Effect of peracetic acid on biofilms formed by Listeria monocytogenes strains isolated from a Brazilian cheese processing plant

ABSTRACT This study aimed to investigate the effect of peracetic acid (PAA, 0.5%) on adherent cells of three strains of Listeria monocytogenes strains belonging to serotypes 4b and 1/2b that had been previously isolated from the environment of a Brazilian cheese plant. The assays were conducted using polystyrene microplates and stainless steel coupons and the adhered cells were treated with PAA for 60, 120 and 180 s. On stainless steel, biofilms were partially inactivated by PAA after 60 s and almost 100% of the cells were damaged within 180 s using epifluorescence microscopy with LIVE/DEAD® staining. On polystyrene microplates, PAA decreased (P<0.05) biofilm biomass produced by the three L. monocytogenes isolates at 60 s, when compared with controls (no PAA treatment). However, PAA did not completely eliminate L. monocytogenes cells on polystyrene microplates (decreasing 1.8-2.5 log cycles after treatment with PAA for 180 s). The correct concentration and contact time of PAA is critical for eliminating biofilms formed by L. monocytogenes on stainless steel surfaces, although further studies are needed for defining efficient PAA treatments to remove adherent cells of this pathogen on plastic polymers

Prevalence and phenotypic characterization of Enterococcus spp. isolated from food in Brazil

We evaluated the frequency of enterococci from food and found 95.2% of positivity, being E. faecium and E. faecalis the most frequent species. High-level streptomycin resistance was observed, as well as gelatinase and hemolysis activity, showing the potential role of environmental strains as reservoir of virulence and resistance traits.

Produção in vitro de biofilme por Staphylococcus spp. isolados de salgadinhos e lanches / In vitro biofilm production by Staphylococcus spp. strains isolated from finger-foods and snacks

Staphylococcus aureus is one of the most important food-borne pathogens, and although BrazilianSanitation Surveillance Agency (ANVISA) does not specifically regards for coagulase-negativeStaphylococcus (CNS) isolation from foods, it is known that this group of bacteria possesses genesassociated with biofilm formation and enterotoxins production. In this context, the present study aimedat identifying the S. aureus and CNS in finger-foods and snacks samples, and to evaluate the ability ofthese strains to produce biofilm in vitro by means of two methodologies: Congo Red agar and polystyrenemicroplates cultures. Twenty-two staphylococcal isolates belonging to eight species were obtainedfrom 122 finger-foods, sandwiches and ready-to-eat (RTE) food products. S. aureus, S. warneri and S.haemolyticus were the most frequent isolates. Biofilm production by Staphylococcus spp. was observedin seven (31.8 %) isolates by Congo Red agar technique and three (13.6 %) by polyestirene microplatemethodology. There was no positive isolate biofilm producer by both methodologies. Despite the lownumber of isolates, a concordance of 59.1 % between the tests was found. The ability to produce biofilmis an important virulence factor in Staphylococcus spp., and it can support to define the role of CNS asfood-borne pathogen.

Qualidade microbiológica de lanches e salgados / Microbiological quality of finger food and snacks

Although finger food is convenient, it may be easily contaminated from the stage of preparation to themoment of consumption. This study aimed at evaluating the microbiological quality of finger food and sandwiches sold in Botucatu – SP, Brazil, by following the standards established by the Brazilian Health Surveillance Agency, ANVISA. The analysis was conducted according to APHA. A hundred and twenty two samples of meat, chicken, shrimp, cheese, and vegetable finger food and sandwiches were tested fromAugust 2008 to March 2009. Seventeen (13.9 %) samples of meat, cheese, vegetables and chicken were indisagreement with the ANVISA standards — some of them in more than one parameter. High counting of thermotolerant coliforms and coagulase-positive staphylococci were found in ten (8.2 %) and eight(6.5 %) samples, respectively. Salmonella spp. was detected in two samples (1.6 %). No Bacillus cereus andsulfite-reducing clostridia were isolated. Although only 10 samples (8.2 %) showed pathogenic bacteriacontamination, these results are relevant, since they indicate that the population is generally exposedto risks of acquiring foodborne diseases. Thus, the sanitary authorities might implement actions forsupervising the quality of the food sold in Botucatu, and to strengthen the food sellers to improve thehygienic conditions and be aware of the risks of food contamination.

Neste trabalho foi avaliada a qualidade microbiológica de salgados e sanduíches comercializados emBotucatu-SP, seguindo-se a legislação em vigor. As análises foram realizadas de acordo com APHA. Foramanalisadas 122 amostras de salgados de carne, frango, camarão, queijo e vegetais, e sanduíches no períodode agosto/2008 a março/2009. Dezessete (13,9 %) amostras de carne, queijo, vegetais e frango, e em algumasem mais de um parâmetro, estavam em desacordo com a legislação em vigor. Foram detectadas elevadascontagens de coliformes termotolerantes e estafilococos coagulase-positiva, respectivamente, em dez (8,2 %)e oito (6,5 %) amostras. Salmonella spp. foi isolada em duas amostras (1,6 %). As contagens de Bacillus cereuse de Clostrídio Sulfito Redutor não ultrapassaram os padrões da legislação. A maioria dos salgados mostrouresultados dentro dos padrões estabelecidos pela legislação. A presença de bactérias patogênicas comoS. aureus e Salmonella spp. foi demonstrada em 10 amostras (8,2 %); e este resultado é relevante, pois indicaque a população está exposta a riscos de doenças veiculadas por alimentos. Torna-se necessário colocarem prática a vigilância dos alimentos comercializados em Botucatu, incentivar a melhoria de condiçõesde higiene pelos comerciantes, e ter ciência dos riscos e das implicações da contaminação microbiológicados alimentos.