Pathogenicity of Escherichia coli O115:K"V165" strains isolated from pigs with diarrhea.
Eighteen strains of Escherichia coli serogroup O115:K"V165" isolated from 1- to 8-week-old pigs with diarrhea were tested for toxigenicity, pathogenicity in pigs and mice, serum resistance, mannose-resistant hemagglutination (MRHA), F165 and other surface antigens, colicin V (Col V), aerobactin, and biotype. Twelve strains were positive for heat-stable enterotoxin (STb), MRHA-negative, and F165-negative; 5 strains were enterotoxin-negative, MRHA-positive, and F165-positive; and 1 strain was MRHA-positive, but F165- and enterotoxin-negative. Six of the 12 STb-positive strains moderately colonized the ileum of newborn colostrum-deprived pigs within 24 hours after inoculation. Two of the colonizing strains were able to induce watery diarrhea. All 12 STb-positive strains were nonpathogenic for adult mice and were serum-sensitive; 11 of 12 were Col V-negative, 9 of 12 did not produce aerobactin, and 10 of 12 belonged to biotypes other than 1 or 2. All 6 enterotoxin-negative strains colonized the small and large intestines, associated with peritoneal serosal surfaces, and induced septicemia and polyserositis in newborn colostrum-deprived pigs 1 to 2 days after inoculation. In contrast, 3 STb-positive strains poorly colonized the intestines and did not induce septicemia in pigs at 3 days after inoculation. All 6 enterotoxin-negative strains were Col V-positive, produced aerobactin, and belonged to biotype 1 or 2. Of the 5 enterotoxin-negative, F165-positive strains, only 4 were pathogenic for intraperitoneally inoculated adult mice and were serum-resistant. The enterotoxin-negative, F165-negative strain was neither serum-resistant nor mouse-pathogenic.(ABSTRACT TRUNCATED AT 250 WORDS)
Fairbrother
J M
JM
Faculty of Veterinary Medicine, Groupe de Recherche sur les Maladies Infectieuses du Porc, University of Montreal, Saint Hyacinthe, Quebec, Canada.
Broes
A
A
Jacques
M
M
Larivière
S
S
D000818:Animals; D000942:Antigens, Bacterial / Q000032:analysis; D001770:Blood Bactericidal Activity; D003106:Colon / Q000382:microbiology / Q000473:pathology / Q000648:ultrastructure; D003967:Diarrhea / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D004768:Enterotoxins / Q000096:biosynthesis; D004926:Escherichia coli / Q000276:immunology / Q000302:isolation & purification / Q000472:pathogenicity* / Q000648:ultrastructure; D004927:Escherichia coli Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D006384:Hemagglutination; D007421:Intestine, Small / Q000382:microbiology / Q000473:pathology / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D013552:Swine / Q000382:microbiology; D013553:Swine Diseases / Q000382:microbiology* / Q000473:pathology; D014774:Virulence
D000942:Antigens, Bacterial; D004768:Enterotoxins