Isolation, Enumeration, and Characterization of Aeromonas from Polluted Waters Encountered in Diving Operations

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Abstract
Counts of total viable, aerobic, heterotrophic bacteria, indicator organisms and Aeromonas spp. were made at a diver training site on the Anacostia River in Washington, D.C. [USA]. The numbers of Aeromonas cells in Anacostia River sediment and water increased during periods of elevated water temperature, to maxima of 4 .times. 105 cells/g sediment and 300 cells/ml water. Aeromonas counts dropped 2-4 logs as the water temperature decreased to 0-0.5.degree. C. Cultures taken by sterile swabs from the ears and face masks of divers after a 30 min swim in the Anacostia River yielded bacterial types and numbers similar to those found in the river. The nasal passages of the divers apparently did not become contaminated by swimming, possibly because of the protective effect of the face masks used by the divers. Properties associated with virulence in A. hydrophila and A. sobria strains isolated from the river, sediment and divers were investigated. Nearly 40% of the strains of both species collected during the study produced cytotoxic activity for mouse Y-1 adrenal cells and elastase. Enterotoxin activity, detected by the Y-1 assay, was observed in 3% (1 of 35) of the strains of A. sobria and in 6% (19 of 330) of the A. hydrophila strains. Fluid accumulation in rabbit ileal loops induced by both Aeromonas spp. varied greatly among the 17 strains examined. Fluid accumulation of at least 0.4 ml/cm was correlated with positive cytotoxin- or enterotoxin-like response in the Y-1 tissue culture assay.