Bacteriocins of Gram-positive bacteria having activity spectra extending beyond closely-related species.

Bacteriocins are bacterially-produced antimicrobial peptides that have killing activity principally against other relatively closely-related bacteria. Some bacteriocins of the lactic acid bacteria (LAB) have for many years been extensively applied in food biopreservation. However, especially during the last decade, a number of reports have appeared about unanticipated extensions to the generally rather narrow anti-bacterial activity spectrum of some of the LAB bacteriocins and novel applications have been proposed for bacteriocins ranging from controlling the growth of an increasingly-heterogeneous variety of pathogens, including Gram-negative multidrug resistant bacteria, viruses, yeasts, and in particular, difficult to control Mycobacterium spp., to their potential application as anticancer agents. How best can we assess this now rapidly-accumulating stream of reports on potential future applications of bacteriocins? Where is the line between realistic, science-based proposals and highly-speculative fiction and what are the 'critical points' that might help us to draw this line? In this review, we have attempted to analyse a selection of the presently-available data concerning relatively 'unorthodox' (i.e. beyond food preservation) applications of bacteriocins, and, by utilising our set of 'critical points', we endeavour to identify essential or/and missing information that appear crucial for success of the proposed applications.

Soymilk fermentation by Enterococcus faecalis VB43 leads to reduction in the immunoreactivity of allergenic proteins ß-conglycinin (7S) and glycinin (11S).

Food allergies represent a serious problem affecting human health and soy proteins rank among the most allergenic proteins from food origin. The proteolytic enzymes produced by lactic acid bacteria (LAB) can hydrolyse the major allergens present in soybean, reducing their immunoreactivity. Many studies have reported the ability of LAB to ferment soy-based products; while the majority of them focus on the improvement of the sensory characteristics and functionality of soy proteins, a lack of information about the role of lactic fermentation in the reduction of immunoreactivity of these proteins exists. The aim of the present study was to evaluate the capability of the proteolytic strain Enterococcus faecalis VB43 to hydrolyse the main allergenic proteins present in soymilk and to determine the immunoreactivity of the obtained hydrolysates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) results of fermented soymilk demonstrated complete hydrolysis of the ß-subunit from ß-conglycinin and the acidic polypeptide from glycinin. Reversed phase high performance liquid chromatography (RP-HPLC) analysis of the peptides released after hydrolysis revealed the appearance of new peptides and the disappearance of non-hydrolysed proteins, indicating extensive hydrolysis of the substrate. Results from competitive enzyme-linked immunosorbent assay (ELISA) tests clearly indicated a reduction in the immunoreactivity (more than one logarithmic unit) in the fermented sample as compared to the non-fermented control. Our results suggest that the soymilk fermented by E. faecalis VB43 may induce lower allergic responses in sensitive individuals. The strain E. faecalis VB43 may be considered as an excellent candidate to efficiently reduce the immunoreactivity of soymilk proteins.

Isolation and characterization of a nisin-like bacteriocin produced by a Lactococcus lactis strain isolated from charqui, a Brazilian fermented, salted and dried meat product.

A Lactococcus lactis subsp. lactis strain (L. lactis 69) capable to produce a heat-stable bacteriocin was isolated from charqui, a Brazilian fermented, salted and sun-dried meat product. The bacteriocin inhibited, in vitro, Listeria monocytogenes, Staphylococcus aureus, several lactic acid bacteria isolated from foods and spoilage halotolerant bacteria isolated from charqui. The activity of the bacteriocin was not affected by pH (2.0-10.0), heating (100 °C), and chemical agents (1% w/v). Treatment of growing cells of L. monocytogenes ScottA with the cell-free supernatant of L. lactis 69 resulted in complete cell inactivation. L. lactis 69 harbored the gene for the production of a nisin-like bacteriocin, and the amino acid sequence of the active peptide was identical to sequences previously described for nisin Z. However, differences were observed regarding the leader peptide. Besides, the isolate was able to survive and produce bacteriocins in culture medium with NaCl content up to 20%, evidencing a potential application as an additional hurdle in the preservation of charqui.

