Non-typable Haemophilus influenzae (NTHi) is a dominant strain causing invasive diseases in Taiwan

Abstract

To determine the relations between Haemophilus influenzae (Hi) genotypes (antibiotic resistance and active IgA1 protease) and infectious diseases, strains from infected blood, pus, sputum, bronchial washing and thorax patient samples with invasive diseases were cloned, and assayed for IgA1 protease activity and the enzymic subtype, as well as antibiotic resistance. Clinic samples of patients aged 1 to over 71 with invasive diseases of pneumonia, sinusitis, bacteremia, bronchitis, chronic obstructive of pulmonary diseases (COPD), conjunctivitis or otitis media were analyzed. Results showed that all Hi isolates contained IgA gene, but only 80% contained active IgA1 protease. Majority of Hi isolates (84%) are non-typable Haemophilus influenzae (NTHi), suggesting that NTHi had become major population in causing invasive diseases. Protease assays showed that 76% NTHi and 85% Haemophilus influenzae (THi) contained active IgA1 protease. Pulse-field agarose gel electrophoresis (PFGE) analysis showed that none of the Hi isolates had identical genome. Phenotypic comparison of bacterial strains showed a weak relation between active IgA1 protease and antibiotic resistance. Deoxyribonucleic acid (DNA) sequencing showed that mutations in silent IgA gene are common in Hi isolates. In conclusion, the antibiotic resistance and active IgA1 protease are two essential but independent phenotypes for NTHi infection and colonization. Key words: Haemophilus influenzae (Hi), IgA1 protease, invasive diseases, non-typableHaemophilus influenzae (NTHi), typable Haemophilus influenzae (THi).