Effect of oxytetracycline as a turkey feed additive.

Turkeys were given oxytetracycline (OTC) as a feed supplement at levels of 0 g, 50 g, and 200 g OTC per ton of feed. After 8, 16, and 18 weeks the birds were sacrificed and bacteria were isolated from heart blood and liver tissue. When these isolates were tested for resistance against eight antibiotics, a direct correlation was observed between the level of supplement and the level of antibiotic resistance in the bacterial isolates. In postmortem studies on the livers from birds consuming both levels of OTC, an increase in the occurrence of lesions was observed. The livers from control birds appeared to have more granulomas.

Effect of dietary oxytetracycline on microorganisms in turkey feces.

Thirty-six two-day old male turkey poults were divided into three groups and fed three levels of oxytetracycline; 0, 110 or 440 mg. per kg. of ration, respectively, for nine weeks. The poults were given an oral spectinomycin plus vitamin treatment at the hatchery but were not fed before the start of the experiment. Defecated feces from each group were sampled at weekly intervals and analyzed for bacteriological content, especially for members of the Enterobacteriaceae. Total aerobic counts of 3 x 10(8) and total anaerobic counts of 2 x 10(9) were obtained. The majority of the Enterobacteriaceae were Escherichia coli but some Klebsiella sp., the Bethesda-Ballerup group of paracolon bacteria and Arizona sp. were also isolated. Antibiograms of the enteric isolates indicated that an increase in multiple antibiotic resistance occurred when increased amounts of antibiotic were fed.

Quantitative antibiotic sensitivities of ruminal bacteria.

Fifteen species of ruminal bacteria were tested against 10 antibiotics in concentrations ranging from 0.1 to 200 mug/ml in an anaerobic tube dilution system.

Antibiotic susceptibility of anaerobic ruminal bacteria.

This study demonstrated that 15 species of ruminal bacteria with no previous history of contact with antibiotics are susceptible to bacitracin, chloramphenicol, chlortetracycline, erythromycin, novobiocin, oleandomycin, oxytetracycline, penicillin, tetracycline, tylosin, and vancomycin. A number of the species were not inhibited by kanamycin, neomycin, polymyxin, and streptomycin. The data suggest that antibiotic-resistant cells occur within susceptible cultures of these species. Streptococcus bovis FD-10 and a nonruminal anaerobe, Bacteroides melaninogenicus BE-1, showed similar antibiotic susceptibilities.