Study on carriage status and typing of Haemophilus influenzae among children in Zhejiang,2007-2008

Objective To investigate the nasopharyngeal carriage status of Haemophilus influenzae (Hi) among the children less than 5 years old in Zhejiang and find out the type distribution,prevalence and variation of Hi in different surveillance areas. Methods Nasopharygeal samples were taken from 301 healthy children less than 5 years old,and 43 strains of Hi were isolated and were under biotyping,serotyping and PFGE typing along with 28 strains of Hi isolated from clinical sputum samples. Drug susceptibility test of 51 strains of Hi to 12 antibiotics were conducted by Kirby-Bauer method. The variation and homology of strains were analyzed with Bionumerics software according to PFGE patterns. Results Among 43 strains of Hi isolated from healthy children,2 were Hib strains and others were non-typable Hi (NTHi) strains. The carriage rate was 0.7% for Hib (2/301) and 13.6% for NTHi. Seven biotypes were detected among 71 strains of Hi (43+28) with biotype Ⅱ and III predominant (38.0% and 39.4%). Hi isolates were sensitive to most antibiotics (89.7%) with exception of sulphamethoxazole/trimethoprim (the resistance rate:67.2%). The positive rate of penicillinase was higher in clinically isolated samples than in healthy children's samples. Out of 28 strains of Hi isolated clinically,2 BLNAR strains (7.1%) were detected. The PFGE restriction patterns showed a wide diversity of genotypes. Conclusion Most strains of Hi isolated in Zhejiang were non-typeable and the Hib carriage rate was considerably low. This might explain the low incidence of Hib-caused meningitis in Zhejiang. In addition,the detection rate of BLNAR strain of Hi was 7.1% among the strains isolated clinically,to which close attention should be paid.