Toxigenic Escherichia coli, detection in healthy pigs in Buenos Aires Province, Argentina.

MOREDO F., PIÑEYRO P., QUIROGA M., LEOTTA G.A.

Buenos Aires

Simposio; 7th International Symposium on Shiga Toxin (Verocytotoxin) - Producing Escherichia coli infections.; 2009

Shiga toxin-producing /Escherichia coli/ is an important emergingpathogen. STEC strains have been isolated from some pork productsassociated with human infections. In pigs the diarrhea has become aneconomically important disease. Neonatal diarrhea is associated withenterotoxigenic /E. coli/, postweaning diarrhea and edema disease arecaused by Stx2e-producing /E. coli/. The aim of the study was todetect the presence of STEC and ETEC, in healthy pigs of differentages from eleven pig farms in Buenos Aires province, Argentina. Across sectional study was carried out in 11 pig farms. For samplingconvenience the whole population was divided in three differentstratums upon the age and stage production as follow: M3 (weaningpiglet, 21± 3 days old); M6 (nursery piglets, 86 ± 3 days old); M8(finishing pigs, 165 ± 3 days old). Rectal swab were individuallyobtained from a group of 30 pigs in each farm and stage. At thelaboratory, rectal swabs were streaked on MacConkey agar andincubated for 24 h at 37°C. Confluent growth zones were screened for/eltA/ (toxin LT), /estI/ (toxin STa) /stx1/, /stx2/, /stx2e/ and/rfbO157/ genes by PCR. The /stx1/ and /stx2/ genes were detected in45.5% and 18.1% respectively at the farms at M3. None stx genes infecal samples of farms at M6 and M8 were detected. /rfbO157/ genewere detected in 63.6%, 90.1% and 36.6% of the farms at M3, M6 and M8respectively. The prevalence of this gene observed was as follow:4.57% (IC 2.16-6.98), 19.81% (IC 15.3-24.28) and 6.7% (IC 3.84-9.56)of M3, M6 and M8 respectively. The /estI /gene was detected in 54.5%,90.1% and 45.4% of the farms at M3, M6 and M8 respectively. The /eltA/gene was detected in 27.2%, 18.1% and 36.6% of the farms at M3, M6 andM8 respectively. The overall prevalence of these genes was as follow:/estI /was observed in 4.26% (IC 1.92-6.60), 28.04% (IC 23.03-33.06)and 5.48% (IC 2.87-8.10) of M3, M6 and M8 respectively, and /eltA/gene was observed at 1.82% ( IC 0.22-3.43), 1.52% (IC 0.49-3.52) and1.82% (IC 0.22-3.43) at M3, M6 and M8, respectively. From the view ofanimal health, the presence of /eltA/ and /estI /genes in M6 and M8are not clinically important, the average rate of each gene observedthrough the different stages was constant only with a slight increaseof the prevalence of estI at 86 days which could not be related withan increase of clinical signs. None farms with E. coli carrying/stx2e/ gene was observed at M3 but 63.6% and 54.4% became positiveat M6 and M8 respectively. The total prevalence observed at the sameage was 22.86% (IC 18.16-27.56) and 10.67% (IC 7.17-14.16)respectively. These results and the lack of clinical signs observedin the prevalence of bacteria carrying /stx2e/ genes might beassociated with the age-related expression of the receptor for F18pili. From the view of public health, is important consider that atthe risk population (M8) was detected E. coli O157 stx-negative. Thiswork provides new data about the distribution of ETEC, STEC and E.coli O157 stx-negative in pig farms in Buenos Aires province.