[The rate of inducible clindamycin resistance and susceptibilities to other antimicrobial agents in staphylococci].

Staphylococci are one of the most common pathogens isolated from nosocomial and community acquired infections. Antibiotics used by oral route such as erythromycin, clindamycin, trimethoprim-sulphamethoxazole (TMP-SMX) and quinolones are of value especially in the treatment of community acquired infections and resistance to those antibiotics may lead to therapeutic failure. Therefore in this study, susceptibility of staphylococci to TMP-SMX, rifampin, tetracycline, gentamicin, ciprofloxacin and vancomycin and the presence of inducible clindamycin resistance were investigated in two distinct university hospitals in Turkey. A total of 286 staphylococcus strains [184 Staphylococcus aureus, 102 coagulase negative staphylococci (CoNS)] were studied. Of the 90 hospital-acquired S. aureus, 44.6% were methicillin-resistant while all of the community acquired strains were methicillin-susceptible. All of the CoNS strains were isolated from nosocomial infections and 71.6% of them were resistant to methicillin. Inducible clindamycin resistance rate of CoNS strains (34.3%) was higher than that of S. aureus strains (7.1%) and the difference was statistically significant (p= 0.00001). Positive D-test among CoNS were significantly higher in S. hominis strains (p= 0.00001). Susceptibilities of S. aureus strains to tetracycline, rifampin, ciprofloxacin, gentamicin and TMP-SMX were 56%, 59%, 56%, 56% and 99%, respectively. Susceptibilities of CoNS strains to tetracycline, rifampin, ciprofloxacin, gentamicin and TMP-SMX were 73%, 72%, 39%, 40% and 46%, respectively. None of these strains were vancomycin resistant. Differences between tetracycline, rifampin, ciprofloxacin and gentamicin resistance rates among D-test positive and negative S. aureus strains were found statistically significant. Although among CoNS isolates, no statistically significant difference was found between the resistance rates, D-test positive strains were determined to be more resistant. Differences between tetracycline, rifampin, ciprofloxacin and gentamicin resistance rates among D-test positive S. aureus and CoNS strains were found statistically significant. It can be concluded that inducible clindamycin resistance should be tested for staphylococci during routine antibiotic susceptibility testing. According to the presented data, clindamycin still can be used empirically in methicillin-susceptible S. aureus infections in our region, however, the routine use of rapid, easy, reproducible and economic D-test for the determination of inducible clindamycin resistance in erythromycin resistant strains should be considered in clinical microbiology laboratories. Inducible clindamycin resistance must be anticipated carefully while considering therapeutic options especially for CoNS infections.