| Objective:To identify Acinetobacter baumannii in Acinetobacter calcoaceticus-Acinetobacter baumannii complex by genotyping;thendetect?-lactamase related resistance genes by polymerase chain reaction(PCR)to explore the distribution characteristics of ?-lactamase genes in cefoperazone/sulbactam-resistant Acinetobacter baumanniiand using MALDI-TOF MS technology homology analysis of the main drug-resistant genes co-expression patterns in key departments,to explore the epidemic characteristics of cefoperazone/sulbactam-resistant Acinetobacter baumannii in key departments and the application value of MALDI-TOF MS technology in homology research.Methods:A total of 255 strains of Acinetobacter calcoaceticus-Acinetobacter baumannii complex were preliminarily identified by VITEK 2 Compact automatic microbiological system in our hospital from January 2018 to June 2019.160 strains of Acinetobacter calcoaceticus-Acinetobacter baumannii complex resistant to cefoperazone/sulbactam were screened by instrument drug sensitivity test combined with disk agar diffusion method(K-B method)and identified by recA and ITS genotyping.The resistance genes related to ?-lactamase were detected by PCR,including Class A(ESBLs):GES and TEM;Class B(metalloenzymes):IMP,VIM and DNM;Class D(oxacillinases):OXA-51,OXA-23,OXA-24 and OXA-58.The homology of some drug-resistant Acinetobacter baumannii in Neurosurgery department and ICU were analyzed by matrix-assisted laser desorption/ionization time-flight mass spectrometry(MALDI-TOF MS),andthe cluster analysis of the co-expression patterns of drug-resistant genes OXA-51,TEM and OXA-23 were performed.Result:157 strains of Acinetobacter baumannii were identified from 160 strains of cefoperazone/sulbactam-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex by recA and ITS genotyping.Drug susceptibility analysis showed that cefoperazone/sulbactam-resistant Acinetobacter baumannii was resistant tomany conventional clinical drugs.The drug resistance rate of imipenem and ceftazidime was 99.4%,amikacin,gentamicin and tobramycin was over 70%,and minocycline was 45.2%.However,tigecycline resistance rate was only 5.7%.The detection rates of?-lactamase genes were OXA-51(100%),TEM(98.7%),OXA-23(93.6%),GES(53.5%),VIM(47.8%),IMP(17.8%),and OXA-58(16.6%),respectively.NDM and OXA-24 genes were not detected.There were 11 drug-resistance gene combinations,among which the drug-resistance gene combination A(OXA-51,TEM and OXA-23 co-expressed)was the dominant one(n=62,39.74%).23 strains of cefoperazone/sulbactam-resistant Acinetobacter baumannii from neurosurgery department were randomly selected,and MALDI-TOF MS cluster analysis was performed to form two clusters(7 strains of type ?,16 strains of type ?).Type ? was divided into four small clusters(5 strains of type ?a,4 strains of type ?b,2 strains of type?c,and 5 strains of type ?d).Compared with neurosurgery department,the homology of 28 strains from ICU was more than 65%,and greater than that in neurosurgery.Moreover,14 co-expressed strains of OXA-51,TEM and OXA-23 were randomly selected,and the same cluster was found by MALDI-TOF MS cluster analysis.Conclusion:The co-expressed pattern of ?-lactamase gene OXA-51,TEM and OXA-23 was one of the major drug-resistance mechanisms of cefoperazone/sulbactam-resistant Acinetobacter baumannii in our hospital.Cefoperazone/sulbactam-resistant Acinetobacter baumannii from neurosurgery department showed clustering distribution,and the infection mode was staged homogeneous strain spreading.However,strains from ICU were scattered and more closely related than neurosurgery.The MALDI-TOF MS is expected to become a new method for molecular epidemiological research. |
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