patients. HRV was measured and the domains of low frequencies (LF, index of the sympathetic modulation) and high frequencies (HF, index of the parasympathetic modulation) were recorded. As assessed by the LF/HF RATIO, sympathovagal balance is altered in SSc patients because of increased sympathetic modulation and reduced parasympathetic activity. BMI positively correlates with LF (r=0.57; p less than 0.01) and LF/HF RATIO during daytime (r= 0.46; p less than 0.05). Similarly, BSA positively correlates with LF (r= 0.51; p less than 0.05), LF day time (r= 0.53; p less than 0.05) and LF/HF RATIO night time (r=-0.51; p less than 0.05). In SSc patients the autonomic dysfunction is characterized by increased sympathetic modulation. We observed a correlation between autonomic dysfunction and nutritional status in SSc patients.

Daptomycin remains as one of the main treatment options for Methicillin-Resistant Staphylococcus aureus (MRSA). Sporadic resistance cases reported in patients treated with either daptomycin or glycopeptides are a growing concern. In a previous study, we described a clinical case of a patient with a community-acquired MRSA infection resistant to daptomycin and with intermediate resistance to vancomycin who developed a recurrent infection with a susceptible isogenic strain. In the present work, we further investigated the sequential events to determine whether the switch from a daptomycin resistance to a susceptible phenotype was due to a phenomenon of resistance reversion or recurrent infection with a susceptible strain. Pairwise competition experiments showed that the susceptible clinical recurrent SA6850 strain had increased fitness when compared to the resistant counterpart SA6820 strain. In fact, although we have demonstrated that reversion of daptomycin resistance to daptomycin susceptible can occur in vitro after serial passages in drug-free media, phylogenetic analysis suggested that the in vivo process was the result of a recurrent infection with a previous susceptible isolate carried by the patient rather than a resistance reversion of the strain. Whole genome sequence of evolved strains showed that daptomycin resistance in MRSA is associated with a high fitness cost mediated by mutations in mprF gene, revealed as a key element of the biological cost. Moreover, we determined that daptomycin resistance-associated fitness cost was independent of vancomycin intermediate resistance phenotype, as demonstrated in additional clinical MRSA vancomycin susceptible strains. This study highlights important observations as, despite daptomycin offers a useful treatment option for the patients with persistent infections, it has to be carefully monitored. The high fitness cost associated to daptomycin resistance may explain the reduced dissemination of daptomycin resistance and the absence of daptomycin reported outbreaks.

Invasive methicillin-resistant Staphylococcus aureus (MRSA) treated with vancomycin (VAN) is associated with reduced VAN susceptibility and treatment failure. VAN combination therapy is one strategy to improve response, but comprehensive assessments of combinations to prevent resistance are limited. This study identifies optimal combinations to prevent the emergence of VAN-intermediate Staphylococcus aureus (VISA). Two standard MRSA and two heterogeneous VISA (hVISA) strains were exposed for 28 days in vitro to VAN alone, VAN with cefazolin (CFZ), fosfomycin, gentamicin, meropenem, rifampin, piperacillin-tazobactam (TZP), or trimethoprim-sulfamethoxazole. In addition to VAN susceptibility testing, cell wall thickness (CWT), carotenoid content, and membrane fluidity were determined for Mu3. VAN plus any β-lactam limited the VAN MIC increase to 1 to 4 mg/liter throughout the 28-day exposure, with CFZ and TZP being the most effective agents (VAN MIC = 1 to 2 mg/liter). Similar MIC trends occurred with the lipo-/glycopeptide agents daptomycin and telavancin, where β-lactam combinations with VAN prevented MIC increases to these agents as well. Combinations with non-β-lactams were ineffective in preventing VAN MIC increases with VAN MICs of 4 to 16 mg/liter emerging during weeks 2 to 4 of treatment. VAN plus β-lactam decreased CWT significantly, whereas VAN plus other antibiotics significantly increased the CWT. No correlation was observed between carotenoid content or membrane fluidity and antibiotic exposure. Only the combination exposures of VAN plus β-lactam suppress the development of VISA. Rational selection of VAN plus β-lactam should be further explored as a long-term combination treatment of MRSA infections due to their ability to suppress VAN resistance.

