ARS | Publication request: Does a multi-drug resistant Escherichia coli facilitate dissemination of resistance to Salmonella in dairy calves?

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 22, 2010
Publication Date: N/A

Technical Abstract: Previous research conducted by our laboratory investigated the incidence of multi-drug resistant (MDR) Salmonella in dairy cattle and reported that individual cattle, and most often calves, can shed multiple Salmonella serotypes that vary in the degree of antibiotic resistance. More recently, we discovered a high incidence of a MDR generic E. coli (MDR GEC) in dairy calves. Taken together, this suggests the generic E. coli population may be an important reservoir for resistance elements that could potentially spread to Salmonella. Therefore, the objective of the current research was to determine if resistance transfers from MDR GEC in naturally-colonized calves to inoculated strains of pan-susceptible Salmonella (Experiment I) and to examine the role of protozoa on resistance transfer (Experiment II). Both experiments utilized Holstein calves (approx. 3 weeks old) naturally-colonized with MDR GEC and fecal culture negative for Salmonella. Fecal samples were collected for culture of Salmonella and MDR GEC throughout both experiments following experimental inoculation with the pan-susceptible Salmonella strains. Results from Experiment I suggests that resistance did transfer from the MDR GEC to the inoculated strains of Salmonella, with these stains demonstrating multiple antibiotic resistance following in vivo exposure to MDR GEC. In the second experiment, all fecal samples in all treatments were Salmonella negative, indicating that resistance transfer did not occur from MDR GEC to the inoculated Salmonella under these experimental conditions. Based on the results, it appears that antimicrobial resistance can transfer from MDR GEC to Salmonella, but the role of protozoa could not be determined.