Study On The Drug Resistance Of Sulbactam Mediated By TEM-1 Beta-lactamase And Porin CarO In Acinetobacter Baumannii Strains From Clinical Source

Acinetobacter baumannii is a gram-negative,aerobic,non-fermentative,which is widely detected in the hospital environment.It is one of the important opportunistic pathogens of hospital infection and is resistant seriously to antibiotic.Doctors sometimes use sulbactam as one of important drugs to treat carbapene-resistant Acinetobacter baumannii infection.However,the resistant rate to sulbactam is increasing year by year,which make it more difficult to cure Acinetobacter baumannii infection disease.TEM-1 beta-lactamase and porin CarO are main mechanism of Acinetobacter baumannii resistanting to sulbactam.In the study,RT-PCR was used to detect the mRNA expression of bla_TEM-1EM-1 and carO genes.The objective of the study was to investigate the drug resistance mechanism of sulbactam mediated by TEM-1beta-lactamase and porin CarO in clinical Acinetobacter baumannii strains.Objective:To investigate the drug resistance mechanism of sulbactam mediated by TEM-1beta-lactamase and porin CarO in clinical Acinetobacter baumannii strains.Materials and methods:1?Strains and dividing groups:All Acinetobacter baumannii clinial strains were isolated from patients'sputum and urine of the Second Hospital of Tianjin Medical University.By tesing the MICs of the strains to sulbactam,the strains were divided into two groups,sensitive strains?6 strains?and insensitive strains?12 resistant strains and 6 intermediary strains?.All strains were indetified by biochemical-test.2?Antimicrobial susceptibility test:Test the clinical Acinetobacter baumannii strains'susceptibility to meropenem,imipenem,cefoperazone,ciprofloxacin,gentamicin,ampicillin by Kirby-Bauer.3?PCR:Bla_TEM-1 and carO genes were amplified by PCR to detect the positive rate of bla _TEM-1 and carO.Aplicons of bla _TEM-1 were sequenced for four strains?A3?A5?1327?C1?.Analyze the sequences by BLAST software to lerarn the bla_TEM-1 gene in detail.4?RT-PCR:Extract the total RNA of clinical Acinetobacter baumannii strains,and the bla_TEM-1 and carO genes in the two groups strains at transcriptional level were tested by quantitative real-time RT-PCR.Results:1?24 strains were isolated.Resistant rate of the sensitive strains for meropenem,imipenem,cefoperazone,ciprofloxacin,gentamicin,ampicillin were 1/6,2/6,3/6,1/6,5/6,5/6,and insensitive strains were 6/18,10/18,18/18,18/18,18/18.2?Bla_TEM-1 genes were amplified in 16 insensitive strains,and bla _TEM-1 was negative in sensitive strains;all strains had carO genes.There was no significative mutation in the 4 strains'bla_TEM-1 genes.The promoters of the strains A3,A5,1327were P4,C1 was P3.3?There was a positive correlation between the mRNA expressions of bla_TEM-1and the MICs of sulbactam.The correlation index of spearman was 0.551,P<0.05.There was no difference in the mRNA expression of carO between the two groups.Conclusion:1?The clinical strains in the study were seriously resistant to antibiotics,especially sulbactam insensitive strains.2?The main resistance mechanism of clinical Acinetobacter baumannii strains to sulbactam was high expression of bla_TEM-1 on mRNA,and the promoter may be one of the reasons of high expression of TEM-1.