JACOBS MR, GOOD CE, BOZDOGAN B, PALAVECINO EL, BAJAKSOUZIAN S, APPELBAUM PC; Interscience Conference on Antimicrobial Agents and Chemotherapy (43rd: 2003: Chicago, Ill.).

Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2003 Sep 14-17; 43: abstract no. C2-87.

Case Western Reserve University, Cleveland, OH.

BACKGROUND: Common macrolide resistance mechanisms in staphylococci are ribosomal methylase encoded by erm genes (ery[R] cli[R] phenotype), and efflux pump encoded by msr genes (ery[R ]cli[S] phenotype). However, erm can be inducible, and such isolates will also have the ery[R] cli[S] phenotype with standard test methods. As clindamycin can induce expression of clindamycin resistance in vivo, isolates with the ery[R] cli[S] phenotype cannot be assumed to be cli[S]. Objective: To determine the prevalence and mechanisms of macrolide resistance in staphylococci with the ery[R] cli[S] phenotype by standard test methods. Methodology: Staphylococcus aureus and S. epidermidis with ery[R] cli[S] phenotype by NCCLS microdilution method, selected from our culture collections, were tested by the double disk diffusion method using ery and cli disks placed 5 mm apart, and determined to have inducible clindamycin resistance if growth occurred around the cli disk on the side where the ery disk was placed. The genetic mechanisms of macrolide resistance were determined by PCR on representative strains using primers known to deterct erm and msr genes. RESULTS: While most ery[R] islates were cli[R], 148 staphylococci with the ery[R] cli[S] phenotype with standard test methods were found. The double disk test showed that 117 of these isolates (105 S. aureus, 11 S. epi.) had inducible cli resistance (ind-cli[R)], and, in selected isolates, carried either ermA or ermC genes. The remaining 32 isolates (15 S. aureus, 17 S. epi.) remained cli[S] and all carried the msrA gene. CONCLUSIONS: These results show that the majority (79%) of ery[R] cli[S] phenotype isolates of staphylococci tested by standard methods have inducible cli[R], for which clindamycin should be used with caution. Laboratories should either test for inducible cli[R], or report these strains as being cli[R] or potentially cli[R]. Standard methods to detect these strains are needed.

Publication Types:

• Meeting Abstracts

Keywords:

• Anti-Bacterial Agents
• Clindamycin
• Erythromycin
• Polymerase Chain Reaction
• Staphylococcus
• Staphylococcus aureus

Other ID:

• GWAIDS0026620

UI: 102266244

From Meeting Abstracts