scholarly journals SpoVG Regulates Cell Wall Metabolism and Oxacillin Resistance in Methicillin-Resistant Staphylococcus aureus Strain N315

2016 ◽  
Vol 60 (6) ◽  
pp. 3455-3461 ◽  
Author(s):  
Xiaoyu Liu ◽  
Shijie Zhang ◽  
Baolin Sun
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Aureus Strain ◽  
Cell Wall Metabolism ◽  
Mobility Shift ◽  
Entire Family ◽  
Positive Role ◽  
Methicillin Resistant ◽  
Oxacillin Resistance ◽  
Mrsa Strains

Increasing cases of infections caused by methicillin-resistantStaphylococcus aureus(MRSA) strains in healthy individuals have raised concerns worldwide. MRSA strains are resistant to almost the entire family of β-lactam antibiotics due to the acquisition of an extra penicillin-binding protein, PBP2a. Studies have shown thatspoVGis involved in oxacillin resistance, while the regulatory mechanism remains elusive. In this study, we have found that SpoVG plays a positive role in oxacillin resistance through promoting cell wall synthesis and inhibiting cell wall degradation in MRSA strain N315. Deletion ofspoVGin strain N315 led to a significant decrease in oxacillin resistance and a dramatic increase in Triton X-100-induced autolytic activity simultaneously. Real-time quantitative reverse transcription-PCR revealed that the expression of 8 genes related to cell wall metabolism or oxacillin resistance was altered in thespoVGmutant. Electrophoretic mobility shift assay indicated that SpoVG can directly bind to the putative promoter regions oflytN(murein hydrolase),femA, andlytSR(the two-component system). These findings suggest a molecular mechanism in which SpoVG modulates oxacillin resistance by regulating cell wall metabolism in MRSA.

scholarly journals Role of PknB Kinase in Antibiotic Resistance and Virulence in Community-Acquired Methicillin-Resistant Staphylococcus aureus Strain USA300

2010 ◽  
Vol 78 (8) ◽  
pp. 3637-3646 ◽  
Author(s):  
Sandeep Tamber ◽  
Joseph Schwartzman ◽  
Ambrose L. Cheung
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Antibiotic Resistance ◽  
Aureus Strain ◽  
Cell Wall Metabolism ◽  
Methicillin Resistant ◽  
Enhanced Sensitivity ◽  
Threonine Kinases

ABSTRACT The regulation of cellular processes by eukaryote-like serine/threonine kinases is widespread in bacteria. In the last 2 years, several studies have examined the role of serine/threonine kinases in Staphylococcus aureus on cell wall metabolism, autolysis, and virulence, mostly in S. aureus laboratory isolates in the 8325-4 lineage. In this study, we showed that the pknB gene (also called stk1) of methicillin-resistant S. aureus (MRSA) strain COL and the community-acquired MRSA (CA-MRSA) strain USA300 is involved in cell wall metabolism, with the pknB mutant exhibiting enhanced sensitivity to β-lactam antibiotics but not to other classes of antibiotics, including aminoglycosides, ciprofloxacin, bactrim, and other types of cell wall-active agents (e.g., vancomycin and bacitracin). Additionally, the pknB mutant of USA300 was found to be more resistant to Triton X-100-induced autolysis and also to lysis by lysostaphin. We also showed that pknB is a positive regulator of sigB activity, resulting in compromise in its response to heat and oxidative stresses. In association with reduced sigB activity, the expression levels of RNAII and RNAIII of agr and the downstream effector hla are upregulated while spa expression is downmodulated in the pknB mutant compared to the level in the parent. Consistent with an enhanced agr response in vitro, virulence studies of the pknB mutant of USA300 in a murine cutaneous model of infection showed that the mutant was more virulent than the parental strain. Collectively, our results have linked the pknB gene in CA-MRSA to antibiotic resistance, sigB activity, and virulence and have highlighted important differences in pknB phenotypes (virulence and sigB activity) between laboratory isolates and the prototypic CA-MRSA strain USA300.

