The results of a survey of the bacterial flora in many sites in 21 homes are discussed. In all areas both wet and dry, coagulase negative, Gram positive cocci and Bacillus spp. were found. Wet areas such as kitchen sinks and drains contained large numbers of Escherichia coli and sometimes Klebsiella pneumoniae, Citrobacter and Enterobacter spp. In toilet areas, little evidence was found of contamination with organisms of faecal origin. Of 47 samples taken from teacloths and towels 22 were contaminated with Staphylococcus aureus although the actual numbers of this organism were low. Pseudomonas aeruginosa was isolated from several sites in one home only. 002 1-8847/78/030357+08$01.00/0 13571 0 1978 The Society for Applied Bacteriology 18 1 1 m 2 m 3: 0 z m * Wet areas sampled with MacConkey agar and dry areas with PPD agar. w m 0

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

SYNOPSIS One hundred and five samples of clear, soluble phenolic disinfectants were obtained from varying sites in the wards of six hospitals. The concentration of disinfectant in each sample was measured by a colorimetric method and bacterial contamination was measured by an 'in-use' test and a membrane filter technique. The concentrations of disinfectant in 24/105 (23 %) samples were at the recommended level and 53 (505 %) were below. Bacterial contamination with Gram-negative bacilli was found in 26/49 (53 %) samples containing less than 0-8 % of disinfectant and 5/86 (8-9 %) samples containing more than 0-8 %. The concentrations in two of the heavily contaminated samples were 1.5% and 1.6% respectively.The wide variety of disinfectants used in hospitals has been described in several surveys (eg, Public Health Laboratory Service Report, 1965;Ayliffe, Brightwell, Collins, and Lowbury, 1969). Since these reports were published, disinfectant policies have been introduced in many hospitals, but others either have no policy or still use expensive and often inappropriate disinfectants for treating the environment. The principles of formulating a policy were described by Kelsey (1970), and the 'in-use' dilutions are usually chosen from the manufacturers' recommendations or on the basis of the capacity test (Kelsey and Sykes, 1969). However, a laboratory test cannot reproduce the wide range of conditions which exist when the disinfectant is in use, and it is, therefore, advisable to carry out in-use tests for bacterial contamination (Kelsey and Maurer, 1966) when a new disinfectant is introduced into a hospital and at intervals afterwards. The in-use test will not determine whether contamination is due to an inadequate concentration of disinfectant or whether organisms are surviving or growing at or above the recommended concentration; inadequate concentrations of disinfectant in the absence of bacterial contamination will also not be detected. In this study, concentrations of disinfectants were measured under in-use conditions by means of a colorimetric test and bacterial contamination was assessed by an in-use test (Kelsey and Maurer, 1966) and by a technique using a membrane filter. MethodsSamples were collected from six hospitals, all of Received for publication 30 March 1972. whichhaveadisinfectantpolicyand mainly use aclear, soluble phenolic disinfectant, Stericol, for environmental disinfection. One hundred and five samples of solutions of the phenolic disinfectant were collected from mop buckets, toilet-brush holders, thermometer holders, containers for contaminated instruments, and other in-use situations. Some samples of chlorhexidine, Savlon, and other disinfectants were also collected. COLORIMETRIC MEASUREMENT OF CONCEN-TRATION OF PHENOLIC DISINFECTANTOf 2 %/aminophenazone, 0-1 ml and 9-8ml of 0025 % sodium carbonate were added to 0-1 ml of the disinfectant. Then 01 Iml of 2% potassium fernicyanide was added, and after mixing readings were made in a spectrophotometer at 545 nm. A standard curve was pr...

A technique with the use of miniature brushes and single inoculum onto multiple slants or plates is described. The technique drastically reduced the time usually required for the preparation of replicate cultures in the teaching of mycology without the sacrifice of macroscopic or microscopic cultural characteristics.

A spatiotemporal model for antibiotic accumulation in bacterial biofilm microcolonies which leverages heterogenous porosity and attachment site profiles replicated the periphery sequestration phenomena reported in prior experimental studies on Pseudomonas aeruginosa PAO1 biofilm cell clusters. These P. aeruginosa cell clusters are in vitro models of the chronic P. aeruginosa infections found in adult cystic fibrosis patients, which display resistance to antibiotic treatments, leading to exacerbated morbidity and mortality. This resistance has been partially attributed to periphery sequestration, where antibiotics are unable to penetrate biofilm cell clusters. The underlying physical phenomena driving this periphery sequestration have not been definitively established. This paper introduces mathematical models to account for two proposed physical phenomena driving periphery sequestration: biofilm matrix attachment and volume-exclusion due to variable biofilm porosity. An antibiotic accumulation model which incorporated these phenomena was able to better fit observed periphery sequestration data compared to previous models.