ABSTRACT
Listeria monocytogenes is a pathogen frequently found in dairy products. Its control in fresh cheeses is difficult, due to the psychrotrophic properties and salt tolerance. Bacteriocinogenic lactic acid bacteria (LAB) with proven in vitro antilisterial activity can be an innovative technological approach but their application needs to be evaluated by means of in situ tests. In this study, a novel bacteriocinogenic Lactococcus lactis strain (Lc. lactis DF4Mi), isolated from raw goat milk, was tested for control of growth of L. monocytogenes in artificially contaminated fresh Minas type goat cheese during storage under refrigeration. A bacteriostatic effect was achieved, and counts after 10 days were 3 log lower than in control cheeses with no added LAB. However, this effect did not differ significantly from that obtained with a non-bacteriocinogenic Lc. lactis strain. Addition of nisin (12.5 mg/kg) caused a rapid decrease in the number of viable L. monocytogenes in the cheeses, suggesting that further studies with the purified bacteriocin DF4Mi may open new possibilities for this strain as biopreservative in dairy products.
Subject(s)
Animals , Antibiosis , Bacteriocins/metabolism , Cheese/microbiology , Goats , Lactococcus lactis/isolation & purification , Listeria monocytogenes/drug effects , Milk/microbiology , Bacterial Load , Food Preservation/methods , Food Safety/methods , Lactococcus lactis/metabolismABSTRACT
Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi) was isolated from goat milk, and studied for its antimicrobial activity. The bacteriocin presented a broad spectrum of activity, was sensitive to proteolytic enzymes, resistant to heat and pH extremes, and not affected by the presence of SDS, Tween 20, Tween 80, EDTA or NaCl. Bacteriocin production was dependent on the components of the culture media, especially nitrogen source and salts. When tested by PCR, the bacteriocin gene presented 100% homology to nisin Z gene. These properties indicate that this L. lactis subsp. lactis DF4Mi can be used for enhancement of dairy foods safety and quality.
Subject(s)
Animals , Anti-Bacterial Agents/metabolism , Bacteriocins/metabolism , Lactococcus lactis/metabolism , Milk/microbiology , Amino Acid Sequence , Anti-Bacterial Agents/chemistry , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Bacteriocins/chemistry , Bacteriocins/genetics , Culture Media/chemistry , Detergents , DNA, Bacterial/genetics , Goats , Hydrogen-Ion Concentration , Lactococcus lactis/growth & development , Molecular Sequence Data , Polymerase Chain Reaction , Protein Stability , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Sodium Chloride/metabolism , TemperatureABSTRACT
Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi) was isolated from goat milk, and studied for its probiotic potential. Lc. lactis DF4Mi was resistant to acidic pH and oxbile, presented co-aggregation with Listeria monocytogenes, and was not affected by several drugs from different generic groups, being sensitive to most tested antibiotics. These properties indicate that this Lc. lactis strain can be used for enhancement of dairy foods safety and quality, in combination with potential probiotic properties.
Subject(s)
Animals , Bacteriocins/metabolism , Goats , Lactococcus lactis/isolation & purification , Lactococcus lactis/metabolism , Milk/microbiology , Probiotics , Bacterial Adhesion , Bile/metabolism , Food Safety/methods , Hydrogen-Ion Concentration , Lactococcus lactis/drug effects , Listeria monocytogenes/physiology , Microbial Viability/drug effectsABSTRACT
Bacillus cereusis an ubiquitous, spore-forming bacteria that can survive pasteurization and the majority of the heating processes used in the dairy industry. Besides, it is a pathogen responsible for different types of food poisoning. One type of foodborne disease caused by B.cereusis the diarrheal syndrome, which is caused by the ingestion of vegetative cells producing toxins in the small intestine. One virulence factor for the diarrheal syndrome is the toxin hemolysin BL (HBL), a three-component protein formed by the L1, L2 and B components. In order to evaluate the presence of diarrheal strains isolated from milk and dairy products, 63 B. cereus isolates were obtained from 260 samples of UHT milk, pasteurized milk and powdered milk, sold in commercial establishments and from different brands. The isolates were subjected to the Polymerase Chain Reaction (PCR) for the detection of the encoding genes for the L1, L2 and B components and the toxin production capacity were evaluated with an immunoassay. A total of 23 [36.5%] isolates were identified carrying simultaneously the three tested genes, from which, 20 [86.9%] showed toxigenic capacity. 26 [41.3%] isolates did not carry any of genes tested and the other 14 [22.2%] were positive for one or two of them. The results showed a high toxigenic capacity among the B. cereus isolates able to produce the HBL, indicating a potential risk for consumers.
