Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 5/8/1997
Publication Date: N/A
Technical Abstract: The effect of 2 antimicrobials on Salmonella heidelberg infection in swine was studied. Forty-four Salmonella-free pigs were placed into 4 groups. Groups 1, 2, and 3 (n=12 each) received 10**9 CFU intranasally at 6 weeks of age. Group 4 (n=8) served as controls. On D2 through D4 post-inoculation (PI), Group 1 received 4 mg/kg Naxcel (ceftiofur) intramuscularly (IM) and Group 2 received 4 mg/kg Baytril (enrofloxacin) IM. Groups 3 and 4 did not receive antibiotics. Pigs (4/group and 1 control) were necropsied at 2, 4, and 6 weeks PI. Tonsil, nasal, and rectal swabs, rectal temperatures, blood and clinical signs were monitored throughout the study. Mild to moderate diarrhea and coughing were observed in Groups 1, 2, and 3. Groups 1 and 2 had 58.3% and 5.6% positive swabs on D5 PI, respectively, while Group 3 had 88.9% positive swabs. On D5, Groups 1 and 3 were shedding 4.05 and 5.37 logs, respectively, while Group 2 was not shedding any Salmonella. However, shedding increased to 3.42 and 1.94 logs on D10 for Groups 1 and 2, respectively. More tissues were positive from Group 3 than any other group at each necropsy. The tissues with the highest numbers of Salmonella recovered were the tonsil from Group 1 and ileocolic junction from Groups 2 and 3. No increase in resistance was observed for any isolate obtained throughout the study. Baytril appeared to be more effective than Naxcel in reducing Salmonella levels. However, these data indicate that regardless of the antibiotic used, an initial decrease in the levels of Salmonella shed is followed by an increase after cessation of treatment.