The distribution of carbapenem-resistant acinetobacter baumannii in older adults / 中华老年医学杂志

ABSTRACT

Objective To study the main types and their distribution of molecular typing of carbapenem-resistant Acinetobacter baumannii (CRAB)in Beijing.Methods Seventy-eight non-repeated CRAB strains were isolated and collected from patients aged over 60 years in hospitals in Beijing from 2010 to 2014.The drug susceptibilities of 11 antimicrobial agents were tested by microdilution method.A modified Hodge assay was used to preliminarily screen the carbapenemases.A multiplex PCR assay was used for detection of the carbapenemases genes:OXA-23-like,OXA-24-like,OXA-51-like,OXA-58-like,IMP-1,and VIM-2 of Acinetobacter baumannii.We also detected the insertion sequence IsAbal of OXA-23-like and OXA-51-like,and the preliminary classification of homology of carbapenem-resistant Acinetobacter baumannii (CRAB)was conducted by 3LST technique.According to the drug susceptibility,carbapenemases gene typing,3LST primary screen,and hospital distribution,22 strains were selected to conduct MLST classification.Results The test of OXA enzyme gene in 78 strains of CRAB showed that all the strains(100％)carried oxa-51-like,and 74/78 strains(94.8％)carried oxa-23-like.Additionally,all products of ISAbal-oxa-23 were positive in OXA-23-like positive strains.In the examined five β-lactamase genes,74 strains(94.8％)showed positive AmpC gene;50 strains (64.1％) showed positive TEM-1 gene;5 strains (6.4％) showed positive PER-1 gene;48 strains(61.5％)showed positive genes of TEM-1 and AmpC and 3 strains showed positive genes of TEM-1,Amp C,and PER-1.By using 3LST technique for preliminary classification,we found 74 strains were in type Ⅰ of group types belonging to the European Ⅱ cloning spectrum.Of the six ST types found in MLST classification,the ST195,ST208,ST218 and ST368 belonged to the clone complex 92(CC92);the ST103 and ST500 were two newly discovered types in Chinese population.Conclusions CC92 clone cluster is the major epidemic strain of CRAB in Beijing,which belongs to the classic European Ⅱ cloning spectrum,and its insertion sequence,Abalinduced OXA-23-like carbapenemases is the major molecular of carbapenem resistant Acinetobacter baumannii(CRAB) in Beijing.Both AmpC and TEM-type 1 β-lactamase genes are detected to be positive in most of strains.The newly discovered two types are mainly CC103 clone complex.