Subject(s)
Animals , Bacillus cereus/isolation & purification , Bacterial Proteins/analysis , Bacterial Proteins/genetics , Dairy Products/microbiology , Hemolysin Proteins/analysis , Hemolysin Proteins/genetics , Milk/microbiology , Brazil , Bacillus cereus/genetics , DNA, Bacterial/genetics , Immunoassay , Polymerase Chain ReactionABSTRACT
In recent years, an increase in the occurrence of antimicrobial resistance among Salmonella enterica has been observed in several countries, which is worrisome because S. enterica is one of the most common causes of human gastroenteritis worldwide. The aim of this study was to characterize class 1 integrons and antibiotic resistance genotypes in Salmonella enterica isolates recovered from foodstuff and related sources. Nineteen multidrug-resistant (MDR) Salmonella enterica isolates were recovered. Higher resistance rates to tetracycline (90 percent), streptomycin (80 percent), sulfamethoxazole-trimethoprim (80 percent), ampicillin (60 percent) and nalidixic acid (70 percent) were related to the presence of the tetA, aadA, sul1/sul2, blaTEM-1 genes, and a codon mutation at position 83 of the gyrA gene, respectively. Class 1 integrons harboring aadA, blaTEM-1, sul1 or dhfr1 genes were detected in nine (45 percent) Salmonella enterica strains belonging to serotypes Brandenburg, Panama, Agona, Mbandaka and Alachua. Finally, clonal dissemination of S. Panama, S. Derby and S. Mbandaka was confirmed by PFGE. Detection of clonally related MDR Salmonella enterica suggests that endemic serotypes can be supported by class 1 integron-borne gene cassettes and/or mutations in drug targets. Emergence and dissemination of multidrug-resistant Salmonella enterica can have a major public health impact in an environment where large-scale suppliers ship their products.
ABSTRACT
Salmonella is one of the most important agents of foodborne disease in Brazil and in other countries, with meat and meat products being identified as important vehicles of salmonelosis. A total of 54 Salmonella strains isolated from a commercial salami processing line were first serotyped and then their antibiotic resistance and macro restriction profiles were determined. 11.1 percent of the strains showed resistance to 3 or more antibiotics with profile AmpCStxTe being the most frequent. PFGE generated 9 and 12 profiles with enzymes XbaI and SpeI, respectively. It was observed that different serotypes of Salmonella could be found in the different steps of the processing line. The genetic profile of the strains had low relationship indicating the genetic diversity of the tested strains.
Salmonella é um dos principais agentes de enfermidades transmitidas por alimentos (ETA) no Brasil e em outros países, sendo os derivados cárneos frequentemente associados como veículos de surtos de salmonelose. Um total de 54 cepas de Salmonella sp., isoladas a partir de amostras de salame coletadas nas diferentes etapas de uma linha de produção industrial, foram sorotipadas e posteriormente caracterizadas quanto a sua sensibilidade a antimicrobianos e perfil PFGE. Entre as cepas avaliadas, 11,1 por cento apresentaram resistência a três ou mais dos antimicrobianos, sendo o perfil AmpCStxTe mais freqüente. Foram obtidos 9 e 12 perfis PFGE, empregando-se as enzimas XbaI e SpeI, respectivamente. Os perfis de ambas as enzimas foram agrupados, obtendo-se 12 perfis PFGE combinados que puderam ser separados em dois grupos empregando-se a análise de UPGMA. A linha de produção industrial de salame avaliada apresentou etapas em que há contaminação por diferentes sorotipos de Salmonella sp. Os perfis genéticos encontrados indicam origens distintas para muitas cepas estudadas, uma vez que estes foram pouco relacionados entre si.