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

Abstract

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 blaIMP, blaVIM, blaOXA-23, blaOXA-24, blaOXA-58, blaOXA-51 and blaADC-7. To detect insertion sequences ISAba1/blaOXA-23, ISAba1/blaOXA-51 and ISAba1/blaADC-7, mapping by PCR using combinations of reverse primers ISAba1 and reverse primers of blaOXA-23, blaOXA-51 and blaADC-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 blaOXA-23 gene, 4 contained ISAba1 upstream of blaOXA-51 gene, and 6 contained ISAba1 upstream of blaOXA-23 gene. Eighteen of these isolates carried the blaADC-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.

The role of the genetic elements bla oxa and IS Aba 1 in the Acinetobacter calcoaceticus-Acinetobacter baumannii complex in carbapenem resistance in the hospital setting

“…baumannii complex. However, resistance to carbapenems has increased, thereby limiting the use of this class of antibiotics (15) . The present study demonstrated that the presence of the ISAba1 promoter sequence associated with the bla OXA-23-like gene in A. calcoaceticus-A.…”

“…Higher carbapenem hydrolysis rates have been reported to result from the acquisition of insertion sequences (ISs) that affect the expression of the bla OXA genes encoding oxacillinases (10) (11) (12) (13) (14) . These elements are the smallest and most abundant transposable elements and are capable of causing mutations and rearrangements in the genome, thereby contributing to the spread of resistance and virulence determinants in various bacterial species (15) . Different ISs have been described in the A. calcoaceticus-A.…”

“…Different ISs have been described in the A. calcoaceticus-A. baumannii complex in association with specifi c genes; these sequences play a key role in the development of carbapenem resistance (15) . Insertion sequence Acinetobacter baumannii 1 (ISAba1) belongs to the IS4 family and has been identifi ed in association with several antibiotic resistance genes in the A. calcoaceticus-A.…”

“…Insertion sequence Acinetobacter baumannii 1 (ISAba1) belongs to the IS4 family and has been identifi ed in association with several antibiotic resistance genes in the A. calcoaceticus-A. baumannii complex (14) (15) . The role of ISAba1 in increasing gene expression was demonstrated for the bla ampC gene encoding cephalosporinase and the bla OXA-23-like genes encoding an OXA that hydrolyzes carbapenems (15) .…”

“…baumannii complex (14) (15) . The role of ISAba1 in increasing gene expression was demonstrated for the bla ampC gene encoding cephalosporinase and the bla OXA-23-like genes encoding an OXA that hydrolyzes carbapenems (15) . Some studies have also linked the presence of the ISAba1 sequence upstream of the bla OXA-51-like gene to carbapenem resistance phenotypes (4) (15) .…”