Potential of Klebsiella pneumoniae cytotoxin toxoid as vaccine against klebsiellosis in rabbits and mice.

The protective efficacy of toxoids prepared from crude cytotoxin (polymyxin-B extract, PBE) and purified Klebsiella cytotoxins (KCTs) was studied in rabbits and mice. The toxoids of KCT-I and PBE were found to be protective against homologous as well as heterologous Klebsiella challenges, while toxoids of KCT-II and KCT-III afforded protection in mice against homologous Klebsiella infections. KCT-I and PBE toxoids also induced good humoral anti-Klebsiella response in rabbits with ELISA titres ranging from 20480 to 81480. Immunized female rabbits passed protective anti-Klebsiella immunoglobulins to their offsprings through colostra. Baby rabbits fed on colostrum of immunized rabbits withstood lethal Klebsiella infection up to 1 month of age, but not on the 50th day. Baby rabbits having an anti-Klebsiella IgG titre > or =1280 were fully protected against lethal dose of Klebsiella. The study revealed a significant protective efficacy of KCT-I and PBE toxoids against klebsiellosis in mice and rabbits.