Meropenem-Resistant gram negative infections among returned australian travellers - Improving local laboratory diagnosis

Abstract

<h3>Aims</h3> (1) Document the patients infected or colonised with multi-drug-resistant gram negatives at the Austin Hospital between 2011-2013, who have recently travelled; (2) determine the anti-biogram of these organisms and the mechanism of resistance; (3) optimise laboratory diagnosis of meropenem-resistant isolates (MRs) by determining the: (a) limit of detection (LOD) of chro-mogenic media (chromID ESBL, chromID Carba, Brilliance CRE), and (b) performance of the Carba-NP assay for carbape-nemase detection. <h3>Methods</h3> Susceptibility testing was done using Vitek2 and Etest. LOD was performed by serial dilution. Carba-NP and <i>bla</i>_OXA-23-like PCR was performed as previously published.^1,2 <h3>Results</h3> There were 10 patients with 17 multidrug-resistant Gram negatives - 12 of these were meropenem resistant (MRs). Resistance mechanisms for carbapenemase producers included <i>bla</i>_KPC_₂, <i>bla</i>_VIM, <i>bla</i>_{VIM_23}. The LOD for MRs was ~10×l0CFU/mL on chromogenic media for most isolates. However, Brilliance CRE failed to detect one KPC-2-producing <i>E. coli</i>. The Carba-NP assay failed to detect <i>Acinetobacter baumannii</i> containing bla_OXA_₂₃. In response to this result, a <i>bla</i>_OXA-23-like PCR was developed. <h3>Discussion</h3> There appears to be a high risk of colonisation or infection MRs in patients who are repatriated from overseas. Optimising local laboratory diagnosis of these organisms is essential in preventing outbreaks in our hospitals.