Abstract
Coagulase-positive staphylococci (cps) were detected during the process of powdered milk production in three plants in Hokkaido. Isolated stra ins were classified into phage types. It was confirmed that contamination with CPS during tne manufacturing process was the secondary contamination of the balance tank of concentrated milk. Potential sources of contamination were presumed to be straining cloth and a mixture of dust in the air and scattered particles of powdered milk containing CPS. Such mixture seemed to enter the balance tahk directly or through the intermediary of workers. Part of the CPS thus mixed with concentrated milk multiplied in a hollow portion of the pump equipped in the drier for pushing the milk forward. It was made clear that CPS invaded the powdered milk in this manner.
