Listeria monocytogenes is common in wild birds in Helsinki region and genotypes are frequently similar with those found along the food chain

Abstract

Aims: To evaluate the prevalence and genetic diversity of Listeria monocytogenes in wild birds and to compare the genotypes with isolates previously collected from foods and food processing environments.

Methods and results: Samples of wild birds' faeces (n = 212) were collected from a municipal landfill site and from urban areas in the Helsinki region and analysed by two-step enrichment and plating onto L. monocytogenes-selective agar. The overall prevalence of L. monocytogenes in bird faeces was 36% (95% CI 30-43%), and prevalence on the landfill site was significantly higher. All isolates were analysed with pulsed-field gel electrophoresis and compared with the L. monocytogenes profiles in an existing collection. Similar pulsotypes were found in birds and in isolates collected along the food chain.

Conclusions: Birds commonly carry L. monocytogenes, and strains are frequently similar with those detected in foods and food processing environments. Thus, birds may disseminate L. monocytogenes in nature and may also contaminate foods when entering the food processing environments and outdoor market places.

Significance and impact of the study: Populations of L. monocytogenes in wild birds and along the food processing chain overlap. Our findings add to the epidemiological data on this significant foodborne pathogen.