SYNOPSIS A membrane filter was used for assessing the surface disinfecting activity of phenolic disinfectants and a chloroxylenol disinfectant. The influence of the type of organism, inoculum size, and hardness of water was investigated. Pseudomonas aeruginosa was chosen for the standardized test. Disinfectant solutions were prepared in water of 300 ppm hardness and applied for two and a half minutes and eight minutes to the bacteria deposited from filtration of 1 ml of a suspension containing 106 bacteria. The membrane filter test has certain advantages over many tests, eg, all organisms surviving after treatment can be counted and residual disinfectant is easily removed.Membrane filtration has been used with considerable success in many branches of microbiology. The technique has been used for studying the activity of antimicrobial drugs (Meers and Churcher, 1974) and also for testing disinfectants (Prickett and Rawal, 1972). Its use offers more flexibility than most other suspension or surface tests, residual disinfectant is more readily removed, and it allows sampling of large volumes of mixtures of disinfectant and organisms.In this study, a test is described using membrane filters for assessing the activity of phenolic disinfectants and a chloroxylenol disinfectant. An attempt has been made to evaluate the influence of various factors, eg, time of exposure to the disinfectant, inoculum size, and hardness of water, on the performance of several disinfectants. Materials and Methods ORGANISMSThe following organisms were used in the experiments:-Staphylococcus aureus (NCTC 9717), Escherichia coli (NCTC 8196), Proteus vulgaris (NCTC 4635), Pseudomonas aeruginosa (NCTC 6749), and Klebsiella aerogenes (JP 1970

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SYNOPSIS Tests of effectiveness of disinfection of metal and polypropylene bedpans were made in a washer fitted with a steam generator. Broth cultures of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, or Streptococcus faecalis (approximately 4 x 108 organisms) were sealed in lengths of capillary tubing and attached to the surface of the pans. In other tests, pans were contaminated with an artificial soil containing Str. faecalis (0I organisms/ml). In both series of tests, counts of surviving organisms were made at the end of the washing and disinfection cycle. The tests using capillary tubes showed that the Gram-negative bacilli were effectively killed, but not necessarily Gram-positive cocci. However, when incorporated in standard soil, Str. faecalis was killed or removed during the cycle.The results indicate that the disinfection process was effective for metal bedpans, but less so for polypropylene. Possible disadvantages and modification of the machine are suggested.

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