Methods based on plate count techniques were used to enumerate S. aureus and E. coli. Enrichment
methods in combination with a modified most probable number detection method were used to monitor samples
for the presence of E. coli O157:H7, Listeria, Campylobacter and Salmonella. Salmonella was not detected in
this study, and Campylobacter was isolated once (0.34%). E. coli was present at b100 cfu/ml in 99% of samples
and exceeded 103 cfu/ml in 0.7% of samples. E. coli O157:H7 was not detected whereas non-pathogenic E. coli
O157 strains (i.e. lacking genes for stx1, stx2, eae and Hly A) were detected in 1% of samples. S. aureus was not
detected (b1 cfu/ml) in 21% of samples; levels were >1 but b100 cfu/ml in 60% of samples and on one occasion
(0.34%) S. aureus exceeded 104 cfu/ml. L. monocytogenes was isolated from 0.68% of samples and L. innocua was
present in 4% of samples. The results demonstrate that raw milk sampled from farm vats in New Zealand, as in
other countries, inevitably contains recognised pathogens and, hence, control by pasteurisation or an equivalent
treatment of raw milk remains paramount. Even so, the prevalence of most of these pathogens was lower than
those reported in many of the studies performed in other countries.