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.

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 Effect of exogenous glycine on peptidoglycan composition and resistance in a methicillin-resistant Staphylococcus aureus strain.

1996 ◽  
Vol 40 (6) ◽  
pp. 1498-1503 ◽  
Author(s):  
B L de Jonge ◽  
Y S Chang ◽  
N Xu ◽  
D Gage
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Aureus Strain ◽  
Methicillin Resistant ◽  
Resistance Phenotype ◽  
Concomitant Decrease

A highly homogeneously methicillin-resistant Staphylococcus aureus strain was grown in the presence of various concentrations of exogenous glycine. Increasing concentrations of glycine in the medium resulted in a decrease in methicillin resistance and the appearance of a heterogeneous resistance phenotype. Parallel to the gradual changes in resistance was an alteration in the muropeptide composition of peptidoglycan. Increasing concentrations of glycine in the medium resulted in peptidoglycan in which muropeptides with a D-alanyl-D-alanine terminus were replaced with D-alanyl-glycine-terminating muropeptides. The disappearance of D-alanyl-D-alanine-terminating muropeptides in peptidoglycan and the concomitant decrease in resistance indicate a central role for D-alanyl-D-alanine-terminating precursors in methicillin resistance.

scholarly journals Introduction of the mec Element (Methicillin Resistance) into Staphylococcus aureus Alters In Vitro Functional Activities of Fibrinogen and Fibronectin Adhesins

1998 ◽  
Vol 42 (3) ◽  
pp. 564-570 ◽  
Author(s):  
Pierre E. Vaudaux ◽  
Vincenza Monzillo ◽  
Patrice Francois ◽  
Daniel P. Lew ◽  
Tim J. Foster ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Bacterial Colonization ◽  
Protein A ◽  
Methicillin Resistant ◽  
Functional Activities ◽  
Extracellular Matrix Components ◽  
Resistant Strains ◽  
The Impact

ABSTRACT Some methicillin-resistant strains of Staphylococcus aureus are defective in the production of major surface components such as protein A, clumping factor, or other important adhesins to extracellular matrix components which may play a role in bacterial colonization and infection. To evaluate the impact of methicillin resistance (mec) determinants on bacterial adhesion mediated by fibrinogen or fibronectin adhesins, we compared the in vitro attachment of two genetically distinct susceptible strains (NCTC8325 and Newman) to protein-coated surfaces with that of isogenic methicillin-resistant derivatives. All strains containing an intactmec element in their chromosomes were found to be defective in adhesion to fibrinogen and fibronectin immobilized on polymethylmethacrylate coverslips, regardless of the presence or absence of additional mutations in the femA,femB, or femC gene, known to decrease expression of methicillin resistance in S. aureus. Western ligand affinity blotting or immunoblotting of cell wall-associated adhesins revealed similar contents of fibrinogen- or fibronectin-binding proteins in methicillin-resistant strains compared to those of their methicillin-susceptible counterparts. In contrast to methicillin-resistant strains carrying a mec element in their genomes, methicillin-resistant strains constructed in vitro, by introducing the mecA gene on a plasmid, retained their adhesion phenotypes. In conclusion, the chromosomal insertion of themec element into genetically defined strains of S. aureus impairs the in vitro functional activities of fibrinogen or fibronectin adhesins without altering their production. This effect is unrelated to the activity of the mecA gene.

scholarly journals Clonal Distribution of Methicillin-Resistant Staphylococcus aureus in Poland

1998 ◽  
Vol 36 (12) ◽  
pp. 3532-3539 ◽  
Author(s):  
T. Leski ◽  
D. Oliveira ◽  
K. Trzcinski ◽  
I. Santos Sanches ◽  
M. Aires de Sousa ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Gel Electrophoresis ◽  
Methicillin Resistance ◽  
Pulsed Field Gel Electrophoresis ◽  
Hospital Environment ◽  
Type I ◽  
Methicillin Resistant ◽  
Pulsed Field ◽  
Clonal Distribution ◽  
Heterogeneous Expression

