Use of a novel medium, the Polymyxin Ceftazidime Oxford Medium, for isolation of Listeria monocytogenes from raw or non-pasteurized foods

Prevalence, Antibiogram and Biofilm Production of Listeria Monocytogenes from Faeces and Foetuses of Slaughtered Pregnant Cows: Environmental and Public Health Implications

The indiscriminate slaughter of pregnant animals which characterizes most developing countries poses increasing environmental and public health risks from Listeria monocytogenes infections which are endemic in such settings. The available reports show increasing trends of Listeria monocytogenes infections in both humans and animals in Nigeria. This study examined the prevalence, antibiogram and biofilm production of L. monocytogenes from faeces and foetuses of slaughtered pregnant cows in Ibadan Central Abattoir, Nigeria. Faecal (n = 118) and foetal (n = 118) swabs were cultured and isolates tested for antibiotic susceptibility by Kirby-Bauer assay, while biofilm production was quantified following the standard procedures. The data were analysed using the Chi Square and Student’s t-test at P < 0.05. Listeria monocytogenes were isolated from five (4.2 %) and three (2.5 %) faeces and foetus swabs, respectively, without significant association with sample type (P = 0.50). The isolates were resistant to all the antibiotics tested except gentamicin; with significantly higher production of biofilm by those from foetal samples (P = 0.012). The detection of widespread antibiotic-resistant L. monocytogenes from faeces and foetuses has important environmental and public health implications, given the risk of contamination through faecal shedding and foetal handling. The biofilm production by the pathogen connotes its ability to persist in the environment, suggestive of the challenging effects to its control. Campaigns against indiscriminate slaughter of pregnant animals, and proper hygiene are advocated to ultimately safeguard human and animal health.

Salmonella, Listeria monocytogenes, and Indicator Microorganisms on Hass Avocados Sold at Retail Markets in Guadalajara, Mexico

Hass avocados may become contaminated with Salmonella and Listeria monocytogenes at the farm and the packing facility or later during transportation and at retail. In Mexico, avocados are frequently sold in bulk at retail markets, where they are stored at room temperature for several hours or days and exposed to potential sources of microorganisms. These conditions may favor the entry, adhesion, survival, and biofilm formation of Salmonella and L. monocytogenes. The aim of this study was to determine the occurrence of Salmonella, L. monocytogenes, and other Listeria species and the levels of indicator microorganisms on the surface of avocados sold at retail markets. A total of 450 samples (Persea americana var. Hass) were acquired from retail markets located in Guadalajara, Mexico. One group of 225 samples was evaluated for the presence of Salmonella and for enumeration of aerobic plate counts, yeasts and molds, Enterobacteriaceae, coliforms, and Escherichia coli. The other 225 samples were processed for isolation of L. monocytogenes and other Listeria species. Microbial counts (log CFU per avocado) were 4.3 to 9.0 for aerobic plate counts, 3.3 to 7.1 for yeasts and molds, 3.3 to 8.2 for Enterobacteriaceae, 3.3 to 8.4 for coliforms, and 3.3 to 6.2 for E. coli. Eight samples (3.5%) were positive for Salmonella. Listeria spp. and L. monocytogenes were detected in 31 (13.8%) and 18 (8.0%) of 225 samples, respectively. Listeria innocua, Listeria welshimeri, and Listeria grayi were isolated from 7.6, 1.3, and 0.9% of samples. These results indicate that avocados may carry countable levels of microorganisms and could be a vehicle for transmission of Salmonella and L. monocytogenes.

Risk factors associated with fecal shedding of Listeria monocytogenes by dairy cows and calves

BACKGROUND

Listeria monocytogenes (LM) is an important foodborne pathogen affecting animals and humans. Listeriosis outbreaks in humans caused by consumption of unpasteurized dairy products are of serious concern.

OBJECTIVE

To determine risk factors associated with fecal shedding of LM in family dairy farms.

ANIMALS

Fecal samples were collected from cows and calves on 20 family dairy farms in 2-week intervals for a period of 1 year.

METHODS

Longitudinal study. LM was detected using qPCR. Univariate mixed effect model and multivariate analyses were performed to associate risk factors (dietary change, breed, mastitis, other diseases, antibiotic treatment, other treatments, heat index, and meteorological season) with fecal shedding of LM.

RESULTS

LM was isolated from all farms on at least 1 sampling day. The average yearly prevalence was 18.2% (98/540) and 8.4% (43/511) in cows and calves, respectively. Heat index (P = .05) and meteorological season (P = .04) affected fecal shedding of LM on a farm level. Meteorological season only influenced fecal shedding of LM in cows (P = .04), whereas heat index (P = .01) influenced fecal shedding of LM in calves. Spring season was identified as the major risk factor associated fecal shedding of LM on a farm level (P = .01) and in cows (P = .01). Dietary changes were associated with lower odds for fecal shedding of LM in calves (P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

Fecal shedding of LM is associated with environmental temperatures and the meteorological season. Farmers and veterinarians should use this information when implementing strategies to reduce risks for LM dissemination in animals and in the community.