Imipenem-resistant Acinetobacter baumannii carrying the ISAba1-bla(OXA-23,51) and ISAba1-bla(ADC-7) genes in Monteria, Colombia

The purpose of this study was to identify the genes coding for resistance to ceftazidime and imipenem and describe the molecular epidemiology of A. baumannii strains isolated from a clinical center in Colombia. Twenty isolates of imipenem-resistant A. baumannii from an equal number of patients with nosocomial infections were obtained. Primers were used to amplify genes bla(IMP), bla(VIM), bla(OXA-23), bla(OXA-24), bla(OXA-58), bla(OXA-51) and bla(ADC-7). To detect insertion sequences ISAba1/bla(OXA-23,) ISAba1/bla(OXA-51) and ISAba1/bla(ADC-7), mapping by PCR using combinations of reverse primers ISAba1 and reverse primers of bla(OXA-23), bla(OXA-51) and bla(ADC-7) were used. The amplification products were purified and cloned into PCR 2.1-TOPO vector and transformed into chemically competent Escherichia coli TOP10. These amplicons were then sequenced. PFGE was performed on DNA of A. baumannii isolates digested with ApaI. Results. The DNA profiles obtained included 9 clusters with, four 2–7 isolates per profile, and 5 single-isolate profiles. Of the 20 isolates resistant to imipenem, 15 carried bla(OXA-23) gene, 4 contained ISAba1 upstream of bla(OXA-51) gene, and 6 contained ISAba1 upstream of bla(OXA-23) gene. Eighteen of these isolates carried the bla(ADC-7) gene, with 9 of the isolates having ISAba1 located upstream of this gene. This is the first report of the ISAba1/ADC-7 associated with OXAs genes in A. baumannii isolates from Colombia.