Short communication: Temperature sensibility of Prototheca blaschkeae strains isolated from bovine mastitic milk

Dairy cow mastitis associated with microalgae of the genus Prototheca has been reported worldwide. This alga is extremely resistant to most antimicrobials commonly used in mastitis therapy. In milk processing, different thermal treatments are generally efficient at inactivating and eliminating microorganisms. Until recently, no reports on Prototheca blaschkeae susceptibility to heat treatment have been described. Thus, considering the potential zoonotic risk that Prototheca may represent, the objective of this study was to test the susceptibility of P. blaschkeae field isolates retrieved from bovine mastitis to different temperature/time ratios that are generally used in the milk processing industry: 62°C/15 min and 30 min; 70°C/20 s, 15 min, and 30 min; 75°C/20 s; 90°C/1 s; and 100°C/1 s. The results showed a growth reduction of all isolates after the heat treatments, but only at 100°C was a total growth inhibition observed.