分离自老年病房的鲍曼不动杆菌耐药机制初步研究*

目的:检测老年住院患者分离的鲍曼不动杆菌的主要耐药基因,并研究不同耐药基因型与耐药表型之间的对应关系。方法:用PCR方法检测分离自老年住院患者的不同标本来源的170例非重复鲍曼不动杆菌的耐药基因。检测的耐药基因包括D类碳青霉烯酶:bla_(OXA-51),bla_(OXA-23),bla_(OXA-24),bla_(OXA-58),B类金属碳青霉烯酶:bla_(VIM),bla_(IMP),bla_(SIM),bla_(GIM),bla_(DIM),bla_(NDM-1),以及A类超广谱β-内酰胺酶:blaKPC,共计11种。根据检测结果对菌株进行基因分型,并研究不同基因型与CRAB和CSAB这两种耐药表型之间的对应关系。结果:170株鲍曼不动杆菌的固有基因bla_(OXA-51)均为阳性,此外,主要检出基因为bla_(OXA-23),共124株。另外检测出blaKPC12株,bla OXA-58 6株,bla_(NDM-1)3株,bla_(SIM)2株,bla_(OXA-24)、bla_(VIM)和bla_(DIM)各1株,IMP和GIM未检出。根据检出耐药基因的不同组合,分为bla OXA-51+bla_(OXA-23)阳性为基础的A型(124株)及bla_(OXA-23)阴性为基础的B型(bla_(OXA-51),39株)、C型(bla_(OXA-51)+bla_(OXA-58),6株)、D型(bla_(OXA-51)+bla_(OXA-24),1株)共计四类基因型。从耐药表型来看,128株碳青霉烯耐药菌中有122株bla_(OXA-23)为阳性,在CRAB中占95.3%(122/128),42株碳青霉烯敏感株中,有40株bla_(OXA-23)为阴性,在CSAB中占95.2%(40/42)。结论:老年病房流行的耐碳青霉烯鲍曼不动杆菌的耐药基因型以bla_(OXA-23)阳性为主。其与鲍曼不动杆菌CRAB耐药表型、bla_(OXA-23)阴性与CSAB耐药表型之间有良好的对应关系。

The Preliminary Research on Resistance Mechanism of Acinetobacter baumannii Prevalent in Geriatric Wards*

ABSTRACT Objective: To detect the major resistance genes of A. baumannii isolated from elderly hospitalized inpatients, and to research the relationship between the resistance genotype and the drug resistant phenotype. Methods: PCR was used to detect the resistance genes of 170 non repetitive AB isolated from different specimens of elderly inpatients, and the resistant genes included the class D carbapenem enzyme: bla_OXA-51, bla_OXA-23, bla_OXA-24, bla_OXA-58, class B carbapenem enzyme: bla_VIM, bla_IMP, bla_SIM, bla_GIM, bla_DIM, bla_NDM-1, and type A extended spectrum beta lactamases: bla_KPC. Genotyping was applied according to the test results, and the corresponding relationships between different genotypes and phenotypes (including CRAB and CSAB)were investigated. Results: bla_OXA-51 was detected in all 170 isolates and bla_OXA-23 was detected in 124 isolates. The other test results were as follows: bla_KPC (12 strains), bla_OXA-58 (6 strains), bla_NDM-1 (3 strains), bla_SIM (2 strains), bla_OXA-24 (1 strains), bla_VIM(1 strains) and bla_DIM (1 strains), and bla_IMP and bla_GIM genes were not detected any more. According to the different combination of drug resistance genes, 170 strains were divided into four genotypes: type A was based on bla_OXA-51 + bla_OXA-23 (124 strains), and others were based on negative of bla_OXA-23: type B (bla_OXA-51, 39 strains), type C (bla_OXA-51 + bla_OXA-58, 6 strains), type D (bla_OXA-51 + bla_OXA-24, 1 strain). In the resistant phenotype, 122 of the 128 carbapenems resistant strains were positive for bla_OXA-23, bla_OXA-23 positive strains in CRAB accounted for 95.3% (122/128), 40 of 42 carbapenems susceptible strains were negative for bla_OXA-23, bla_OXA-23 negative strains in CSAB accounted for 95.2% (40/42). Conclusion: The resistant genotypes of carbapenem resistant AB prevalent in geriatric wards were mainly bla_OXA-23 positive. There was a good correspondence between bla_OXA-23 positive and CRAB phenotype, and correspondingly between bla_OXA-23 negative and CSAB phenotype.