Antibacterial Activity of Antisera Against Homologous and Heterologous Escherichia coli of Porcine Origin C. C. Enweani, C. L. Gyles and D. A. Barnum*
ABSTRACT Fourteen enteropathogenic and five nonenterotoxigenic Escherichia coli strains isolated from pigs were used for producing antisera in rabbits and pigs. These antisera were used in an in vitro test system for antibacterial activity against homologous and heterologous porcine E. coli strains. Antibacterial titres were determined against the homologous strains and the percent reduction in CFU/ml caused by a 1/200 dilution of the sera against heterologous strains was determined. The results indicated that following immunization the antibacterial activity of serum against homologous and heterologous strains was significantly increased. This activity did not appear to be influenced by 0 and K antigen relationships among the organisms or by enterotoxigenicity of the vaccine strains. When antiserum produced against a combination of three enteropathogenic E. coli was tested against 20 strains a wider spectrum of heterologous antibacterial activity was obtained than with antiserum produced against any individual strain. The results indicate the existence in E. coli strains of porcine origin of common antigenic determinants not related to the serological formula and that a selected combination of strains can be expected to induce antibacterial activity against a wide variety of serological types of porcine enteropathogenic E. coli.
RESUME Les auteurs ont utilise 14 souches porcines
d'Escherichia coli enteropathogenes et cinq autres ne produisant pas d enterotoxine, pour
*Department of Veterinary Microbiology and Immunology, University of Guelph, Gueiph, Ontario, Canada. Submitted January 15, 1974.
54
preparer des antiserums chez le lapin et le porc. Ils utiliserent ces immun-serums dans un systeme d'epreuves in vitro destine a en ve;rifier le pouvoir antibacterien a l'egard dsouches porcines d'E. coli homologues et heterologues. Ils determinerent les titres antibacteriens de ces antiserums 'a l'endroit des souches homologues, ainsi que le pourcentage de r6duction des unites formatrices de colonies/ml cause par une dilution 1:200 de ces immun-sirums 'a l'endroit des souches heterologues. Les resultats revelerent qu'apries l'immunisation, l'activite antibacterienne du serum a' l'endroit des souches homologues et heterologues subissait une hausse appreciable. Cette activite ne sembla pas subir l'influence des relations entre les antigenes 0 et K des differentes souches, ni celle du pouvoir enterotoxigene des souches vaccinales. Quand on soumit 'a l'influence de 20 souches l'antiserum prepare a l'aide d'un ensemble de trois souches d'E. coli enteropathogenes, on obtint une activite antibacterienne heterologue d'une plus grande envergure qu'avec un antiserum prepare contre l'une ou l'autre de ces souches. Les resultats revilent l'existence chez les souches porcines de facteurs antigeniques communs non relies 'a la formule serologique; ils indiquent aussi qu'on peut s'attendre 'a ce qu'une combinaison choisie de souches suscite une activite antibacterienne 'a l'endroit d'une grande variete de serotypes d'E. coli porcins
enteropathogienes.
INTRODUCTION
Escherichiac coli strains which are en-
teropathogenic for a particular host usual-
ly belong to several different serological types (2, 16). However, organisms belonging to different serotypes may share certain recognized surface antigens such as the K88 antigen (10) as well as other antigens which are not employed in determining serotype. Furthermore, there is
Can. J. comp. Med.
evidence that E. coli strains enteropathogenic for pigs may be more closely related than is indicated by the diversity in their serological formulae (17, 18). Thus, Sweeney (18) found that there was marked interconversion of 0 antigens among different serological types of E. coli enteropathogenic for pigs. The following antigenic changes were demonstrated by Sweeney: 0141 +40157, 098 +0157, 045
ABSTRACT Fourteen enteropathogenic and five nonenterotoxigenic Escherichia coli strains isolated from pigs were used for producing antisera in rabbits and pigs. These antisera were used in an in vitro test system for antibacterial activity against homologous and heterologous porcine E. coli strains. Antibacterial titres were determined against the homologous strains and the percent reduction in CFU/ml caused by a 1/200 dilution of the sera against heterologous strains was determined. The results indicated that following immunization the antibacterial activity of serum against homologous and heterologous strains was significantly increased. This activity did not appear to be influenced by 0 and K antigen relationships among the organisms or by enterotoxigenicity of the vaccine strains. When antiserum produced against a combination of three enteropathogenic E. coli was tested against 20 strains a wider spectrum of heterologous antibacterial activity was obtained than with antiserum produced against any individual strain. The results indicate the existence in E. coli strains of porcine origin of common antigenic determinants not related to the serological formula and that a selected combination of strains can be expected to induce antibacterial activity against a wide variety of serological types of porcine enteropathogenic E. coli.
RESUME Les auteurs ont utilise 14 souches porcines
d'Escherichia coli enteropathogenes et cinq autres ne produisant pas d enterotoxine, pour
*Department of Veterinary Microbiology and Immunology, University of Guelph, Gueiph, Ontario, Canada. Submitted January 15, 1974.
54
preparer des antiserums chez le lapin et le porc. Ils utiliserent ces immun-serums dans un systeme d'epreuves in vitro destine a en ve;rifier le pouvoir antibacterien a l'egard dsouches porcines d'E. coli homologues et heterologues. Ils determinerent les titres antibacteriens de ces antiserums 'a l'endroit des souches homologues, ainsi que le pourcentage de r6duction des unites formatrices de colonies/ml cause par une dilution 1:200 de ces immun-sirums 'a l'endroit des souches heterologues. Les resultats revelerent qu'apries l'immunisation, l'activite antibacterienne du serum a' l'endroit des souches homologues et heterologues subissait une hausse appreciable. Cette activite ne sembla pas subir l'influence des relations entre les antigenes 0 et K des differentes souches, ni celle du pouvoir enterotoxigene des souches vaccinales. Quand on soumit 'a l'influence de 20 souches l'antiserum prepare a l'aide d'un ensemble de trois souches d'E. coli enteropathogenes, on obtint une activite antibacterienne heterologue d'une plus grande envergure qu'avec un antiserum prepare contre l'une ou l'autre de ces souches. Les resultats revilent l'existence chez les souches porcines de facteurs antigeniques communs non relies 'a la formule serologique; ils indiquent aussi qu'on peut s'attendre 'a ce qu'une combinaison choisie de souches suscite une activite antibacterienne 'a l'endroit d'une grande variete de serotypes d'E. coli porcins
enteropathogienes.
INTRODUCTION
Escherichiac coli strains which are en-
teropathogenic for a particular host usual-
ly belong to several different serological types (2, 16). However, organisms belonging to different serotypes may share certain recognized surface antigens such as the K88 antigen (10) as well as other antigens which are not employed in determining serotype. Furthermore, there is
Can. J. comp. Med.
evidence that E. coli strains enteropathogenic for pigs may be more closely related than is indicated by the diversity in their serological formulae (17, 18). Thus, Sweeney (18) found that there was marked interconversion of 0 antigens among different serological types of E. coli enteropathogenic for pigs. The following antigenic changes were demonstrated by Sweeney: 0141 +40157, 098 +0157, 045
