The presence of some pathogen micro organisms, yeasts and moulds in cheese samples produced at small dairy-processing plants

Abstract

The presence of pathogenic and some indicator micro organisms was studied in 40 samples of
cheese comprising 14 curd samples, 13 samples of soft ripened salted or non-salted cheese and
13 samples of semi-hard cheese manufactured at five small dairy-processing plants. The mean
number of coagulase-positive staphylococci in all tested samples was 2.5 × 104
cfu*
g–1
, while
the number of E. coli bacteria was 1.4 × 106
cfu g–1
. In 20.0% out of 40 samples tested, the
number of coagulase-positive staphylococci exceeded the prescribed regulations, particularly in
soft cheese (12.5%) and curd (7.5%). About 17.5% of samples were contaminated with E. coli in
higher concentrations than national valid regulations allowed. The number of E. coli was mostly
exceeded in soft cheese and curd in 12.5% and 5.0% of all examined samples, respectively. One
sample of semi hard cheese was contaminated with sulphite-reducing clostridia. Proteus was
detected in 3 samples (7.5%) and L. grayi in 1 (2.5%) sample. Salmonela and L. monocytogenes
were not detected. According to the valid regulations 9 (22.5%) samples in our investigation did
not reach the adequate microbiological quality. Both, yeasts and moulds were isolated from 60% of tested cheese samples with average concentrations of 5.8 × 104 cfu g–1 and 2.0 × 104 cfu g–1, respectively. The genera Geotrichum (91.9%), Moniliella (5.4%) and Aspergillus (2.7%) were the most frequently isolated strains from examined cheese samples. The Aspergillus strains did not belong to the species A. flavus or A. parasiticus and did not produce aflatoxins.