In vitro resistance rates of Streptococcus pneumoniae and Haemophilus influenzae clinical isolates to the antibiotics used in therapy

Streptococcus pneumoniae and Haemophilus influenzae which cause infections with high morbidity and mortality all over the world, are also the most important bacterial pathogens of community-acquired pneumoniae. In recent years S.pneumoniae is becoming increasingly resistant to a variety of antibiotics. The aim of this study was to detect the in vitro resistance rates of S.pneumoniae and H.influenzae strains isolated from different clinical samples to the antibiotics which are used in the therapy of infections due to these pathogens. Between the period of January 2005 to May 2006, 77 S.pneumoniae (44 sputum, 20 blood, 8 bronchoalveolar lavage, 4 pleural fluids and 1 tracheal aspirate isolate) and 31 H.influenzae (30 sputum and 1 bronchoalveolar lavage isolate) strains isolated from patients who were admitted to Baskent University Hospital, Research and Practice Center of Adana (located in southern Turkey), were included to the study. The antibiotic susceptibility tests were performed by disc diffusion method according to CLSI (Clinical and Laboratory Standards Institute; M100-S13) guidelines. The MIC values of S.pneumoniae which gave an inhibition zone diameter of >= 19 mm in with disc diffusion test, were detected by E-test (AB Biodisk, Sweden). Intermediate and high resistance rates of pneumococci to penicilin were found as 38.9% (30/77) and 10.4% (8/77), respectively, with a total resistance rate of 49.4%. Trimethoprim-sulphamethoxazole (TMP/SMX), erithromycin, tetracyclin, clindamycin and chloramphenicol were the other antibiotics which followed penicillin with the resistance rates of 42.8%, 37.6%, 31.1%, 23.3% and 10.3%, respectively. Amongst H.influenzae strains, one (3.2%) was found to be a beta-lactamase producer and it was resistant to both ampicillin and azitromycin. Eight (25.8%) of H.influenzae isolates were resistant to TMP/SMX, and two (6.4%) were resistant to chloramphenicol. As a result, the high penicilin and erithromycin resistance rates of S.pneumoniae clinical isolates in our hospital emphasize that the empirical use of these antibiotics should be limited and well-controlled in our region.