Determination of antimicrobial resistance profile and inducible clindamycin resistance of coagulase negative staphylococci in pediatric patients: the first report from Iran

Background: Currently, coagulase negative staphylococci (CoNS) have got much attention as a serious health problem especially in neonates and children. High incidence of antibiotic resistance, in particular methicillin resistance, has complicated the treatment of these organisms. The aim of this study is to determine the susceptibility to different antimicrobial agents and the prevalence of macrolides-lincosamides-streptogramins B (MLSB) resistance in CoNS isolates obtained from pediatric patients. Methods: Totally 157 CoNS isolates from various clinical samples were examined for antibiotic resistance using disk diffusion and E-test methods. Double-disk test was applied to detect constitutive and inducible MLSB resistance (cMLS(B) and iMLS(B)) phenotypes. Results: Resistance to methicillin was seen in 98(62.4%) isolates. All isolates were susceptible to vancomycin and linezolid. The prevalence of resistance to antibiotics tested was as follows: fusidic acid (n=58, 36.9%), gentamicin (n=73, 46.5%), ciprofloxacin (n=81, 51.6%), clindamycin (n=112, 71.3%), erythromycin (n=129, 82.2%) and trimethoprim/sulfamethoxazole (n=133, 84.7%). iMLS(B) phenotype was seen in 14 (8.9%) isolates, and 18 (11.5%) and 98(62.4%) isolates showed MS and cMLS(B) phenotypes, respectively. We observed that high overall antibiotic resistance rates were associated significantly with methicillin resistance. Conversely, iMLS(B) phenotype was correlated neither with methicillin resistance nor with invasiveness. Conclusion: Given the similarity observed between the prevalence of iMLS(B), and MS phenotypes, the performance of disk diffusion induction test is strongly recommended in our region.