title: Effect of penicillin and virginiamycin on drug resistance in lactose-fermenting enteric flora.
abstract: Three groups of beagle dogs were fed either a control diet, a diet containing virginiamycin (55 microgram/g of diet), or a diet containing penicillin (110 microgram/g of diet). The proportions of lactose-fermenting organisms in their feces that were resistant to ampicillin, dihydrostreptomycin, tetracycline, or chloramphenicol were measured by a comparative plate-counting procedure. Both antibiotic-supplemented diets resulted in an increase (P < 0.001) in the occurrence of ampicillin, dihydrostreptomycin, and tetracycline resistances during the time of their administration. The occurrence of these resistances was greater (P < 0.001) in the group receiving penicillin than in the group receiving virginiamycin. In addition to the above resistances, a greater (P < 0.001) occurrence of resistance to a sulfonamide (sulfamethoxypyridazine) due to treatment was found by susceptibility testing of isolates. Representative isolates were able to transfer their resistance to a strain of Escherichia coli K-12.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism; D004096:Dihydrostreptomycin Sulfate / Q000494:pharmacology; D004285:Dogs; D005260:Female; D005285:Fermentation; D005503:Food Additives; D007422:Intestines / Q000382:microbiology; D007785:Lactose / Q000378:metabolism; D008297:Male; D010403:Penicillin Resistance / Q000187:drug effects*; D010406:Penicillins / Q000494:pharmacology*; D013752:Tetracycline / Q000494:pharmacology; D014769:Virginiamycin / Q000494:pharmacology*
chemical_list: D005503:Food Additives; D010406:Penicillins; D014769:Virginiamycin; D000667:Ampicillin; D013752:Tetracycline; D007785:Lactose; D004096:Dihydrostreptomycin Sulfate