Friday, November 16, 2012

Difference in agr Dysfunction and Reduced Vancomycin Susceptibility between MRSA Bacteremia Involving SCCmec Types IV/IVa and I-III.

Difference in agr Dysfunction and Reduced Vancomycin Susceptibility between MRSA Bacteremia Involving SCCmec Types IV/IVa and I-III.

2012

Source

Department of Infectious Diseases, Chonnam National University Medical School, Gwang-ju, Republic of Korea.

Abstract


BACKGROUND:

Dysfunction of agr, with reduced susceptibility or hetero-resistance to vancomycin, is thought to be associated with a worse outcome of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (MRSAB). However, the difference in agr dysfunction according to the SCCmec type in MRSA infection is undetermined. We compared the prevalence of agr dysfunction, reduced vancomycin susceptibility and the outcomes of SCCmec IV/IVa and I-III MRSAB.

METHODS:

The study included 307 cases of MRSAB. SCCmec types were determined by multiplex PCR. The clinical and microbiological features and outcomes of 58 SCCmec IV/IVa MRSAB were compared with those of 249 SCCmec I-III MRSAB.

RESULTS:

Compared with SCCmec I-III MRSAB, SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction, three percent versus forty three percent, vancomycin minimum inhibitory concentration (MIC) = 2 µg/mL three perecent versus fifteen percent, and hetero-resistance to vancomycin zero versus eight percent. However, the 30-day and S. aureus-related mortality in patients with SCCmec IV/IVa MRSAB were not different from those in patients with SCCmec I-III MRSAB in multivariate analyses

CONCLUSIONS:

SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction and hetero-resistance to vancomycin and a lower vancomycin MIC, compared with SCCmec I-III MRSAB. However, the outcomes of SCCmec IV/IVa MRSAB did not differ from those of SCCmec I-III MRSAB.