Antimicrobial resistance is recognized as one of the principal threats to public health worldwide, yet the problem is increasing. Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains are among the most difficult to treat in clinical settings due to the resistance of MRSA to nearly all available antibiotics. The cyclic anionic lipopeptide antibiotic daptomycin (DAP) is the clinical mainstay of anti-MRSA therapy. The decreased susceptibility to DAP (DAP resistance [DAP r ]) reported in MRSA is frequently accompanied by a paradoxical decrease in β-lactam resistance, a process known as the “seesaw effect.” Despite the observed discordance in resistance phenotypes, the combination of DAP and β-lactams has been proven to be clinically effective for the prevention and treatment of infections due to DAP r MRSA strains. However, the mechanisms underlying the interactions between DAP and β-lactams are largely unknown. In the study described here, we studied the role of mprF with DAP-induced mutations in β-lactam sensitization and its involvement in the effective killing by the DAP-oxacillin (OXA) combination. DAP-OXA-mediated effects resulted in cell wall perturbations, including changes in peptidoglycan insertion, penicillin-binding protein 2 (PBP 2) delocalization, and reduced membrane amounts of PBP 2a, despite the increased transcription of mecA through mec regulatory elements. We have found that the VraSR sensor-regulator is a key component of DAP resistance, triggering mutated mprF -mediated cell membrane (CM) modifications that result in impairment of PrsA location and chaperone functions, both of which are essential for PBP 2a maturation, the key determinant of β-lactam resistance. These observations provide for the first time evidence that synergistic effects between DAP and β-lactams involve PrsA posttranscriptional regulation of CM-associated PBP 2a.

Ceftaroline is the first member of a novel class of cephalosporins approved for use in the United States. Although prior studies have identified eight ceftaroline-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolates in Europe and Asia with MICs ranging from 4 to 8 mg/liter, high-level resistance to ceftaroline (>32 mg/liter) has not been described in MRSA strains isolated in the United States. We isolated a ceftaroline-resistant (MIC > 32 mg/liter) MRSA strain from the blood of a cystic fibrosis patient and five MRSA strains from the respiratory tract of this patient. Whole-genome sequencing identified two amino acid-altering mutations uniquely present in the ceftaroline-binding pocket of the transpeptidase region of penicillin-binding protein 2a (PBP2a) in ceftaroline-resistant isolates. Biochemical analyses and the study of isogenic mutant strains confirmed that these changes caused ceftaroline resistance. Thus, we identified the molecular mechanism of ceftaroline resistance in the first MRSA strain with high-level ceftaroline resistance isolated in the United States.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important infectious human pathogen responsible for diseases ranging from skin and soft tissue infections to life-threatening endocarditis. β-Lactam resistance in MRSA involves acquisition of penicillin-binding protein 2a (PBP2a), a protein with low affinity for β-lactams that mediates cell wall assembly when the normal staphylococcal PBPs (PBP1 to -4) are blocked by these agents. Many MRSA strains display heterogeneous expression of resistance (HeR) against β-lactam antibiotics. The β-lactam-mediated homoresistant (HoR) phenotype is associated with both expression of the mecA gene and activation of the LexA-RecA-mediated SOS response, a regulatory network induced in response to DNA damage. Ceftaroline (CPT) is the only FDA-approved cephalosporin targeting PBP2a. We investigated the mechanistic basis of CPT activity against HeR-MRSA strains, including a set of strains displaying an intermediate level of resistance to CPT. Mechanistically, we found that 1 exposure of HeR-MRSA to subinhibitory concentrations of CPT selected for the HoR derivative activated the SOS response and increased mutagenesis. Importantly, CPT-selected HoR cells remained susceptible to CPT while still being resistant to most β-lactams, and 2-CPT activity in HeR-MRSA resided in an attenuated induction of mecA expression in comparison to other β-lactams. In addition, 3-CPT intermediate-resistant strains displayed a significant increase in CPT-induced mecA expression accompanied by mutations in PBP2, which together may interfere with the complete repression by CPT of both PBP2a and PBP2a-PBP2 interactions and thus be a determining factor in the low level of CPT resistance in the absence of mecA gene mutations. The present study provides mechanistic evidence that CPT represents an alternative therapeutic option for the treatment of heteroresistant MRSA strains.

