LETHAL TOXIN TO MICE PRODUCED BY Escherichia coli ISOLATED FROM CHICKENS WITH SWOLLEN HEAD SYNDROME

SALVADORI, M.R.(1), FIGUEIRÊDO, P.(1), FURUMURA, M.T.(1), CHUDZINSKI-TAVASSI, A.M.(2), BACCARO, M.R.(3), PRADO-FRANCESCHI, J.(4), YANO, T.(1)

(1)Departamento de Microbiologia e Imunologia, IB, Unicamp, Campinas (2)Laboratório de Bioquímica e Biofísica, Instituto Butantan, São Paulo, (3)Departamento de Patologia, Faculdade de Medicina Veterinária e Zootecnia, USP, São Paulo, (4)Departamento de Farmacologia, Faculdade de Ciências Médicas, Unicamp, Campinas.

Objective:In this study we investigated whether E. coli isolated from chickens with Swollen Head Syndrome (SHS) present lethal activity in mice.

Materials and Methods:The E. coli strains were cultivated in LB medium, and the culture were harvested by centrifugation, filtered through a 0.22 mm membrane filter. The pathogenicity and LD₅₀ were determined in female BALB/c mice (20±2g, 5/groups) injected i.v. with 0.5ml of E. coli culture supernatants. The nature of the lethality-inducing molecule was identified, by heating E. coli culture supernatants at 60°C and 100°C for 30 min, and treatment with trypsin, and then testing for lethal activity. Specimens from lungs, heart, liver and kidney from mice inoculated with E. coli were collected and stained with H&E for histopathological analysis.

Results and Conclusions:The lethal activity was heat-labile protease-sensitive and as lethal as a toxin from Bacillus cereus killing mice within 10 min. Light microscopy revealed histopathological lesions in the liver and kidney, but the principal organ affected was the lung. In conclusion, E. coli produce a novel toxin with lethal activity in mice similar to that of B. cereus strains responsible for food poisoning. Additional studies are necessary to characterize this toxin since this occurs in SHS in broiler chickens and may represent a risk to public health.

CORRESPONDENCE TO:

MarciaRegina Salvadori, Rua: Albuquerque Lins, 480, Salto, SP, CEP: 13320-340, Brasil, Email: mrsalvadori@yahoo.com.br