bla _IMP-4 in Different Genetic Contexts in Enterobacteriaceae Isolates from Australia

Abstract

The IMP-4 metallo-␤-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.

Predictability of Phenotype in Relation to Common β-Lactam Resistance Mechanisms in Escherichia coli and Klebsiella pneumoniae

“…All E. coli (50/50) and K. pneumoniae (50/50) isolates with bla IMP also had bla TEM , aac(3)-II, and aac(6=) genes; most (76/ 100) isolates also had a qnrB gene, and 96/100 isolates had an IncL/M replicon (see Table S8A and B in the supplemental material), consistent with the expected associations of bla IMP-4 in local isolates (15). Although direct relationships between plasmid type and resistance genes were not experimentally determined, associations between other resistance genes and replicons identified in each strain by PBRT (26,27,32) were also as expected.…”

“…We selected unique clinical isolates of E. coli and K. pneumoniae collected from microbiology laboratories in Sydney between 2005 and 2013, with almost all coming from Westmead Hospital (see Tables S1 to S8 in the supplemental material). These were chosen on the basis of antimicrobial susceptibility (Phoenix automated susceptibility test NMIC-101; BD Diagnostic Systems, Sparks, MD, USA) and the presence of relevant antibiotic resistance genes, as determined by PCR for bla TEM (12), plasmid AmpC genes (13), common ESBL genes (14), and for bla IMP (15). Isolates were grouped according to the bla genes identified by multiplex PCR/reverse line blot (mPCR/RLB) (16,17): bla TEM (n ϭ 33), bla CMY-2 -like genes (n ϭ 23), bla CMY-2 -like plus bla TEM (n ϭ 18), bla DHA (n ϭ 28), bla CTX-M (n ϭ 116), or bla IMP (n ϭ 100).…”

Plasmid-Mediated Quinolone Resistance

“…qnrB1 has also been found linked to an upstream truncated orf1005 and a downstream IS26 (72,73), while the qnrB20 allele is sandwiched between an upstream IS26 and a downstream orf1005 (72). Alleles qnrB2, qnrB4, qnrB6, and qnrB10 are associated with ISCR1, usually as a single copy (73)(74)(75), but in some plasmids two copies of ISCR1surround qnrB2 (76,77). qnrB19 has been found in three genetic environments: within large plasmids associated with ISEcp1C-based transposons, in large plasmids bracketed by IS26, and in small ColE1-type plasmids (~3-kb) lacking insertion sequences in which a flanking oriT locus and Xer recombination site have been proposed to be involved in site-specific recombination (73,(78)(79)(80)(81)(82).…”

The genetic analysis of Enterobacteriaceae plasmids to provide insights into the acquisition and spread of the blaNDM gene

“…Conjugation would have to involve a plasmid type that complements the recipient strain based on their genera or possibly species, in order for the strain to retain the plasmid and particular plasmid-mediated AMR genes. Consequently this would suggest a requirement for an exchange of AMR genes between plasmid types.Chapter 6 AMR genes (39,40, 60, 62, 64,286,287), however, they will not be discussed in full here. The insights into plasmid-mediated blaNDM acquisition and spread described in this thesis raise many scientific questions and unknown avenues for further investigation.…”

“…Chapter 6 AMR genes (39,40, 60, 62, 64,286,287), however, they will not be discussed in full here. The insights into plasmid-mediated blaNDM acquisition and spread described in this thesis raise many scientific questions and unknown avenues for further investigation.…”