A prospective cohort epidemiological-microbiological study was carried out at 10 beaches in Ontario, Canada. Lake water and sediment samples collected at the beaches were analyzed for fecal coliforms, fecal streptococci, heterotrophic bacteria, Pseudomonas aeruginosa, and total staphylococci. Mean fecal coliform levels in the surface water of the lakes were within accepted guidelines. Bacterial densities were found to be approximately 10 times higher

During the summer of 1980, both swimmers and nonswimmers were enlisted in a prospective epidemiological study to determine the relationship between swimming, water quality, and the incidence of illness. Results of 4,537 telephone follow-up interviews showed that crude morbidity rates were 69.6 per 1,000 swimmers

Various types of swimming pools were investigated for the quantitative isolation of Pseudomonas aeruginosa. Incidence of the organism increased when the free chlorine residual dropped below 0.4 mg/L in pool water which ad a pH of 6.9-8.9. As the water pH became more alkaline the efficiency of disinfection decreased. Excessive slime production caused certain strains to become more resistent to chlorine treatment. Immunotyping and phage typing, used to study the dynamics of P. aeruginosa populations in swimming pool waters, demonstrated that high densities of the organism consisted mainly of single predominant strains.

S U M M A R YTwo hundred and seventy Gram-negative strains, representing aquatic members of the genus Acinetobacter, were isolated and compared with 48 related clinical isolates and reference strains from a variety of genera. For each isolate, a total of 96 coded characters derived from 89 characteristics was determined using morphological, physiological, nutritional and biochemical features, in addition to sensitivities to several antibiotics and inhibitory agents. The data were analysed by computer to obtain a simple matching coefficient for each pair of strains. Clustering was performed by the unweighted pair-group method of association.Two major phenons were formed which excluded the oxidase-positive, motile or facultatively anaerobic strains. Within each phenon, thee ' subphenons ' were delimited. The two phenons, comprising 29 I isolates, were tentatively differentiated at the species level, while their shared characteristics indicated that both phenons should be included in the genus Acinetobacter. Phenon 2 contained most of the clinical isolates and corresponded to the type species Aci. calcoaceticus as described originally by Baumann, Doudoroff & Stanier (1968). Phenon I was composed almost entirely of aquatic isolates and may prove to represent a second species of a less biochemically-active nature. Distinguishing characters have been suggested as diagnostic criteria for the differentiation of these two phenons.

An electronic computer was used to analyze the data obtained for 82 strains of streptococci, lactobacilli, and propionibacteria. The lactobacilli were divided into three major taxonomic groups which correspond to the subgenera Thermobacterium, Streptobacterium, and Betabacterium described by Orla-Jensen (14). Three clusters observed among the streptococcal strains also correlate with Sherman's (19) classification of pyogenic, fecal, and lactic groups of streptococci. The results are in agreement with present classifications. No justification for including the genus Lactobacillus in the same family as genus Propionibacterium was found.