Abstract
Listeria monocytogenes can persist in food production facilities, resulting in serious threats to consumers due to the high mortality associated with listeriosis, especially in the very young, old and pregnant. We subtyped 124 strains of L. monocytogenes isolated from a meat processing facility in Switzerland by serotyping, multi locus sequence typing (MLST) typing and whole genome sequencing. We then analyzed their ability to form biofilms and their resistance to the disinfectants benzalkonium chloride (BC) and peracetic acid (PAA). The genotyping results of the strains showed that several clonal populations of L. monocytogenes belonging to CC9, CC204 and CC121 had persisted in this meat processing facility for at least four years. All of the strains showed biofilm forming capacity comparable to a known high biofilm forming strain. Known efflux pumps for BC were present in CC204, CC9 (brcABC) and CC121 (qacH) strains, while strains from other CC showed very low minimal inhibitory concentrations (MICs) for BC. For PAA, minimal bactericidal concentrations of 1.2–1.6% for 20 min and minimal inhibitory concentrations between 0.1 and 0.2% were observed. These values were close to or above the recommended concentration for use (0.5–1%), suggesting that PAA might be ineffective at controlling L. monocytogenes in this and potentially other meat processing facilities.
Highlights
Listeria monocytogenes is a food-borne pathogen that causes disease mainly in vulnerable populations such as very young, old, pregnant or immunocompromised individuals
Subtyping of 124 Listeria Monocytogenes Isolated from a Swiss Meat Plant
We showed that several clonal populations of L. monocytogenes persisted in a meat processing facility in Switzerland for at least four years
Summary
Listeria monocytogenes is a food-borne pathogen that causes disease mainly in vulnerable populations such as very young, old, pregnant or immunocompromised individuals. The high mortality rate of 15–30 deaths per 100 cases of listeriosis [1,2,3,4] is mostly attributable to severe central nervous system infections, septicemia, abortions and neonatal listeriosis. In the United States alone, listeriosis is estimated to cause an annual loss of 8800 disease adjusted live years (DALY), of which the majority are premature deaths [5]. Human cases of listeriosis often trace back to food products that were contaminated during production, with subsequent growth of L. monocytogenes to high numbers. Ready-to-eat products such as salads or deli meat are of special concern due to the lack of a heating step prior to consumption. The frequent occurrence of L. monocytogenes in the environment results in a high probability of introducing the organism into facilities, either on raw materials, through equipment or via employees
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