A taxonomic study was conducted to clarify the relationships of two bacterial populations belonging to the genus Weissella. A total of 39 strains originating mainly from Malaysian foods (22 strains) and clinical samples from humans (9 strains) and animals (6 strains) were analysed using a polyphasic taxonomic approach. The methods included classical phenotyping, whole-cell protein electrophoresis, 16S and 23S rDNA RFLP (ribotyping), determination of 16S rDNA sequence homologies and DNA-DNA reassociation levels. Based on the results, the strains were considered to represent two different species, Weissella confusa and a novel Weissella species, for which the name Weissella cibaria sp. nov. is proposed. Weisella confusa possessed the highest 16S rDNA sequence similarity to Weisella cibaria, but the DNA-DNA reassociation experiment showed hybridization levels below 49 % between the strains studied. The numerical analyses of Weisella confusa and Weisella cibaria strains did not reveal any specific clustering with respect to the origin of the strains. Based on whole-cell protein electrophoresis, and ClaI and HindIII ribotyping patterns, food and clinical isolates were randomly located in the two species-specific clusters obtained.
bRefrigerated food processing facilities are specific man-made niches likely to harbor cold-tolerant bacteria. To characterize this type of microbiota and study the link between processing plant and product microbiomes, we followed and compared microbiota associated with the raw materials and processing stages of a vacuum-packaged, cooked sausage product affected by a prolonged quality fluctuation with occasional spoilage manifestations during shelf life. A total of 195 samples were subjected to culturing and amplicon sequence analyses. Abundant mesophilic psychrotrophs were detected within the microbiomes throughout the different compartments of the production plant environment. However, each of the main genera of food safety and quality interest, e.g., Leuconostoc, Brochothrix, and Yersinia, had their own characteristic patterns of contamination. Bacteria from the genus Leuconostoc, commonly causing spoilage of cold-stored, modified-atmosphere-packaged foods, were detected in high abundance (up to >98%) in the sausages studied. The same operational taxonomic units (OTUs) were, however, detected in lower abundances in raw meat and emulsion (average relative abundance of 2% ؎ 5%), as well as on the processing plant surfaces (<4%). A completely different abundance profile was found for OTUs phylogenetically close to the species Yersinia pseudotuberculosis. These OTUs were detected in high abundance (up to 28%) on the processing plant surfaces but to a lesser extent (<1%) in raw meat, sausage emulsion, and sausages. The fact that Yersinia-like OTUs were found on the surfaces of a high-hygiene packaging compartment raises food safety concerns related to their resilient existence on surfaces. R efrigeration is used throughout the modern food chain to ensure the safety and quality of perishable products. Chilling has also been extended to food processing facilities to ensure that food manufacture complies with the legislative requirements governing maximum food temperature. Perishable food is usually packaged under a carbon dioxide-containing modified atmosphere to suppress bacterial growth. These modern food manufacturing practices have changed the order of prevalence of food-borne bacteria. Instead of aerobic Gram-negative bacteria, (facultatively) anaerobic Gram-positive bacteria prevail in modified-atmosphere-packaged (MAP) foods (1). In addition to refrigeration, the daily cleaning and sanitizing procedures used at the processing facilities might lead to the resilience of certain microbes and thus persistent contamination.Hygiene in a food processing facility is monitored through an internal control procedure, including hazard analysis of critical control points. The manufacturer is responsible for guaranteeing the safety and quality of its products during the shelf life set for each respective product. In routine hygiene monitoring, the microbiological quality of the raw materials, cleanliness of the surfaces, and quality of the end products are included in these internal control protocols. Bacterial contaminat...
Lactic acid bacteria are considered a major component of th e microbial population found on various types of vacuum-package d cooked sausages . Lactobacillus sake and Lactobacillus curvatu s have been shown to be common species in these products . L . sak e seems to form the predominant part of the spoilage population . Lactic acid bacterial growth on the surface of the sausage s produces undesirable sensory attributes, such as sour aroma an d taste . A specific spoilage phenomenon of commercial significance , characterized by long, stretchy, polysaccharide ropes betwee n sausages or sausage slices, has also been found . L . sake strains play a major role in this spoilage phenomenon as well . Cooking o f sausages during manufacturing destroys lactic acid bacteria on th e surface of the sausages . Sausages are recontaminated with spoilag e lactic acid bacteria mainly during the processing stages afte r cooking . During the chilling process, product contamination apparently results from exposure to airborne microorganisms . Workers and equipment are among the most likely sources of contamination during packaging and slicing . Spoilage strains originating from ra w material may spread to other areas in the production facility (i .e . , chill, slicing, and packaging rooms) via the air, workers and equipment . Decontamination methods can be used to prevent th e growth of spoilage microorganisms and to extend the shelf life o f vacuum-packaged sausages after packaging .
Seventy-eight Enterococcus faecium strains from various sources were characterized by random amplified polymorphic DNA (RAPD)-PCR, amplified fragment length polymorphism (AFLP), and pulsed-field gel electrophoresis (PFGE) analysis of SmaI restriction patterns. Two main genomic groups (I and II) were obtained in both RAPD-PCR and AFLP analyses. DNA-DNA hybridization values between representative strains of both groups demonstrated a mean DNA-DNA reassociation level of 71%. PFGE analysis revealed high genetic strain diversity within the two genomic groups. Only group I contained strains originating from human clinical samples or strains that were vancomycin-resistant or beta-hemolytic. No differentiating phenotypic features between groups I and II were found using the rapid ID 32 STREP system. The two groups could be further subdivided into, respectively, four and three subclusters in both RAPD-PCR and AFLP analyses, and a high correlation was seen between the subclusters generated by these two methods. Subclusters of group I were to some extent correlated with origin, pathogenicity, and bacteriocinogeny of the strains. Host specificity of E. faecium strains was not confirmed.
Febrile gastroenteritis in five healthy persons was associated with the consumption of vacuum-packed cold-smoked rainbow trout containingListeria monocytogenes. L. monocytogenes isolates from the incriminated fish product lot and the stool samples were all of serotype 1/2a and were indistinguishable by pulsed-field gel electrophoresis employing AscI and SmaI.
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