Biofilm formation is considered to be a selective advantage for Staphylococcus aureus mastitis isolates by facilitating bacterial persistence in the udder. It requires attachment to mammary epithelium, proliferation and accumulation of cells in multilayers. The objective of this study was to determine the sensitivity and specificity of three techniques for the detection of S. aureus biofilm-positive strains. Two phenotypic tests, including growth on microtitre plates and Congo red agar, were compared with a PCR technique using 94 S. aureus strains obtained from cows with subclinical mastitis from two farms in the state of São Paulo. These strains were characterised by in vitro slime production on Congo red agar, biofilm formation on microtitre plates and the presence of the icaA and icaD genes. The results revealed that 85% of the isolates tested produced slime on the Congo red agar, 98.9% of the isolates produced biofilms in vitro by adhering to sterile 96-well “U” bottom polystyrene tissue culture plates, and 95.7% of the isolates carried the icaA and icaD genes. The results of the phenotypic tests for biofilm formation were compared with those of the molecular analysis, and the sensitivity and specificity of the Congo red agar test were 88.9% and 100%, respectively, while those of the microtitre plate test were 100% and 25%, respectively. When the phenotypic methods for the detection of biofilm producers, namely growth on microtitre plates and Congo red agar, were compared, the sensitivity and specificity were 86% and 100%, respectively. Therefore, growth on Congo red agar and the microtitre plate test are methods that could be used to determine whether an isolate has the potential for biofilm production.

Biofilms constitute a physical barrier, protecting the encased bacteria from detergents and sanitizers. The objective of this work was to analyze the effectiveness of sodium hypochlorite (NaOCl) against strains of Staphylococcus aureus isolated from raw milk of cows with subclinical mastitis and Staphylococcus aureus isolated from the milking environment (blowers and milk conducting tubes). The results revealed that, in the presence of NaOCl (150ppm), the number of adhered cells of the twelve S. aureus strains was significantly reduced. When the same strains were evaluated in biofilm condition, different results were obtained. It was found that, after a contact period of five minutes with NaOCl (150ppm), four strains (two strains from milk , one from the blowers and one from a conductive rubber) were still able to grow. Although with the increasing contact time between the bacteria and the NaOCl (150ppm), no growth was detected for any of the strains. Concerning the efficiency of NaOCl on total biofilm biomass formation by each S. aureus strain, a decrease was observed when these strains were in contact with 150 ppm NaOCl for a total period of 10 minutes. This study highlights the importance of a correct sanitation protocol of all the milk processing units which can indeed significantly reduce the presence of microorganisms, leading to a decrease of cow´s mastitis and milk contamination.

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ResumoO objetivo da presente pesquisa foi avaliar as condições microbiológicas de alimentos servidos em restaurantes "self-service" em Itumbiara-GO. No total, foram estudados 23 restaurantes e os alimentos coletados foram macarronada, salada de tomate e pepino, maionese e carne de panela. As amostras foram adquiridas com o apoio de fi scais da Vigilância Sanitária Municipal de Itumbiara-GO. Foram pesquisados mesófi los totais, estafi lococos coagulase positivo e coliformes termotolerantes. Tanto o preparo das amostras como de suas diluições foram realizadas segundo as técnicas recomendadas pelo Compendium of Methods for the Microbiological Examination of Foods. Em apenas um restaurante não foi detectado contaminação de alimentos. Em 16 (69,6%) deles houve pelo menos três tipos de alimentos contaminados com contagens acima do padrão microbiológico permitido por lei. Todos os patógenos pesquisados foram detectados em pelo menos um tipo de alimento. O patógeno mais freqüente foi o estafi lococos coagulase positivo (86,5%). Os resultados são alarmantes, havendo a presença nos alimentos de microrganismos potencialmente patogênicos, o que demonstra a baixa qualidade higiênico-sanitária durante o preparo dos alimentos pesquisados. Unitermos: alimentos, avaliação microbiológica, restaurantes AbstractMicrobiological contamination of food at self-service restaurants. The purpose of this study was to evaluate the microbiological conditions of food served in self-service restaurants in Itumbiara-GO. In total, we studied 23 restaurants and the foods collected were: pasta, tomato and cucumber salad, mayonnaise and meat from the pan. The samples were acquired with the support of the municipality's sanitary inspectors. Our research was focused on total mesophiles, coagulase positive staphylococci and heat tolerant coliforms. The sample preparations and their dilutions were performed according to the technique recommended by the Compendium of Biotemas, 23 (4): 129-133, dezembro de 2010