[Antibiotic resistance and serotype distribution of Streptococcus pneumoniae strains isolated from patients at Hacettepe University Medical Faculty]

Abstract

The emergence of penicillin and multidrug resistant pneumococci has become a global concern. In this study, the in-vitro susceptibilities of 212 Streptococcus pneumoniae strains, isolated from different clinical specimens, to penicillin, erythromycin, cefaclor, cefotaxime, vancomycin, rifampin, tetracycline, chloramphenicol and ciprofloxacine were tested by agar dilution method. Penicillin resistance and intermediate penicillin resistance were found in 7.08% and 41.51% of isolates, respectively. Overall percentages of resistance to erythromycin, cefaclor, cefotaxime, rifampin, tetracycline, chloramphenicol and ciprofloxacine were 13.7%, 17.5%, 2.3%, 2.1%, 18.9%, 2.3% and 1%, respectively. Vancomycin resistance was not detected in the tested strains. All penicillin-susceptible S. pneumoniae isolates were also found to be susceptible to cefaclor, cefotaxime, chloramphenicol and ciprofloxacine. Resistance to other antimicrobial agents was higher among the penicillin-resistant group than the penicillin-susceptible one. Although high level penicillin resistance rate was low, 41.51% of pneumococci were intermediately resistant to penicillin. These results indicated that penicillin resistant S. pneumoniae isolates might probably become a major problem in the near future. Serotyping of penicillin intermediate and resistant S. pneumoniae isolates (n:103) by the capsular swelling test (Quellung reaction) revealed serotypes 19 (n:21), 23 (n:17), 9 (n:8), 14 (n:5), 6 (n:5), 3 (n:4), 15 (n:3), 8 (n:2), 1 (n:2), 20 (n:2) and serotypes 5, 10, 33, 22, 7 and 4 as single isolates. Twenty six S. pneumoniae isolates failed to be serotyped by the antisera set used. All serotype 9 pneumococci strains were found to be multidrug-resistant. Other multidrug-resistant pneumococci strains belonged to serotypes 19, 23 and nontypable group. The serotypes detected among the penicillin intermediate and resistant pneumococci in our study, are among the serotypes covered by 23-valent and 7-valent conjugated pneumococcal vaccine, indicating the possible preventive role of the vaccine against drug-resistant pneumococcal infections.