Study on resistant mechanism of multidrug-resistant Acinetobacter baumanniito β-lactam antibiotics

OBJECTIVE To study the resistance mechanism of multidrug-resistant Acinetobacter baumannii(MDR-AB)to β-lactam antibiotics.METHODS Twenty MDR-AB strains were isolated from inpatients from the third affiliated hospital of Sun Yat-sen university from Apr.to Aug.2009,.Drug susceptibility testing was done to detect MDR-AB to 13 kinds of antimicrobial agents by K-B disk diffusion tests.Twenty-eight genes of β-lactamase,as well as carO gene were analyzed by PCR and verified by DNA sequencing.RESULTS The genes of TEM,OXA-23 and ADC were positive,the positive rate were 100.0%,65.0%,100.0%,respectively;the others were negative.All of MDR-AB have carO gene.CONCLUSION The mechanism of MDR-AB resistant to β-lactam antibiotics was the presence of OXA-23 carbapenemase and ADC type AmpC enzyme.OXA-23 carbapenemase plays an important role in MDR-AB resistance to carbapenem,and has nothing to do with metallo-β-lactamases and the loss of porin.