Toxigenic Escherichia coli isolated from pigs in Argentina.

The presence of porcine toxigenic E. coli (ETEC, VTEC) in 28 piggeries (5% of total) of the central and northeast region of Argentina was studied for a better understanding of the epidemiology of porcine strains. Samples were taken by rectal swabs from healthy piglets and from those with diarrhoea, in addition to their dams. Between 5-10 colonies were isolated from each one of 223 animals sampled from 1992 to 1997. By using specific primers each strain was screened by PCR for VT1, VT2all, VT2e, STIa, and LTI toxin genes. Only strains positive for any of the toxins mentioned above were screened for STb. Their O serogroups were determined by agglutination. All of the above enterotoxins and verocytotoxins were found in E. coli isolated from the animals. The STIa gene was detected in E. coli isolated from 27/127 piglets with diarrhoea, in comparison with LTI (4/127 pigs). No toxin gene was amplified from E. coli isolated from either healthy piglets or their dams. When strains isolated from 48 piglets without diarrhoea but showing delayed growth were analysed by PCR, their toxin profile was determined to be VT1 (1/48 piglets), VT2all (5/48), STIa (1/48), LTI (3/48) and VT2e (3/48). Serogroup O64 prevailed among ETEC; O138 prevailed for ETEC/VTEC strains. This is the first extensive study regarding porcine toxigenic E. coli in Argentina and constitutes an important database for the implementation of prevention measures.

[Colibacillosis in swine: proof of vaccine efficacy]. / Colibacilosis en lechones: prueba de eficacia de una vacuna.

The damage caused in the economy and animal sanity by the porcine colibacilosis are significant and they deserve the investigation of preventive measures that give answers to the producers. Existing at the present time approximately 21,000 pigs in Corrientes and 110,000 in Chaco provinces of Argentine, the losses for diarrhea that exterminate whole litters, acquire relevance, specially if they can be prevented or cured. For that reason, having 21 strains of enteropathogenic and verocitotoxigenic E. coli (ETEC/VTEC) isolated from pigs of the North East of Argentine, that were recognized by PCR, two were selected, containing the genes for STIa, STIb, LTI, VT2e (SLT-IIv) and F4 (K88). They were spread on nutrient agar and Minca medium, to obtain the suspension in PBS, which was inactivated with formol. After the sterility and innocuity controls, it was diluted to a 12 x 10(8) concentration to make the mouse protection test in 20 mice, of 18-20 g, inoculating the vaccine the days 1, 4, 7 and 10, by the intraperitoneal route, doses of 0.25 ml each one. The day 21 after beginning the test the animals were challenged with 50 LD50, and a protection of 85% was obtained. To determine the LD50, we prepared a suspension in physiologic solution, corresponding to Mac Farland's tube No 10, making dilutions from 10(-1) to 10(-5) and applying the statistical method of Reed and Muench. These first results encourage us to continue working after a prophylactic measure that were effective, potent and elaborated with strains of this area.