title: Immunological characterization of diphtheria toxin recovered from Corynebacterium pseudotuberculosis.
abstract: Diphtheria toxin (DT) is a potent toxin produced by the so-called diphtheria group which includes Corynebacterium diphtheriae (C. diphtheriae), Corynebacterium ulcerans (C. ulcerans), and Corynebacterium pseudotuberculosis (C. pseudotuberculosis). The present investigation is aimed to study in detail the production of DT by C. pseudotuberculosis. Twenty isolates were obtained from sheep diseased with caseous lymphadenitis (CLA) and twenty-six isolates were obtained from 26 buffaloes diseased with oedematous skin disease (OSD). All isolates were identified by standard microbiological and DT production was assayed serologically by modified Elek test and immunoblotting. All sheep isolates were nitrate negative, failed to hydrolyze starch and could not produce DT, while all buffalo isolates (biotype II) revealed positive results and a specific band of 62 kDa, specific to DT, was resulted in all concentrated cell fractions (CF), but was absent from non-toxigenic biotype I isolates. At the same time, another band of 31 kDa specific to the PLD gene was obtained with all isolates of biotype I and II. Moreover, all isolates showed positive synergistic hemolytic activity and antagonistic hemolysis with β-hemolytic Staphylococci. The obtained results also indicated that C. pseudotuberculosis could be classified into two strains; non-toxigenic biotype I strain, which failed to produce DT as well as being negative to nitrate and starch hydrolysis, and toxigenic biotype II strain, which can reduce nitrate, hydrolyze starch as well as produce DT.
authors.affiliation: Department of Microbiology, Faculty of Veterinary Medicine, Cairo University, P.O. 2446, Cairo, 14242 Giza, Egypt.
authors.forename: Salha Abdelkareem
authors.initials: SA
authors.lastname: Selim
authors.affiliation: Department of Microbiology, Faculty of Veterinary Medicine, Cairo University, P.O. 2446, Cairo, 14242 Giza, Egypt.
authors.forename: Farida Hessain
authors.initials: FH
authors.lastname: Mohamed
authors.affiliation: Department of Microbiology, Faculty of Veterinary Medicine, Cairo University, P.O. 2446, Cairo, 14242 Giza, Egypt; Department of Health Science, College of Applied Studies and Community Service, King Saud University, P.O. Box 22459, Riyadh 11495, Saudi Arabia.
authors.forename: Ashgan Mohamed
authors.initials: AM
authors.lastname: Hessain
authors.affiliation: Department of Microbiology, Faculty of Veterinary Medicine, Cairo University, P.O. 2446, Cairo, 14242 Giza, Egypt; Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Ihab Mohamed
authors.initials: IM
authors.lastname: Moussa
keywords: C. pseudotuberculosis; Diphtheria toxin; Immuno-blotting technique; Immunological characterization; Modified Elek test