Putative new heat-stable cytotoxic and enterotoxic factors in culture supernatant of Escherichia coli isolated from drinking water

Ribeiro DA (1), Niemann FS (1), Gatti MSV (1), Lanna MCS (2), Tsuji T (3), Yano T (1)

(1) Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of Campinas, UNICAMP, Campinas, São Paulo State, Brazil; (2) Laboratory of Microbiology, Department of Exact and Biological Sciences, ICEB, Federal University of Ouro Preto, UFOP, Ouro Preto, Minas Gerais State, Brazil; (3) Department of Microbiology, School of Medicine, Fujita Health University, Toyoake, Aichi, Japan.

Abstract: Enteric infections caused by the ingestion of contaminated water, especially by Escherichia coli, are important to define the virulence properties of these bacteria. Due to frequent infantile diarrhea in the city of Ouro Preto, Minas Gerais state, Brazil, the phenotypic and genotypic diarrheagenic properties of E. coli isolated from drinking water were studied. The culture supernatants of 39 (40%) among a total of 97 E. coli isolates from drinking water were positive by suckling mouse assay and induced cytotoxic effects on Vero cells. The enterotoxic and cytotoxic activities were present in the fraction with less than 10 kDa and were not lost when heated up to 60°C and 100°C for 30 minutes. PCR assays showed that among these 39 Vero cytotoxigenic E. coli, four (10.2%) were positive for ST II (estB) and two (5%) positive for αHly (hlyA). Gene amplification of SLT (stx 1, stx 2), ST I (estA), LT (eltI, eltII), EAST1 (astA), EHly (enhly) and plasmid-encoded enterotoxin (pet) were not observed. This heat-stable cytotoxic enterotoxin of E. coli is probably a new putative diarrheagenic virulence factor, as a toxin presenting these characteristics has not yet been described.

Key words: Escherichia coli, drinking water, cytotoxin, enterotoxin.

ACKNOWLEDGMENTS

We would like to thank Ana Stella Menegon Degrossoli, who provided technical assistance.

COPYRIGHT

© CEVAP 2011

SUBMISSION STATUS

Received: January 24, 2011.

Accepted: January 26, 2011.

Abstract published online: January 26, 2011.

Full paper published online: February 28, 2011.

CONFLICTS OF INTEREST

There is no conflict.

FINANCIAL SOURCE

The Coordination for Improvement of Higher Education Personnel (CAPES), The National Council for Scientific and Technological Development (CNPq) and The State of São Paulo Research Foundation (FAPESP) provided the financial grants.

ETHICS COMMITTEE APPROVAL

The present study was approved by the Ethics Committee of the State University of Campinas (protocol number 748-1).

CORRESPONDENCE TO

Tomomasa Yano, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, UNICAMP, Cidade Universitaria ”r;Zeferino Vaz”, Campinas, SP, 13083-862, Brasil. Phone/fax: +55 19 3521 6254. Email: tyano@unicamp.br.