Virulence of B. avium Hag mutants

StrainHag genotypeHag phenotypeID50 × 10−6aID50 statistically different from that of 197Nb
197NWild type+2 ± 3NA
197N/pLAFR5Wild type/vector+7
PAS667 /pLAFR5ΔhagB/vector>30+
PAS667/phagBΔhagB/phagB+2 ± 2
  • a Fifty percent infectious dose (ID50) values were determined as described previously (29). The values indicate the dose needed to recover the inoculated strain from the tracheas of 50% of turkeys at 2 weeks postinoculation. The “greater than” sign (>) indicates that no isolates were recovered from colonized turkeys exhibiting the inoculated Hag phenotype at any dose given. The numeric value shown after the > indicates the lowest possible ID50 achievable (i.e., it represents the ID50 value generated if all birds were colonized at a dose 1 order of magnitude higher than the highest dose employed in the actual experiment). The standard deviation of the mean ID50 is indicated. For the parental strain, the ID50 values from seven independent and identical experiments were averaged. For PAS667/phagB, the values from two experiments were averaged.

  • b The statistical analysis was performed using the log10 ID50 values shown in the table. +, significant difference; −, no difference (P > 0.05). The Z test was employed as described previously (29) in those cases where a single ID50 determination was performed. NA, not applicable.