Table 2.

Virulence of S. typhimurium strains for 3- to 4-week-old Friesian-Holstein calves

StrainGenotypeResult for infection with 1010 CFU/animal
No. dead/no. totalAvg time to death (days)Avg fecal scorea
IR715Wild type8/83.13.1
STN61 hilA 0/4 NAb 1.9
STN119 spiB 2/22.33.8
STN162 prgH 0/2NA2.1
STN166 rfaJ 1/233.4
STN272 spvR 2/21.24
SVM255 sopB 2/243.8
BA1567 sopB 2/243.1
CL1509 aroA 0/2NA2.1
  • a Fecal scores were used to assess the severity of diarrhea, where 1 = normal feces; 2 = soft feces with loss of distinct conformation; 3 = diarrhea, loose feces with reduced solid matter; and 4 = diarrhea, aqueous feces with markedly reduced or little solid matter, blood, or fibrin.

  • b NA, not applicable.