scholarly journals VraT/YvqF Is Required for Methicillin Resistance and Activation of the VraSR Regulon in Staphylococcus aureus

2012 ◽  
Vol 57 (1) ◽  
pp. 83-95 ◽  
Author(s):  
Susan Boyle-Vavra ◽  
Shouhui Yin ◽  
Dae Sun Jo ◽  
Christopher P. Montgomery ◽  
Robert S. Daum
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Methicillin Resistance ◽  
Regulatory System ◽  
Microarray Experiments ◽  
Content Type ◽  
Genome Wide ◽  
Mrsa Strains

ABSTRACTStaphylococcus aureusinfections caused by strains that are resistant to all forms of penicillin, so-called methicillin-resistantS. aureus(MRSA) strains, have become common. One strategy to counter MRSA infections is to use compounds that resensitize MRSA to methicillin.S. aureusresponds to diverse classes of cell wall-inhibitory antibiotics, like methicillin, using the two-component regulatory system VraSR (vra) to up- or downregulate a set of genes (the cell wall stimulon) that presumably facilitates resistance to these antibiotics. Accordingly, VraS and VraR mutations decrease resistance to methicillin, vancomycin, and daptomycin cell wall antimicrobials.vraSandvraRare encoded together on a transcript downstream of two other genes, which we callvraUandvraT(previously calledyvqF). By producing nonpolar deletions invraUandvraTin a USA300 MRSA clinical isolate, we demonstrate thatvraTis essential for optimal expression of methicillin resistancein vitro, whereasvraUis not required for this phenotype. The deletion ofvraTalso improved the outcomes of oxacillin therapy in mouse models of lung and skin infection. SincevraTexpressed intransdid not complement avraoperon deletion, we conclude that VraT does not inactivate the antimicrobial. Genome-wide transcriptional microarray experiments reveal that VraT facilitates resistance by playing a necessary regulatory role in the VraSR-mediated cell wall stimulon. Our data prove that VraTSR comprise a novel three-component regulatory system required to facilitate resistance to cell wall agents inS. aureus. We also provide the firstin vivoproof of principle for using VraT as a sole target to resensitize MRSA to β-lactams.

scholarly journals Reduced Vancomycin Susceptibility in anIn VitroCatheter-Related Biofilm Model Correlates with Poor Therapeutic Outcomes in Experimental Endocarditis Due to Methicillin-Resistant Staphylococcus aureus

2013 ◽  
Vol 57 (3) ◽  
pp. 1447-1454 ◽  
Author(s):  
Wessam Abdelhady ◽  
Arnold S. Bayer ◽  
Kati Seidl ◽  
Cynthia C. Nast ◽  
Megan R. Kiedrowski ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Wall Thickness ◽  
Biofilm Formation ◽  
Methicillin Resistant ◽  
Content Type ◽  
Biofilm Model ◽  
Mrsa Strains

ABSTRACTStaphylococcus aureusis the most common cause of endovascular infections, including catheter sepsis and infective endocarditis (IE). Vancomycin (VAN) is the primary choice for treatment of methicillin-resistantS. aureus(MRSA) infections. However, high rates of VAN treatment failure in MRSA infections caused by VAN-susceptible strains have been increasingly reported. Biofilm-associated MRSA infections are especially prone to clinical antibiotic failure. The present studies examined potential relationships between MRSA susceptibility to VAN in biofilmsin vitroand nonsusceptibility to VAN in endovascular infectionin vivo. Using 10 “VAN-susceptible” MRSA bloodstream isolates previously investigated for VAN responsiveness in experimental IE, we studied the mechanism(s) of suchin vivoVAN resistance, including: (i) VAN binding to MRSA organisms; (ii) the impact of VAN on biofilm formation and biofilm composition; (iii) VAN efficacy in anin vitrocatheter-related biofilm model; (iv) effects on cell wall thickness. As a group, the five strains previously categorized as VAN nonresponders (non-Rsp) in the experimental IE model differed from the five responders (Rsp) in terms of lower VAN binding, increased biofilm formation, higher survival in the presence of VAN within biofilms in the presence or absence of catheters, and greater biofilm reduction upon proteinase K treatment. Interestingly, sub-MICs of VAN significantly promoted biofilm formation only in the non-Rsp isolates. Cell wall thickness was similar among all MRSA strains. These results suggest that sublethal VAN levels that induce biofilm formation and reduce efficacy of VAN in thein vitrocatheter-associated biofilms may contribute to suboptimal treatment outcomes for endovascular infections caused by “VAN-susceptible” MRSA strains.

