Serotype Distribution and Antibiotic Resistance of Streptococcus pneumoniae Strains Isolated from the Adult Patients in a Turkish University Hospital

Infections caused by Streptococcus pneumoniae are the most important cause of morbidity and mortality worldwide. S. pneumoniae is the most common cause of community-acquired pneumonia, especially in adults. Invasive pneumococcal disease can usually occur in the elderly, children and immunocompromised individuals. Usage of the vaccines for the protection against S. pneumoniae infections, is an effective method to reduce the burden of disease in both children and adults. Serotypes frequently isolated from purified capsular polysaccharides of S. pneumoniae are used in polyvalent vaccines. Significant differences are observed between countries and regions in serotypes and antibiotic resistance of S. pneumoniae strains. For this reason, each country and region should determine their own serotypes and antibiotic resistance. The aim of this study was to determine serotype distribution, antibiotic resistance and vaccine coverage rates in S. pneumoniae strains isolated from invasive and non-invasive samples of adult patients in our hospital. A total of 100 S. pneumoniae isolates from invasive and non-invasive samples of adult patients between March 2007 and August 2014 were used in this study. S. pneumoniae strains were identified by conventional methods. Serogrouping was performed with the latex particle agglutination and serotyping was made with the conventional Quellung reaction using a commercial type-spesific antisera (Statens Serum Institute, Copenhagen, Denmark). Antibiotic susceptibility testing for penicillin G, cefotaxime and erythromycin was performed by gradient test and evaluated according to the breakpoints of Clinical and Laboratory Standards Institute (CLSI). Sixty four percent of of the S. pneumoniae strains were isolated from non-invasive and 36% were isolated from invasive samples. Serotype 3 (20%), 19F (9%), 8 (7%), 14 (7%), 23F (6%), 6A (6%) were most common determined serotypes among all strains. Among S. pneumoniae strains isolated from invasive samples serotype 3 (22%), 14 (14%), 1 (8%) and in S. pneumoniae strains isolated from non-invasive samples 3 (19%), 19F (11%), 6A (9%), 23F (8%) were the most common serotypes. Among all isolates 2% penicillin and 3% cefotaxime intermediate resistance were detected. Erythromycin resistance was detected in 25% of invasive, 37% of non-invasive strains and a total of 33% in all of the isolates. Vaccine coverage rates were found to be 68% for PCV13 and 78% for PPV23 among all isolates. In our study penicillin resistance was lower compared with the other similar studies in the world, but resistance against erythromycin was almost similar. This study is important to show that serotype 3 predominated in serious pneumococcal infections in the adult population of our hospital. For this reason, administration of routine pneumococcal vaccination program in adults and especially in the elderly is recommended. In conclusion, it is important to know the serotype distribution and antibiotic resistance of S. pneumoniae to monitor the empirical treatment in serious pneumococcal infections