Correlation of enterotoxicity with biotype in Aeromonas spp

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Abstract
Enterotoxin production correlated with biotype in a study of 686 strains of Aeromonas spp. from Indonesia, Thailand, the USA and Western Australia. Most strains were isolated from feces; nonfecal human isolates and environmental strains were also included. Of Voges-Proskauer (VP)-positive strains, classified as A. hydrophila, 80% were enterotoxigenic in the suckling mouse assay as were 90% of VP-positive, arabinose-negative strains. An association between positive VP, arabinose fermentation and failure to produce enterotoxins was found only with environmental strains. VP-negative strains which did not oxidize gluconate or produce gas from glucose were classified as A. punctata ssp. caviae. Of the 286 strains, 2 produced enterotoxins; both were from Indonesian fecal samples. There were a few remaining VP-negative strains, classified as A. punctata ssp. punctata; of these, .apprx. 1/2 were enterotoxigenic. Regardless of source and species, 97% of Aeromonas spp. were correctly classified in relation to enterotoxin production with a hemolysin assay. A combination of biochemical testing and hemolysin assay should be suitable for diagnostic laboratories to identify enterotoxigenic Aeromonas spp. which, in children, are associated with diarrhea, unlike non-enterotoxigenic strains.