Effect of Different Heat Treatments and Disinfectants on the Survival of Prototheca zopfii

Abstract

Bovine mastitis caused by the yeast-like alga Prototheca zopfii represents a serious veterinary problem and may result in heavy economic losses to particular dairy farms. The purpose of this study was to evaluate the survival of 50 isolates of P. zopfii in milk subjected to different heat treatments and the survival of further 106 P. zopfii isolates after exposure to three classes of teat disinfectants: iodine (Dipal), quaternary ammonium compounds (Teat), and dodecylbenzenesulphonic acid (Blu-gard). Of the 50 isolates tested for thermal tolerance, 29 (58%) survived heat treatment at 62 °C for 30 s and 13 (26% of all isolates) of those survived after heat treatment at 72 °C for 15 s. None of the 106 isolates were able to withstand the in-use concentrations of the three disinfectants tested. The highest disinfectant concentrations that permitted survival of at least one isolate were dilutions: 1:1,000 for Dipal (survival rate of 52.8-57.5%), 1:100 for Teat (88.7-90.6%), and 1:10 for Blu-gard (100%). No differences in the survival rates of P. zopfii were observed with respect to the duration of exposure to disinfectant. The results of this study support the previous findings that P. zopfii may resist high-temperature treatments, including that applied in the high-temperature, short-time (HTST) pasteurization process. The obtained data also demonstrate the efficacy of the three classes of teat disinfectants against P. zopfii, with the efficacy of iodine being most pronounced. The study emphasizes the necessity of using higher temperatures in the pasteurization of raw milk to kill the Prototheca algae, as well as the particular suitability of the iodine for the control procedures of protothecal mastitis.

Biofilm-producing ability and efficiency of sanitizing agents against Prototheca zopfii isolates from bovine subclinical mastitis

“…The longer the incubation period, the higher the concentration of sanitizer needed to prevent reproduction of the P. zopfii isolates. Lassa et al (2011) evaluated the effectiveness of 3 sanitizers at preventing reproduction of P. zopfii; however, in contrast to the present study, they reported that the efficiency of the sanitizer depends more on the concentration used than on the incubation period.…”

“…Furthermore, in response to exposure to the IAA/HRP, cellular viability and colony production of P. zopfii were reduced. In another study, the use of teat sanitizers was evaluated and, in contrast to the present study, iodine was the most efficient sanitizer (Lassa et al, 2011).…”

“…After 24 h of incubation, P. zopfii isolates were sensitive in vitro to peracetic acid (MIC 90 ≥0.019 g/L), sodium hypochlorite (MIC 90 ≥0.312 g/L), and iodine solution (MIC 90 ≥0.625 g/L). Similar to the present study, Lassa et al (2011) assessed the efficiency of teat sanitizers in vitro (iodine, didecyldimethylammonium, and dodecylbenzenesulfonic acid) on reproduction of P. zopfii. In that study, of the 3 sanitizers, iodine had the greatest efficiency for prevention of mastitis caused by P. zopfii.…”

“…Studies evaluating the use of sanitizers to reduce contamination of utensils and milking and dairy farm equipment or to prevent the IMI caused by P. zopfii are scarce (Cunha et al, 2010;Marques et al, 2010a;Lassa et al, 2011). Marques et al (2010a) assessed effects of different salt concentrations and pH on Prototheca spp.…”

“…Prototheca zopfii shows high resistance to heat treatment (Melville et al, 1999;Lassa et al, 2011). Such resistance represents a risk to the consumption of milk and dairy products, because heat treatment is used to eliminate many pathogenic agents (Melville et al, 1999).…”