Serotypes of Haemophilus influenzae strains isolated from pediatric patients with respiratory tract infections

Capsular serotypes of 122 respiratory Haemophilus influenzae strains were identified utilizing antigenic examinations (Slide Agglutination Test [SAT] and counter immuno-electrophoresis [CIE]), and PCR method. Results of the two methods were compared to find disagreement. Clinical and bacteriological characteristics of encapsulated strains were analyzed. By utilizing PCR assay, 3 (2.5%) serotype b, 1 (0.8%) serotype f and 118 (96.7%) non-typeable strains were found among 122 tested strains. Discrepancy between the results of antigenic examinations and PCR assay was found in one strain. That strain gave positive results by antigenic tests with capsular type c antiserum but it was determined to be capsular type f by PCR. No serotype b(-) strain was detected. All the encapsulated strains displayed biotype I. All the serotype b strains produced beta-lactamase, but none of those was sulbactam/ampicillin and amoxicillin/clavulanic acid resistant. The serotype f strain was beta-lactamase non-producing ampicillin susceptible. The patients suffered from respiratory infections due to encapsulated strains displayed safe clinical manifestations and good clinical responses to antibiotic treatments using,beta-lactams. In pre-vaccination era, PCR is considered to be a useful method for determination of serotypes of respiratory H. influenzae, which may contribute to reducing a possibility of clonal transmission of serotype b strains among children community, which is one of the potential risk factors for pediatric invasive infections.