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Analysis of antibiotic resistance and resistance mechanism of Haemophilus influenzae in children with acute respiratory tract infection.

??Abstract??Objective??To investigate antibiotic resistance and mechanism of antibiotic resistance of Haemophilus influenzae ??HI?? in children with acute respiratory tract infection in Suzhou. To determine beta-lactamase genes of Haemophilus influenzae?? possible genetic mutation and the possible relationship between minimal inhibitory concentrations??MICs?? of beta-lactamases antibiotic and genetic mutation. Methods??The susceptibility of 135 clinical isolates of Haemophilus influenzae were calculated using E-tests?? and beta-lactamases of these stratins were detected. Besides?? the beta-lactamases genes were detected by net-polymerase chain reaction ??n-PCR?? followed by DNA sequencing. The sequences of drug resistance genes were compared with the published sequence in GeneBank. Results??The beta-lactamase positive rate of HI was 31.1%. The MIC90 and MIC50 of HI to ampicillin??ampicillin/sulbactam??cefaclor and chloramphenicol were??32 μg/mL??1 μg/mL??????2 μg/mL?? 0.75 μg/mL??????24 μg/mL??3 μg/mL?? and ??8 μg/mL??0.5 μg/mL?? respectively. Among the isolated 135?? TEM genes were detected in 53 HI. Beta-lactamase geneTEM was detected in 39.3%of HI??No ROB gene was detected. About 28.3% of TEM gene had been mutated. The mean minimal inhibitory concentration of beta-lactamases antibiotic in HI that had mutant TEM genes was higher than that of no-mutant TEM gene. Conclusion Ampicillin resistance in HI influenzae isolates from children in this region is challenging??The resistance mechanism of beta-lactamase antibiotics is of production beta-lactamase TEM and 28.3% of TEM gene has been mutated. The production of TEM and its mutation is one of the most important factors that leads to the high resistance to beta-lactamase antibiotics.