Filters
Gene emrC Associated with Resistance to Quaternary Ammonium Compounds Is Common among Listeria monocytogenes from Meat Products and Meat Processing Plants in Poland
(1) Background: L. monocytogenes is a food pathogen of great importance, characterized by a high mortality rate. Quaternary ammonium compounds (QACs), such as benzalkonium chloride (BC), are often used as disinfectants in food processing facilities. The effectiveness of disinfection procedures is crucial to food safety. (2) Methods: A collection of 153 isolates of L. monocytogenes from meat processing industry was analyzed for their sensitivity to BC using the agar diffusion method. Genes of interest were detected with PCR. (3) Results: Genes emrC, bcrABC, and qacH were found in 64 (41.8%), 6 (3.9%), and 1 isolate (0.7%), respectively, and 79 isolates (51.6%) were classified as having reduced sensitivity to BC. A strong correlation between carrying QACs resistance-related genes and phenotype was found (p-value < 0.0001). Among 51 isolates originating from bacon (collected over 13 months), 48 had the emrC gene, which could explain their persistent presence in a processing facility. Isolates with the ilsA gene (from LIPI-3) were significantly (p-value 0.006) less likely to carry QACs resistance-related genes. (4) Conclusions: Reduced sensitivity to QACs is common among L. monocytogenes from the meat processing industry. Persistent presence of these bacteria in a processing facility is presumably caused by emrC-induced QACs resistance.
High Prevalence of Virulence-Associated Genes and Length Polymorphism in actA and inlB Genes Identified in Listeria monocytogenes Isolates from Meat Products and Meat-Processing Environments in Poland
Listeria monocytogenes is a human pathogen that has the ability to cause listeriosis, a disease with possible fatal outcomes. The typical route of infection is ingestion of the bacteria with contaminated food. In this study, 13 virulence-associated genes were examined with PCR in the genomes of 153 L. monocytogenes isolates collected from meat products and processing environments in Poland. All isolates possessed genes from LIPI-1—hly, actA, plcA, plcB and mpl—as well as four internalins: inlA, inlB, inlC, inlJ. Invasion-associated protein iap, as well as genes prfA and sigB, encoding regulatory proteins, were also detected in all isolates. Gene flaA, encoding flagellin, was detected in 113 (74%) isolates. This was the only gene that was not detected in all isolates, as its presence is serotype-dependent. Gene actA showed polymorphism with longer and shorter variants in PCR amplicons. Two isolates were characterized by truncated inlB genes, lacking 141 bp in their sequence, which was confirmed by gene sequencing. All isolates were positive in hemolysis assays, proving the synthesis of functional PrfA and Hly proteins. Four genotypes of L. monocytogenes based on actA polymorphism and two genotypes based on inlB polymorphism were distinguished within the isolates’ collection.