A one-year longitudinal study of enterohemorrhagic Escherichia coli O157 fecal shedding in a beef cattle herd

LUIS C. RHADES; LARZABAL MARIANO; BENTANCOR ADRIANA; SABIO Y GARCÍA JULIA; FRANCISCO JOSE BABINEC; CATALDI ANGEL; AMIGO NATALIA; VALERIA N. BALDONE; LUCAS URQUIZA; PABLO J. DELICIA; MARCELO FORT

RESEARCH IN VETERINARY SCIENCE

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2019

0034-5288

AbstractBovines are the primary reservoir of enterohemorrhagic Escherichia coli (EHEC) O157:H7 and the main source of itstransmission to humans. Here, we present a one-year longitudinal study of fecal shedding of E. coli O157. E. coli O157obtained from recto-anal mucosal samples were characterized by multiplex PCR. The E. coli O157 prevalence rangedfrom 0.84% in July to 15.25% in November. The confinement within pens resulted in prevalence of 11%. Most animals(61.86%; 75/118) shed E. coli O157 at least in one sampling occasion. Of the positive animals, 82.19%, 16.44%, and1.37% were stx positive on one, two and three sampling occasions, respectively. All the E. coli O157 isolated strainscarried the genes eae and rfbO157, whereas 11%, 33% and 56% contained stx1, stx2 and stx1/stx2, respectively. Thestx1/stx2 and stx2 types were significantly higher during the grazing and finishing periods, respectively, in comparisonwith the rearing and grazing periods. The presence of stx2a subtype was evident in four isolates, whereas stx2c waspresent in at least seven. However, both subtypes were present simultaneously in two isolates. The stx1/stx2c,stx1/stx2d and stx1/stx2NT genotypes occurred in 24, 2 and 15 isolates, respectively. The simultaneous occurrence ofstx1 and stx2c significantly increased during grazing. Some cases of within-pen and between-pen transmissionoccurred throughout the study. Contagion levels during in-field grazing were higher than during permanentconfinement in the pens. Thus, the individual patterns of shedding varied depending on the proportion of animalsshedding the bacteria within pens and the time of shedding.