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Published on: September 9, 2015
Relationship between agr dysfunction and reduced vancomycin susceptibility in methicillin-susceptible Staphylococcus
Esther Viedma1, Francisca Sanz, M Angeles Orellana
1Microbiology Department, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain.
The Journal of Antimicrobial Chemotherapy
|August 27, 2013
Summary
Methicillin-susceptible Staphylococcus aureus (MSSA) with reduced vancomycin susceptibility (RSV) shows decreased agr expression, particularly with the agr II genotype. This suggests agr dysfunction may contribute to increased mortality in MSSA infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Limited data exist on agr dysfunction's role in vancomycin susceptibility in methicillin-susceptible Staphylococcus aureus (MSSA).
- Understanding factors influencing vancomycin resistance in MSSA is crucial for effective treatment.
Purpose of the Study:
- To investigate the clinical and molecular epidemiology of MSSA causing bacteremia.
- To determine the relationship between reduced vancomycin susceptibility (RSV) phenotype and agr dysfunction in MSSA.
Main Methods:
- Analysis of 84 MSSA bloodstream isolates from 2010.
- Antimicrobial susceptibility testing, time-kill experiments, multilocus sequence typing, and agr genotyping.
- DNA microarray analysis of virulence factors and assessment of agr dysfunction via phenotyping and RT-PCR for RNAIII.
Main Results:
- 65.5% of MSSA isolates exhibited the RSV phenotype (MIC ≥ 1.5 mg/L).
- agr II polymorphism was more prevalent in RSV isolates (41.8% vs. 17.2%, P = 0.023).
- Higher average RNAIII gene expression levels were observed in RSV isolates, indicating greater agr dysfunction (ΔCt 4.05 ± 3.29 vs. 1.5 ± 2.11, P = 0.005).
Conclusions:
- A correlation exists between the RSV phenotype in MSSA and reduced agr expression, especially with the agr II genotype.
- Agr dysfunction may play a role in the increased mortality observed in MSSA infections.
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