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AIMS: To demonstrate the stability of microorganisms preserved in LENTICULE discs, employed by the EQUAL Scheme for Indicator Organisms. METHODS AND RESULTS: Five sample batches containing several indicator organism parameters were each despatched in two separate distributions at intervals of up to 24 months apart. A comparison of participants' median counts and bar charts of their cumulated results was then made. CONCLUSIONS: The results demonstrated that LENTICULE discs provided a remarkably stable preparation format for the maintenance of viable organisms in reproducible numbers. SIGNIFICANCE AND IMPACT OF THE STUDY: Complex mixtures of organisms can be maintained in stable numbers for extended periods of time at a freezer temperature of -20 degrees C and satisfactorily transported without the requirement for cold chain conditions.
A study, using four types of water samples ranging from relatively pure stream water to water containing industrial and domestic effluents, was carried out to investigate the effect of storage temperature on four bacterial parameters: total coliform, fecal coliform, fecal streptococcus, and heterotrophic bacteria. In the study, each water sample was cooled immediately after collection to approximately 1.5 degrees C by storage in crushed ice. At 2-, 24-, 30-, and 48-h intervals, the sample was mixed, and a subsample was removed and tested. Three separate analyses for each parameter were made on each subsample. The data available for statistical analyses contained, in some cases, the values obtained for the three subsamples and, in others, the means of the three values. The data were analysed as replicated data and as part of the entire set. The analysed data indicated (i) that with the exception of heterotrophic populations, more than 75% of the samples were microbiologically stable for at least 24 h, (ii) that at least 50% of samples tested for heterotrophic densities were stable for a minimum period of 24 h, (iii) that the original water temperature and bacterial load do not appear to be consistent factors in the preservation of samples for microbiological analysis, and (iv) that nutrient levels, also, do not seem to be consistent factors in the preservation of water samples for microbiological analyses.
Test strains suspended in skim milk, quickly frozen in dry ice-ethanol, and stored at - 70 degrees C can be used as quality control samples that are immediately available by quickly thawing at 37 degrees C. The samples remain homogeneous and stable for at least 1 year, except for Aeromonas hydrophila, which decreases 20 to 30% in 1 year.
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As a physical disinfection method without chemicals required the ultraviolet irradiation was tested for disinfection of drinking water. The survival was measured as a function of exposure to radiation for S. enteritidis, E. cloacae, C. freundii, S. marcescens, E. coli, K. pneumoniae und S. faecium. The bacteria were grown in trypton soya broth until they were well into the exponential phase. Two different UV-disinfection units were tested. Both consist of cylindrical shaped chambers with one low-pressure mercury-discharge lamp with their longitudinal axis parallel to the chambers. With 10(6) cfu/ml the experiments were done with three different rates of flow of 7,2 m3/h, 4,0 m3/h and 2,0 m3/h. The minimum exposures to radiation necessary to cause a 99.999% reduction were 10-86 mWs/cm2 depending on the test bacterium and on the UV-disinfection unit. The minimum doses ranged for S. enteritidis up to 13 mWs/cm2, for E. coli up to 21 mWs/cm2, for K. pneumoniae up to 39 mWs/cm2, for S. faecium up to 42 mWs/cm2, for E. cloacae up to 43 mWs/cm2, for C. freundii up to 72 mWs/cm2, and for S. marcescens up to 86 mWs/cm2.
Untreated surface water of a total bacterial count of approximately 10(4) cfu/ml was contaminated additionally with suspensions of E. coli and S. faecium, which contained about 10(6) cfu/ml. At flow rates of 7.2 m3/h, 4.0 m3/h and 2.0 m3/h the survival of bacteria as a function of exposure to radiation was measured with two different U.V.-disinfection units. In surface water, -without an additional contamination -minimum doses of radiation up to 74 mWs/cm2 were necessary to cause a reduction of 99.99% for total bacterial counts and counts of lactose-positive colonies. When suspensions of E. coli or S. faecium were added, a reduction of 99.99% for total bacterial count was attainable with minimum doses up to 71 mWs/cm2. To reduce the number of lactose-positive colonies or the number of D-streptococci to 99.99% a minimum dose up 56 mWs/cm2 or 18 mWs/cm2 was necessary.
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Over the last hundred and fifty years, hygienists and health-related water microbiologists have laid down rules of public hygiene and sanitary systems to protect the health of populations. This program has proven to be particularly effective against "fecal peril". But in developed countries waterborne infectious disease nevertheless still persists. This fact has led to much research on contamination due to waterborne micro-organisms. The emergence of the paradigm of risk assessment should allow microbiologists to focus their research effort on priority areas of prevention.
Microbiological examinations of mouth-cleaning, cooling, and turbine spray waters from various types of dental units showed different degrees of water contamination. The detection of Pseudomonas aeruginosa, because of the classification of this organism as a "problem germ", indicates the necessity for a more critical analysis of water used in stomatology including the elimination of possible sources of contamination.
Drinking water quality depends on standards, monitoring and treatment. Israel's microbiologic water standards are less stringent than those currently recommended internationally, and have focused primarily on bacteriologic levels. Compliance with routine monitoring requirements averaged 86% in 1985-86. However, compliance with retesting of contaminated samples averaged 49% in 1985-86. Compliance with treatment recommendations of district sanitary engineers has also been poor. Poor water quality continues to be a public health problem in Israel, and has contributed to a relatively high incidence of waterborne disease. Current international guidelines recommend filtration and chlorination, particularly for surface water and other contaminated sources. Israel should make this a major public health priority.