Abstract
Although rates of listeriosis are low in comparison to other foodborne pathogenic illness, listeriosis poses a significant risk to human health as the invasive form can have a mortality rate as high as 30%. Food processors, especially those who produce ready-to-eat (RTE) products, need to be vigilant against Listeria monocytogenes, the causative pathogen of listeriosis, and as such, the occurrence of L. monocytogenes in food and in the food processing environment needs to be carefully monitored. To examine the prevalence and patterns of contamination in food processing facilities in Ireland, 48 food processors submitted 8 samples every 2 months from March 2013 to March 2014 to be analyzed for L. monocytogenes. No positive samples were detected at 38% of the processing facilities tested. Isolates found at the remaining 62% of facilities were characterized by serotyping and Pulsed Field Gel Electrophoresis (PFGE). A general L. monocytogenes prevalence of 4.6% was seen in all samples analyzed with similar rates seen in food and environmental samples. Differences in prevalence were seen across different food processors, food sectors, sampling months etc. and PFGE analysis allowed for the examination of contamination patterns and for the identification of several persistent strains. Seven of the food processing facilities tested showed contamination with persistent strains and evidence of bacterial transfer from the processing environment to food (the same pulsotype found in both) was seen in four of the food processing facilities tested.
Highlights
Mild listeriosis, an infection of the gastrointestinal tract by Listeria monocytogenes, generally presents itself with typical “food poisoning” symptoms including abdominal cramps, nausea and diarrhea
Food processors need to be vigilant against L. monocytogenes as the bacterium is ubiquitous in the environment, contamination of the food processing environment is highly likely and cross-contamination of L. monocytogenes to foods is seen to be a major route of food contamination (Pérez-Rodríguez et al, 2008)
2006 samples were analyzed for the presence of L. monocytogenes, which accounted for 1574 environmental samples and 432 food samples
Summary
An infection of the gastrointestinal tract by Listeria monocytogenes, generally presents itself with typical “food poisoning” symptoms including abdominal cramps, nausea and diarrhea. L. monocytogenes has the ability to cross the epithelial barrier of the intestinal tract to cause more serious infection throughout the body including bacteremia. It can cross the blood-tissue barrier which allows the bacteria to infect organs such as the brain or uterus, where it can cause severe life-threatening infections such as meningitis, encephalitis, spontaneous abortion, or miscarriage. Consistent identification of specific L. monocytogenes strains in food processing facilities over many years has shown that strains can persist in food processing environments. Holch et al (2013) used genome sequencing to demonstrate the persistence of two separate strains over 6 years in two different fish processing facilities and Vongkamjan et al (2013) used ribotyping to show the 11 year persistence of a L. monocytogenes strain in a smoked fish processing facility (Vongkamjan et al, 2013)
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