Antimicrobial susceptibility patterns of Salmonella isolates from cattle in feedlots.
OBJECTIVE
To evaluate the antimicrobial susceptibility patterns of Salmonella isolates from feedlot cattle.


METHODS
Cross-sectional study.


METHODS
263 Salmonella isolates.


METHODS
Fecal samples were collected from the floor of 2 pens in each of 100 feedlots. Two hundred eighty Salmonella isolates were recovered after bacteriologic culture from 38 pens. Of these, 263 isolates were available for antimicrobial susceptibility testing to 16 antimicrobials, using microbroth dilution breakpoint plates.


RESULTS
Less than 5% of isolates were resistant to any of the antimicrobials tested, with the exception of sulfamethoxazole (15; 5.7%) and tetracycline (61; 23.2%). Most isolates (197; 74.9%) were susceptible to all antimicrobials tested, whereas 18 (6.8%) were resistant to 2 or more antimicrobials. The percentage of isolates with resistance to any antimicrobial varied by serotype. The percentage of isolates resistant to various antimicrobials was not related to concurrent use of antimicrobials in the feed.


CONCLUSIONS
With the exception of tetracycline and sulfamethoxazole, resistance of Salmonella isolates to any of the antimicrobials was uncommon. Most isolates were susceptible to all antimicrobials tested. Antimicrobial resistance was not related to the presence of antimicrobials in the ration being fed at the time of sample collection.
United States Department of Agriculture-Animal and Plant Health Inspection Service, Centers for Epidemiology and Animal Health, Fort Collins, CO 80521, USA.
David A
DA
Dargatz
Paula J
PJ
Fedorka-Cray
Scott R
SR
Ladely
Kathleen E
KE
Ferris
Alice L
AL
Green
Marcia L
ML
Headrick
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000382:microbiology*; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial; D005243:Feces / Q000382:microbiology; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D012475:Salmonella / Q000187:drug effects* / Q000302:isolation & purification; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000382:microbiology*; D012703:Serotyping / Q000662:veterinary
D000900:Anti-Bacterial Agents