Influência de diferentes tipos de micro-organismos na contagem bacteriana total por citometria de fluxo do leite cru refrigerado / Influence of different types of microorganisms in total bacterial count by flow cytometry of refrigerated raw milk

Contagens bacterianas de 179 amostras de leite cru refrigerado, provenientes de diferentes bacias leiteiras de Minas Gerais, foram realizadas pelos métodos de citometria de fluxo e contagem padrão em placas. O estudo das associações entre a contagem bacteriana total e as contagens bacterianas dos diferentes grupos de micro-organismos foi realizado pela correlação de Pearson. Houve uma forte correlação positiva e significativa entre os valores de contagem de psicrotróficos (r = 0,67) e mesófilos (r = 0,70), determinados pelo método de referência, e os valores da contagem bacteriana total, determinados pela citometria de fluxo. Foi possível estabelecer uma curva de calibração para o citômetro de fluxo utilizando equações de regressão linear. As equações para a contagem bacteriana obtida por citometria de fluxo em função da contagem de mesófilos e psicrotróficos foram: log (CBI) = 0,701 log mesófilos + 1,9091 e log (CBI) = 0,4703 log psicrotróficos + 3,2784, respectivamente. Não foi possível estabelecer curvas de calibrações para termófilos e termodúricos, pois as correlações obtidas entre as contagens desses micro-organismos e a contagem bacteriana total, determinada por citometria de fluxo, foram fracas (r = 0,30 e 0,27, respectivamente).(AU)

Total Bacterial count was performed in 179 raw milk samples from different dairy farms in Minas Gerais State, Brazil, through flow cytometry and standard plate count, that was regarded as the reference method. There was significant strong correlation between the values of psychrotrophic and mesophilic counts determined by the reference method with the values of bacterial count determined by flow cytometry (r = 0.67 and 0.70, respectively), which allowed to establish linear regression equations for bacterial count to calibrate the flow cytometry and estimate the count of mesophilic (log bacterial individual count (BIC) by flow cytometry = 0.701 log mesophilic + 1.9091) and psychrotrophic (log BIC by flow cytometry = 0.4703 log psychrotrophic + 3.2784) bacteria. It was not possible to establish calibration curves for thermophiles and thermodurics due to the weak to moderate correlation coefficients found among these microorganism counts and total bacterial count determined by flow cytometry (r = 0.30 and 0.27, respectively).(AU)

Molecular identification and thermoresistance to boiling of Nocardia farcinica and Nocardia cyriacigeorgica from bovine bulk tank milk

Two strains of Nocardia spp. were isolated from bovine milk of two individual bulk tank. Molecular identification classified the strains as Nocardia farcinica and Nocardia cyriacigeorgica. The thermorresistance to boiling of the isolates was carried out and was observed bacterial growth after boiling. Our findings indicate the potential risk of pathogen transmission to humans through contaminated milk with Nocardia spp.

Association between milking practices and psychrotrophic bacterial counts in bulk tank milk / Asociación entre prácticas de ordeño y recuento de organismos psicrótrofos en leche de tanque de frío

The objective of this work was to determine on-farm risk factors for psychrotrophic bacterial counts in bulk tank milk from dairy farms in Argentina. Raw milk samples from bulk tanks of 27 dairy farms were examined for total psychrotrophic counts (TPC), proteolytic psychrotrophic counts (PPC) and lipolytic psychrotrophic counts (LPC) (dependent or outcome variables). A survey recording infrastructure conditions, milking equipment and milking management (independent variables) was performed. Bivariate association proofs and logistic regression analyses were used to determine association between independent variables and psychrotrophic bacterial counts. Milk cooled in plate heat exchangers or barrel tanks were 16.39 and 10.52 times more likely to yield TPC and PPC above the standard established for high quality milk compared with milk cooled in bulk tanks, respectively. Periodic cleaning of cooling tanks (3 times a week or daily) was associated with lower TPC (approximately 1.5 log CFU/ml) than weekly cleaning frequency and farms where milkers did not wash their hands during milking time were 7.81 times more likely to have higher PPC. No association was found between LPC and any of the independent variables. The only variable associated with TPC and PPC in a logistic regression model was the refrigeration system used on the farm. Dairy farms that possessed bulk milk cooling tanks yielded the lowest bacterial counts. Results of this study highlight the importance of both the type of cooling system used on the farm and its adequate hygienic maintenance for obtaining low pshychrotrophic counts at dairy farm.

