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Applied and Environmental Microbiology, July 2006, p. 4782-4795, Vol. 72, No. 7
0099-2240/06/$08.00+0 doi:10.1128/AEM.02885-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Immunology and Molecular Diagnostic Research Unit, Elizabeth Macarthur Agriculture Institute, New South Wales Department of Primary Industries, Woodbridge Rd., Menangle, New South Wales 2568, Australia,1 Department of Biological Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia,2 Microbiological Diagnostic Unit, Public Health Laboratory, Department of Microbiology and Immunology, University of Melbourne, Melbourne, Victoria 3010, Australia,3 Department of Primary Industries, Midland Hwy. and Taylor St., Epsom, Victoria 3554, Australia,4 School of Veterinary Science, The University of Queensland, St. Lucia, Queensland 4072, Australia5
Received 8 December 2005/ Accepted 29 April 2006
A combination of uni- and multiplex PCR assays targeting 58 virulence genes (VGs) associated with Escherichia coli strains causing intestinal and extraintestinal disease in humans and other mammals was used to analyze the VG repertoire of 23 commensal E. coli isolates from healthy pigs and 52 clinical isolates associated with porcine neonatal diarrhea (ND) and postweaning diarrhea (PWD). The relationship between the presence and absence of VGs was interrogated using three statistical methods. According to the generalized linear model, 17 of 58 VGs were found to be significant (P < 0.05) in distinguishing between commensal and clinical isolates. Nine of the 17 genes represented by iha, hlyA, aidA, east1, aah, fimH, iroNE. coli, traT, and saa have not been previously identified as important VGs in clinical porcine isolates in Australia. The remaining eight VGs code for fimbriae (F4, F5, F18, and F41) and toxins (STa, STb, LT, and Stx2), normally associated with porcine enterotoxigenic E. coli. Agglomerative hierarchical algorithm analysis grouped E. coli strains into subclusters based primarily on their serogroup. Multivariate analyses of clonal relationships based on the 17 VGs were collapsed into two-dimensional space by principal coordinate analysis. PWD clones were distributed in two quadrants, separated from ND and commensal clones, which tended to cluster within one quadrant. Clonal subclusters within quadrants were highly correlated with serogroups. These methods of analysis provide different perspectives in our attempts to understand how commensal and clinical porcine enterotoxigenic E. coli strains have evolved and are engaged in the dynamic process of losing or acquiring VGs within the pig population.
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