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ABSTRACTOur objectives were to study the prevalence, risk factors for carriage, and transmission dynamics of extended-spectrum-ß-lactamase (ESBL)-producing Enterobacteriaceae(ESBLPE) in a national survey of cattle. This was a point prevalence study conducted from July to October 2013 in Israel. Stool samples were collected from 1,226 cows in 123 sections on 40 farms of all production types. ESBLPE were identified in 291 samples (23.7%): 287 contained Escherichia coliand 4 contained Klebsiella pneumoniae. The number of ESBLPE-positive cows was the highest in quarantine stations and on fattening farms and was the lowest on pasture farms (P= 0.03). The number of ESBLPE-positive cows was the lowest in sections containing adult cows (age, >25 months) and highest in sections containing calves (age, <4 months) (P< 0.001). Infrastructure variables that were significant risk factors for ESBLPE carriage included crowding, a lack of manure cleaning, and a lack of a cooling (P< 0.001 for each), all of which were more common in sections containing calves. Antimicrobial prophylaxis was given almost exclusively to calves and was associated with a high number of ESBLPE carriers (P< 0.001). The 287 E. coliisolates were typed into 106 repetitive extragenic palindromic (REP)-PCR types and mostly harbored blaCTX-M-1or blaCTX-M-9group genes. The isolates on the six farms with =15 isolates of ESBLPE were of 4 to 7 different REP-PCR types, with one dominant type being harbored by about half of the isolates. Fourteen types were identified on more than one farm, with only six of the farms being adjacent to each other. The prevalence of ESBLPE carriage is high in calves in cowsheds where the use of antimicrobial prophylaxis is common. ESBLPE disseminate within cowsheds mainly by clonal spread, with limited intercowshed transmission occurring.