Serotype Distribution and Antibiotic Susceptibilities of Clinical Streptococcus pneumoniae Strains

Abstract

Purpose: Streptococcus pneumoniae is a pathogen that cause significant mortality and morbidity in humans. In particular, bacteremia,pneumonia, meningitis and middle ear inflammation. S.pneumoniae can cause many diseases in children and adults. Recently, S.pneumoniaeis the most important cause of acute respiratory tract diseases in developing countries. Increasing antibiotic resistance in S.pneumoniae strainshas recently gained importance. The aim of our study was to investigate the antimicrobial susceptibility and distribution of pneumococcalserotypes of S.pneumoniae strains isolated in our University Hospital.Methods: In this study we evaluated 80 S.pneumoniae strains isolated from adults and children between September 2012 and September 2013.The isolates were obtained from sputum (n=56), nasal secretions (n=4), throat swabs (n=1), blood (n=9), tracheal aspirat (n=2), conjunctivalsmear (n=1), bronchoalveolar lavage (n=6), and biopsy (n=1). Seventy-six isolates were from adults and four were from children. Antibioticsusceptibility testing to penicillin were performed on Mueller-Hinton agar supplemented with 5% sheep blood by the E-test method(bioMerieux, France); erythromycin, clindamycin, vancomycin, chloramphenicol, tetracycline, ofloxacine, levofloxacin, trimethoprim/sulfamethoxazole, rifampin, linezolid, and oxacillin susceptibilities performed by disc diffusion method and 7-10-13-valent Pneumotest-Latex(Statens Serum Institude, Denmark) kit was used for serotyping.Results: A total of 39/80 isolates (48.75%) were intermediate, and 5/80 (6.25%) were resistant to penicillin according to Clinical & LaboratoryStandards Institude (CLSI) guidelines for oral penicillin. Penicillin resistance was not found for parenteral penicillin. Resistance rates oferythromycin, clindamycin, vancomycin, chloramphenicol, tetracycline, ofloxacine, levofloxacin, trimethoprim/sulfamethoxazole, rifampin,and linezolid were as 31.25%, 21.25%, 0%, 5%, 28.75%, 15%, 2.5%, 45%, 0%, and 0% respectively. The most common S.pneumoniae serotypeswere determined as serotypes 19, 6, and 23. Serotyping showed serotype 19 to be the leading serotype among the macrolide-resistant isolates,and serotype coverage of 7-10-13-valent pneumococcal vaccine was 68.75%.Conclusion: The increase in intermediate penicillin resistance in S.pneumoniae in our hospital should be monitored carefully and thedistribution of pneumococcal serotypes is similar to countries where the Pneumococcal Conjugate Vaccine (PCV) has been introduced.