Studies Of Beta-lactamase Produced By Nosocomial Multidrug-resistant Acinetobacter Baumannii

Acinetobacter baumannii is an important opportunistic pathogen with a wide distribution in the nature, the hospital environment and human skin. The isolating number of which in nonfermentative bacteria was exclusively lower than Bacillus aeruginosus. It could cause a wide range of severe infections such as catheter-associated pneumonia, septicemia, urinary system infection and meningitis in immunocompromised patients. With the increase of antimicrobial application, multidrug- resistant A. baumannii (simultaneously resistance to more than three different antibiotics such as ?-lactams, aminoglycosides and fluoroquinolones) increased rapidly year by year and frequently caused epidemic outbreak in ICU and hematopathy ward with a high mortality. The previous studies have shown that besides outer membrane permeability decrease, outer membrance protein loss and upregulation of multi-drug efflux pump, the producing ?-lactamase was the main reason of A. baumannii resistant to ?-lactam antibiotics. Since the nosocomial infections caused by multi-drug resistant A. baumannii only emerged recently, the study on the resistance mechanisms in which was still in the beginning stage, even the reports about ?-lactamase produced in A. baumannii there was a little so far. In this study, clinical isolates of A. baumannii from nosocomial infections in south-west hospital of the third military medical university collected during April to September in 2004 and, 2005 were emploied as the target of investigation. Based on the determination of the resistant spectrum of antibiotics, the gene coded ?-lactamase was analyzed by polymerase chain reaction(PCR), gene sequencing and homogenous analyzing so as to understand the ?-lactamase producing in A. baumannii. Furthermore, enzyme kinetics and the inhibitory activity of ?-lactamase AmpC were studied in one strain of A. baumannii. The study was expected to be able to provide the basis for the appropriate use of antibiotics to control the nosocomial infections of A. baumannii.The study was divided into four parts as follows:...