title: Genotypic and Antimicrobial Susceptibility of Carbapenem-resistant Acinetobacter baumannii: Analysis of is Aba Elements and bla OXA-23-like Genes Including a New Variant.
abstract: Carbapenem-resistant Acinetobacter baumannii (CR-AB) causes serious nosocomial infections, especially in ICU wards of hospitals, worldwide. Expression of bla OXA genes is the chief mechanism of conferring carbapenem resistance among CR-AB. Although some bla OXA genes have been studied among CR-AB isolates from Iran, their bla OXA-23-like genes have not been investigated. We used a multiplex-PCR to detect Ambler class A, B, and D carbapenemases of 85 isolates, and determined that 34 harbored bla OXA-23-like genes. Amplified fragment length polymorphism (AFLP) genotyping, followed by DNA sequencing of bla OXA-23-like amplicons of CR-AB from each AFLP group was used to characterize their bla OXA-23-like genes. We also assessed the antimicrobial susceptibility pattern of CR-AB isolates, and tested whether they harbored insertion sequences ISAba1 and ISAba4. Sequence comparison with reference strain A. baumannii (NCTC12156) revealed five types of mutations in bla OXA-23-like genes; including one novel variant and four mutants that were already reported from China and the USA. All of the bla OXA-23-like genes mutations were associated with increased minimum inhibitory concentrations (MICs) against imipenem. ISAba1 and ISAba4 sequences were detected upstream of bla OXA-23 genes in 19 and 7% of isolates, respectively. The isolation of CR-AB with new bla OXA-23 mutations including some that have been reported from the USA and China highlights CR-AB pervasive distribution, which underscores the importance of concerted national and global efforts to control the spread of CR-AB isolates worldwide.
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences Tehran, Iran.
authors.forename: Abbas
authors.initials: A
authors.lastname: Bahador
authors.affiliation: Legal Medicine Research Center, Legal Medicine Organization Tehran, Iran ; Innovative Medical Research Center, Islamic Azad University Mashhad, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Raoofian
authors.affiliation: Pediatrics Infectious Disease Research Center, School of Medicine, Tehran University of Medical Sciences Tehran, Iran.
authors.forename: Babak
authors.initials: B
authors.lastname: Pourakbari
authors.affiliation: Department of Microbiology and Virology, Shiraz University of Medical Sciences Shiraz, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Taheri
authors.affiliation: Department of Microbiology and Virology, Shiraz University of Medical Sciences Shiraz, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Hashemizadeh
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences Tehran, Iran.
authors.forename: Farhad B
authors.initials: FB
authors.lastname: Hashemi
keywords: Acinetobacter baumannii; blaOXA-23-like gene; carbapenemase; novel mutations