scholarly journals Full-Genome Sequencing Identifies in the Genetic Background Several Determinants That Modulate the Resistance Phenotype in Methicillin-Resistant Staphylococcus aureus Strains Carrying the Novel mecC Gene

2017 ◽  
Vol 61 (3) ◽  
Author(s):  
Catarina Milheiriço ◽  
Hermínia de Lencastre ◽  
Alexander Tomasz
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Genetic Background ◽  
Beta Lactam ◽  
Methicillin Resistant ◽  
Content Type ◽  
Resistance Phenotype ◽  
Beta Lactam Antibiotics ◽  
Oxacillin Resistance ◽  
Mrsa Strains

ABSTRACT Most methicillin-resistant Staphylococcus aureus (MRSA) strains are resistant to beta-lactam antibiotics due to the presence of the mecA gene, encoding an extra penicillin-binding protein (PBP2A) that has low affinity for virtually all beta-lactam antibiotics. Recently, a new resistance determinant—the mecC gene—was identified in S. aureus isolates recovered from humans and dairy cattle. Although having typically low MICs to beta-lactam antibiotics, MRSA strains with the mecC determinant are also capable of expressing high levels of oxacillin resistance when in an optimal genetic background. In order to test the impact of extensive beta-lactam selection on the emergence of mecC-carrying strains with high levels of antibiotic resistance, we exposed the prototype mecC-carrying MRSA strain, LGA251, to increasing concentrations of oxacillin. LGA251 was able to rapidly adapt to high concentrations of oxacillin in growth medium. In such laboratory mutants with increased levels of oxacillin resistance, we identified mutations in genes with no relationship to the mecC regulatory system, indicating that the genetic background plays an important role in the establishment of the levels of oxacillin resistance. Our data also indicate that the stringent stress response plays a critical role in the beta-lactam antibiotic resistance phenotype of MRSA strains carrying the mecC determinant.

scholarly journals The Posttranslocational Chaperone Lipoprotein PrsA Is Involved in both Glycopeptide and Oxacillin Resistance in Staphylococcus aureus

2012 ◽  
Vol 56 (7) ◽  
pp. 3629-3640 ◽  
Author(s):  
Ambre Jousselin ◽  
Adriana Renzoni ◽  
Diego O. Andrey ◽  
Antoinette Monod ◽  
Daniel P. Lew ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Wall Stress ◽  
Growth Conditions ◽  
Transcriptional Analysis ◽  
Pharmacological Intervention ◽  
Content Type ◽  
Cell Wall Stress ◽  
Oxacillin Resistance ◽  
Mrsa Strains

ABSTRACTUnderstanding in detail the factors which permitStaphylococcus aureusto counteract cell wall-active antibiotics is a prerequisite to elaborating effective strategies to prolong the usefulness of these drugs and define new targets for pharmacological intervention. Methicillin-resistantS. aureus(MRSA) strains are major pathogens of hospital-acquired and community-acquired infections and are most often treated with glycopeptides (vancomycin and teicoplanin) because of their resistance to most penicillins and a limited arsenal of clinically proven alternatives. In this study, we examined PrsA, a lipid-anchored protein of the parvulin PPIase family (peptidyl-prolylcis/transisomerase) found ubiquitously in all Gram-positive species, in which it assists posttranslocational folding at the outer surface of the cytoplasmic membrane. We show by both genetic and biochemical assays thatprsAis directly regulated by the VraRS two-component sentinel system of cell wall stress. Disruption ofprsAis tolerated byS. aureus, and its loss results in no detectable overt macroscopic changes in cell wall architecture or growth rate under nonstressed growth conditions. Disruption ofprsAleads, however, to notable alterations in the sensitivity to glycopeptides and dramatically decreases the resistance of COL (MRSA) to oxacillin. Quantitative transcriptional analysis reveals thatprsAandvraRare coordinately upregulated in a panel of stable laboratory and clinical glycopeptide-intermediateS. aureus(GISA) strains compared to their susceptible parents. Collectively, our results point to a role forprsAas a facultative facilitator of protein secretion or extracellular folding and provide a framework for understanding whyprsAis a key element of the VraRS-mediated cell wall stress response.

