Isolation and Characterization of Unidentified Listeria Strains Showing Phenotypic and Genetic Similarities to a Novel Group of Listeria Species from Malaysian Pekin Ducks

A total of Five Listeria-like strains were isolated from ducks and the environment in Penang, Malaysia between 2009 and 2010. These strains were small Gram-positive rods, utilize dextrose, esculin and maltose and fitted well into the description of Listeria spp. 16S ribosomal RNA sequence analysis confirmed a close phylogenetic similarity (99 bootstrap value) to Listeria sp. 102, Listeria fleischmannii LU2006-1 and Listeriaceaec bacterium TTUM1-001 and a more distant relationship to other Listeria spp. The five Listeria-like strains also harboured the virulence-associated gene, hlyA (haemolysin gene). Plasmid DNA band sizes ranged from 2.1 -25 kb and were detected in all isolates. All the isolates were susceptible to ampicillin and nitrofurantoin, but resistant to cefotaxime nalidixic acid and tetracycline. Genotyping by amplified polymorphic deoxyribonucleic acid (RAPD), Enterobacterial Repetitive Intergenic Consensus (ERIC) and repetitive extragenic palindromic (REP) grouped the Listeria-like strains into four similar types at a coefficient of 0.63. This study draws attention to the emerging importance of foodborne pathogens and the need for monitoring changes in antibiotic resistance patterns so that efficient risk and control management strategies can be developed.