ABSTRACT
AIM: To investigate Listeria monocytogenes contamination and behaviour in naturally contaminated French cold-smoked salmon (CSS). METHOD AND RESULTS: Between 2001 and 2004, L. monocytogenes was detected in 104 of 1010 CSS packs, produced by nine French plants, with different prevalence (from 0% to 41%). The initial contamination, measured with a sensitive filtration method, was low (92% of contaminated products below 1 CFU g(-1)) and growth was limited. CONCLUSION: Growth was consistent with results of a predictive model including microbial competition. SIGNIFICANCE AND IMPACT OF THE STUDY: To be included in a quantitative risk assessment.
Subject(s)
Food Microbiology , Food Preservation , Listeria monocytogenes/growth & development , Listeria monocytogenes/isolation & purification , Salmon/microbiology , Animals , Cold Temperature , Colony Count, Microbial , Food Packaging , Risk AssessmentABSTRACT
AIMS: In order to study the transmission of Listeria monocytogenes in a poultry and a pork meat plant, we analysed the contamination by this pathogen over several months. METHODS AND RESULTS: Five hundred and two isolates of L. monocytogenes were collected and characterized by genotyping and serotyping. Thirty-seven genotypes were obtained by ApaI-restriction analysis-pulsed field gel electrophoresis (REA-PFGE) and 35 by SmaI-REA-PFGE and resulted in 50 combined genotypes. The tracing of the contamination in both plants showed that some clones were able to survive for several months. However, some other clones were found only during processing operations, were not detectable after cleaning and seemed to enter continuously into the plant. CONCLUSIONS: Some L. monocytogenes strains may persist for a long period in the plant environment. Different genotypes can be associated with poultry as well as pork meat. SIGNIFICANCE AND IMPACT OF THE STUDY: Listeria monocytogenes contamination can be due to contaminated raw materials, bacterial spread and also ineffective cleaning procedures.
Subject(s)
Food-Processing Industry , Listeria monocytogenes/classification , Listeria monocytogenes/isolation & purification , Listeriosis/epidemiology , Molecular Epidemiology , Animals , DNA Restriction Enzymes/metabolism , Deoxyribonucleases, Type II Site-Specific , Electrophoresis, Gel, Pulsed-Field , Environmental Microbiology , Food Contamination , Food Handling , Listeria monocytogenes/genetics , Listeriosis/microbiology , Listeriosis/veterinary , Meat/microbiology , Meat Products/microbiology , Poultry , Poultry Diseases/microbiology , Serotyping , Swine , Swine Diseases/microbiologyABSTRACT
1. The efficiency of the AvGard (or Assur-Rince in the USA) trisodium phosphate poultry carcase decontamination process was evaluated during both manual and industrial trials against total aerobic mesophilic count (TAMC), thermotolerant coliforms, Pseudomonas, Enterobacteriaceae, Campylobacter, Listeria monocytogenes and Salmonella. 2. The TSP treatment proved to have significant effects on the bacterial decontamination of poultry neck skin, lowering the contamination by a factor of about 10 for TAMC and of 100 for Coliform and Pseudomonas. 3. Numeration of Salmonella with an innovative miniaturised most probable number method has proved that the effect upon these micro-organisms was also close to 2 log10 reduction. 4. The effect of TSP treatment on the ecological balance of psychrotrophic bacterial flora was also investigated to study the origin of the shelf-life flora of treated carcases (Pseudomonas being reduced to the limit of detection) and to ascertain whether L. monocytogenes might gain a competitive advantage. In fact AvGard reduced the number of L. monocytogenes on poultry carcases. 5. As a consequence of the virtual elimination of the Pseudomonas usually present, Brochothrix thermosphacta became the main species responsible for putrefaction. 6. Because the growth rate of Brochothrix thermosphacta was greater than that of L. monocytogenes at refrigeration temperature, it was considered that putrefaction would occur before the emergence of large numbers of L. monocytogenes.
Subject(s)
Food Handling , Meat/microbiology , Phosphates/pharmacology , Poultry , Animals , Bacteria, Aerobic/drug effects , Bacteria, Aerobic/isolation & purification , Campylobacter/drug effects , Campylobacter/isolation & purification , Enterobacteriaceae/drug effects , Enterobacteriaceae/isolation & purification , Food Contamination/prevention & control , Listeria monocytogenes/drug effects , Listeria monocytogenes/isolation & purification , Meat/standards , Muscle, Skeletal/microbiology , Pseudomonas/drug effects , Pseudomonas/isolation & purification , Salmonella/drug effects , Salmonella/isolation & purification , Skin/microbiologyABSTRACT
During a recent outbreak of foodborne listeriosis which occurred in France in 1992, investigations were carried out in order to identify the plants associated with the production of contaminated products. These investigations were made in six 'suspect' delicatessen plants following the first epidemiological investigations, and in one 'control plant'. The first visits were made during working operations. Two hundred and seventy samples were taken ('environmental' swabs, air samples, products), with 68% of the swabs being positive for Listeria monocytogenes in raw product areas, and 33% positives in the finished product area. The epidemic phagovar was identified in a single plant preparing pork tongues in aspic. The major causes of contamination identified were contact of cooked products with soiled surfaces, cross-contamination between 'raw' and 'cooked' channels and the inadequacy of cleaning and disinfection procedures. A second visit was also made to five plants to provide validation of their cleaning and disinfection procedures. Among 112 swabs collected, 17% of the samples from raw product surfaces and 7% from finished product surfaces were found to be positive. These results suggest that cleaning and disinfection procedures were unable to eliminate sources of L. monocytogenes when not correctly applied.