We report on a study of 158 methicillin-resistantStaphylococcus aureus (MRSA) clinical isolates obtained from 1990 to 1996 in 18 different hospitals in Poland. All isolates were recovered from infection and carriage sites of patients, carriage sites of health care personnel, and hospital environment samples. Fifty-seven MRSA strains described here were studied previously and these were divided into two different clusters according to the degree of heterogeneity of methicillin resistance expression. The aim of this study was to extend the correlation between the two clusters and identify the clonal identities among all isolates by a combination of different methodologies: (i) analysis of mecA polymorphs and Tn554 insertion patterns and (ii) determination of pulsed-field gel electrophoresis patterns of chromosomalSmaI digests. Ninety-seven of 158 strains showed a heterogeneous expression of resistance to methicillin. Among these, 75 (77.3%) were ClaI-mecA type I,ClaI-Tn554 type NH (NH, no homology with transposon Tn554), and pulsed-field gel electrophoresis (PFGE) pattern A (I::NH::A); 10 isolates were III::B::M (10.3%); and the remaining clones included a few or single isolates. The isolates with homogeneous expression of resistance to methicillin (n = 61) were predominantly ClaI-mecA type III (49 of 61 [80.3%]) but had great variability in theirClaI-Tn554 and PFGE patterns. This study confirmed the existence of two main clusters of MRSA in Poland.

Staphylococcus aureus strains differ in their in vitro responsiveness to human urokinase: evidence that methicillin-resistant strains are predominately nonresponsive to the growth-enhancing effects of urokinase

1996 ◽  
Vol 42 (10) ◽  
pp. 1024-1031 ◽  
Author(s):  
David A. Hart ◽  
Carol Reno ◽  
Thomas Louie ◽  
Wallace Krulicki
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Clinical Isolates ◽  
Growth Enhancement ◽  
Western Canada ◽  
Methicillin Resistant ◽  
Resistant Strains ◽  
The Uk ◽  
Regulation Of Growth

Clinical isolates of Staphylococcus aureus were found to exhibit strain-specific heterogeneity to the growth-enhancing effects of human urokinase (UK), a proteinase with plasminogen activator activity. Nine out of fourteen (64%) methicillin-sensitive strains of S. aureus were responsive to UK in "in vitro" cultures. In contrast, 3/29 (10%) methicillin-resistant strains were responsive to the proteinase. When only strains isolated from western Canada were considered, 6/11 methicillin-sensitive strains and 1/26 methicillin-resistant strains were responsive to UK. The single western Canadian methicillin-resistant strain (strain 456) responsive to UK was one of two isolated from the same patient, indicating that the two strains were phenotypically different. Strain 456, resistant to 32 μg mefhicillin/mL, was responsive to as little as 50 U UK/mL and enhancement of growth was evident by 9 h of incubation at 37 °C. This growth enhancement was specific to UK and not duplicated by equivalent concentrations of other proteins (bovine serum albumin, trypsin, plasminogen). The results presented indicate differences in the frequency of the UK-responsive phenotype between methicillin-sensitive and -resistant S. aureus. These findings indicate that the UK phenotype of S. aureus may have utility in both phenotyping clinical isolates, as well as providing insights into the regulation of growth in this clinically important organism.Key words: Staphylococcus aureus, growth, urokinase, methicillin resistance.

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.

Treatment of Infection and Colonization Caused by Methicillin-Resistant Staphylococcus aureus

1991 ◽  
Vol 12 (01) ◽  
pp. 29-35 ◽  
Author(s):  
Henry F. Chambers
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Active Agent ◽  
Methicillin Resistant ◽  
Drug Of Choice ◽  
Serious Infections ◽  
Combination Regimens ◽  
Higher Doses

AbstractThe mechanism of methicillin resistance confers resistance to all available B-lactam antibiotics; consequently, B-lactam antibiotics have no role in therapy of methicillin-resistant Staphylococcus aureus (MRSA) infections. Vancomycin remains the drug of choice. Teicoplanin and daptomycin are two investigational antibiotics related to vancomycin in structure and in spectrum of activity. In clinical trials employing relatively low doses, neither was as effective as vancomycin. Trials at higher doses are on-going. Quinolones, ciprofloxacin in particular, have been used successfully to treat infections caused by MRSA; however, the usefulness of quinolones may be limited by the tendency of resistance to emerge during therapy. Quinolones probably should be used only in combination with another active agent, such as rifampin, when treating serious infections caused by MRSA. Other agents may be active in vitro against MRSA, but clinical data showing their effectiveness are lacking. Rifampin combination regimens appear most effectively to eradicate colonization with MRSA.

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