Epidemiological Survey of Listeria monocytogenes in a gravlax salmon processing line / Epidemiologia de Listeria monocytogenes em uma linha de processamento de salmão gravlax

Listeria monocytogenes is a cause of concern to food industries, mainly for those producing ready-to-eat (RTE) products. This microorganism can survive processing steps such as curing and cold smoking and is capable of growing under refrigeration temperatures. Its presence in RTE fish products with extended shelf life may be a risk to the susceptible population. One example of such a product is gravlax salmon; a refrigerated fish product not exposed to listericidal processes and was the subject of this study. In order to evaluate the incidence and dissemination of L. monocytogenes 415 samples were collected at different steps of a gravlax salmon processing line in São Paulo state, Brazil. L. monocytogenes was confirmed in salmon samples (41 percent), food contact surfaces (32 percent), non-food contact surfaces (43 percent) and of food handlers' samples (34 percent), but could not be detected in any ingredient. 179 L. monocytogenes isolates randomly selected were serogrouped and typed by PFGE. Most of L. monocytogenes strains belonged to serogroup 1 (73 percent). 61 combined pulsotypes were found and a dendrogram identified six clusters: most of the strains (120) belonged to cluster A. It was suggested that strains arriving into the plant via raw material could establish themselves in the processing environment contaminating the final product. The wide dissemination of L. monocytogenes in this plant indicates that a great effort has to be taken to eliminate the microorganism from these premises, even though it was not observed multiplication of the microorganism in the final product stored at 4ºC up to 90 days.

Listeria monocytogenes é um patógenode grande preocupação para as indústrias alimentícias, principalmente aquelas produtoras de alimentos prontos para consumo (RTE). Este microrganismo pode sobreviver às etapas de cura e defumação a frio, além de tolerar temperaturas de refrigeração. A presença de L. monocytogenes em pescados RTE com vida de prateleira longa representa um risco para a população susceptível, sendo o salmão gravlax deste tipo de produto. No presente estudo avaliou-se a incidência e disseminação de L. monocytogenes em 415 amostras de salmão gravlax obtidas de diferentes etapas de processamento de uma indústria localizada no Estado de São Paulo. A presença de L. monocytogenes foi confirmada em amostras de salmão (41 por cento), superfícies de contato (32 por cento) e não contato (43 por cento) e manipuladores (34 por cento), porém não se isolou o microrganismo em nenhum ingrediente. Do total de cepas isoladas, 179 destas foram escolhidas aleatoriamente e submetidas a sorologia e tipagem por PFGE. A maioria dos isolados pertenceu ao sorogrupo 1 (73 por cento), sendo identificados 61 pulsotipos quando se combinou os resultados de sorologia e PFGE e 6 clusters foram distribuídos em um dendrograma. O cluster A agrupou a maioria das cepas (120). Pode-se sugerir que as cepas foram introduzidas na linha de processamento por meio da matéria prima e contaminando o produto final. Estes resultados indicam que a eliminação de L. monocytogenes deste estabelecimento requer um grande esforço, ainda que o microrganismo não se multiplicou no produto final estocado a 4ºC por 90 dias.

Epidemiological Survey of Listeria monocytogenes in a gravlax salmon processing line.

