Research on Haemophilus influenzae biotypes and resistance gene in adult respiratory tract infection in Xinshao area

Objective To investigate the Haemophilus influenzae biotypes in adult respiratory tract infection in Xinshao area and the relationships between the biotypes andβ- lactamase resistance genes and the antibiotics resistance. Methods Twenty- four strains of Haemophilus influenzae isolated from adults with respiratory tract infection in the People's Hospital of Xinshao County were collected from October, 2011 to August 2013. The strains were identified by satellite tests with factor V, X and V+ X and biochemical identification cards, and their biotypes were classified. Theβ- lactamase production was detected by chromogenic cephalosporin(nitrocefin)test. The susceptibility was determined by both the Haemophilus susceptibility test card and the K- B test. The resistance genes, TEM and ROB, were detected by polymerase chain reaction(PCR). Results Seven biotypes(Ⅰ,Ⅱ,Ⅲ,Ⅴ,Ⅵ,Ⅶ,Ⅷ)were detected among the 24 strains. The main types are typeⅡ(10 strains, 41.7%)and typeⅢ(7 strains, 29.2%), and typeⅣ was not detected. TEM gene was detected in 22 strains(91.7%)and all the strains are ROB gene negative. The strains had high resistance rates to tetracycline(54.2%) and trimethoprim- sulfamethoxazole(58.3%). On the contrary, the strains were all susceptible to cefaclor, imipenem and aztreonam. Conclusions Haemophilus influenzae of biotypeⅡ andⅢ are the main epidemic biotypes that cause adult respiratory tract infection in Xinshaoarea. TEMβ- lactamase is the principal mechanism of antibiotic resistance of Haemophilus influenzae in this area. Cefaclor,imipenem and aztreonam should be the leading choices for clinical treatment forβ- lactamase production Haemophilus influenzae.