What groups of bacteria affect the PIC?
Murphy: The PIC selects for bacteria that grow best at cooler temperatures. Gram-negative psychotropic (cold tolerant) rods are more likely to show a significant increase under these conditions, though other environmental contaminants may as well. Other bacteria may show a more moderate increase, perhaps doubling the count in a PIC compared to a standard plate count (SPC). Bacteria that grow at cool temperatures are often associated with dirty equipment. The prime suspect is a milk cooling system, and possibly dirty cows. Patteson: Cold tolerant, gram-negative bacteria are the most common type affecting the PIC. 2. Do mastitis-causing bacteria affect the PIC? Murphy: Most mastitis bacteria aren’t capable of significant growth under the conditions of the PIC. There may be exceptions to the rule since many different strains of bacteria cause mastitis. It’s important to compare the PIC to the SPC. If a PIC is used alone, a high count that consists primarily of a mastitic organism may be m