scholarly journals Ceftobiprole EfficacyIn Vitroagainst Panton-Valentine Leukocidin Production andIn Vivoagainst Community-Associated Methicillin-Resistant Staphylococcus aureus Osteomyelitis in Rabbits

2012 ◽  
Vol 56 (12) ◽  
pp. 6291-6297 ◽  
Author(s):  
Azzam Saleh-Mghir ◽  
Oana Dumitrescu ◽  
Aurélien Dinh ◽  
Yassine Boutrad ◽  
Laurent Massias ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistant ◽  
Content Type ◽  
The Mean ◽  
Mrsa Strains ◽  
Time Kill ◽  
Panton Valentine Leukocidin ◽  
Valentine Leukocidin

ABSTRACTCommunity-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) can cause osteomyelitis with severe sepsis and/or local complications in which a Panton-Valentine leukocidin (PVL) role is suspected.In vitrosub-MIC antibiotic effects on growth and PVL production by 11 PVL+MRSA strains, including the major CA-MRSA clones (USA300, including the LAC strain; USA400; and USA1000), and 11 PVL+methicillin-susceptibleS. aureus(MSSA) strains were tested in microplate culture. Time-kill analyses with ceftobiprole at its MIC were also run with LAC. Efficacies of ceftobiprole (40 mg/kg of body weight subcutaneously [s.c.] four times a day [q.i.d.]) or vancomycin (60 mg/kg intramuscularly [i.m.] twice a day [b.i.d.]) alone or combined with rifampin (10 mg/kg b.i.d.) against rabbit CA-MRSA osteomyelitis, induced by tibial injection of 3.4 × 107CFU of LAC, were compared. Treatment, started 14 days postinoculation, lasted 14 days.In vitro, 6/11 strains cultured with sub-MICs of ceftobiprole produced 1.6- to 4.8-fold more PVL than did the controls, with no link to specific clones. Rifampin decreased PVL production by all tested strains. In time-kill analyses at the LAC MIC (0.75 mg/liter), PVL production rose transiently at 6 and 8 h and then declined 2-fold at 16 h, concomitant with a 2-log10-CFU-count decrease.In vivo, the mean log10CFU/g of bone for ceftobiprole (1.44 ± 0.40) was significantly lower than that for vancomycin (2.37 ± 1.22) (P= 0.034), with 7/10 versus 5/11 bones sterilized, respectively. Combination with rifampin enhanced ceftobiprole (1.16 ± 0.04 CFU/g of bone [P= 0.056], 11/11 sterile bones) and vancomycin (1.23 ± 0.06 CFU/g [P= 0.011], 11/11 sterile bones) efficacies. Ceftobiprole bactericidal activity and the rifampin anti-PVL effect could play a role in these findings, which should be of interest for treating CA-MRSA osteomyelitis.

scholarly journals β-Lactams Increase the Antibacterial Activity of Daptomycin against Clinical Methicillin-Resistant Staphylococcus aureus Strains and Prevent Selection of Daptomycin-Resistant Derivatives

2012 ◽  
Vol 56 (12) ◽  
pp. 6192-6200 ◽  
Author(s):  
Shrenik Mehta ◽  
Christopher Singh ◽  
Konrad B. Plata ◽  
Palas K. Chanda ◽  
Arundhati Paul ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Mutant Selection ◽  
Methicillin Resistant ◽  
Content Type ◽  
Oxacillin Resistance ◽  
Worm Model ◽  
Mrsa Strains ◽  
Selection Of

ABSTRACTMethicillin-resistantStaphylococcus 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 (DAPr) 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 DAPrMRSA 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 (DAPs)/DaprMRSA strains originally obtained from patients that failed DAP monotherapy. Bothin vitro(MIC, synergy-kill curve) andin 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 DAPrMRSA 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 ofin vitromutant selection was observed when DAPsMRSA strains were exposed to DAP. Importantly, the combination of DAP and a β-lactam prevented the selection of DAPrvariants. In summary, our data show that the DAP–β-lactam combination may significantly enhance both thein vitroandin vivoefficacy of anti-MRSA therapeutic options against DAPrMRSA infections and represent an option in preventing DAPrselection in persistent or refractory MRSA infections.

scholarly journals ThemecAHomologmecCConfers Resistance against β-Lactams in Staphylococcus aureus Irrespective of the Genetic Strain Background

