Correlation of the suicide phenomenon in Aeromonas species with virulence and enteropathogenicity.

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Certain strains of mesophilic aeromonads (Aeromonas hydrophila, A. sorbria, and A. caviae), when grown in broth containing 0.5% glucose, undergo growth inhibition concomitant with acetate accumulation. Because these strains are nonviable after 24 h, this phenomenon is termed suicide. We investigated suicidal strains of Aeromonas species as a means of understanding animal virulence and enteropathogenicity. To assess virulence, batches of five white mice were inoculated intraperitoneally with 10(7) cells (washed) of suicidal and nonsuicidal strains of A. hydrophila and A. sobria and suicidal strains of A. caviae. The three nonsuicidal strains of A. sobria tested showed lethality as early as 12 h and were uniformly fatal within 36 h postinoculation. After 36 h, the three suicidal strains killed only 1 of 15 mice inoculated. Four A. hydrophila strains tested which showed the suicide phenomenon at 37 degrees C were variably lethal (40 to 100%). None of three suicidal strains of A. caviae were lethal. Enteropathogenicity was studied by orally inoculating three white mice each with the same Aeromonas strains (10(8) cells, in skim milk) and assessing diarrhea and intestinal fluid accumulation. Diarrhea and fluid accumulation were present in all mice inoculated with two nonsuicidal strains of A. sobria and in 4 of 12 mice given four suicidal strains of A. hydrophila. Two suicidal strains each of A. sorbria and A. caviae failed to elicit any gastrointestinal disturbances. These data suggest that the suicide phenomenon may explain strain-specific (A. sobria and A. hydrophila) and species-specific (A. caviae) virulence and enteropathogenicity.

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