Characteristics and frequency of detection of fecalListeria monocytogenesshed by livestock, wildlife, and humans

Abstract

Listeria monocytogenes is a facultative intracellular pathogen that can be carried asymptomatically in various animals and can be shed in feces. We investigated the prevalence and characteristics of L. monocytogenes isolated from livestock, wildlife, and human potential sources of contamination in 2 areas in Ontario, Canada. From February 2003 to November 2005, a total of 268 fecal samples were collected from different animals. Listeria monocytogenes was isolated using selective enrichment, isolation, and confirmation procedures, and 15 samples (6%) yielded to the isolation of 84 confirmed strains. Listeria monocytogenes was isolated from livestock (beef and dairy), wildlife (deer, moose, otter, and raccoon), and human (biosolids and septic) fecal sources. Thirty-two isolates were from serovar 1/2a, 34 from serovar 1/2b, 1 from serovar 3a, and 17 from serovar 4b. Listeria monocytogenes populations were resolved into 13 EcoRI ribotypes, and 18 ApaI and 18 AscI pulsotypes, with Simpson indexes of discrimination of 0.878 and 0.907, respectively. A majority (59%) of L. monocytogenes isolates exhibited potential virulence linked to the production of a functional internalin A, which was supported by higher entry into Caco-2 cells (9.3%) than isolates producing truncated and secreted internalin A (1.3% of entry). Listeria monocytogenes fecal isolates were on average resistant to 6.4 +/- 2.5 antibiotics out of 17 tested, and potentially virulent isolates exhibited an enhanced resistance to kanamycin, gentamicin, streptomycin, and rifampicin. Livestock, wildlife, and human L. monocytogenes fecal communities exhibited overlapping but distinct populations, and some genotypes and phenotypes were similar to those previously described for surface water isolates in the same area.

Risk Factors Associated with Salmonella and Listeria monocytogenes Contamination of Produce Fields

“…Future studies may choose to measure the impact of wildlife and potential pathogen contamination by objective measures (e.g., the use of infrared cameras to detect wildlife in fields). Our study does provide quantitative data to support previous studies (2,12,19,25,32) that suggested that wildlife may be a source of pathogen contamination in fields. Furthermore, wildlife has also been suspected as the source of pathogen contamination in a number of produce-associated outbreaks (13,70,71).…”

“…Manas et al (30) determined that lettuce plants irrigated with nonpotable water had significantly higher rates of total coliforms and Salmonella contamination than lettuce irrigated with drinking water. A number of studies also have linked sporadic or repeated contamination events in produce fields to wildlife fecal deposits (21), with a variety of bacterial food-borne pathogens, including Salmonella and L. monocytogenes, regularly isolated from fecal samples collected from wildlife and domesticated animals (3,(31)(32)(33)(34)(35)(36). Salmonella can also survive in the soil for long periods of time (e.g., up to 230 days in one study [37]) when introduced by contaminated poultry or cow manure.…”

Increased In Vitro Adherence and On-Farm Persistence of Predominant and Persistent Listeria monocytogenes Strains in the Milking System

“…Wildlife and birds can be carriers of L. monocytogenes (15,22,32). A potential role of feral animals in the maintenance and/or spreading of the pathogen on the study farm cannot be ruled out, as L. monocytogenes was previously isolated from one sample of feral animal feces collected from a feed bunker in June 2004 (29).…”

“…Listeria monocytogenes has been isolated from many locations within dairy farms, including feces (32,39,40), animal drinking water (29,37,40), feeds or feed components (37,39), and milking equipment (29,30). A potential link between animal production systems and human listeriosis cases exists, as was suggested by previous studies that described the presence of L. monocytogenes ribotypes (39) or pulsed-field gel electrophoresis (PFGE) types (3,17) from farms that matched those observed for isolates from human listeriosis cases.…”

Antimicrobial Susceptibilities of Listeria monocytogenes Isolated from the Imported and the Domestic Foods in Japan

“…In Mexico, Rodas-Suarez et al researched fish and seawater and found the 2.3% (1 of 68) of isolates were GM-resistant (Rodas-Suarez, 2006). In Canada, 31.8% (14/44) of isolates from the feces of dairy cow and isolates from the feces of wildlife animals were resistant to GM (Lyautey, 2007). These indicate that the GM-resistant isolates were mainly found from dairy products, clinical specimen and seafood.…”