Enhancement of the virulence of Aeromonas caviae diarrhoeal strains by serial passages in mice

Thirteen clinical Aeromonas caviae isolates from the faeces of 13 children with mild to severe diarrhoea were tested for enhancement of mouse lethalit y, adhesion ability, siderophore and cholera toxin cross-reactive (CTC) fac tor production, by four consecutive passages through mice by intraperitonea l injection of A. caviae suspensions. The passaged A. caviae strains were r e-isolated from monomicrobic cardiac blood samples and inocula were prepare d for the next passage. All A. caviae isolates possessed the ability to adh ere to the mucosal epithelial surface of the rabbit small intestine. Serial passage in mice showed that the virulence of some isolates for mice was in creased in terms of percentage mortality and a lowering of the LD50, For so me of the isolates, but not all, serial passage appeared to increase sidero phore production and adhesion to rabbit small intestinal cells, For the A. caviae isolates tested, increased values of the CTC factor were observed af ter passage. A clear correlation was observed between the lowering of LD50 and the enhancement of CTC factor production after passage in mice. These r esults indicate that the A. caviae isolates possessed virulence factors.