Antibiotic resistance and molecular epidemiology of the beta-lactamase-producing Haemophilus influenzae isolated in Chongqing, China.

This study aimed to determine the antibiotic resistance and molecular epidemiology of Haemophilus influenzae isolated from children with acute respiratory infection in Chongqing, China. To this end, 1967 H. influenzae isolates from 2006 to 2009 were analysed regarding beta-lactamase production and antibiotic resistance. Ninety-nine beta-lactamase-producing H. influenzae isolates from 2010 were analysed for antibiotic resistance and promoter regions of blaTEM-1. beta-lactamase production was found in 35.8% (705/1967) of the strains. All ninety-nine beta-lactamase-producing strains from 2010 were of the TEM-1 type as determined by PCR but did not produce the predicted 1075bp product. According to PCR-SSCP and DNA sequencing, the promoter regions of blaTEM-1 were categorized into 6 genotypes as SSCP1 (Pdel), SSCP2 (Pa/Pb), SSCP3 (P4), SSCP4 (Prpt.b), SSCP5 (2Prpt) and SSCP6 (P3.b). The Pdel, Pa/Pb and Prpt.b were common promoters of blaTEM-1 for H. influenzae isolated from children in Chongqing. Strains with Prpt.b were more resistant to ampicillin (AMP) than strains with Pdel, Pa/Pb and P4 (p<0.05). Therefore, blaTEM-1 beta-lactamase is the main mechanism for resistance of H. influenzae to ampicillin in Chongqing. Furthermore, the Prpt.b promoters may be related to the high resistance of H. influenzae to AMP.