同时产DHA-1型头孢菌素酶和SHV-12型超广谱β内酰胺酶的肺炎克雷伯菌

目的研究头孢菌素酶(AmpC)和超广谱β内酰胺酶(ESBLs)在临床分离肺炎克雷伯菌中的流行、表型及其基因特性。方法先后用标准纸片扩散法、三维试验、等电聚焦、酶抑制试验以及微量稀释法等进行表型检测。然后用接合试验、多重聚合酶链反应(PCR)以及基因测序等方法进行分子生物学研究。结果受试的86株细菌中有4株三维试验阳性，等电聚焦以及酶抑制试验表明这些菌株都产一种等电点(PI)为7．8并具有AmpC性质的β内酰胺酶，基因测序表明和DHA01型AmpC酶一致；它们同时伴随产生一种PI为8．2的ESBLs，基因测序表明其来源为SHV-12。微量稀释法检测表明上述菌株不但对多种三代头孢菌素耐药，而且出现了对头孢吡肟耐药，但对碳青霉烯类抗生素仍敏感。结论本研究发现同时产DHA-1型高产AmpC酶和SHV-12型ESBLs的肺炎克雷伯菌及其耐药表型。此类菌株的出现，将为临床抗感染治疗带来新的困难。

DHA-1 type cephalosporinase accompanied with SHV-12 prevailed in clinical isolates of Klebsiella pneumoniae

OBJECTIVE: To study the prevalence, phenotype and genotype of the AmpC and ESBLs-producing clinical isolate of Klebsiella pneumoniae. METHODS: The clinical isolates of Klebsiella pneumoniae were examined by standard disk diffusion susceptibility tests, three-dimensional methods, isoelectric focusing (IEF) and microdilution methods. The conjugation experiment, multiplex PCR and DNA sequencing methods were used for further analysis. RESULTS: Four out of a total of 86 isolates tested were shown to be highly AmpC-producing by three-dimensional method. IEF showed that these strains produced a AmpC like beta-lactamase with a PI of 7.8, and DNA sequencing showed that the gene which expressed this AmpC like beta-lactamase was identical to DHA-1, a plasmid mediated cephalosporinase gene. These strains also produced an ESBL like beta-lactamase with a PI of 8.2 and the gene which expressed this beta-lactamase was identical to SHV-12. These strains were resistant not only to most of the third generation cephalosporins, but also to cefepime. However they were still susceptible to carbapenem. CONCLUSIONS: Highly AmpC-producing DHA-1 accompanied with SHV-12 in Klebsiella pneumoniae was reported here for the first time. They result in a significant rise in antibiotic resistance, which is regarded as a great challenge for clinical antibiotic therapy.