ABSTRACT
This research was carried out to investigate the differences in adhesion and growth during biofilm formation of L. monocytogenes from different sources and clonal complexes. Biofilm by L. monocytogenes (isolates CLIST 441 and 7: both lineage I, serotype 1/2b, CC3; isolates 19 and 508: both lineage II, serotype 1/2c, CC9) was grown on stainless steel coupons under different stressing conditions (NaCl, curing salts and quaternary ammonium compounds-QAC), to determine the expression of different genes involved in biofilm formation and stress response. CLIST 441, which carries a premature stop codon (PMSC) in agrC, formed high-density biofilms in the presence of QAC (7.5% w/v) or curing salts (10% w/v). Reverse Transcriptase-qPCR results revealed that L. monocytogenes isolates presented differences in transcriptional profile of genes related to biofilm formation and adaptation to environmental conditions. Our results demonstrated how L. monocytogenes can survive, multiply and form biofilm under adverse conditions related to food processing environments. Differences in transcriptional expression were observed, highlighting the role of regulatory gene networks for particular serotypes under different stress responses.
Subject(s)
Bacterial Proteins/genetics , Biofilms/growth & development , Culture Media/pharmacology , Listeria monocytogenes/physiology , Stainless Steel/chemistry , Bacterial Adhesion , Bacteriological Techniques , Biofilms/drug effects , Culture Media/chemistry , Food Microbiology , Gene Expression Profiling , Gene Expression Regulation, Bacterial/drug effects , Listeria monocytogenes/drug effects , Listeria monocytogenes/genetics , Quaternary Ammonium Compounds/chemistry , Quaternary Ammonium Compounds/pharmacology , Reverse Transcriptase Polymerase Chain Reaction , Sodium Chloride/chemistry , Sodium Chloride/pharmacology , Stress, PhysiologicalABSTRACT
Listeria monocytogenes is a relevant pathogen usually associated with meat and ready-to-eat products. This study aimed to assess the distribution, adhesion, virulence and antibiotic resistance of L. monocytogenes in a pork production chain. Environment, carcass and food samples (nâ¯=â¯894) were obtained from different steps of a pork production chain over a 6-month period (10 samplings), including from farms and the slaughterhouse (reception, slaughtering, processing, storage and end products). L. monocytogenes was detected in samples from the reception (lairage floor, 1/10), slaughtering (drains, 2/20) and cutting room stages (conveyor belts in the final packing stage - 11/20, knife - 1/40, and cutting boards - 1/20). Positive results for conveyor belts were recorded in seven consecutive samplings. L. monocytogenes isolates (nâ¯=â¯87) were characterized as belonging to serogroup IVb and presented positive PCR results for inlA, inlB, inlC, inlJ, hlyA, plcA, actA and iap. Isolates were selected according to the original samples (nâ¯=â¯31) and subjected to Pulsed Field Gel Electrophoresis (PFGE), demonstrating their high clonal identity (98.4-100%). According to PFGE results and their original samples, isolates were selected (nâ¯=â¯16) and subjected to phenotypic assay to assess their adhesion potential and tested for resistance against 15 antibiotics; all tested isolates presented weak adhesion potential and were resistant to ampicillin. The present study demonstrated the persistence of L. monocytogenes in the pork processing facility, indicating the potential risk for cross-contamination with a potential virulent and resistant clone.
Subject(s)
Abattoirs , Bacterial Adhesion , Food Microbiology , Listeria monocytogenes/drug effects , Listeria monocytogenes/pathogenicity , Pork Meat/microbiology , Animals , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Brazil , Drug Resistance, Multiple, Bacterial , Farms , Listeria monocytogenes/genetics , Swine , VirulenceABSTRACT
Beef jerky is a ready-to-eat product that does not require refrigeration at the point of sale. Here, we evaluated the occurrence of Listeria monocytogenes in the production process of beef jerky, the presence of virulence genes and the genomic relatedness of the isolates, to assess the safety of the final product. The raw material, surfaces with and without contact with the product and the final product were evaluated along the beef jerky processing line. The samples were evaluated by VIDAS immunoassay system, and the L. monocytogenes isolates were confirmed and evaluated for the presence of several virulence genes by PCR. Listeria monocytogenes was identified in six of the 84 samples (7.14%), and no genetic relationship was observed among isolates. Samples of raw material (2/7), food contact surface (1/56), and work surfaces without contact with food (3/14) presented contamination by L. monocytogenes. The final product was not contaminated, demonstrating that barriers to multiplication of pathogens used during the production process were effective for its control.
ABSTRACT
The present study aimed to assess the antimicrobial resistance and the presence of virulence markers in 137 Listeria monocytogenes isolates obtained from meat-processing environments, beef products, and clinical cases. All isolates were subject to molecular serogrouping and their antibiotic resistance profiles were assessed against 12 antimicrobials. In addition, isolates were subjected to detection of virulence marker genes (inlA, inlC, inlJ). The isolates were classified into serogroups 4b, 4d, 4a, or 4c (46%), 1/2c or 3c (27%), 1/2a or 3a (13.9%), and 1/2b or 3b (13.1%). All tested isolates presented sensitivity to the majority of the tested antimicrobials, but most of them presented resistance or intermediate resistance to clindamycin (88.3%) and oxacillin (73.7%). Virulence markers were detected in all isolates, demanding further analysis to better characterize their pathogenic potential.