scholarly journals Modulation ofccrABExpression and SCCmecExcision by an Inverted Repeat Element and SarS in Methicillin-Resistant Staphylococcus aureus

2015 ◽  
Vol 59 (10) ◽  
pp. 6223-6232 ◽  
Author(s):  
Shijie Zhang ◽  
Ronghua Ma ◽  
Xiaoyu Liu ◽  
Xu Zhang ◽  
Baolin Sun
Keyword(s):  
Staphylococcus Aureus ◽  
Inverted Repeat ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Regulatory Mechanism ◽  
Human Pathogen ◽  
Entire Family ◽  
Methicillin Resistant ◽  
Content Type ◽  
Mrsa Strains ◽  
Dna Affinity Chromatography

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) is a notorious human pathogen that can cause a broad spectrum of infections. MRSA strains are resistant to almost the entire family of β-lactam antibiotics due to the acquisition of staphylococcal cassette chromosomemec(SCCmec). The chromosome cassette recombinases A and B, encoded byccrABgenes located on SCCmec, play a key role in the excision of SCCmec. Studies have shown thatccrABgenes are expressed in only a minority of cells, suggesting the involvement of a subtle regulatory mechanism inccrABexpression which has not been uncovered. Here, we found that an inverted repeat (IR) element, existing extensively and conservatively within theccrABpromoter of different SCCmectypes, played a repressive role inccrABexpression and SCCmecexcision in MRSA strain N315. Replacement of the IR sequence led to a significant increase inccrABexpression and curing of SCCmecfrom strain N315 cells. In addition, we identified the transcriptional regulator SarS using DNA-affinity chromatography and further demonstrated that SarS can bind to the IR sequence and upregulateccrABexpression and SCCmecexcision. These findings reveal a molecular mechanism regulatingccrABexpression and SCCmecexcision and may provide mechanic insights into the lateral transfer of SCCmecand spread of antibiotic resistance inS. aureus.

scholarly journals Prolonged Colonization with the Methicillin-Resistant Staphylococcus aureus Strain USA300 among Residents of Extended Care Facilities

2010 ◽  
Vol 31 (8) ◽  
pp. 838-841 ◽  
Author(s):  
Simone M. Shurland ◽  
O. Colin Stine ◽  
Richard A. Venezia ◽  
Jennifer K. Johnson ◽  
Min Zhan ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Odds Ratio ◽  
Retrospective Cohort ◽  
Adjusted Odds Ratio ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Aureus Strain ◽  
Methicillin Resistant ◽  
Extended Care ◽  
Care Facilities ◽  
Mrsa Strains

We performed a retrospective cohort study (n = 129) to assess whether residents of extended care facilities who were initially colonized or infected with the methicillin-resistant Staphylococcus aureus (MRSA) strain USA300 were less likely to have prolonged colonization than were residents colonized or infected with other MRSA strains. We found no difference in prolonged colonization (adjusted odds ratio, 1.1 [95% confidence interval, 0.5–2.4]).

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.

Cloning and characterization of the fmt gene which affects the methicillin resistance level and autolysis in the presence of triton X-100 in methicillin-resistant Staphylococcus aureus.

1997 ◽  
Vol 41 (11) ◽  
pp. 2355-2361 ◽  
Author(s):  
H Komatsuzawa ◽  
M Sugai ◽  
K Ohta ◽  
T Fujiwara ◽  
S Nakashima ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Binding Proteins ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Insertion Mutant ◽  
Resistance Level ◽  
Methicillin Resistant ◽  
Penicillin Binding Proteins ◽  
Oxacillin Resistance ◽  
Mrsa Strains ◽  
Triton X