Summary Although iron under anaerobic conditions is more accessible and highly reactive because of its reduced form, iron-dependent regulation is not well known in anaerobic bacteria. Here, we investigated iron- and hemin-dependent gene regulation in Porphyromonas gingivalis, an established periodontopathogen that primarily inhabits anaerobic pockets. Whole-genome microarrays of P. gingivalis genes were used to compare the levels of gene expression under iron-replete and iron-depleted conditions as well as under hemin-replete and hemin-depleted conditions. Under iron-depleted conditions, the expression of genes encoding proteins that participate in iron uptake and adhesion/invasion of host cells was increased, while that of genes encoding proteins involved in iron storage, energy metabolism, and electron transport was decreased. Interestingly, many of the genes with altered expression had no known function. Limiting the amount of hemin also resulted in a reduced expression of the genes encoding proteins involved in energy metabolism and electron transport. However, hemin also had a significant effect on many other biological processes such as oxidative stress protection and lipopolysaccharide synthesis. Overall, comparison of the data from iron-depleted conditions to those from hemin-depleted ones showed that although some regulation is through the iron derived from hemin, there also is significant distinct regulation through hemin only. Furthermore, our data showed that the molecular mechanisms of iron-dependent regulation are novel as the deletion of the putative Fur protein had no effect on the expression of iron-regulated genes. Finally, our functional studies demonstrated greater survivability of host cells in the presence of the iron-stressed bacterium than the iron-replete P. gingivalis cells. The major iron-regulated proteins encoded by PG1019–20 may play a role in this process as deletion of these sequences also resulted in reduced survival of the bacterium when grown with eukaryotic cells. Taken together, the results of this study demonstrated the utility of whole-genome microarray analysis for the identification of genes with altered expression profiles during varying growth conditions and provided a framework for the detailed analysis of the molecular mechanisms of iron and hemin acquisition, metabolism and virulence of P. gingivalis.

The new detector CHIMERA, in its final 4π configuration, has been installed at Laboratori Nazionali del Sud (LNS) in Catania in January 2003. Beams of different energies ranging from protons to Au ions were delivered by the Tandem and the Super Conducting Cyclotron for nuclear reaction studies, in agreement with the approval of the Scientific Advisory Committee of LNS. Recent experimental results confirm very low energy thresholds of the trigger (below 0.5 MeV/nucleon), ensured within a wide dynamical range. Good characteristics of identification of light charged particles and heavy fragments have been obtained by using three detection techniques: Δ E-E , Δ E -time of flight, and the Pulse-Shape discrimination method. We present results of recent analysis concerning the production of intermediate mass fragments (IMF) in semi-peripheral collisions. Our results combined with theoretical Boltzmann-Nordheim-Vlasov simulations clearly demonstrate the presence of very fast processes of IMF production in the overlapping region of the target and projectile nuclei during re-separation, i.e. in the time scale comparable with the collision time. Evidence for slower, sequential-like production of IMF's is also shown.

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged to be one of the most important pathogens both in health care and in community-onset infections. Daptomycin (DAP) is a cyclic anionic lipopeptide recommended for treatment of skin infections, bacteremia, and right-sided endocarditis caused by MRSA. Resistance to DAP (DAP r ) has been reported in MRSA and is mostly accompanied by a parallel decrease in oxacillin resistance, a process known as the “seesaw effect.” Our study provides evidence that the seesaw effect applies to other β-lactams and carbapenems of clinical use, including nafcillin (NAF), cefotaxime (CTX), amoxicillin-clavulanic (AMC), and imipenem (IMP), in heterogeneous DAP r MRSA strains but not in MRSA strains expressing homogeneous β-lactam resistance. The antibacterial efficacy of DAP in combination with β-lactams was evaluated in isogenic DAP-susceptible (DAP s )/Dap r MRSA strains originally obtained from patients that failed DAP monotherapy. Both in vitro (MIC, synergy-kill curve) and in vivo (wax worm model) approaches were used. In these models, DAP and a β-lactam proved to be highly synergistic against both heterogeneous and homogeneous clinical DAP r MRSA strains. Mechanistically, β-lactams induced a reduction in the cell net positive surface charge, reverting the increased repulsion provoked by DAP alone, an effect that may favor the binding of DAP to the cell surface. The ease of in vitro mutant selection was observed when DAP s MRSA strains were exposed to DAP. Importantly, the combination of DAP and a β-lactam prevented the selection of DAP r variants. In summary, our data show that the DAP–β-lactam combination may significantly enhance both the in vitro and in vivo efficacy of anti-MRSA therapeutic options against DAP r MRSA infections and represent an option in preventing DAP r selection in persistent or refractory MRSA infections.

