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Arquivos do Instituto Biológico

On-line version ISSN 1808-1657

Arq. Inst. Biol. vol.79 no.2 São Paulo Apr./June 2012

https://doi.org/10.1590/S1808-16572012000200016 

SCIENTIFIC ARTICLE ARTIGO CIENTÍFICO

 

Detection of virulence genes in Escherichia coli strains isolated from diarrheic and healthy feces of dairy calves in Brazil

 

Detecção de genes de virulência em amostras de Escherichia coli isoladas de fezes de bezerros com e diarreia no Brasil

 

 

C. de Moura; M. Ludovico; G.F. Valadares; M.S.V. Gatti; D.S. Leite

Universidade de Campinas, Instituto de Biologia, Departmento de Microbiologia e Imunologia, CP 6109, CEP 13083-970, Campinas, SP, Brazil. E-mail: cmoura.bio@gmail.com

 

 


ABSTRACT

The aim of this work was to test 101 strains of E. coli for virulence factors associated with enterotoxigenic and enterohemorrhagic pathotypes of E. coli isolated from diarrheic and non-diarrheic calves. The virulence factors of E. coli Stx1 (Shiga toxin), Stx2, Ehly (Enterohemolysin), the eae gene, LT-II (heat-labile enterotoxin), STa (heat-stable toxin), and adhesins K99 and F41 were detected by PCR. Serogroups were determined by serological methods and Stx production was observed by biological assays in Vero cells. The frequency of the eae gene was higher in isolates from diarrheic calves (35/58, 60.3%) than in non-diarrheic calves (8/43, 18.6%; P < 0.001). The gene for Stx1 occurred at high frequencies in the diarrheic strains (24/58, 41.3%) as well as in non-diarrheic (19/43, 44.2%) ones and all strains that were Stx positive by PCR showed cytotoxicity in Vero cells. Stx2 was found in ten strains, Ehly in eight strains, and LT-II in only two strains. Twenty-eight strains were negative for all of the PCR assays, including for F41 and K99 adhesins. The serogroups O7, O23, O4, O8, O153 and O156 were observed most frequently. Our results show that strains of E. coli isolated from cattle have similar virulence factors genes to strains isolated from cases of diseases in humans and may be a source of potentially pathogenic STEC for humans.

Key words: Escherichia coli, diarrhea, cattle, PCR, shiga toxin.


RESUMO

O objetivo deste trabalho foi detectar em 101 amostras de E. coli isoladas de bezerros com e sem diarreia, fatores de virulência associados aos patotipos de E. coli enterotoxigênica e enterohemorrágica. Os fatores de virulência de E. coli Stx1 (Shiga toxina), Stx2, Ehly (Enterohemolisina), o gene eae, LT-II (enterotoxina termo-lábil), STa (toxina termo-estável), e adesinas K99 e F41 foram detectados por PCR. Os sorogrupos foram determinados por métodos sorológicos e a produção de Stx foi observada através de ensaios biológicos em células Vero. A frequência de detecção do gene eae foi maior nos isolados de bezerros com diarreia (35/58, 60,3%) do que em bezerros saudáveis (8/43, 18,6%; P < 0.001). O gene da toxina Stx1 foi detectado em alta frequência em amostras diarreicas (24/58, 40,3%), bem como em amostras não diarréicas (19/43, 44,2%) e todas as amostras positivas para toxina Stx em PCR mostraram citotoxicidade em células Vero. Stx2 foi encontrada em dez amostras, Ehly em oito amostras, e LT-II em duas amostras. Vinte e seis amostras foram negativas para todos os ensaios de PCR, incluindo para as adesinas F41 e K99. Os sorogrupos O7, O23, O4, O8, O153 e O156 foram detectados com maior frequência. O trabalho mostra que amostras de E. coli isoladas de bovinos apresentam fatores de virulência semelhantes à isolados de casos de doenças em humanos e possivelmente é uma fonte para STEC potencialmente patogênicas para humanos.

Palavras-chave: Escherichia coli, diarreia, bovinos, PCR, shiga toxina.


 

 

Full text available only in PDF format.

Texto completo disponível apenas em PDF.

 

ACKNOWLEDGEMENTS

This work was supported by grants from the "Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP (02/06522-4)". C. Moura was the recipient of a research fellowship from Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq. We also thank Erivaldo J. Silva for skillful technical assistance.

 

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Received on 27/9/10
Accepted on 3/11/11

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