The results from this study demonstrate that coagulase-negative as well as coagulase-positive staphylococci isolated from dairy products are capable of genotypic and phenotypic enterotoxigenicity. Furthermore, these data demonstrate that PCR is a sensitive and specific method for screening outbreak isolates regardless of coagulase expression.

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RESUMO A indústria leiteira, visando a aumentar o rendimento industrial de seus produtos e melhorar a qualidade desses para atender à demanda do mercado consumidor, tem sido cada vez mais exigente com seus fornecedores de matéria-prima. Supõe-se que o tipo de ordenha e metodologias de coleta influenciam a composição físico-química e a contagemProcedimentos de coleta de leite cru individual e sua relação com a composição físico-química e a contagem de células somáticas

RESUMOEste trabalho se propôs a desenvolver um modelo preditivo para identificação de perda de estabilidade e de sedimentação em leite UAT por determinação da atividade enzimática de aminopeptidase no leite por espectrofotometria. Foram analisadas amostras de leite cru, pasteurizado e UAT após envase durante seis meses, na região Sul do Brasil. Acidez, crioscopia, gordura, extrato seco total, extrato seco desengordurado e densidade foram analisados nos leites cru e pasteurizado. Amostras de leite cru foram ainda submetidas à análise de contagem de psicrotróficos e à atividade de aminopeptidase, e amostras de leite UAT estocadas foram analisadas quanto ao grau de proteólise mediante análises sensoriais e atividade de aminopeptidase. Alterações sensoriais foram observadas em tempos de estocagem menores para amostras originadas de leite cru com contagem de psicrotróficos acima de 10 7 UFC mL -1. Não houve correlação entre a atividade de aminopeptidase e proteólise e também não foi observada correlação significativa entre os parâmetros físico-químicos e a ocorrência de proteólise no leite estocado. O modelo estudado não foi apto para predizer perda de estabilidade e ocorrência de proteólise no leite UAT.

The most acceptable criteria for diagnosing bovine intramammary infections include results of bacteriological culture and measures of inflammation. Therefore, information on the diagnostic characteristics of the procedures used to identify infected quarters is required. Thus, this study was designed to evaluate a set of criteria to classify the infectious status of an udder at the quarter (single and duplicate milk samples) and cow (composite milk sample) levels, and to compare the infectious status with somatic cell counts (SCCs) of the samples. Here, the SCC thresholds determined by receiver operating characteristic curve analysis had a higher Youden index using mammary quarter duplicate milk samples as the gold standard for testing compared with single quarter and composite milk samples, especially for samples for which at least one of the duplicates was microbiologically positive, regardless of the mastitis pathogen isolated. The kappa coefficient for bacteriological results of the single quarter milk samples (single S1 and S2) was 0.85+0.019, indicating that single quarter milk sampling can be useful in mastitis control programs. Therefore, the use of composite milk samples to detect mastitis pathogens may be limited to the detection of major pathogens, given their predictive values. Thus, our findings suggest that the milk SCCs and microbiological examinations, although regarded as the most reliable indicators of ongoing mastitis, should be used in an integrated manner in mastitis control programs. Furthermore, the accuracy of single, duplicate and composite microbiological analyses to diagnosis mastitis should be considered for its implications in mastitis control strategies.INDEX TERMS: Somatic cell count, mastitis, intramammary infection, sensitivity, specificity, udder health status, dairy cow.

Staphylococcus aureus is one of the pathogens most frequently isolated from cases of mastitis worldwide. To decrease the effect of S. aureus mastitis in dairy farming, alternative strategies for controlling mastitis are needed that depend on a better knowledge of cowto-cow variations in S. aureus antibody production. The present study sought to explore the diversity of S. aureus antibodies produced by dairy cows with a distinct mastitis history and vaccinated with a polyvalent mastitis vaccine. We obtained protein extracts from S. aureus isolates derived from persistent subclinical mastitis. Proteins were fractionated using 2-dimensional gel electrophoresis and Western blotting. Then, Western blotting membranes were exposed to sera from 24 dairy cows that had been divided into the following groups: vaccinated dairy cows that were infected with S. aureus, further subdivided according to whether they (a) remained infected by S. aureus or (b) recovered from the intramammary infection; unvaccinated dairy cows infected with S. aureus; and vaccinated healthy dairy cows with no history of S. aureus mastitis. Proteins found to be reactive by Western blot were identified by mass spectrometry (MALDI/TOF-TOF). Our most important finding was that F 0 F 1 ATP synthase subunit α, succinyl-diaminopimelate desuccinylase, and cysteinyl-tRNA synthetase were potential candidate proteins for the prevention of S. aureus mastitis. This study strengthens the notion that variations among animals should not be ignored and shows that the heterogeneity of antibody production against anti-staphylococcal antigens in animals may enable the identification of new immunotherapy targets.

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