In methicillin-resistant Staphylococcus aureus (MRSA) strains, Triton X-100 reduced the oxacillin resistance level, although the degree of reduction varied from strain to strain. To study the responses of MRSA strains to Triton X-100, we isolated a Tn551 insertion mutant of the COL strain that became more susceptible to oxacillin in the presence of 0.02% Triton X-100. The Tn551 insertion of the mutant was transduced back to the parent strain, other MRSA strains (strains KSA8 and NCTC 10443), and methicillin-susceptible strain RN450. All transductants of MRSA strains had reduced levels of resistance to oxacillin in the presence of 0.02% Triton X-100, while those of RN450 did not. Tn551 mutants of KSA8 and NCTC 10443 also had reduced levels of resistance in the absence of 0.02% Triton X-100. The autolysis rates of the transductants in the presence of 0.02% Triton X-100 were significantly increased. Amino acid analysis of peptidoglycan and testing of heat-inactivated cells for their susceptibilities to several bacteriolytic enzymes showed that there were no significant differences between the parents and the respective Tn551 mutants. The Tn551 insertion site mapped at a location different from the previously identified fem and llm sites. Cloning and sequencing showed that Tn551 had inserted at the C-terminal region of a novel gene designated fmt. The putative Fmt protein showed a hydropathy pattern similar to that of S. aureus penicillin-binding proteins and contained two of the three conserved motifs shared by penicillin-binding proteins and beta-lactamases, suggesting that fmt may be involved in cell wall synthesis.

scholarly journals Complete Genome Sequence of a USA100 Methicillin-Resistant Staphylococcus aureus Strain

2019 ◽  
Vol 8 (11) ◽  
Author(s):  
George E. Chlipala ◽  
Zhengdeng Arden Lei ◽  
Mark Maienschein-Cline ◽  
Kevin Kunstman ◽  
Koh Okamoto ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Genome Sequence ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Reference Genome ◽  
Aureus Strain ◽  
Surgical Intensive Care Unit ◽  
Surgical Intensive Care ◽  
Methicillin Resistant ◽  
Content Type ◽  
Mrsa Strains

We report the genome sequence of a methicillin-resistant Staphylococcus aureus (MRSA) strain, isolated from a surgical intensive care unit. This completely closed genome of a USA100 isolate contains a major chromosome and a plasmid and will serve as a reference genome for genetic analysis of MRSA strains.

scholarly journals Identification and Phenotypic Characterization of a β-Lactam-Dependent, Methicillin-Resistant Staphylococcus aureus Strain

2007 ◽  
Vol 51 (7) ◽  
pp. 2514-2522 ◽  
Author(s):  
Fred Goldstein ◽  
Jiri Perutka ◽  
Arabela Cuirolo ◽  
Konrad Plata ◽  
Diego Faccone ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
In Vitro Selection ◽  
Methicillin Resistance ◽  
Constitutive Expression ◽  
Aureus Strain ◽  
Phenotypic Characterization ◽  
Type I ◽  
Methicillin Resistant ◽  
Oxacillin Resistance

ABSTRACT Methicillin resistance in Staphylococcus aureus is primarily mediated by the acquired penicillin-binding protein PBP 2a, which is encoded by mecA. PBP 2a acts together with native PBP 2 to mediate oxacillin resistance by contributing complementary transpeptidase and transglycosylase activities, respectively. In this study, we have investigated a phenotype of β-lactam dependence in a clinical methicillin-resistant S. aureus strain (strain 2884D) obtained by in vitro selection with ceftobiprole. 28884D, which grew very poorly in blood agar, required the presence of the β-lactam antibiotics to grow. On the basis of this observation, we hypothesized that a gene or genes essential for growth were dependent on oxacillin induction. Identification and analysis of genes regulated by oxacillin were performed by both real-time reverse transcription-PCR and spotted microarray analysis. We found that mecA was constitutively expressed in strain 2884D and that the constitutive expression resulted from perturbations in the two systems involved in its regulation, i.e., MecI/MecR1 (staphylococcal chromosome cassette mec type I) and BlaI/BlaR1 (nonfunctional penicillinase operon). PBP 2 appeared to be poorly induced by oxacillin in 2884D. Further analysis of the PBP 2 two-component VraSR regulatory system showed that it was nonfunctional, accounting for the lack of response to oxacillin. Together, these results support the notion that limited PBP 2 availability may have led 2884D to become dependent on oxacillin-mediated mecA induction as a required survival mechanism.

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