To evaluate the impact of ceftiofur treatment in @entity291 on fecal shedding of @entity2756 -resistant bacteria, 3 female Holstein dairy @entity291 were treated by intramuscular injection with EXCENEL RTU ( @entity21563 , Pharmacia and Upjohn) at a therapeutic dosage of 2.2 mg/kg/day for 5 consecutive days following label directions. Three untreated @entity291 were housed separately and served as controls. One to 3 days following the initial administration of ceftiofur, there was a 14% and 2% increase of fecal bacteria resistant to 16 and 64 microg @entity2756 /mL, respectively. This response remained unchanged from days 6 to 13, and increased resistance was seen at day 17. Randomly selected isolates of gram-positive and gram-negative bacteria with elevated resistance to @entity2756 (minimal inhibitory concentration (MIC) >or=64 microg @entity2756 /mL) were isolated from @entity291 feces and identified. In vitro conjugation experiments revealed that both the @entity2756 -resistance gene bla (CMY-2) and class 1 integron were transferred from two bacterial species to Salmonella spp. at a frequency of 10(7) to 10(5). MIC data revealed that Salmonella transconjugants acquired either reduced susceptibility or resistance to @entity2756 as well as to multiple antibiotics. This genetic transfer occurred both within and between genera. Treatment of @entity291 with therapeutic dosages of ceftiofur can significantly increase for at least 17 days following the initial treatment the fecal excretion of @entity2756 -resistant bacteria, including Salmonella species.

Analysis of fecal microbial flora for antibiotic resistance in ceftiofur-treated XXXX .

@entity21563 :: ('MESH:C053503', 'Chemical') :: ['ceftiofur hydrochloride'] @entity2756 :: ('MESH:D002443', 'Chemical') :: ['ceftriaxone'] @entity291 :: ('9913', 'Species') :: ['calves', 'calf']
@entity291 :: (9913,Species) :: ['calves']
