AUTHOR=Bahador Abbas , Raoofian Reza , Pourakbari Babak , Taheri Mohammad , Hashemizadeh Zahra , Hashemi Farhad B. 

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

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.01249

DOI=10.3389/fmicb.2015.01249

ISSN=1664-302X

ABSTRACT=<p>Carbapenem-resistant <italic>Acinetobacter baumannii</italic> (CR-AB) causes serious nosocomial infections, especially in ICU wards of hospitals, worldwide. Expression of <italic>bla</italic><sub>OXA</sub> genes is the chief mechanism of conferring carbapenem resistance among CR-AB. Although some <italic>bla</italic><sub>OXA</sub> genes have been studied among CR-AB isolates from Iran, their <italic>bla</italic><sub>OXA-23-like</sub> 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 <italic>bla</italic><sub>OXA-23-like</sub> genes. Amplified fragment length polymorphism (AFLP) genotyping, followed by DNA sequencing of <italic>bla</italic><sub>OXA-23-like</sub> amplicons of CR-AB from each AFLP group was used to characterize their <italic>bla</italic><sub>OXA-23-like</sub> genes. We also assessed the antimicrobial susceptibility pattern of CR-AB isolates, and tested whether they harbored insertion sequences IS<italic>Aba</italic>1 and IS<italic>Aba</italic>4. Sequence comparison with reference strain <italic>A. baumannii</italic> (NCTC12156) revealed five types of mutations in <italic>bla</italic><sub>OXA-23-like</sub> genes; including one novel variant and four mutants that were already reported from China and the USA. All of the <italic>bla</italic><sub>OXA-23-like</sub> genes mutations were associated with increased minimum inhibitory concentrations (MICs) against imipenem. IS<italic>Aba</italic>1 and IS<italic>Aba</italic>4 sequences were detected upstream of <italic>bla</italic><sub>OXA-23</sub> genes in 19 and 7% of isolates, respectively. The isolation of CR-AB with new <italic>bla</italic><sub>OXA-23</sub> 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.</p>