Genotypic and phenotypic identification of aeromonas species and carbapenem resistance in Queensland, Australia

Abstract

Aims This study defines the population of Aeromonas spp. in Queensland and carbapenem resistance due to carbapenemase production, CphA. Phenotypic tests were correlated with the presence of the cphA gene. Methods Isolates from blood (22), wound (46), sterile sites (11), stool (18), eye (2) and sputum (1) were characterised by rpoB and gyrB sequencing. Disc diffusion and meropenem E-test MIC were determined. Carbapenemase production was assessed by Carba NP test and cphA by PCR. Results Isolates identified as A. dhakensis (39), A. veronii (21), A. hydrophila (20), A. caviae (14), A. jandaei (4), A. bestiarum (1), and A. sanarellii (1). Disc diffusion and E-test failed to demonstrate carbapenem resistance. Carba NP test performed with 97.4% sensitivity and 95.7% specificity. The cphA gene was detected in A. veronii (21; 100%), A. hydrophila (18; 90%), A. dhakensis (34; 87.2%), A. jandaei (2; 50%), A. bestiarum (1; 100%) and not A. caviae . Discussion Phylogenetic analysis revealed A. dhakensis caused majority of infection, an unrecognised pathogen in this region. Carbapenem resistance due to cphA was prevalent. The Carba NP was a reliable phenotypic test. Adequate speciation and detection of carbapenem resistance in Aeromonas spp. is essential to guide appropriate antimicrobial therapy.