Differential resistance to Staphylococcus aureus challenge in major histocompatibility (B) complex congenic lines

Ten inbred B-congenic Leghorn lines were challenged with two isolates of Staphylococcus aureus at 3 days and 6 wk of age. Significant differences in mortality were observed among such lines when challenged at 3 days with either S. aureus Isolate P4L (moderately pathogenic) or S. aureus Isolate 3727 (highly pathogenic). Line 331 (B2/B2 genotype) had lower mortality than either Line 004 (B17/B17, chi 2 = 4.13, P < .05) or Line 253 (B18/B18, chi 2 = 4.23, P < .05) challenged with Isolate P4L. The use of a susceptibility index allowed for the detection of additional differences among the various lines challenged by Isolate 3727. Line 336 (BQ/BQ) was more resistant than either Line 335 (B19/B19, P < .01) or Line 330 (B21/B21, P < .01). No significant differences were found among the lines challenged at 6 wk by either isolate. The results provide additional evidence for the importance of the B complex in genetically determined disease resistance, and further demonstrate the usefulness of congenic lines in such investigations.