Study On Resistant Mechanism Of Acinetobacter Bauannii To β-Lactam Antibiotics

ObjectTo investigate the clinical distribution and resistance of Acinetobacter baumannii in the Northern region of Sichuan province,study the features ofβ-lactamases from Acinetobacter baumannii and analyze theβ-lactamase gene, comprehend the role ofβ-lactamases in resistant formation of Acinetobacter baumannii to antibacterial drugs,and elucidate the resistant mechanism of Acinetobacter baumannii toβ-lactam antibiotics.Method1. Analyze the clinical distribution of Acinetobacter baumannii in the hospital infections;2. Determine the MIC of 16 antibacterials to 78 Acinetobacter baumannii isolated from the clinical patients by the agar plate method and analyze the antibiotic resistance and obtain the resistant strains;3. Determine the activity ofβ-lactamases from multidrug resistant Acinetobacter baumannii with CTL; detect ESBLs by KirbKirby-Bauer method and extract DNA-plasmids; take use of specificity primer to amplify plasmids DNA by PCR in order to ensure the position and categrory of gene; take DNA sequencing on PCR amplification and analyze the same origin.Result1. among 78 strains of Acinetobacter baumannii were mainly isolated from sputum specimen of patients in Intensive care unit (ICUs). All of them were sensitive to IMP,but about 1.3%,37.2%,and more than 60% showed resistance to MEP,Cefoperazone/sulbactam,and other 13 antibacterial drugs tested respectively.2. There were 38 strains to produceβ-lactamases among the 40 strains of multidrug resistant Acinetobacter baumannii detected by CTL and 9 stains with ESBLs were found by KirbKirby-Bauer method from 21 stains with highβ-lactamase activity.3. 21 strains of Acinetobacter baumannii containing plasmids with bla-TEM were detected by PCR,among which 7 strains and 14 strains still had plasmids with either bla-CTX-M, or bla-SHV.4. Plasmid DNA sequencing showed that Acinetobacter baumannii in our regions mainly carried out bla-TEM-128, and some also carried out bla-SHV and bla-CTX-M,;About 66.6% resistant strains contained more than 2β-lactamase genes.Conclusion1. The respiratory tract infection of the heavy patients is mainly caused by Acinetobacter baumannii in this region;2.The sensetivity of Acinetobacter baumannii in this region on IMP,MEP and CPE/SB is high, but more than 60% of the strains is resistant to the other antibacterials, especially cephalosporins and multidrug resistance is serious, which suggest that it is better to prescribe the carbopenemsfor the patients with multidrug resistant Acinetobacter baumannii infection.3.The main resistance mechanism of Acinetobacter baumannii toβ-lactam antibiotics is to produceβ-lactamases, and its gene categories are mainly bla-TEM-128, as well as SHV and CTX-M.