2014 ◽  
Vol 58 (7) ◽  
pp. 3791-3798 ◽  
Author(s):  
Britta Ballhausen ◽  
André Kriegeskorte ◽  
Nina Schleimer ◽  
Georg Peters ◽  
Karsten Becker
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Regulatory System ◽  
Wild Type ◽  
Beta Lactam ◽  
Beta Lactams ◽  
Content Type ◽  
Genetic Strain ◽  
Mrsa Strains ◽  
Strain Background

ABSTRACTIn staphylococci, methicillin resistance is mediated bymecA-encoded penicillin-binding protein 2a (PBP2a), which has a low affinity for beta-lactams. Recently, a novel PBP2a homolog was described as being encoded bymecC, which shares only 70% similarity tomecA. To prove thatmecCis the genetic determinant that confers methicillin resistance inStaphylococcus aureus, amecCknockout strain was generated. TheS. aureusΔmecCstrain showed considerably reduced oxacillin and cefoxitin MICs (0.25 and 4 μg/ml, respectively) compared to those of the corresponding wild-type methicillin-resistantS. aureus(MRSA) strain (8 and 16 μg/ml, respectively). Complementing the mutant intranswith wild-typemecCrestored the resistance to oxacillin and cefoxitin. By expressingmecCandmecAin differentS. aureusclonal lineages, we found thatmecCmediates resistance irrespective of the genetic strain background, yielding oxacillin and cefoxitin MIC values comparable to those withmecA. In addition, we showed thatmecCexpression is inducible by oxacillin, which supports the assumption that a functional beta-lactam-dependent regulatory system is active in MRSA strains possessing staphylococcal cassette chromosomemec(SCCmec) type XI. In summary, we showed thatmecCis inducible by oxacillin and mediates beta-lactam resistance in SCCmectype XI-carrying strains as well as in differentS. aureusgenetic backgrounds. Furthermore, our results could explain the comparatively low MICs for clinicalmecC-harboringS. aureusisolates.

scholarly journals Role of the Accessory Gene Regulatoragrin Community-Associated Methicillin-Resistant Staphylococcus aureus Pathogenesis

2011 ◽  
Vol 79 (5) ◽  
pp. 1927-1935 ◽  
Author(s):  
Gordon Y. C. Cheung ◽  
Rong Wang ◽  
Burhan A. Khan ◽  
Daniel E. Sturdevant ◽  
Michael Otto
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Regulatory System ◽  
Accessory Gene ◽  
Methicillin Resistant ◽  
Content Type ◽  
Fibrinogen Binding ◽  
Gene Regulatory System ◽  
Differential Gene ◽  
Mrsa Strains

ABSTRACTThe molecular basis underlying the pathogenic success of community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) is not completely understood, but differential gene expression has been suggested to account at least in part for the high virulence of CA-MRSA strains. Here, we show that theagrgene regulatory system has a crucial role in the development of skin infections in the most prevalent CA-MRSA strain USA300. Importantly, our data indicate that this is due to discrepancies between theagrregulon of CA-MRSA and those of hospital-associated MRSA and laboratory strains. In particular,agrregulation in strain USA300 led to exceptionally strong expression of toxins and exoenzymes, upregulation of fibrinogen-binding proteins, increased capacity to bind fibrinogen, and increased expression of methicillin resistance genes. Our findings demonstrate thatagrfunctionality is critical for CA-MRSA disease and indicate that an adaptation of theagrregulon contributed to the evolution of highly pathogenic CA-MRSA.

scholarly journals YycH and YycI Regulate Expression of Staphylococcus aureus Autolysins by Activation of WalRK Phosphorylation

2020 ◽  
Vol 8 (6) ◽  
pp. 870
Author(s):  
Mike Gajdiss ◽  
Ian R. Monk ◽  
Ute Bertsche ◽  
Janina Kienemund ◽  
Tanja Funk ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Teichoic Acid ◽  
Regulatory System ◽  
Regulatory Function ◽  
Wall Teichoic Acid ◽  
Dependent Cell ◽  
Severe Infections

