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 emerging pathogen. STEC strains have been isolated from some pork products associated with human infections. In pigs the diarrhea has become an economically important disease. Neonatal diarrhea is associated with enterotoxigenic /E. coli/, postweaning diarrhea and edema disease are caused by Stx2e-producing /E. coli/. The aim of the study was to detect the presence of STEC and ETEC, in healthy pigs of different ages from eleven pig farms in Buenos Aires province, Argentina. A cross sectional study was carried out in 11 pig farms. For sampling convenience the whole population was divided in three different stratums upon the age and stage production as follow: M3 (weaning piglet, 21± 3 days old); M6 (nursery piglets, 86 ± 3 days old); M8 (finishing pigs, 165 ± 3 days old). Rectal swab were individually obtained from a group of 30 pigs in each farm and stage. At the laboratory, rectal swabs were streaked on MacConkey agar and incubated 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 in 45.5% and 18.1% respectively at the farms at M3. None stx genes in fecal samples of farms at M6 and M8 were detected. /rfbO157/ gene were detected in 63.6%, 90.1% and 36.6% of the farms at M3, M6 and M8 respectively. 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 and M8 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) and 1.82% (IC 0.22-3.43) at M3, M6 and M8, respectively. From the view of animal health, the presence of /eltA/ and /estI /genes in M6 and M8 are not clinically important, the average rate of each gene observed through the different stages was constant only with a slight increase of the prevalence of estI at 86 days which could not be related with an increase of clinical signs. None farms with E. coli carrying /stx2e/ gene was observed at M3 but 63.6% and 54.4% became positive at M6 and M8 respectively. The total prevalence observed at the same age 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 observed in the prevalence of bacteria carrying /stx2e/ genes might be associated with the age-related expression of the receptor for F18 pili. From the view of public health, is important consider that at the risk population (M8) was detected E. coli O157 stx-negative. This work provides new data about the distribution of ETEC, STEC and E. coli O157 stx-negative in pig farms in Buenos Aires province.