Comparison of in vitro susceptibility of Haemophilus influenzae strains to various antimicrobial drugs

Abstract

Haemophilus species are the members of the normal flora of human upper respiratory tract. Haemphilus influenzae is the prominent organism in terms of morbidity and mortality. Haemophilus spp. cause serious infections that can progress to death. The aim of this study is to determine the frequency and antimicrobial susceptibility pattern of H. influenzae strains isolated from clinical samples between 2005 and 2010. H. influenzae strains from clinical samples were identified by BBL Crystal AutoReader or Vitek 2 Compact automated system. Antibiotic susceptibility tests were performed according to the standards of CLSI for H. influenzae strains. One hundred and fifty-eight H. influenzae strains isolated from clinical samples were included in the study. H. influenzae strains were isolated most commonly from samples sent by chest diseases clinics (25.3%). It was observed that H. influenzae was isolated most commonly from lower respiratory tract samples (sputum and tracheal aspirate). In the study period, 29.1% and 13.9% of the isolates were found to be resistant to trimethoprim sulfamethoxazole and ampicillin, respectively. Antibiotic resistance rate was 3.7% for ceftazidime and no resistance was detected for meropenem, imipenem and cefuroxime. We found a statistically significant difference in the resistance to ampicillin and trimethoprim sulfamethoxazole between 2005 and 2010 (p<0.05). But, there was no significant difference in the resistance to ceftazidime, chloramphenicol, aztreonam and rifampicin over the years (p>0.05). We suggest that trimethoprim-sulfamethoxazole and ampicillin are not appropriate options for the treatment of infections caused by H. influenzae in our hospital. Second generation cephalosporins and quinolones can be used for this purpose. We suggest that determination of the frequency of H. influenzae from clinical samples and its antibiotic susceptibility pattern may produce data for epidemiological studies and guide empirical antibiotic therapy. © 2013 OMU.