Abstract Listeria monocytogenes is a gram-positive bacterium that can survive in food production environments and food products. This microorganism is associated with listeriosis, a serious infection caused by the consumption of contaminated food. The aim of this study was to conduct an integrative literature review on the regulation of L. monocytogenes in food in Brazil, its occurrence and methodologies used for identification in studies published from 2001 to 2021, and the epidemiological surveillance of cases of infection. The current regulations for L. monocytogenes prohibit ready-to-eat foods of more than 102 per gram or milliliter. Officially, only two cases of outbreaks have been identified in the Epidemiological Surveillance of Foodborne Diseases system; however, the circulation of L. monocytogenes was observed in foods of different origins, with occurrence ranging from 3.1 to 48.7. The most commonly used identification method was ISO 11290. The isolation and identification methods for this pathogen are expensive and laborious, making it difficult to implement these methodologies in many laboratories. This scenario contributes to the underreporting of cases of listeriosis and therefore represents a risk for the population that is exposed to potentially contaminated food.

Abstract The psychrotrophic bacteria count and the profile of Gram-negative bacteria present in commercial Brazilian organic dairy products (27 samples, pasteurized whole milk, Minas Frescal cheese, and yoghurt, equally distributed) as well as the biofilm-producing capacity and the production of deteriorating enzymes were investigated. Most of the samples (59%) presented psychrotrophic bacteria counts higher than 4 log CFU/g, indicating problems in the microbiological quality of the products. The identification of Gram-negative bacteria revealed the presence of micro-organisms that can be potentially harmful (39.4% Acinetobacter baumanii/calcoaceticus, 23.2% Burkoderia pseudomallei, 10.1% Halfnia alvei) and/or deteriorating micro-organisms (6.1% Pseudomonas aeruginosa) with the capacity of producing proteases (36.4%), lecithinases (41.4%), and lipases (4%). Roughly, 68.7% of micro-organisms were non-producers of biofilms, 28.3% were medium biofilm producers, and 3.0% were high biofilm producers. The findings suggest there are problems related to the good practices of obtaining organic milk and in the manufacture of dairy products.

Neste trabalho, a produção de substâncias antimicrobianas por estirpes de Pseudomonas sp. isoladas de leite pasteurizado e seu potencial de ação contra bactérias associadas a alimentos foram investigados. As amostras de leite pasteurizado foram adquiridas em estabelecimentos comerciais, arbitrariamente escolhidos, da cidade do Rio de Janeiro-RJ, Brasil. Dentre as quatro amostras analisadas, três apresentaram várias colônias típicas de Pseudomonas. Cerca de cem colônias foram escolhidas e submetidas a testes bioquímicos para confirmação da identificação. Dezoito estirpes do gênero Pseudomonas foram identificadas e submetidas aos testes de produção de substâncias antimicrobianas. Doze estirpes (66,7%) foram identificadas como Pseudomonas fluorescens; quatro (22,2%) como P. aeruginosa; uma (5,5%) como P. mendocina, e uma (5,5%) como P. pseudoalcaligenes. Apenas duas estirpes de P. fluorescens não foram capazes de produzir qualquer substância antimicrobiana contra os microorganismos indicadores testados. A maioria das estirpes apresentou um amplo espectro de ação, inibindo estirpes de referência e associadas a alimentos, como Proteus vulgaris, Proteus mirabilis, Hafnia alvei, Yersinia enterocolitica, Escherichia coli e Salmonella Typhi. Cinco estirpes produtoras de substâncias antimicrobianas, que apresentaram o mais amplo espectro de ação, também foram testadas contra estirpes de referência de Staphylococcus aureus e contra 26 estirpes de Staphylococcus sp. isoladas a partir de alimentos, sendo, algumas delas, resistentes a antibióticos. As estirpes produtoras 8.1 e 8.3, ambas P. aeruginosa, foram capazes de inibir todas as estirpes de Staphylococcus testadas. As substâncias antimicrobianas produzidas pelas estirpes 8.1 e 8.3 não parecem ser bacteriocinas típicas, uma vez que foram resistentes às três enzimas proteolíticas testadas. Experimentos envolvendo a caracterização destas substâncias estão sendo realizados, a fim de avaliar a sua aplicação biotecnológica.

In this work, the production of antimicrobial substances by strains of Pseudomonas sp. isolated from pasteurized milk and their potential action against food-related bacteria were investigated. Samples of pasteurized milk were purchased from arbitrarily chosen commercial establishments in the city of Rio de Janeiro, Brazil. Of the four samples analyzed, three presented several typical colonies of Pseudomonas. About 100 colonies were chosen and subjected to biochemical tests for confirmation of their identity. Eighteen strains of the Pseudomonas genus were identified and submitted to tests for the production of antimicrobial substances. Twelve strains (66.7%) were identified as Pseudomonas fluorescens, four (22.2%) as P. aeruginosa, one (5.5%) as P. mendocina and one (5.5%) as P. pseudoalcaligenes. Only two P. fluorescens strains were unable to produce any antimicrobial substance against any of the indicator strains tested. Most of the strains presented a broad spectrum of action, inhibiting reference and food-related strains such as Proteus vulgaris, Proteus mirabilis, Hafnia alvei, Yersinia enterocolitica, Escherichia coli and Salmonella typhi. Five antimicrobial substance-producing strains, which presented the broadest spectrum of action, were also tested against Staphylococcus aureus reference strains and 26 Staphylococcus sp. strains isolated from foods, some of which were resistant to antibiotics. The producer strains 8.1 and 8.3, both P. aeruginosa, were able to inhibit all the staphylococcal strains tested. The antimicrobial substances produced by strains 8.1 and 8.3 did not seem to be typical bacteriocins, since they were resistant to the three proteolytic enzymes tested. Experiments involving the characterization of these substances are being carried out in order to evaluate their biotechnological application.

The common bean is one of the most important legumes in the human diet, but little is known about the endophytic bacteria associated with the leaves of this plant. The objective of this study was to characterize the culturable endophytic bacteria of common bean (Phaseolus vulgaris. leaves from three different cultivars (Vermelhinho, Talismã, and Ouro Negro) grown under the same field conditions. The density of endophytic populations varied from 4.5 x 10² to 2.8 x 10³ CFU g-1 of fresh weight. Of the 158 total isolates, 36.7% belonged to the Proteobacteria, 32.9% to Firmicutes, 29.7% to Actinobacteria, and 0.6% to Bacteroidetes. The three P. vulgaris cultivars showed class distribution differences among Actinobacteria, Alphaproteobacteria and Bacilli. Based on 16S rDNA sequences, 23 different genera were isolated comprising bacteria commonly associated with soil and plants. The genera Bacillus, Delftia, Methylobacterium, Microbacterium, Paenibacillus, Staphylococcus and Stenotrophomonas were isolated from all three cultivars. To access and compare the community structure, diversity indices were calculated. The isolates from the Talismã cultivar were less diverse than the isolates derived from the other two cultivars. The results of this work indicate that the cultivar of the plant may contribute to the structure of the endophytic community associated with the common bean. This is the first report of endophytic bacteria from the leaves of P. vulgaris cultivars. Future studies will determine the potential application of these isolates in biological control, growth promotion and enzyme production for biotechnology.