Microbial surveys in Estonian dairies

Milk contains low numbers of bacteria when it is milked from healthy cows. Drinking and fodder places in the cow shed, milking machines, utensils and equipment at farms, during transportation and in processing may add contaminants to the milk. The aim of this study was to investigate hygiene at the dairies, to find critical points where special attention or improved cleaning is needed by using various microbial sampling methods and by determining the occurrence of Bacillus cereus, Mycobacterium spp. and Listeria monocytogenes. Surfaces were examined with Hygicult® and Rida®Count. DryCult® TPC total bacterial count was used for the determination of microbial counts in liquid samples. The detection of L. monocytogenes was performed according to ISO 11290-1 using the API Listeria test in the identification. The detection of Mycobacteria spp. was performed using Middlebrook 7H10 agar, Mycobacterium tubes 1 and 2 with confirmation based on Ziehl-Neelsen staining. Detection of B. cereus was performed according to ISO 7932 using β-haemolysis on sheep blood agar and API 50CHB test in the identification. These results showed that food contact surfaces were mostly clean from microbes, but the noncontact surfaces were often contaminated with enterobacteria, fungi and aerobic bacteria.