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Applied and Environmental Microbiology, October 2009, p. 6282-6291, Vol. 75, No. 19
0099-2240/09/$08.00+0     doi:10.1128/AEM.00873-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Virulence Genes and Molecular Typing of Different Groups of Escherichia coli O157 Strains in Cattle{triangledown}

István Tóth,1* Herbert Schmidt,2 Gábor Kardos,3 Zsuzsanna Lancz,4 Kristina Creuzburg,2 Ivelina Damjanova,5 Judit Pászti,5 Lothar Beutin,6 and Béla Nagy1

Veterinary Medical Research Institute of the Hungarian Academy of Sciences, Budapest, Hungary,1 University of Hohenheim, Institute of Food Science and Biotechnology, Laboratory of Food Microbiology, Stuttgart, Germany,2 National Veterinary Institute, Microbiology, Debrecen, Hungary,3 National Food Investigation Institute, Budapest, Hungary,4 National Center for Epidemiology, Budapest, Hungary,5 Federal Institute for Risk Assessment, Berlin, Germany6

Received 17 April 2009/ Accepted 20 July 2009

Characterization of an Escherichia coli O157 strain collection (n = 42) derived from healthy Hungarian cattle revealed the existence of diverse pathotypes. Enteropathogenic E. coli (EPEC; eae positive) appeared to be the most frequent pathotype (n = 22 strains), 11 O157 strains were typical enterohemorrhagic E. coli (EHEC; stx and eae positive), and 9 O157 strains were atypical, with none of the key stx and eae virulence genes detected. EHEC and EPEC O157 strains all carried eae-gamma, tir-gamma, tccP, and paa. Other virulence genes located on the pO157 virulence plasmid and different O islands (O island 43 [OI-43] and OI-122), as well as espJ and espM, also characterized the EPEC and EHEC O157 strains with similar frequencies. However, none of these virulence genes were detected by PCR in atypical O157 strains. Interestingly, five of nine atypical O157 strains produced cytolethal distending toxin V (CDT-V) and carried genes encoding long polar fimbriae. Macro-restriction fragment enzyme analysis (pulsed-field gel electrophoresis) revealed that these E. coli O157 strains belong to four main clusters. Multilocus sequence typing analysis revealed that five housekeeping genes were identical in EHEC and EPEC O157 strains but were different in the atypical O157 strains. These results suggest that the Hungarian bovine E. coli O157 strains represent at least two main clones: EHEC/EPEC O157:H7/NM (nonmotile) and atypical CDT-V-producing O157 strains with H antigens different from H7. The CDT-V-producing O157 strains represent a novel genogroup. The pathogenic potential of these strains remains to be elucidated.

* Corresponding author. Mailing address: Veterinary Medical Research Institute of the Hungarian Academy of Sciences, 1143 Budapest, Hungária krt. 21, Hungary. Phone: 36-1-2522455. Fax: 36-1-2521069. E-mail: tothi{at}vmri.hu

{triangledown} Published ahead of print on 14 August 2009.

Applied and Environmental Microbiology, October 2009, p. 6282-6291, Vol. 75, No. 19
0099-2240/09/$08.00+0     doi:10.1128/AEM.00873-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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