Infection status and the epidemic characteristics of Haemophilus influenzae isolated from children with respiratory tract infection

Objective To investigate the infection status,epidemic characteristics and resistance to common antibiotics of Haemophilus influenzae(HI)among children subjected to respiratory tract infection in order to provide scientific evidences for preventing, alleviating and controlling HI infection in this region.MethodsHI strains were isolated from throat swabs from children subjected to respiratory tract infection. These strains were cultured and identified by conventional methods, and were biotyped based on ornithine decarboxylase, urease and indol production. The cefinase test was used to detect β-lactamase. The in vitro resistance to 13 antibiotics were determined with Kirby-Bauer diffusion method. Finally,random amplified polymorph DNA(RAPD)was usded to identify the genotype and homology of these strains.ResultsForty-nine HI strains were isolated from 128 samples of children suffering from respiratory tract infection, positive rate being 38.3%. All of the 49 HI strains were sensitive to imipenem, chloromycetin and cefaclor. The resistant rate to ampicillin was 42.9%, and 19 strains were β-lactamase positive, accounting for 38.8%. Biotypes Ⅵ and Ⅷ were the prevalent biotypes accounting for 38.8% and 36.9%, respectively.The cluster analysis using RAPD indicated that isolated stains were divided into 8 types, among which the number of the largest and major epidemic type was 15 stains, accounting for 30.6% of all isolates.ConclusionsHI can be isolated from about 40% children with respiratory tract infection in this region, and the ampicillin resistance rate is high. Major epidemic strains are Ⅵ and Ⅷ,and there is clonal propagation clone.