Prevalence of Staphylococcus aureus in Raw and Pasteurized Milk Used for Commercial Manufacturing of Brazilian Minas...

Raw and pasteurized milks used for cheesemaking were surveyed in a dairy plant, Juiz de Fora, MG, Brazil from 1978 to 1979. Raw milk samples were collected from 78 of 127 milk producers supplying 12,000-15,000 liters of milk daily to the plant. The TPC ranged from (log₁₀) 4 CFU/ml to 7.17 CFU/ml with a (log₁₀) mean of 5.59 CFU/ml. S. aureus cells were present in 46.9% of the samples. Mean number of S. aureus was (log₁₀) 4.69 ± 0.54 CFU/ml; the highest number was (log₁₀) 5.99 CFU/ml. Counts based on isolation on TPEY medium and confirmation on coagulase agar plate (CAP) did not differ significantly (P >0.05) from counts based on isolation on Plate Count Agar/DNA agar and confirmation of nuclease-positive colonies on CAP. Fifty bulk pasteurized milk samples were collected from five milk collection systems. TPC had a mean (log₁₀) of 4.02 ± 0.62 CFU/ml with the highest count being (log₁₀) 5.6 CFU/ml. The pH of the milk ranged from 6.55 to 6.89. Type of collection system did not affect the pH of the milk or the TPC (P >0.05). Three samples contained S. aureus at levels of (log₁₀) 3, 2.3 and 4.43 CFU/ml. Detection of S. aureus was based on methods used for raw milk plus use of Baird-Parker/CAP method.