NON - SPECIFIC RESISTANCE TO EXPERIMENTAL CHOLERA Materials

Thus, Bohnhoff et al. (1) made mice more susceptible to oral challenge with a streptomycin-resistant strain of Salmonella enteritidis by pretreatment with streptomycin. They concluded that this increase in susceptibility resulted from a disturbance of the normal intestinal microflora. Using a similar method, Freter (2-4) was able to induce an asymptomatie carrier state in guinea pigs and mice with drug-resistant strains of Shigella and Vibrlo cholerae. Feeding an Esckeriekia coil strain together with the pathogen prevented this carrier state and also increased the resistance of guinea pigs to a fatal enteric infection established by oral challenge following fasting. The developing chick embryo has found wide application in the study of experimental infections and, as emphasized by Buddingh (5) and Cox (6), much may yet be learned from this experimental system. While the chick embryo appears to be an ideal tool for the study of combined infections, it seems to have been applied only, in this regard, by Bang (7) in the swine influenza system. The susceptibility of the chick embryo to infection with Vibrio cholerae was first demonstrated by Wilson (8). His observations were extended by Lankford and his students (9-11) who studied the chick embryo virulence of a large series of cultures, including colonial and antigenic variants of recent isolates from a cholera outbreak in Calcutta. Reproducible LDs0 values were obtained by intra-allantoic inoculation of 13-day-old chick embryos provided that only deaths occurring within 24 hours are considered. There was some indication that virulence of cholera strains for the chick embryo may be correlated with pathogenicity for man.