Genotypic and Antimicrobial Susceptibility of Carbapenem-resistant Acinetobacter baumannii: Analysis of ISAba Elements and blaOXA-23-like Genes Including a New Variant

• Published in: Frontiers in microbiology 2015-11, Vol.6
• Main Authors: Bahador, Abbas, Raoofian, Reza, Pourakbari, Babak, Taheri, Mohammad, Hashemizadeh, Zahra, Hashemi, Farhad B.
• Format: Article
• Language: English
• Subjects: Acinetobacter baumannii; BlaOXA-23 like gene; carbapenemases; Microbiology; novel mutations; Tehran
• ISSN: 1664-302X
• DOI: 10.3389/fmicb.2015.01249

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 IS Aba 1 and IS Aba 4. 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. IS Aba 1 and IS Aba 4 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.