MICROBIOLOGICAL CHARACTERISATION OF HAEMOPHILUS INFLUENZAE STRAINS ISOLATED FROM PATIENTS WITH INVASIVE AND RESPIRATORY DISEASES

A total of 175 H. influenzae strains were collected between 1994 and 2009 from all aged patient groups. The strains were isolated from patients with invasive and community-acquired respiratory tract infections. All strains were identified according to standard microbiological methods. Serotyping was done by a coagglutination test and by molecular PCR capsular genotyping. Beta-lactamase production was determined by the chromogenic cephalosporin test with nitrocephin as substrate. Most of the isolated H. influenzae strains were from children under 5 years of age (57.7%). Overall, 61 strains belonged to serotype b (34.9%) by the means of PCR capsular typing, 1 strain was type f, and 113 isolates (64.6%) were non-typeable (non-encapsulated) H. influenzae. Among the infants and children with meningitis or other invasive infections, aged 2 month to 5 years, all strains, except one, were serotype b. In respiratory tract infections (pneumonia, otitis media, sinusitis and people with chronic pulmonary diseases- exacerbations of COPD, bronchiectasis, cystic fibrosis) the most common- 96.5 % were non-typeable strains in both groups children and adults. Overall, the prevalence of beta-lactamase production was 19.4%. But, it was much higher for invasive strains from CSF isolates-37.7%, 25 % in blood samples, and 37.5 % in otitis media causative strains. Beta-lactamase production was less frequent in respiratory tract isolates- in sputum 13.3 % and in URT samples- 2.3%. The rate of beta-lactamase production in CSF isolates has not changed for the last 10 years. PCR capsular genotyping method has to be performed for all non-b-type strains. The implementation of Hib vaccine in our country will be accompanied by a reduction in invasive diseases caused by H. influenzae type b in children, but it is not useful in preventing infections caused by non-typeable H. influenzae strains. Key words: H. influenzae, capsular genotyping, non-typeable H. influenzae, beta-lactamas