ISAba825 controls the expression of the chromosomal b/aOXA-51-like and the plasmid borne blaOXA-58 gene in clinical isolates of Acinetobacter baumannii isolated from the USA

Abstract

Clin Microbiol Infect 2012; 18: E446–E451 Abstract Four non‐repetitive, clonally related (ST114), carbapenem‐resistant Acinetobacter baumannii strains isolated in the USA were examined to understand the mechanisms of carbapenem resistance including screening for the presence of an insertion sequence upstream of the blaOXA‐51‐like gene, which could be involved in the control and expression of the antibiotic‐resistance gene. We observed that the main mechanisms of carbapenem resistance were the result of the over‐expression of the blaOXA‐58‐like and the blaOXA‐65 gene, both of which had the presence of ISAba825 upstream of the genes. The importance of this element was shown by isolating plasmid‐cured isogenic strains that had lost the plasmid with the ISAba825‐blaOXA‐58‐like genes but during that same process also lost the chromosomal ISAba825 element present upstream of the blaOXA‐65 gene. A 16‐fold decrease in minimum inhibitory concentration of imipenem and an eight‐fold decrease in the minimum inhibitory concentration of meropenem were seen in the isogenic strains that lost the plasmid. The study presents the first report of ISAba825 simultaneously governing the blaOXA‐65 gene and the blaOXA‐58‐like gene expression and also highlights the importance of this element in carbapenem‐sensitive isogenic strains, which were once carbapenem resistant.

High prevalence of multidrug-resistance in Acinetobacter baumannii and dissemination of carbapenemase-encoding genes blaOXA-23-like, blaOXA-24-like and blaNDM-1 in Algiers hospitals

“…bla OXA-51-like were found associated with ISAba1 in only 10 strains, while this IS was detected in 116 (92.8%) strains and it was described as the most frequently associated with bla OXA-51-like [40] . However, other IS such as ISAba825 can provide effective promoters to bla OXA-51-like gene, contributing to carbapenem resistance [41]. Almost all detected bla OXA-23-like genes (87.3%) were found associated with ISAba1 or ISAba4, in agreement with previous studies showing the role of these sequences in overexpression of bla OXA-23-like in A. baumannii [25,27,40] .…”

The transferability of blaOXA-23 gene in multidrug-resistant Acinetobacter baumannii isolates from Saudi Arabia and Egypt

“…S1 nuclease digestion was performed followed by PFGE, to determine the location of bla OXA-23 gene (Lopes et al, 2012).…”

“…ApaI macrorestriction followed by PFGE was used to characterise the epidemiological relatedness of the isolates by technique described elsewhere (Lopes et al, 2012). The gels were stained with 0.1% SafeView solution (NBS Biologicals Ltd., Cambridgeshire, UK) and viewed using the Diversity Database software image capturing system (Bio-Rad Laboratories Ltd., UK).…”

Complete Sequence of a bla NDM-1 -Harboring Plasmid in an Acinetobacter bereziniae Clinical Strain Isolated in Argentina

“…Evidence that bla NDM-1 was located in a plasmid was first obtained by plasmid curing (14) in which HPC229 was cultured in 5 ml of LB liquid medium containing 0.2 ml of 10% SDS for 48 h at 40°C. This procedure allowed the isolation of HPC229c, which showed a marked increase in susceptibility to ␤-lactams (Table 1).…”