CAPSULE AND FIMBRIAE EXPRESSED BY HAEMOPHILUS INFLUENZAE ISOLATES FROM NASOPHARYNGEAL CARRIAGE IN BULGARIAN CHILDREN

H. influenzae possesses an array of important virulence factors, which are found in certain strains and give them a selective advantage. We aimed to investigate the presence of fimbriae and encapsulated and non-capsulated variants from nasopharyngeal carriage in children at the onset of upper respiratory tract infections.Methods. The capsule detection was performed by PCR for the bexA gene. All encapsulated H.influenzae were categorized into serotypes "a" to "f" by PCR-serotyping. The presence of haemagglutinating fimbriae was made by PCR for the hifA gene.Results. A total of 163 nasopharyngeal H.influenzae isolates were studied. Most of them (96.3%) were non-capsulated variants, also known as non-typeable strains (NTHi). The presence of a capsule was detected in six strains. The PCRserotyping disclosed three serotype "a" isolates, two isolates from serotype "f" and one from serotype "c". The PCR for hifA gene demonstrated 16.6% fimbriated isolates.Conclusion. NTHi is predominant in nasopharyngeal carriage among children. The fimbriae are involved in the adherence to human epithelial cells, but there is no categorical evidence that the deficiency of fimbriae may influence significantly the pathogenesis of a disease. A better molecular understanding is essential to clarify the pathogenesis of the NTHi and non-fimbriated H.influenzae isolates.