Global spread of carbapenem-resistant Acinetobacter baumannii

TLDR

The study used broth microdilution and Etest to determine MICs, PCR to detect carbapenemase genes, and rep‑PCR, sequence‑type multiplex PCR, and PFGE for molecular epidemiology. Imipenem non‑susceptibility in A.

Abstract

We have investigated the molecular epidemiology and distribution of carbapenemase genes in 492 imipenem-non-susceptible Acinetobacter baumannii worldwide isolates (North and Latin America, Europe, Asia, South Africa and Australia). MICs were determined by broth microdilution and Etest. The presence of carbapenemase-encoding genes was investigated by PCR. Molecular epidemiology was performed by repetitive sequence-based PCR (rep-PCR; DiversiLab), sequence-type multiplex PCR and PFGE. Imipenem non-susceptibility was associated with ISAba1 upstream of the intrinsic blaOXA-51-like or the acquired carbapenemase blaOXA-23-like, blaOXA-40-like or blaOXA-58-like. Isolates were grouped into eight distinct clusters including European clones I, II and III. European clone II was the largest (246 isolates) and most widespread group (USA, pan-Europe, Israel, Asia, Australia and South Africa). The global dissemination of eight carbapenem-resistant lineages illustrates the success this organism has had in epidemic spread. The acquired OXA enzymes are widely distributed but are not the sole carbapenem resistance determinant in A. baumannii.