Influence of Subtherapeutic Levels of a Combination of Neomycin and Oxytetracycline on Salmonella typhimurium in Swine, Calves, and Chickens

Abstract

Subtherapeutic levels of oxytetracycline plus neomycin in animal feeds did not bring about increases in the quantity, prevalence, or shedding of Salmonella typhimurium in swine, calves, or chickens. In fact, the medication generally reduced the proportion of animals carrying S. typhimurium . The medicated groups were fed rations containing oxytetracycline plus neomycin commencing 5 days prior to oral inoculation with S. typhimurium and continuing through a 28-day postinoculation period. Colonization of S. typhimurium occurred in all three animal species, as evidenced by clinical signs of infection and/or colony counts in feces. Only from swine and on only one occasion was a single resistant colony isolated. It is concluded that no evidence has been obtained which would implicate the continuous low-level feeding of oxytetracycline and neomycin for a 4-week period to a potential increased incidence of disease in animals or as a hazard to humans.

The Association between Sub‐Therapeutic Antibiotics andSalmonellaTyphimurium in Market‐Weight Swine: A Systematic Review and Summation of Evidence from 1950 to 2007

“…Oxytetracycline 150 g/ton -5 days prior to exposure and throughout the experimental period S. Typhimurium 1.4 · 10 11 cfu orally Girard et al (1976) Randomly assigned Oxytetracycline 150 g and Neomycin 150 g/ton -5 days prior to exposure and throughout the experimental period S. Typhimurium 1.4 · 10 11 cfu orally Gutzmann et al (1976) Blocked by litter, sex and weight T 1 . Chlortetracycline 220.5 g/metric ton -starting from 5 days before exposure and throughout the experimental period S. Typhimurium 1 · 10 11 cfu orally T 2 .…”

“…Chlortetracycline 110 g/ton of feed 5 days prior to exposure and throughout the experimental period S. Typhimurium 6.5 · 10 10 cfu orally mann et al, 1976;Williams et al, 1978;Jones et al, 1983;Claussen et al, 1998;Delsol et al, 2003). Four studies described the use of tetracycline in combination with another antibiotic (Girard et al, 1976;Gutzmann et al, 1976;Wilcock and Olander, 1978;Ebner and Mathew, 2000). Two studies described the use of bambermycin (Dealy and Moeller, 1976;Letellier et al, 2000).…”

“…Two manuscripts reported only binary data for multiple time points (Claussen et al, 1998;Letellier et al, 2000). Only two manuscripts provided sufficient detail to enable the reader to understand the approach used to control for the longitudinal nature of the data (Evangelisti et al, 1975;Girard et al, 1976). Of the five studies published after 1995, two did not provide any description of a method to control for the longitudinal nature of the data and lack of independence between observations.…”

The Effect of Subtherapeutic Chlortetracycline on Antimicrobial Resistance in the Fecal Flora of Swine

“…Previous research regarding Salmonella shedding and antimicrobial resistance subsequent to antimicrobial therapy has been conducted in laboratory facilities involving experimental infection with S. enterica. 1,4,9,10,16,18,21,23,26,27,38,53,54 This may not represent the typical subclinical Salmonella infections on swine farms, which often involve multiple serovars and variable time and dose of Salmonella exposure. 20,29 There are limited observational investigations that evaluated the impact of antimicrobial use on the antimicrobial resistance profiles between farms.…”

Antimicrobial Growth Promoters andSalmonellaspp.,Campylobacterspp. in Poultry and Swine, Denmark

“…Studies have shown that antimicrobial drugs reduce part of the intestinal flora while potentially decreasing pathogen shedding ( 1 – 3 ). For these reasons, producers believed that removing antimicrobial growth promoters could cause human pathogenic intestinal bacteria in food animals to increase.…”