Serotyping strains of Haemophilus influenzae isolated from clinical specimens and investigating their susceptibilities towards certain antimicrobials

Abstract

Aim: Haemophilus influenzae is an agent of severe pediatric infections, and a significant cause of mortality and morbidity in children. Its capsulated strains are grouped from ‘a’ to ‘f’ in six groups, the most invasive among which is Type B. The other serotypes are also capable of causing severe infections and invasive diseases. Antibiotic sensitivity testing proves to be useful in directing course of treatment in view of the beta-lactamase-negative and ampicillin-resistant strains as well as the ever-increasing production of beta-lactamase. In this study it has been aimed to serotype Haemophilus influenzae strains isolated from various clinical specimens, and to investigate their status of beta-lactamase production and susceptibilities towards antimicrobials. Materials and Methods: 100 samples of H. influenzae proliferating in various clinical specimens were included in the study. The bacteria were identified according to their requirements of X and V factors, or through the usage of API NH. Detection of beta-lactamase production was made with nitrocefin disks. Serotyping was performed via slide agglutination method with specific antiserums. Susceptibilities towards various antimicrobials were specified with gradient test in Haemophilus Test Medium. Results: 59 of the specimens were sputum, 23 were nasotracheal aspirates, 3 were bronchoalveolar lavages, 7 were middle ear fluids, 3 were cerebrospinal fluids, 2 were eye fluids, 2 were pleural fluids, and 1 was a blood sample. The ranking was made without keeping age groups in regard and turned out as a>b>d>THi>c>e. Serotype f was not found among the strains. Type b was isolated from all of sterile body cavity fluids. Beta-lactamase positivity was found as 2% and the BLNAR ratio was found as 2%. All were found as susceptible towards cefotaxime and siprofloxacin while 66.6% were susceptible towards azithromycin, and 93% were susceptible towards TMP-SMX. Conclusion: It will be appropriate to perform standardized susceptibility tests in routine in order to monitor antimicrobial resistance. Serotyping is important as inclusion of H. influenzae type b in vaccination programs may cause an increase in infections with non-Hib isolates.