Application Value Of Triton X-100 To Modified Hodge Test And Carbapenem Inactivation Method In The Detection Of Acinetobacter Baumannii Carbapenemase

Aim:(1)The drug resistance status of carbapenem-resistant Acinetobacter baumannii(CRAB)in our hospital was analyzed,and related carbapenemase gene and drug resistance mechanism were studied,so as to provide reference for clinical treatment and hospital infection control.(2)To compare the sensitivity and specificity before and after the addition of Triton X-100 in the modified Hodge test(MHT)and carbapenem inactivation method(CIM)for the detection of carbapenemase in Acinetobacter baumannii.Materials and Methods:(1)A total of 83 CRAB strains isolated from the clinical microbiology laboratory of the First Affiliated Hospital of Anhui Medical University during 2019 were collected.Vitek 2 Compact apparatus and K-B(Kirby–Bauer)method were used in drug susceptibility test.52 strains of carbapenemase-sensitive Acinetobacter baumannii(CSAB)were used as negative controls in the test of carbapenemase phenotype detection.(2)The carbapenemase genotypes(KPC,IMP,VIM,NDM,OXA-23,OXA-24,OXA-51,OXA-58,ISAba1/OXA-23,ISAba1/OXA-51)were detected using PCR.(3)Carbapenemase phenotypes were tested using the MHT,Triton-MHT(THT),CIM,modified CIM(m CIM),and Triton-CIM(TCIM).(4)Different concentrations(0.05%,0.1%,0.25%,and 0.5% v/v)of Triton X-100 were used in the TCIM.Results:(1)The proportion of 83 CRAB strains from ICU was the highest(59.04%),followed by neurosurgery(15.66%)and cardio-vascular surgery(6.02%).(2)The drug resistance rates of 83 CRAB strains to minocycline,tigacycline,cotrimoxazole and polymyxin B was 7.22%,7.22%,6.02% and 4.82%,respectively,which could be used as basic drug in combination.The drug resistance rate of 83 CRAB strains to amikacin was low(57.83%),and to other penicillins,carbapenems,cephalosporins and quinolones was more than 95%.(3)The positive rates of carbapenase gene in 83 CRAB strains were 100%(83/83,OXA-51),100%(83/83,OXA-23),100%(83/83,ISABA1 /OXA-23),2.4%(OXA-24),2.4%(OXA-58),2.4%(IMP-4)and 1.2%(NDM),respectively.ISAba1 /OXA-51,KPC and VIM genes were not detected.All52 CSAB strains carried OXA-51 gene,and no other carbapenemase genes were detected.(4)The sensitivity was determined to be 59.03%(MHT),100%(THT),6.02%(CIM),8.43%(mCIM),71.08%(TCIM 0.05%),100%(TCIM 0.1%),97.59%(TCIM 0.25%),and 96.38%(TCIM 0.5%),and the specificity for each of these methods was 100%.Conclusion:(1)The 83 CRAB strains showed multidrug resistance and were sensitive to minocycline,tigacycline,cotrimoxazole and polymyxin B,which could be used as the base drug of the combination.(2)The insertion of ISAba1 in OXA-23 gene is the main mechanism of resistance of Acinetobacter baumannii to carbapenems in our hospital.The single existence of OXA-51 gene does not result in resistance of Acinetobacter baumannii to imipenem and meropenem.(3)The addition of Triton X-100 while using the MHT and CIM could significantly improve the sensitivity in the detection of A.baumannii carbapenemase with a specificity of 100%.(4)A concentration of 0.1% v/v Triton X-100 showed the best results in TCIM.