Enteropathogenicity of Aeromonas species isolated from infants: a cohort study.

The significance of Aeromonas spp. as potential enteric pathogens was evaluated in a cohort of 187 infants aged 3-18 months during a 16-week summer period. Aeromonas spp. were isolated from 14 of the 196 (7.1%) diarrhoeal episodes detected and from eight (5.2%) of 153 samples from paired asymptomatic infants. Carriage of bacterial enteropathogens excluding Aeromonas spp. was detected in a high proportion (23%) of the asymptomatic children. Almost all of the seven isolates of Aeromonas sobria were enterotoxigenic, invasive and beta-haemolytic. In contrast, none of the seven Aeromonas caviae strains had these virulence-associated characteristics. The only isolate of Aeromonas hydrophila produced cytotoxic enterotoxin and was invasive. Plasmid analysis of selected strains did not correlate with these two properties or with antibiotic resistance. Nevertheless, the latter was found in an important proportion of the isolates. The diarrhoeal episodes, in which Aeromonas spp. were detected, lasted significantly longer, i.e. 17.2 days when the strains were invasive and/or toxigenic as compared with 4.3 days (P less than 0.001) in patients harbouring strains lacking both traits. These results reinforce the need to characterise virulence determinants before assigning any pathogenic role to Aeromonas spp. isolated from faecal specimens. Our findings also suggest the need for adequate antibiotic treatment in patients with confirmed Aeromonas spp. having enterotoxigenic and/or invasive properties.