Viabilidad in vitro y colonización en ratones neonatos de una formulación vacunal de la cepa 638 de Vibrio cholerae

Abstract

The viability and the colonization capacity of the lyophilized vaccinal formulation of 638 strain Vibrio cholerae biotype El Tar Ogawa [cttxF, ce/A⁺] from C7258 strain resuspended with sodium bicarbonate solution were evaluated. Two batches (00 and 01) were obtained and a sub-batch preserved for 7 d at 45°C. The lyophilized were resuspended in phosphate buffer solution (PBS) or in sodium bicarbonate solution (1.3 17b). Positive control suspensions of 638 strain were prepared also, from fresh plate culture (triptose soy agar without glucose). The viability was evaluated by colony forming units (CFU)/mL determination at 0, 10, 20,40 and 60 min of resuspended. The colonization capacity was evaluated at the moment of resuspension of product in neonatal mouse model, by oral inoculation of 50 µL with 10⁵ CFU/mouse. Ten mice per group were used. Number of bacteria recoverable from mice was determined by homogenization of intestine from mice. Suitable serial dilution (1:10) of the homogenates were plated on thiosulphate-citrate-bile salt-sucrose agar for viable counting. The experiments were repeated three times . Analysis of variance and t-Student were applied for statistical comparison of results. No significant differences of viability or colonization when vaccinal formulation
was resuspended with PBS or sodium bicarbonate. solution, in all studied moments was found. The sub-batch conserved 7 d at 45°C showed a significant difference in viability, but not in colonization capacity. Nor it showed any difference with colonization values obtained in mice inoculated with fresh cultures. These results allow to say that the evaluated product resuspended in sodium bicarbonate have a satisfactory response, in viability and colonization in neonatal mouse model.