The effectiveness of certain commercial germicides against ropy slime-producing lactic acid bacteria was studied using the 5-5-5-suspension test and a tray test which simulated surface disinfection conditions in actual use. The rate of the destruction of the bacteria was lower in the tray test, and the bacteria seemed to be more resistant to the germicides on a steel surface than in vitro. The sanitizer products proved to be more effective than the detergent-sanitizer products. Quaternary ammonium products and an acid sanitizer with hydrogen peroxide were more effective than products containing chlorine compounds and polyhexamethylene biguanide chloride. The effectiveness of hypochlorite products appeared to be dependent on the concentration of available chlorine. The resistance of the ropy slime-producing bacteria may prove problematic if ineffective germicides are used. The use of detergent sanitizers and low-concentration hypochlorite products is not recommended.

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