Abstract:

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.

Key words: children, hemophilies influenzae, minimal inhibitory concentration, beta-lactamases, drug resistance gene

摘要：

研究急性呼吸道感染患儿流感嗜血杆菌（HI）耐药及耐药机制；探讨耐β-内酰胺类抗生素耐药基因和可能的耐药基因突变以及由此可能产生的耐药性改变。方法　2007年1月至2008年12月于苏州大学附属儿童医院呼吸科住院的患儿中，符合急性呼吸道感染（ARI）的诊断标准，且深部痰培养流感嗜血杆菌阳性者共135例，采集135株流感嗜血杆菌，采用E-test进行药敏试验，头孢硝噻酚试验检测β-内酰胺酶，分析耐药现状，套式聚全酶链式反应（n-PCR）法进行β-内酰胺酶基因TEM、R0B测定；对所有n-PCR阳性产物进行序列分析，并和基因库中公布的基因序列进行比较，进一步明确耐药机制和可能的突变耐药基因。结果　31.10%的分离株产β-内酰胺酶。流感嗜血杆菌对4种抗生素的体外药敏结果依次为：氨苄西林平均最低抑菌浓度MIC90 32 μg/mL、MIC50 1 μg/mL；氨苄西林/舒巴坦MIC90 2 μg/mL、MIC50 0.75 μg/mL；头孢克洛MIC90 24 μg/mL、MIC50 3 μg/mL；氯霉素MIC90 8 μg/mL、MIC50 0.5 μg/mL。39.3%的HI检测出TEM基因，未检测出ROB基因。53株TEM基因中有15株发生突变，突变基因组β-内酰胺类抗生素MIC高于未发生突变基因组。结论　苏州地区急性呼吸道感染患儿HI对氨苄西林的耐药情况不容乐观，其耐药机制是产生TEM基因并且28.3%TEM基因发生突变，TEM基因及其突变是苏州地区β-内酰胺类抗生素耐药性增高的重要因素。

关键词: 儿童, 流感嗜血杆菌, 最低抑菌浓度, &beta, -内酰胺酶, 耐药基因