Staphylococcus aureus is a facultative pathogen that can encode numerous antibiotic resistance and immune evasion genes and can cause severe infections. Reduced susceptibility to last resort antibiotics such as vancomycin and daptomycin is often associated with mutations in walRK, an essential two-component regulatory system (TCS). This study focuses on the WalK accessory membrane proteins YycH and YycI and their influence on WalRK phosphorylation. Depletion of YycH and YycI by antisense RNA caused an impaired autolysis, indicating a positive regulatory function on WalK as has been previously described. Phosphorylation assays with full-length recombinant proteins in phospholipid liposomes showed that YycH and YycI stimulate WalK activity and that both regulatory proteins are needed for full activation of the WalK kinase. This was validated in vivo through examining the phosphorylation status of WalR using Phos-tag SDS-PAGE with a yycHI deletion mutant exhibiting reduced levels of phosphorylated WalR. In the yycHI knockdown strain, muropeptide composition of the cell wall was not affected, however, the wall teichoic acid content was increased. In conclusion, a direct modulation of WalRK phosphorylation activity by the accessory proteins YycH and YycI is reported both in vitro and in vivo. Taken together, our results show that YycH and YycI are important in the direct regulation of WalRK-dependent cell wall metabolism.

scholarly journals Telavancin in Therapy of Experimental Aortic Valve Endocarditis in Rabbits Due to Daptomycin-Nonsusceptible Methicillin-Resistant Staphylococcus aureus

2012 ◽  
Vol 56 (11) ◽  
pp. 5528-5533 ◽  
Author(s):  
Yan Q. Xiong ◽  
Wessam Abdel Hady ◽  
Arnold S. Bayer ◽  
Liang Chen ◽  
Barry N. Kreiswirth ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Aortic Valve ◽  
Rabbit Model ◽  
Methicillin Resistant ◽  
Content Type ◽  
Bacterial Cell Membrane ◽  
Mrsa Strains ◽  
Time Kill

ABSTRACTA number of cases of both methicillin-susceptibleStaphylococcus aureus(MSSA) and methicillin-resistantS. aureus(MRSA) strains that have developed daptomycin resistance (DAP-R) have been reported. Telavancin (TLV) is a lipoglycopeptide agent with a dual mechanism of activity (cell wall synthesis inhibition plus depolarization of the bacterial cell membrane). Five recent daptomycin-susceptible (DAP-S)/DAP-R MRSA isogenic strain pairs were evaluated forin vitroTLV susceptibility. All five DAP-R strains (DAP MICs ranging from 2 to 4 μg/ml) were susceptible to TLV (MICs of ≤0.38 μg/ml).In vitrotime-kill analyses also revealed that several TLV concentrations (1-, 2-, and 4-fold MICs) caused rapid killing against the DAP-R strains. Moreover, for 3 of 5 DAP-R strains (REF2145, A215, and B2.0), supra-MICs of TLV were effective at preventing regrowth at 24 h of incubation. Further, the combination of TLV plus oxacillin (at 0.25× or 0.50× MIC for each agent) increased killing of DAP-R MRSA strains REF2145 and A215 at 24 h (∼2-log and 5-log reductions versus TLV and oxacillin alone, respectively). Finally, using a rabbit model of aortic valve endocarditis caused by DAP-R strain REF2145, TLV therapy produced a mean reduction of >4.5 log10CFU/g in vegetations, kidneys, and spleen compared to untreated or DAP-treated rabbits. Moreover, TLV-treated rabbits had a significantly higher percentage of sterile tissue cultures (87% in vegetations and 100% in kidney and spleen) than all other treatment groups (P< 0.0001). Together, these results demonstrate that TLV has potent bactericidal activityin vitroandin vivoagainst DAP-R MRSA isolates.

scholarly journals Mutations inmmpLand in the Cell Wall Stress Stimulon Contribute to Resistance to Oxadiazole Antibiotics in Methicillin-Resistant Staphylococcus aureus

2014 ◽  
Vol 58 (10) ◽  
pp. 5841-5847 ◽  
Author(s):  
Qiaobin Xiao ◽  
Sergei Vakulenko ◽  
Mayland Chang ◽  
Shahriar Mobashery
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Wall Stress ◽  
Methicillin Resistant ◽  
Content Type ◽  
Cell Wall Stress ◽  
A Cell ◽  
Putative Member

