Inducible clindamycin resistance among methicillin- sensitive staphylococcus aureus infections in pediatric patients

Background: Staphylococcus aureus infections are a major cause of morbidity and mortality worldwide. Clindamycin is widely used in the treatment of staphylococcal infections; however, it is our impression that in the last few years, inducible clindamycin resistance (ICR) has become more prevalent. Objective: To assess the prevalence of ICR in methicillinsensitive Staphylococcus aureus (MSSA) infections among pediatric patients in Israel. Methods: We reviewed the files of children diagnosed with MSSA infections during the period January 2006 to June 2007 for full antibiogram (including the D-test for ICR), phage typing and randomly amplified polymorphic DNA. Results: Altogether, 240 MSSA isolates were recovered, mainly from wounds and abscesses. ICR was detected in 62 of 68 erythromycin-resistant/clindamycin-sensitive strains (91%); the ICR rate for the total number of isolates was 26% (62/240). Phage type analysis demonstrated that 38 of 61 ICR isolates (62%) were sensitive to group 2, compared to 42 of 172 isolates (24%) that did not express ICR (P < 0.01). On randomly amplified polymorphic DNA, phage type 2 isolates expressing ICR belonged to the same clone, which was different from ICR isolates sensitive to other phages and from isolates not expressing ICR. Conclusions: Inducible clindamycin resistance is common among methicillin-sensitive Staphylococcus aureus in Israeli children. The D-test should be performed routinely in all MSSA isolates.