The goal of the FAZIA Collaboration is the design of a new-generation 4π detector array for heavy-ion collisions with radioactive beams. This article summarizes the main results of the R&D phase, devoted to the search for significant improvements of the techniques for charge and mass identification of reaction products. This was obtained by means of a systematic study of the basic detection module, consisting of two transmission-mounted silicon detectors followed by a CsI(Tl) scintillator. Significant improvements in ΔE-E and pulse-shape techniques were obtained by controlling the doping homogeneity and the cutting angles of silicon and by putting severe constraints on thickness uniformity. Purposely designed digital electronics contributed to identification quality. The issue of possible degradation related to radiation damage of silicon was also addressed. The experimental activity was accompanied by studies on the physics governing signal evolution in silicon. The good identification quality obtained with the prototypes during the R&D phase, allowed us to investigate also some aspects of isospin physics, namely isospin transport and odd-even staggering. Now, after the conclusion of the R&D period, the FAZIA Collaboration has entered the demonstrator phase, with the aim of verifying the applicability of the devised solutions for the realization of a larger-scale experimental set-up.

Expression of the methicillin-resistant S. aureus (MRSA) phenotype results from the expression of the extra penicillin-binding protein 2A (PBP2A), which is encoded by mecA and acquired horizontally on part of the SCC mec cassette. PBP2A can catalyze dd -transpeptidation of peptidoglycan (PG) because of its low affinity for β-lactam antibiotics and can functionally cooperate with the PBP2 transglycosylase in the biosynthesis of PG. Here, we focus upon the role of the membrane-bound PrsA foldase protein as a regulator of β-lactam resistance expression. Deletion of prsA altered oxacillin resistance in three different SCC mec backgrounds and, more importantly, caused a decrease in PBP2A membrane amounts without affecting mecA mRNA levels. The N- and C-terminal domains of PrsA were found to be critical features for PBP2A protein membrane levels and oxacillin resistance. We propose that PrsA has a role in posttranscriptional maturation of PBP2A, possibly in the export and/or folding of newly synthesized PBP2A. This additional level of control in the expression of the mecA -dependent MRSA phenotype constitutes an opportunity to expand the strategies to design anti-infective agents.

Background.The impact of antimicrobial scrubs on healthcare worker (HCW) bacterial burden is unknown.Objective.To determine die effectiveness of antimicrobial scrubs on hand and apparel bacterial burden.Design.Prospective, crossover trial.Setting and Participants.Thirty HCWs randomized to study versus control scrubs in an intensive care unit.Methods.Weekly microbiology samples were obtained from scrub abdominal area, cargo pocket, and hands. Mean log colony-forming unit (CFU) counts were calculated. Compliance with hand hygiene practices was measured. Apparel and hand mean log CFU counts were compared.Results.Adherence measures were 78% (910/1,173) for hand hygiene and 82% (223/273) for scrubs. Culture compliance was 67% (306/460). No differences were observed in bacterial hand burden or in HCWs with unique positive scrub cultures. No difference in vancomycin-resistant enterococci (VRE) and gram-negative rod (GNR) burden was observed. A difference in mean log mediicillin-resistant Staphylococcus aureus (MRSA) CFU count was found between study and control scrubs for leg cargo pocket (mean log CFUs, 11.84 control scrub vs 6.71 study scrub; P = .0002), abdominal area (mean log CFUs, 11.35 control scrub vs 7.54 study scrub; P = .0056), leg cargo pocket at die beginning of shift (mean log CFUs, 11.96 control scrub vs 4.87 study scrub; P = .0028), and abdominal area pocket at die end of shift (mean log CFUs, 12.14 control scrubs vs 8.22 study scrub; P = .0054).Conclusions.Study scrubs were associated witfi a 4–7 mean log reduction in MRSA burden but not VRE or GNRs. A prospective trial is needed to measure die impact of antimicrobial impregnated apparel on MRSA transmission rates.Infect Control Hosp Epidemiol 2012;33(3):268-275

