Control of Salmonella enteritidis infections in poultry by polymyxin B and trimethoprim.
Antimicrobial compounds were screened in vitro in Trypticase soy broth for antimicrobial activity against a virulent strain of Salmonella enteritidis. Of the several compounds tested, polymyxin B showed the strongest inhibition in vitro, preventing growth at a concentration of less than or equal to 10 micrograms/ml. Polymyxin B administered in the drinking water was effective in vivo for preventing infections in 1-day-old chickens but did not remove established infections in 1-week-old chickens. It was found that trimethoprim, which was not active in vitro, prevented colonization and removed existing infections in 1-day-old chickens when it was administered together with polymyxin B sulfate. Enrichment cultures in which selenite-cystine and tetrathionate broth media were used showed that chickens given a combination of 100 micrograms of polymyxin B sulfate per ml and 250 micrograms of trimethoprim per ml 24 h prior to oral inoculation with 10(8) to 10(9) CFU were negative for S. enteritidis after 7 days. Established infections (10(5) to 10(6) CFU/g of feces) in 1-week-old chickens were eliminated by treatment with the polymyxin-trimethoprim system. This antimicrobial agent treatment may be useful for preventing colonization in poultry and for eliminating S. enteritidis from infected flocks.
Goodnough
M C
MC
Department of Food Microbiology and Toxicology, University of Wisconsin, Madison 53706.
Johnson
E A
EA
D000818:Animals; D002645:Chickens; D004352:Drug Resistance, Microbial; D004359:Drug Therapy, Combination / Q000008:administration & dosage; D011112:Polymyxin B / Q000008:administration & dosage*; D011201:Poultry Diseases / Q000188:drug therapy / Q000517:prevention & control*; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000517:prevention & control*; D012477:Salmonella enteritidis / Q000187:drug effects; D014295:Trimethoprim / Q000008:administration & dosage*
D014295:Trimethoprim; D011112:Polymyxin B