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

Abstract

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.