f Class 1 integrons in non-clonal multidrug-resistant Acinetobacter baumannii from Iran, description of the new bla _IMP-55 allele in In1243

Infections and outbreaks caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) are prevalent and have been reported worldwide over the past 20 or more years. Class 1 integron in MDR-AB plays an important role in the spread of antibiotic resistance in clinical settings. This study has been conducted to evaluate the detection of metallo-β-lactamase, characterization of class 1 integron and determination of clonal relatedness among A. baumannii hospital isolates. Sixty-five clinical isolates of MDR-AB were recovered from two Iranian hospital’s intensive care units from February to August 2013. Integrase (intI1) and bla _IMP genes were detected in 70.8 % (n=46/65) and 9.23 % (n=6/65) of the isolates using PCR assay, respectively. No other metallo-β-lactamase genes (bla _VIM, bla _SIM and bla _NDM) were detected. PCR sequencing of integron gene cassette revealed the following arrays: bla _OXA10-aacA4-bla _IMP-55-cmlA5 (as a novel array was designated In1243), aacC1 and aadA1. Analysis of bla _IMP gene revealed a new allele designated as bla _IMP-55. Gene transfer experiment by conjugation showed the 36 kb conjugative plasmid harbouring In1243. The clonal assessment by repetitive extragenic palindromic PCR demonstrated a high-degree relatedness among the strains, but strains harbouring In1243 displayed a different repetitive extragenic palindromic PCR profile. In this study, we found that a novel class 1 integron (In1243) that encoded a new bla _IMP allele resided on a transferable plasmid in non-clonal strains of MDR-AB.