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Genotypic and phenotypic relationships among methicillin-resistant Staphylococcus aureus from three multicentre bacteraemia studies.

Moise PA, Smyth DS, Robinson DA, El-Fawal N, McCalla C, Sakoulas G - J. Antimicrob. Chemother. (2009)

Bottom Line: The agr group II polymorphism was associated with SCCmec II (P < 0.001).One hundred percent of agr II strains were predicted to be members of clonal complex 5.Given that SCCmec IV is a marker for a community-based organism for which less prior vancomycin exposure is predicted, we conclude that prior antibiotic exposure in agr group II organisms may account for their increased vancomycin MICs.

View Article: PubMed Central - PubMed

Affiliation: University of the Pacific, Stockton, CA, USA.

ABSTRACT

Background: At a time when the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) was changing, we sought to characterize several genotypic markers and glycopeptide susceptibility features of clinical isolates from patients with bacteraemia.

Methods: One hundred and sixty-eight MRSA bloodstream isolates obtained from three multicentre clinical trials were microbiologically and genotypically characterized.

Results: All isolates were susceptible to vancomycin (MIC < or = 2 mg/L); 38% belonged to accessory gene regulator (agr) group I, 52% belonged to group II and 10% belonged to group III. Typing of the staphylococcal cassette chromosome mec (SCCmec) showed that 67% were type II and 33% were type IV. The agr group II polymorphism was associated with SCCmec II (P < 0.001). Fifty-three percent of SCCmec II and 27% of SCCmec IV isolates had vancomycin MICs > or =1 mg/L (P = 0.001). One hundred percent of agr II strains were predicted to be members of clonal complex 5. SCCmec II was the genetic marker most predictive of vancomycin MICs of > or =1 mg/L. SCCmec IV isolates were more likely to have vancomycin MICs < or =0.5 mg/L.

Conclusions: Given that SCCmec IV is a marker for a community-based organism for which less prior vancomycin exposure is predicted, we conclude that prior antibiotic exposure in agr group II organisms may account for their increased vancomycin MICs.

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Relationship between SCCmec type and vancomycin MIC values in 163 MRSA bloodstream isolates (P = 0.001).
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DKP047F2: Relationship between SCCmec type and vancomycin MIC values in 163 MRSA bloodstream isolates (P = 0.001).

Mentions: Vancomycin MICs were significantly higher among SCCmec II MRSA (P = 0.001) (Figure 2). Fifty-three percent of SCCmec II and 27% of SCCmec IV isolates had vancomycin MICs ≥1 mg/L. Statistically significant differences in vancomycin MICs were not noted between agr groups or spa types. Among the isolates showing vancomycin MICs of ≥1 mg/L, 49% were agr group II, 42% were agr group I and 33% were agr group III (P = 0.24). Thirty-nine of the 83 (47%) isolates whose spa typing predicted clonal complex 5 and 33 of 81 (41%) other clonal complex types had vancomycin MICs ≥1 mg/L (P = 0.661).


Genotypic and phenotypic relationships among methicillin-resistant Staphylococcus aureus from three multicentre bacteraemia studies.

Moise PA, Smyth DS, Robinson DA, El-Fawal N, McCalla C, Sakoulas G - J. Antimicrob. Chemother. (2009)

Relationship between SCCmec type and vancomycin MIC values in 163 MRSA bloodstream isolates (P = 0.001).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2667134&req=5

DKP047F2: Relationship between SCCmec type and vancomycin MIC values in 163 MRSA bloodstream isolates (P = 0.001).
Mentions: Vancomycin MICs were significantly higher among SCCmec II MRSA (P = 0.001) (Figure 2). Fifty-three percent of SCCmec II and 27% of SCCmec IV isolates had vancomycin MICs ≥1 mg/L. Statistically significant differences in vancomycin MICs were not noted between agr groups or spa types. Among the isolates showing vancomycin MICs of ≥1 mg/L, 49% were agr group II, 42% were agr group I and 33% were agr group III (P = 0.24). Thirty-nine of the 83 (47%) isolates whose spa typing predicted clonal complex 5 and 33 of 81 (41%) other clonal complex types had vancomycin MICs ≥1 mg/L (P = 0.661).

Bottom Line: The agr group II polymorphism was associated with SCCmec II (P < 0.001).One hundred percent of agr II strains were predicted to be members of clonal complex 5.Given that SCCmec IV is a marker for a community-based organism for which less prior vancomycin exposure is predicted, we conclude that prior antibiotic exposure in agr group II organisms may account for their increased vancomycin MICs.

View Article: PubMed Central - PubMed

Affiliation: University of the Pacific, Stockton, CA, USA.

ABSTRACT

Background: At a time when the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) was changing, we sought to characterize several genotypic markers and glycopeptide susceptibility features of clinical isolates from patients with bacteraemia.

Methods: One hundred and sixty-eight MRSA bloodstream isolates obtained from three multicentre clinical trials were microbiologically and genotypically characterized.

Results: All isolates were susceptible to vancomycin (MIC < or = 2 mg/L); 38% belonged to accessory gene regulator (agr) group I, 52% belonged to group II and 10% belonged to group III. Typing of the staphylococcal cassette chromosome mec (SCCmec) showed that 67% were type II and 33% were type IV. The agr group II polymorphism was associated with SCCmec II (P < 0.001). Fifty-three percent of SCCmec II and 27% of SCCmec IV isolates had vancomycin MICs > or =1 mg/L (P = 0.001). One hundred percent of agr II strains were predicted to be members of clonal complex 5. SCCmec II was the genetic marker most predictive of vancomycin MICs of > or =1 mg/L. SCCmec IV isolates were more likely to have vancomycin MICs < or =0.5 mg/L.

Conclusions: Given that SCCmec IV is a marker for a community-based organism for which less prior vancomycin exposure is predicted, we conclude that prior antibiotic exposure in agr group II organisms may account for their increased vancomycin MICs.

Show MeSH
Related in: MedlinePlus