PFGE analysis and class I integron-mediated resistance investigation of multidrug-resistant Acinetobacter baumannii from an intensive care unit

Objective To investigate the positive rate of class Ⅰintegron in Acinetobacter baumannii(AB) isolated from an intensive care unit(ICU),analyze the homology of multidrug-resistant AB(MDR-AB),and explore the molecular mechanisms of class I integron involved in drug resistance and the spread.Methods Forty MDR-AB isolates from the ICU between January 2008 and December 2009 were collected,drug resistance of all isolates were detected by Kirby-Bauer method,PCR and DNA sequencing were undertaken to clarify the context of gene cassette.Pulsed-field gel electrophoresis was used to analyze the homology of MDR-AB.Results ClassⅠintegron was detected in 75.00%(30/40) of all isolates,2 types of gene cassettes were identified,namely aacA4-catB8-aadA1 and aacC1-orfX-orfX-orfX'-aadA1.Forty isolates were classified into 4 distinct genotypes by PFGE analysis,26 isolates belonged to clone B that were predominant epidemic strain.Conclusion class Ⅰintegrons are widespread in MDR-AB,and spread horizontally in ICU.The epidemic of AB in ICU maybe caused by MDR-AB carrying aacA4-catB8-aadA1 cassette.