The Correlation Between Carbapenem-associated Resistance Omp(CarO) And Antibiotic Resistance Of Acinetobacter Baumannii

Objective:To investigate the correlation between the expression of CarO protein and the antibiotic resistance of clinical Acinetobacter baumannii isolates to imipenem and ciprofloxacin;To explore the relationship between the structure of CarO and the antibiotic resistance of Acinetobacter baumannii.Methods:①56 of Clinical Acinetobacter baumannii isolates were collected from four hospitals in Changsha.The antimicrobial susceptibility test was carried out by means of K-B method and microdilution method;②Some clinical ciprofloxacin-sensitive strains were induced into ciprofloxacin-resistant ones by successive selection in media contained increasing concentrations of ciprofloxacin;③The CarO gene was amplified by polymerase chain reaction(PCR) and the PCR products were sequenced;④The gene expression of CarO mRNA was analyzed by real-time PCR;⑤Out membrane protein extracted from Acinetobacter baumannii isolates was analyzed by SDS-PAGE;⑥To contrast the CarO protein structure and function of the sensitive strains with ones of the resistant strains by methods of Bioinformatics.Results:①Of all the collected clinical Acinetobacter baumannii isolates in Changsha,85.7%are ciprofloxacin-resistant strains and 12.5% are imipenem-resistant strains;②Compared with clinical sensitive strains,the CarO gene coding sequences of the clinical resistant strains were very different,and the expression of CarO mRNA and CarO protein is also significantly dissimilar,the same situation happend after inducing some clinical sensitive strains into ciprofloxacin-resistant strains;③Comparing the resistant strains with the sensitive strains by methods of Bioinformatics,amino acid mutations occurred in the extracellular region even more;④There is one more protein kinase C phosphorylation site in the number of 177 in CarO protein amino acid sequences of the resistant strains than in ones of the sensitive strains,it should be proved that this situation relates with bacterial resistance;⑤There may be some difference between the inside hydrogen bond network of the resistant strains and one of the sensitive strains.Conclusions:①The collected clinical Acinetobacter baumannii isolates were more seriously resistable to Ciprofloxacin than to Imipenem;②The antibiotic resistance of clinical Acinetobacter baumannii isolates may be associated with the decline of CarO protein expression;③There is some relationship between CarO protein and ciprofloxacin-resistant Acinetobacter baumannii strains,it proves that CarO protein supports bacteria on multi-drug resistance;④CarO protein may be related to cell signalling;⑤The difference in CarO protein functional sites and structure between the sensitive strains and the resistant strains may be related to bacterial resistance.