ABSTRACTStaphylococcus aureusis a leading cause of hospital- and community-acquired infections, which exhibit broad resistance to various antibiotics. We recently disclosed the discovery of the oxadiazole class of antibiotics, which hasin vitroandin vivoactivities against methicillin-resistantS. aureus(MRSA). We report herein that MmpL, a putative member of the resistance, nodulation, and cell division (RND) family of proteins, contributes to oxadiazole resistance in theS. aureusstrain COL. Through serial passages, we generated twoS. aureusCOL variants that showed diminished susceptibilities to an oxadiazole antibiotic. The MICs for the oxadiazole against one strain (designatedS. aureusCOLI) increased reproducibly 2-fold (to 4 μg/ml), while against the other strain (S. aureusCOLR), they increased >4-fold (to >8 μg/ml, the limit of solubility). The COLRstrain was derived from the COLIstrain. Whole-genome sequencing revealed 31 mutations inS. aureusCOLR, of which 29 were shared with COLI. Consistent with our previous finding that oxadiazole antibiotics inhibit cell wall biosynthesis, we found 13 mutations that occurred either in structural genes or in promoters of the genes of the cell wall stress stimulon. Two unique mutations inS. aureusCOLRwere substitutions in two genes that encode the putative thioredoxin (SACOL1794) and MmpL (SACOL2566). A role formmpLin resistance to oxadiazoles was discerned from gene deletion and complementation experiments. To our knowledge, this is the first report that a cell wall-acting antibiotic selects for mutations in the cell wall stress stimulon and the first to implicate MmpL in resistance to antibiotics inS. aureus.

scholarly journals Old Drugs To Treat Resistant Bugs: Methicillin-Resistant Staphylococcus aureus Isolates withmecCAre Susceptible to a Combination of Penicillin and Clavulanic Acid

2015 ◽  
Vol 59 (12) ◽  
pp. 7396-7404 ◽  
Author(s):  
Xiaoliang Ba ◽  
Ewan M. Harrison ◽  
Andrew L. Lovering ◽  
Nicholas Gleadall ◽  
Ruth Zadoks ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Clavulanic Acid ◽  
Methicillin Resistant ◽  
Content Type ◽  
Novel Approach ◽  
Novel Variant ◽  
Resistance To Penicillin ◽  
Mrsa Strains

ABSTRACTβ-Lactam resistance in methicillin-resistantStaphylococcus aureus(MRSA) is mediated by the expression of an alternative penicillin-binding protein 2a (PBP2a) (encoded bymecA) with a low affinity for β-lactam antibiotics. Recently, a novel variant ofmecA, known asmecC, was identified in MRSA isolates from both humans and animals. In this study, we demonstrate thatmecC-encoded PBP2c does not mediate resistance to penicillin. Rather, broad-spectrum β-lactam resistance in MRSA strains carryingmecC(mecC-MRSA strains) is mediated by a combination of both PBP2c and the distinct β-lactamase encoded by theblaZgene of strain LGA251 (blaZLGA251), which is part ofmecC-encoding staphylococcal cassette chromosomemec(SCCmec) type XI. We further demonstrate thatmecC-MRSA strains are susceptible to the combination of penicillin and the β-lactam inhibitor clavulanic acidin vitroand that the same combination is effectivein vivofor the treatment of experimentalmecC-MRSA infection in wax moth larvae. Thus, we demonstrate how the distinct biological differences betweenmecA- andmecC-encoded PBP2a and PBP2c have the potential to be exploited as a novel approach for the treatment ofmecC-MRSA infections.

scholarly journals In VitroandIn VivoSynergy of the Oxadiazole Class of Antibacterials with β-Lactams

2016 ◽  
Vol 60 (9) ◽  
pp. 5581-5588 ◽  
Author(s):  
Jeshina Janardhanan ◽  
Jayda E. Meisel ◽  
Derong Ding ◽  
Valerie A. Schroeder ◽  
William R. Wolter ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Infection Model ◽  
Postantibiotic Effect ◽  
Bacterial Reduction ◽  
Content Type ◽  
Mrsa Infection ◽  
Time Kill

ABSTRACTThe oxadiazole antibacterials target the bacterial cell wall and are bactericidal. We investigated the synergism of ND-421 with the commonly used β-lactams and non-β-lactam antibiotics by the checkerboard method and by time-kill assays. ND-421 synergizes well with β-lactam antibiotics, and it also exhibits a long postantibiotic effect (4.7 h). We also evaluated thein vivoefficacy of ND-421 in a murine neutropenic thigh infection model alone and in combination with oxacillin. ND-421 hasin vivoefficacy by itself in a clinically relevant infection model (1.49 log10bacterial reduction for ND-321 versus 0.36 log10for linezolid with NRS119) and acts synergistically with β-lactam antibioticsin vitroandin vivo, and the combination of ND-421 with oxacillin is efficacious in a mouse neutropenic thigh methicillin-resistantStaphylococcus aureus(MRSA) infection model (1.60 log10bacterial reduction). The activity of oxacillin was potentiated in the presence of ND-421, as the strain would have been resistant to oxacillin otherwise.

Sign in / Sign up

Export Citation Format

Share Document