Proteolytic behavior of isolated Pseudomonas spp. from refrigerated raw milk in different concentrations and storage temperatures

The objective of the work was to evaluate the multiplication capacity and proteolytic activity of different Pseudomonas spp. cell counts inoculated in milk and storaged under different temperature. Strains isolated from refrigerated raw milk (RRM) were confirmed at genus level by Polymerase Chain Reaction (PCR). The Pseudomonas spp. was cultured in cephalothin-sodium fusidate-cetrimide (CFC) agar-base (30?C for 48 h) until it reached 2 log and 6 log CFU mL-1. Three of eight strains confirmed as Pseudomonas spp were inoculated in sterile reconstituted whole milk powder and incubated at 2°C, 4°C, and 8°C for 96 h. Primary proteolysis indices was determined by the Kjeldahl method. When taking into account the effect of storage time in Pseudomonas spp. population, it was found that the initial population (2 log CFU mL-1) showed significant difference in growth rates only from 0 h to 24 h, keeping at the same levels along 96 h. When a higher initial population was incubated (6 log CFU mL-1), it was not observed a significant difference for times tested. Related to the effect of storage time in proteolysis index, it was not observed a significant difference in samples inoculated with 2 and 6 log CFU mL-1 Pseudomonas spp. When we analyzed the influence of storage temperature on the bacterial multiplication, there was a significant difference in the Pseudomonas spp. population only between 2°C and 8°C after 96 h of milk storage with 2 log CFU/mL of initial inoculum. If we consider the temperature effect in the primary proteolysis index, there were significant differences at the inoculum of 2 log CFU mL-1 where the primary proteolysis at 24 h was lower at 2°C than at 8ºC. Low temperatures or short storage time had no influence on Pseudomonas spp. enumeration or in the primary proteolysis index when high initial contaminations are observed. At lower Pseudomonas spp. initial population, the smaller storage time tested influenced the population control, and linked with the reduction in the storage temperature, lower proteolysis index were observed

Pseudomonas spp. and P. fluorescens: population in refrigerated raw milk

ABSTRACT: Raw milk samples were collected from cooling tanks (after they cooled for 48 h) in five dairy farms and the corresponding bulk tank (bulk milk transportation, BMT) when they arrived to the industry. Routine physical chemical analyzes and quantification of psychrotrophic ( Pseudomonas spp. and P. fluorescens ) and aerobic mesophilic (AM) populations were performed. Only relative density and titratable acidity values for samples of milk from three farms were in agreement to the quality parameters required by law. In the BMT, only the protein content has not reached the minimum value established by law, and counting was performed for AM (>105 colony forming units (CFU) mL-1) and psychrotrophic bacteria (2.8x106CFU mL-1). Pseudomonas spp. counting corresponded to 17.9% of the psychrotrophic population, and P. fluorescens was 3.4% of Pseudomonas spp . count. In milk samples from dairy farms, counts were variable for AM (3.4x105 to 3.7 x107CFU mL-1), psychrotrophic (4.0x104 to 3.1x106CFU mL-1), Pseudomonas spp. (2.3x104 to 1.8x105CFU mL-1), and P. fluorescens (62 to 8.4x103CFU mL-1). For the populations studied, no statistical difference (P>0.05) was observed between counts reported in milk samples collected in dairy farms (cooling tanks) and BMT. Therefore, the genera Pseudomonas spp. and P. fluorescens were not the most frequent psychrotrophic bacteria in this studied milk transportation line

Evaluation of an electrical conductivity portable device as an alternative for subclinical mastitis detection

ABSTRACT: The use of efficient methods for the early diagnosis of subclinical mastitis is of great importance in milk production. By using an electrical conductivity meter (EC), the efficiency of subclinical mastitis diagnosis was evaluated in dairy farms in northern Parana, Brazil, and the results were compared with those obtained by using the California Mastitis Test and the Somatic Cell Count (SCC). Samples from 941 quarters of 259 cows of the Holstein and Jersey breeds were analyzed in four dairy farms between June and July 2014. The EC method correctly evaluated 54.8% of the samples (264 samples with subclinical mastitis) and 250 without infection when compared with the diagnosis by CMT. Of the 445 samples diagnosed as positive by EC, 19.7% were classified by CMT with score 2 and 24.7% with score 3. Of the samples with negative results (496), most of them had scores 0 and 1 (50.4% and 21.4 %). The correlations between EC and SCC (r = 0.14) and EC and CMT (r = 0.17) were positive but low, which generated false positive and false negative results of subclinical mastitis in the herd. Evaluación del dispositivo portátil de la conductividad eléctrica como alternativa para la detección de mastitis subclínica RESUMEN: El uso de métodos eficientes para el diagnóstico rápido de la mastitis subclínica es de gran importancia en la producción de leche. Mediante el empleo de un medidor de conductividad eléctrica (CE), se evaluó la eficacia del diagnóstico de mastitis subclínica en granjas de leche del norte de Paraná, en Brasil, y se compararon los resultados con la Prueba de California para Mastitis (CMT, del inglés California Mastitis Test) y con el conteo de células somáticas (CCS). Se analizaron 941 cuartos mamarios, obtenidos de 259 vacas de las razas Holstein y Jersey en cuatro granjas lecheras, entre junio y julio de 2014. La CE evaluó correctamente 54,8% de las muestras (264 muestras con mastitis subclínica) y 250 sin infección en comparación con el diagnóstico de CMT. De las 445 muestras diagnosticadas como positiva para EC, 19,7% se clasificaron por la CMT, con una puntuación de 2 y 24,7% con una puntuación de 3. Entre los resultados negativos (496 muestras), la mayoría de las muestras tuvieron una puntuación entre 0 y 1 (50,4% y 21,4%). Hubo una correlación positiva (p <0.001); sin embargo, resultó baja entre CE y CCS (r = 0.14) y CE y CMT (r = 0.17), por lo que generaron resultados falsos positivos y falsos negativos de la mastitis subclínica en el hato