Pathogenesis of Campylobacter Fetus Infections: Serum Resistance Associated with High-Molecular-Weight Surface Proteins

Campylobacter fetus subspecies fetus causes both systemic and diarrheal illnesses. We studied 38 strains of C. fetus isolated from 34 patients; underlying illness was present in eight (89%) of nine patients with only systemic isolates compared with three (20%) of 15 patients with only fecal isolates (P = .002). In a standardized assay of susceptibility to normal human serum, 27 (71%) strains were resistant, six (16%) had intermediate susceptibility, and five (13%) were serum sensitive. Major protein bands migrating a 100 kDa or 125 kDa on polyacrylamide gels were present in all of the 25 serum-resistant strains tested but in only four of seven serum-sensitive isolates of C fetus from humans and animals (P = .007). The presence of these bands was associated with type A lipopolysaccharide. A low-passaged strain, 82- 40, was serum resistant and contained the 100-kDa protein; however, a spontaneous mutant of this strain lacked this band and was serum sensitive. The 100-kDa and 125-kDa proteins of three strains of C fetus were antigenically cross reactive or identical and were exposed on the surface of the C fetus cell. Serum resistance is inherent to most C. fetus isolates from humans and is associated with the presence of cross-reactive surface proteins Availability: Pub. in Jnl. of Infectious Diseases, v155 n4 p696- 706 Apr 1987.