bla(IMP-4) in different genetic contexts in Enterobacteriaceae isolates from Australia

Abstract

The IMP-4 metallo-beta-lactamase, originally recognized in Acinetobacter spp. from Hong Kong, more recently appeared simultaneously in isolates of the family Enterobacteriaceae from Sydney and Melbourne, Australia. The bla(IMP-4)-qacG2-aacA4-catB3 cassette array was found in isolates from both cities, but in different wider genetic contexts and on different plasmids, suggesting movement of this array by homologous recombination.

FIG. 1.

Schematic diagram of the structures and contexts of class 1 integrons containing the bla_IMP-4 cassette in isolates from Sydney, Melbourne, and the PRC. (A) Structures related to the Sydney (Syd) MRR; (B) structures differing from the Sydney MRR. Structures are numbered to correspond to the numbers in Table 1, and strain designation/origins are shown on the left (HK, Hong Kong; GZ, Guangzhou). CSs and terminal IRs (IRi and IRt) of class 1 integrons are indicated. Insertion sequences are represented by boxes labeled with the insertion sequence number and selected genes by labeled arrows. Selected PCR products are shown as thin lines labeled with the primer pair used. Thick lines indicate matching regions, with the cassette arrays and the ISCR1-associated genes indicated. The sequences are from GenBank accession nos. AFF550415 (pCTXM-3; Enterobacteriaceae, Poland), AM234698 (Salmonella Keurmassar, Senegal), AJ971343 (pRBDHA; K. pneumoniae, France), and DQ390454 (pLEW517; E. coli).