An outbreak of waterborne cryptosporidiosis in Swindon and Oxfordshire.

An outbreak of cryptosporidiosis resulted in 516 cases in Wiltshire and Oxfordshire. The outbreak caused widespread interest and led to an official inquiry. The majority of cases were in children; 8% of cases were admitted to hospital and the median duration of illness was 3 weeks. The geographical distribution of cases matched the distribution of water supplies from three treatment works and cryptosporidium oocysts were found at these works and in the treated water. Attack rates in electoral wards supplied by the three treatment works were significantly higher than in other wards. The cause of the outbreak appeared to be the failure of normal treatment to remove oocysts. Measures at the treatment works reduced the number of oocysts detected in treated water, after which the outbreak came to an end. The conclusion of the investigations was that cryptosporidiosis is a risk of conventionally treated public water supplies.

Treatment of water for aquatic bacterial growth studies.

The composition of a water is inextricably linked to its nutrient status and hence influences the behaviour of bacteria in artificial water systems. It has not yet been possible to devise a defined liquid medium representative of the complex composition of a treated water. Instead sterilized natural or distilled waters are used to study the growth or survival of aquatic bacteria in the laboratory. This has led to conflicting data and opposing opinions when the same water has proved toxic in some laboratory studies and growth-supporting in others. These differences may be explained by the variations in chemical compositions which occur when water is collected, transported and treated or stored in the laboratory. This study describes a simple, membrane filtration method of preparing a fresh sample of water collected from the environment or a building water system such that it is both sterile and chemically unaltered. The availability of such water may enhance understanding of the behaviour of bacteria in the aquatic environment.

Microbiological evaluation of drinking water construction materials--comparison of two test procedures.

Materials used in contact with drinking water can impair water quality by supporting the growth of aquatic microorganisms. In order to prevent this problem several different test procedures have been developed but to date no comparative study of the performance of these methods has been published. During collaborative studies between the regional laboratories of the Thames Water Authority, London, and the Institute of Hygiene, University Bonn, duplicate samples of 11 PVC materials were exchanged and evaluated by the standard methods used in the United Kingdom (UK) and the Federal Republic of Germany (FRG). There was a good agreement between the results as assessed by the published criteria. When a stricter criterion for interpreting the results of the UK method was applied to the findings, a complete agreement between the methods was observed.

Presence of Legionella in London's water supplies.

Legionella occurs frequently (52 to 54%) in domestic water and cooling water inside commercial, industrial and health care buildings, and these types of water systems are now regarded as a normal habitat for Legionella. The factors that predispose a particular water system to colonization by these organisms are ill-defined, although it is fairly certain that biological and physicochemical environmental factors play an important role in allowing Legionella to multiply in the circulating water. It has been postulated that the organism may gain access to water systems inside buildings by one of three routes: contact with air through open points such as uncovered storage tanks or vents, ingress of soil or surface water during construction or repair, or intermittent seeding with organisms present in low numbers in the public water supply. Three studies in the USA have found Legionella in 0.4 to 8.8% of drinking-water samples, but these were not representative of the public supply network as a whole. The aim of this study was to determine, over a period of 1 year, the frequency of Legionella in London's drinking water--from the treatment plant through to the consumer's tap. To date, Legionella has not been isolated from raw river water entering London's treatment works or from treated water entering the distribution network. Sixty-two monitoring taps in buildings located in 21 supply areas have been sampled twice for Legionella; only 2 (2.4%) have proved positive during the autumn and winter of 1985/86. The strain found was L. pneumophila serotype 1, subgroup Olda, and the numbers ranged from 10(2) to 10(4)/l. Although the survey is incomplete, it is already clear that the public water supplies in London are not a source of strains of Legionella associated with disease.

Distribution and persistence of Legionella in water systems.

The Legionellaceae are common aquatic organisms able to colonize man-made water systems. Inadequately maintained or seldom used systems provide ideal amplification sites, where the organisms grow and can be disseminated in aerosols. Legionellaceae can utilize, for growth, compounds leached from construction materials and the products of other organisms.

Water fittings as sources of Legionella pneumophila in a hospital plumbing system.

An extensive study of the plumbing systems in Kingston Hospital was made over the three years following the 1980 outbreak of legionnaires' disease. The introduction of chlorination and raising the water temperature controlled the outbreak but failed to decontaminate water outlets in the wards. Legionella pneumophila was isolated from rubber washers in shower fittings, and laboratory experiments demonstrated the ability of L pneumophila to grow in water in contact with these rubber components. All the components in the hospital's fittings were replaced with an approved type, and since then L pneumophila has not been isolated from water or components.