Response of gonococcal clinical isolates to acidic conditions

This study examined the response to acidic conditions of four gonococcal is olates NRL38874 (Proto/IB-2), NRL38884 (Pro/IA-2), NRL38953 (Proto/IB-3) an d NRL39029 (Pro/IA-3) - obtained from various sites in patients in whom a d iagnosis of pelvic inflammatory disease had been made by laparoscopic exami nation, Acid tolerance of the clinical isolates was strain and growth phase dependent, Growth of the four strains on solid media was undetectable belo w pH 5.8. In liquid culture, strain NRL38884 did not survive below pH 5.2; strains NRL38874, NRL38953 and NRL39029 survived to pH 4.5, Between pH 4.2 and pH 5.1, the latter three strains exhibited a peak in survival at pH 4.6 -3.7 during log phase, suggesting that there may be a distinct acid toleran ce system operating at this pH, SDS-PAGE of whole-cell, total membrane and outer-membrane fractions of the four strains prepared from pH 7.2 and pH 6. 1 plate cultures revealed numerous differences in protein composition. Acid ic conditions reduced the expression of the reduction modifiable outer-memb rane protein Rmp, and induced the expression of many membrane proteins, inc luding gonococcal hsp63, Immunoblotting studies with matched serum samples and strains from patients with pelvic inflammatory disease indicated that I gG recognition of outer-membrane components from strains cultured in acidic and neutral conditions was quite different. The results suggest that the i mmune system interacts with unique outer-membrane constituents on gonococci colonising sites at different pH.