Antibiotic resistance of streptococcus pneumoniae and haemophilus influenzae isolated from respiratory tract specimens

Abstract

Purpose: Streptococcus pneumoniae and Haemophilus influenzae are two of the major pathogens in respiratory infections, treatment is usually started empirically. The aim of this study was to detect in vitro resistance rates of S. pneumoniae and H. influenzae strains isolated from different lower respiratory clinical samples to the antibotics which are used for therapy of infections due to these pathogens.

Material and Methods: Seventy seven S. pneumoniae and 117 H. influenzae strains, isolated from patients were included in the study. S. pneumoniae isolates which gave an inhibition zone diameter of > 20 mm for oxacillin were considered susceptible for penicilin. For the isolates which had an oxacillin zone diameter of <20 mm, MIC values of penicillin and cefotaxime were obtained by E-test method (bioMerieux, Marcy-l'Etoile, France).

Results: Of 77 S. pneumoniae isolates, 24.6 % were resistant (MIC> 2 mg/l) and 31.1 % were intermediately resistant to parenteral penicillin. Resistance rates to antibiotics were as follows: erythromycin 40 %, trimethoprim/sulphametoxazole (TMP/SMX) 54.5 % and ofloxacin 6.4%. beta-lactamases were detected in 15.6% of the H. influenzae isolates by nitrocefin positivity.

Conclusion: H. influenzae strains (8.6%) were identified as beta-lactamase negative ampicillin resistant (BLNAR) strains. Resistance rates for other antibiotics were as follows: ampicillin 28.6%, cefaclor 36.5%, cefuroxime 30.1%, clarithromycin 9.6%, cloramphenicol 7% and TMP-SMX 43.9%.