Spatial Clustering of Escherichia coli with Reduced Susceptibility to Cefotaxime and Ciprofloxacin among Dairy Cattle Farms Relative to European Starling Night Roosts.

European starlings (Sturnus vulgaris) have been implicated in the dispersal of zoonotic enteric pathogens. However, their role in disseminating antimicrobial-resistant organisms through their home range has not been clearly established. The aim of this study was to determine whether starling night roosts served as foci for spreading organisms with reduced susceptibility to antimicrobials among dairy cattle farms. Bovine faecal pats were collected from 150 dairy farms in Ohio. Each farm was visited twice (in summer and fall) between 2007 and 2009. A total of 1490 samples (10 samples/farm over two visits) were tested for Escherichia coli with reduced susceptibility to cefotaxime and ciprofloxacin. Using a spatial scan statistic, focal scans were conducted to determine whether clusters of farms with a high prevalence of organisms with reduced susceptibility to cefotaxime and ciprofloxacin surrounded starling night roosts. Faecal pats 13.42% and 13.56% of samples carried Escherichia coli with reduced susceptibility to cefotaxime and ciprofloxacin, respectively. Statistically significant (P < 0.05) spatial clusters of faecal pats with high prevalence of Escherichia coli showing reduced susceptibility to cefotaxime and ciprofloxacin were identified around these night roosts. This finding suggests that the risk of carriage of organisms with reduced susceptibility to antimicrobials in cattle closer to starling night roosts was higher compared to cattle located on farms further from these sites. Starlings might have an important role in spreading antimicrobial-resistant E. coli to livestock environments, thus posing a threat to animal and public health.