Listeria monocytogenes is a cause of concern to food industries, mainly for those producing ready-to-eat (RTE) products. This microorganism can survive processing steps such as curing and cold smoking and is capable of growing under refrigeration temperatures. Its presence in RTE fish products with extended shelf life may be a risk to the susceptible population. One example of such a product is gravlax salmon; a refrigerated fish product not exposed to listericidal processes and was the subject of this study. In order to evaluate the incidence and dissemination of L. monocytogenes 415 samples were collected at different steps of a gravlax salmon processing line in São Paulo state, Brazil. L. monocytogenes was confirmed in salmon samples (41%), food contact surfaces (32%), non-food contact surfaces (43%) and of food handlers' samples (34%), but could not be detected in any ingredient. 179 L. monocytogenes isolates randomly selected were serogrouped and typed by PFGE. Most of L. monocytogenes strains belonged to serogroup 1 (73%). 61 combined pulsotypes were found and a dendrogram identified six clusters: most of the strains (120) belonged to cluster A. It was suggested that strains arriving into the plant via raw material could establish themselves in the processing environment contaminating the final product. The wide dissemination of L. monocytogenes in this plant indicates that a great effort has to be taken to eliminate the microorganism from these premises, even though it was not observed multiplication of the microorganism in the final product stored at 4°C up to 90 days.

Quantificação de Listeria monocytogenes em salames fatiados embalados a vácuo / Occurrence of Listeria monocytogenes in pre-sliced vacuum-packaged

There is scarce information in Brazil and other South American countries about the occurrence of Listeria monocytogenes in food, mainly refrigerated ready-to-eat products. The consumption of sliced vacuum-packaged meat products has increased in the last few years. Nevertheless, a complete assessment of the risk associated with L. monocytogenes in these products is still necessary. Because of the production and storage characteristics of these products, they can be considered potential vehicles for L. monocytogenes to humans, mainly immunocompromised, elderly, and pregnant women. The objectives of this study was to evaluate the population of L. monocytogenes in salami, a ready-to-eat meat product with extended shelf life, acquired in retail stores in São Paulo-Brazil. The three-tube most probable number technique was used and the methodology was that from Health Canada. Strains were biochemically identified and serotyped. Among the 45 samples, 3 (6.7 per cent) harboured 9.2 MPN/g of L. monocytogenes and the others < 0.3 MPN/g. All the strains belonged to serotypes 1/2a and 1/2b, the most frequent serotypes found in food everywhere. Even being low, the population of L. monocytogenes found in this product could be a cause of concern to public health authorities as it can pose a threat to population at risk. This contamination highlights the importance of implementing systems like HACCP to assure safe products to consumers.

Prevalence and dissemination of Salmonella serotypes along the slaughtering process in Brazilian small poultry slaughterhouses.

Salmonella is the leading cause of human foodborne infections in Latin America, and poultry meat is one of the main vehicles. Small poultry slaughterhouses (fewer than 200 birds slaughtered per day) represent an important economic activity in certain regions. The slaughtering process in these abattoirs is manual and rudimentary, and frequently the hygienic conditions are poor. This study reports results of a detailed evaluation of the prevalence of Salmonella serotypes in carcasses, utensils, and environmental samples collected in 60 small Brazilian slaughterhouses. In the second step of the study, one of these slaughterhouses was selected to monitor the dissemination of Salmonella along the slaughtering process. For testing, conventional procedures were used: preenrichment in buffered peptone water (35 degrees C for 24 h), selective enrichment in Selenite-cystine (35 degrees C for 24 h), tetrathionate and Rappaport-Vassiliadis broths (42 degrees C for 24 h), plating on bismuth-sulfite and brilliant green agars (35 degrees C for 24 h), proper biochemical testing, and complete serotyping. Forty-one percent of samples harbored Salmonella spp., including 42% of carcasses, 23.1% of utensils, 71.4% of water, and 71.4% of freezers and refrigerators. Seventeen serotypes were detected. Salmonella Enteritidis predominated (30%), followed by Salmonella Albany (12%), Salmonella Hadar (12%), Salmonella Indiana (10%), and I 4,12:z:- (8%). All samples collected along the slaughtering process in the selected slaughterhouse were Salmonella positive. Five serotypes were detected, including Salmonella Albany, Salmonella Hadar, Salmonella Agona, Salmonella Emek, and Salmonella Indiana. More than 30% of the samples contained more than one serotype, and 12.5% presented three serotypes. The widespread occurrence of Salmonella in small slaughterhouses reinforces the need for implementation of effective control measures.