El objetivo del trabajo fue determinar los factores de riesgo para altos recuentos de organismos psicrótrofos en leche de tanques de tambos de la Argentina. Se examinaron muestras de leche cruda de tanques de frío de 27 tambos, y se realizó el recuento de organismos psicrótrofos totales (PT), de psicrótrofos proteolíticos (PP) y de psicrótrofos lipolíticos (PL) (variables dependientes). Se realizó una encuesta para registrar las condiciones de infraestructura, el equipo de ordeño y las prácticas de ordeño (variables independientes). Se utilizaron pruebas bivariadas de asociación y regresión logística para determinar la asociación entre las variables independientes y los recuentos de organismos psicrótrofos. La leche enfriada en sistemas de placas de intercambio o tanques tipo cuba tuvo una probabilidad mayor de dar recuentos elevados de PT y PP (16,39 y 10,52) comparada con la enfriada en tanques tipo "panza fría". La limpieza periódica del equipo de frío (3 veces por semana o diariamente) se asoció con bajos recuentos de PT (aproximadamente 1,5 log de UFC/ml). Los tambos cuyos ordeñadores no se higienizaban las manos durante el ordeño tuvieron una probabilidad 7,81 veces mayor de tener recuentos elevados de PP. No se encontró asociación entre el recuento de PL y las variables independientes. La única variable asociada con los recuentos de PT y PP en el modelo de regresión logística fue el sistema de enfriamiento utilizado en el tambo. El tipo de sistema de refrigeración usado y su adecuado mantenimiento higiénico son importantes para la obtención de leche con baja carga de organismos psicrótrofos en el tambo.

Presence of enterotoxigenic Staphylococcus aureus in bulk tank milk from Argentine dairy farms / Presencia de Staphylococcus aureus enterotoxigénico en leche de tanque de frío de tambos de Argentina

Staphylococcus aureus is the most prevalent bovine mastitis pathogen in Argentina. The ability of this organism to produce enterotoxins is linked to staphylococcal food poisoning. Staphylococcal enterotoxins are low molecular weight proteins, highly resistant to heat and proteolytic enzyme activity. The aim of this study was to determine the ability to produce enterotoxins and types of enterotoxins A through E produced among 94 S. aureus isolated from bulk tank milk in Argentina by enzyme-linked immunosorbent assay. Eleven isolates (11.7 %) produced enterotoxins. Seven of them (7.4 %) produced enterotoxin C, two (2.1 %) enterotoxin D, one (1.1 %) enterotoxin B and one (1.1 %) enterotoxins C-D-E. None of the isolates produced enterotoxins A or E alone. Since presence of staphylococcal enterotoxins constitute a potential risk to public health, these findings underscore the need to control S. aureus bovine mastitis and to limit bacterial multiplication in bulk tank milk.

Staphylococcus aureus es el patógeno causante de mastitis más prevalente en Argentina. Las enterotoxinas producidas por este organismo constituyen una de las causas más importantes de intoxicación alimentaria en seres humanos. Las enterotoxinas estafilocócicas son proteínas de bajo peso molecular, termoestables y resistentes a enzimas proteolíticas. El objetivo del presente trabajo fue determinar por enzimoinmunoensayo la presencia de enterotoxinas A-E y establecer su tipo en 94 aislamientos de Staphylococcus aureus obtenidos de leche de tanque de frío de tambos de Argentina. Se identificaron 11 % aislamientos enterotoxigénicos (11,7 %); siete (7,4 %) produjeron enterotoxina C, dos produjeron enterotoxina D (2,1 %), uno produjo enterotoxina B (1,1 %) y uno produjo enterotoxinas C-D-E (1,1 %). No se detectaron aislamientos que produjeran enterotoxinas A o E solamente. Estos hallazgos indican la necesidad de implementar un eficaz control de la mastitis bovina para disminuir la presencia de S. aureus en leche de tanque y evitar riesgos potenciales para la salud pública.

Qualidade higiênica de leite caprino por contagem de coliformes e estafilococos / Goat's milk quality by coliform's and staphylococci counting

O objetivo deste estudo foi investigar os padrões higiênicos do leite de mistura caprino produzido por oito propriedades associadas a uma cooperativa na região do Vale do Taquari - RS. Foram realizadas duas visitas às propriedades durante o período de maior produção leiteira. As propriedades foram avaliadas quanto às instalações, ao manejo de ordenha e ao armazenamento do leite.Foram coletadas amostras de leite e água em cada visita. As amostras de água apresentaram contagem de coliformes dentro dos limites propostos pela legislação vigente, já as de leite apresentaram contagens de coliformes totais que variaram de zero a 1,4 x 10(6)UFC mL-1. Em apenas duas propriedades foram encontrados coliformes fecais. Não foram identificados estafilococos coagulase-positiva nas amostras. Não foi evidenciada relação significativa entre os sistemas de resfriamento e ordenha empregados na propriedade e a presença de coliformes no leite.

The aim of this work was to evaluate the current hygiene-sanitary quality of milk produced by eight dairy goat farms located in Vale do Taquari region, state of Rio Grande do Sul, Brazil. On each farm, two samplings were performed during the highest milk yield period. At each sampling, bulk milk and water samples were taken, and farms were checked for their facilities, milking management and milk storage. Water samples were subjected to fecal coliform enumeration, while milk samples were tested for total and fecal colifoms as well as for coagulase-positive staphylococci. Water samples presented fecal coliform levels according to the national legislation. In milk samples total coliform counts up to 1.4 x 10(6)CFU mL-1 were found. Coagulase-positive staphylococci were not isolated and fecal coliforms were detected in two farms. No correlation was observed between the number of total coliforms and milking management and milk storage.