Rapid identification of virulence genes in enterotoxigenic Escherichia coli isolates associated with diarrhoea in Queensland piggeries.
OBJECTIVE
To identify virulence genes in enterotoxigenic E coli (ETEC) isolates associated with diarrhoea in neonatal, 1 to 3 week-old and weaned pigs in southeast Queensland.


METHODS
Multiplex PCR and serotyping were applied to E coli isolates obtained over a 5-year period (1998-2002) from cases diagnosed at Toowoomba Veterinary Laboratory.


METHODS
A total of 126 isolates from 25 different Queensland piggeries were tested for haemolytic activity on 5% sheep blood agar and by multiplex PCR for the presence of five commonly recognised fimbrial (F4, F5, F6, F41 and F18) and three enterotoxin genes (STa, STb, LT). A subset of 62 representative isolates were serotyped by slide agglutination. For comparative purposes, multiplex PCR was also performed on the DNA of 31 ETEC isolates from 9 serotypes originating from piggeries in southern New South Wales.


RESULTS
A total of 113 (89.7%) of the isolates from Queensland possessed ETEC virulence genes, including 14 of 15 isolates from neonatal pigs (93.3%), 18 of 23 isolates from 1 to 3 week old pigs (78.3%) and 81 of 88 isolates from weaned pigs (92.1%). F4:STa:STb:LT (serotype O149) was the most prevalent pathotype in neonatal and 1-3 week old pigs and F4:STa:STb:LT (serotype O149) and F18:STa:STb:LT (serotype O141) were most prevalent in weaned pigs. In comparison, isolates obtained from neonatal pigs from New South Wales belonged to a more diverse range of pathotypes and serotypes.


CONCLUSIONS
Multiplex PCR was a rapid and specific method for detecting the presence of ETEC virulence genes in porcine E coli isolates. For isolates obtained from cases of suspected colibacillosis in Queensland, growth of a heavy pure culture of haemolytic E coli was a sensitive prognostic indicator of the presence of ETEC virulence genes in the isolate. ETEC pathotypes and serotypes remained stable in Queensland piggeries over the five-year study period and appear to have changed little over the last three decades.
Do
T
T
School of Veterinary Science, The University of Queensland, Brisbane, Queensland 4072.
Stephens
C
C
Townsend
K
K
Wu
X
X
Chapman
T
T
Chin
J
J
McCormick
B
B
Bara
M
M
Trott
D J
DJ
D000818:Animals; D000831:Animals, Newborn; D001427:Bacterial Toxins / Q000235:genetics; D003967:Diarrhea / Q000175:diagnosis / Q000382:microbiology / Q000662:veterinary*; D004768:Enterotoxins / Q000235:genetics* / Q000276:immunology; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000276:immunology; D005260:Female; D036781:Fimbriae Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008297:Male; D016133:Polymerase Chain Reaction / Q000379:methods / Q000662:veterinary; D011793:Queensland; D012680:Sensitivity and Specificity; D012703:Serotyping; D013552:Swine; D013553:Swine Diseases / Q000175:diagnosis / Q000382:microbiology*; D013997:Time Factors; D014774:Virulence / Q000235:genetics
D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins