No abstract

The occurrence of Aeromonas spp. in the metropolitan water supply of Perth, Western Australia, Australia, was monitored at several sampling points during a period of 1 year. Water within the distribution system conformed to international standards for drinking water but contained Aeromonas spp. in numbers comparable to those in raw surface water, although this water was free of Escherichia coli. Coliforms and E. coli were found in raw surface waters, and Aeromonas spp. were found in raw water from surface and underground sources. Chemical treatment, followed by chlorination at service reservoirs, resulted in water free of E. coli and a decrease in the number of Aeromonas spp. Aeromonas spp. were found in the greatest numbers in summer. Multiple regression analysis showed that growth of Aeromonas spp. in chlorinated water was related to water temperature, residual chlorine, and interaction between these variables. The incidence of Aeromonas-associated gastroenteritis, determined from isolates referred to us for enterotoxin testing, paralleled the pattern of isolation of Aeromonas spp. in water within the distribution systems. We suggest that the presence of Aeromonas spp. in drinking water needs public health appraisal and that further work should be undertaken to permit reevaluation of standards for the quality of drinking water.

A prospective, 12-month study of 975 non-Aboriginal children with diarrhea and age- and sex-matched children without diarrhea, in Perth, Western Australia, was designed to investigate the significance of enterotoxigenic Aeromonas species as a cause of diarrhea. Enterotoxigenic Aeromonas species were found in the fecal specimens of 10.8% of the patients with diarrhea but in only 0.7% of those without diarrhea. Most Aeromonas species were isolated during the summer. Other important bacterial pathogens included Campylobacter, Salmonella, Shigella, and enterotoxigenic Escherichia coli; rotavirus infections appeared to be much less important in the Western Australian environment. Most of the patients were younger than two years of age and about one-quarter had mixed bacterial and/or viral intestinal infections. Enterotoxigenic Aeromonas species can be identified with 97% accuracy using a simple hemolysin assay which should be considered for use by routine diagnostic laboratories, particularly in children's hospitals.

The traditional contour method maps a single component of residual stress by cutting a body carefully in two and measuring the contour of the cut surface. The cut also exposes previously inaccessible regions of the body to residual stress measurement using a variety of other techniques, but the stresses have been changed by the relaxation after cutting. In this paper, it is shown that superposition of stresses measured post-cutting with results from the contour method analysis can determine the original (pre-cut) residual stresses. The general superposition theory using Bueckner's principle is developed and limitations are discussed. The procedure is experimentally demonstrated by determining the triaxial residual stress state on a cross section plane. The 2024-T351 aluminum alloy test specimen was a disk plastically indented to produce multiaxial residual stresses. After cutting the disk in half, the stresses on the cut surface of one half were determined with X-ray diffraction and with hole drilling on the other half. To determine the original residual stresses, the measured surface stresses were superimposed with the change stress calculated by the contour method. Within uncertainty, the results agreed with neutron diffraction measurements taken on an uncut disk.

No abstract

No abstract

Biotypes of Aeromonas spp. correlated well with enterotoxin production in a study of 174 strains. Using biochemical characteristics determined by conventional methods and multitest systems, we correctly classified 93% of the strains with regard to enterotoxin production. Most of the enterotoxigenic strains were Voges-Proskauer (VP) positive and did not hydrolyze arabinose, but VP-positive strains which hydrolyzed arabinose were mainly non-enterotoxigenic. Aeromonas punctata subsp. caviae, which is VP negative and does not oxidize gluconate or produce gas from glucose, was non-enterotoxigenic. Although the number of other VP-negative strains was small, most were enterotoxigenic. Discrimination was improved so that 97% of the strains were correctly classified if the hemolysin assay was used either for all strains or for only the VP-positive, arabinose-positive and VP-negative, non-A. punctata subsp. caviae strains. Because the proposed classification system does not require facilities for carrying out in vivo assays such as suckling mouse or ileal loop methods, the identification of enterotoxigenic Aeromonas strains should be possible in diagnostic laboratories and will facilitate epidemiological studies of the role of these organisms in acute diarrhea. Aeromonas hydrophila has been implicated as a cause of diarrhea in several countries (12). The finding that some strains of A. hydrophila are enterotoxigenic (9) provided further evidence for considering this organism to be an enteric pathogen. However, epidemiological studies of the role of enterotoxigenic Aeromonas spp. in acute diarrhea have been limited by difficulties in isolating these organisms (12) and in identifying enterotoxigenic strains. Aeromonas spp. may produce three types of

ResearchFoundat ion, Per th , Western A us tralia PLATE XXVIII SUMMARY. The suckling-mouse assay was reliable for detecting enterotoxigenic strains of Aeromonas hydrophila when standard conditions for growth and toxin testing were used. Enterotoxins were produced by bacteria grown in tryptone soya broth supplemented with yeast extract and aerated by shaking in an environmental incubator or water bath. When culture supernates together with dye were administered intragastrically to mice less than 6 days old, the presence of enterotoxin was assessed on the basis of a scoring system that incorporated the ratio intestinal weight : remaining body weight, and production of diarrhoea. This method should facilitate the detection of enterotoxigenic strains of Aeromonas in epidemiological studies.