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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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Related in: MedlinePlus

Relationship between delta-haemolysin production (absent or present) and vancomycin MIC values for 163 MRSA bloodstream isolates (P < 0.001).
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DKP047F3: Relationship between delta-haemolysin production (absent or present) and vancomycin MIC values for 163 MRSA bloodstream isolates (P < 0.001).

Mentions: The function at the agr locus was significantly more reduced among MRSA with higher MICs within the susceptible range (Figure 3). Decreased delta-haemolysin production was noted in 86%, 66% and 36% of MRSA with vancomycin MICs of 2, 1 and ≤0.5 mg/L, respectively (P < 0.001).


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 delta-haemolysin production (absent or present) and vancomycin MIC values for 163 MRSA bloodstream isolates (P < 0.001).
© Copyright Policy
Related In: Results  -  Collection

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

DKP047F3: Relationship between delta-haemolysin production (absent or present) and vancomycin MIC values for 163 MRSA bloodstream isolates (P < 0.001).
Mentions: The function at the agr locus was significantly more reduced among MRSA with higher MICs within the susceptible range (Figure 3). Decreased delta-haemolysin production was noted in 86%, 66% and 36% of MRSA with vancomycin MICs of 2, 1 and ≤0.5 mg/L, respectively (P < 0.001).

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