Methicillin-resistant Staphylococcus aureus (MRSA) is a human pathogen and a major cause of hospital-acquired infections. New antibacterial agents that have not been compromised by bacterial resistance are needed to treat MRSA-related infections. We chose the S. aureus cell wall synthesis enzyme, alanine racemase (Alr) as the target for a high-throughput screening effort to obtain novel enzyme inhibitors, which inhibit bacterial growth. Among the ‘hits’ identified was a thiadiazolidinone with chemical properties attractive for lead development. This study evaluated the mode of action, antimicrobial activities, and mammalian cell cytotoxicity of the thiadiazolidinone family in order to assess its potential for development as a therapeutic agent against MRSA. The thiadiazolidones inhibited Alr activity with 50% inhibitory concentrations (IC50) ranging from 0.36 to 6.4 μM, and they appear to inhibit the enzyme irreversibly. The series inhibited the growth of S. aureus, including MRSA strains, with minimal inhibitory concentrations (MICs) ranging from 6.25 to 100 μg/ml. The antimicrobial activity showed selectivity against Gram-positive bacteria and fungi, but not Gram-negative bacteria. The series inhibited human HeLa cell proliferation. Lead development centering on the thiadiazolidinone series would require additional medicinal chemistry efforts to enhance the antibacterial activity and minimize mammalian cell toxicity.

In 129 Xe+ nat Sn central collisions from 8 to 25 MeV/A, the three-fragment exit channel occurs with a significant cross section. We show that these fragments arise from two successive binary splittings of a heavy composite system. The sequence of fragment production is determined. Strong Coulomb proximity effects are observed in the three-fragment final state. A comparison with Coulomb trajec-tory calculations shows that the time scale between the consecutive break-ups decreases with increasing bombarding energy, becoming quasi-simultaneous above excitation energy E * = 4.0$\pm$0.5 MeV/A. This transition from sequential to simultaneous break-up was interpreted as the signature of the onset of multifragmentation for the three-fragment exit channel in this system., Comment: 12 pages; 13 Figures; 4 Table; Accepted for publication in Physical Review C

Background We studied risk factors for nasal colonization with inducible dormant methicillin-resistant Staphylococcus aureus (ID-MRSA) and community-associated MRSA (CA-MRSA) in a cohort of predominantly university students. Methods Nasal surveillance cultures were performed in student health and ambulatory clinics. Molecular features were identified and risk factors for CA-MRSA and ID-MRSA colonization were determined by logistic regression. Results Of the 1000 participants, 89% ( n = 890) were university students. Sixty-four percent were female, 59% Caucasian. The mean age was 23.5 years; 1.6% ( n = 16) were CA-MRSA and 1.4% ( n = 14) were ID-MRSA colonized. Fifteen (94%) of the CA-MRSA strains were PFGE type IV. pvl (Panton–Valentine leukocidin gene) positivity was 75% in CA-MRSA and 57% in ID-MRSA. ID-MRSA isolates were pulsed-field gel electrophoresis (PFGE) type I, 7%; type II, 14%; type V, 7%; and type IV, 71%. CA-MRSA SCC mec classification was 94% type IV and 6% type V. Risk factors for carriage of CA-MRSA were older age (OR 1.046, p =0.040) and dog ownership (OR 1.450, p =0.019). Single family home (OR 0.040, p =0.007) was a protective factor. There were no significant variables of association found for ID-MRSA colonization. Conclusions ID-MRSA/CA-MRSA colonization was low. Most isolates were PFGE types IV and II, pvl -positive and susceptible to several antibiotics. Older age and dog ownership were risk factors for CA-MRSA. Future studies are needed to assess the impact of ID-MRSA carriage.