Abstract
The objectives of the present study were to evaluate the risks involved in the use of Enrofloxacin for Salmonella Enteritidis (SE) or Salmonella Heidelberg (SH) in commercial poultry and determine the effects of a probiotic as an antibiotic alternative. Two experiments were conducted to evaluate the risks involved in the use of Enrofloxacin for SE or SH in commercial poultry. Experiment 1 consisted of two trials. In each trial, chickens were assigned to one of three groups; control + SE challenged; Enrofloxacin 25 mg/kg + SE; and Enrofloxacin 50 mg/kg + SE. Chickens received Enrofloxacin in the drinking water from days 1 to 5 of age. On day 6, all groups received fresh water without any treatment. All chickens were orally gavaged with 107 cfu/chick of SE at 7 days of age and euthanized on 8 days of age. In Experiment 2, turkey poults were assigned to one of the three groups; control + SH; probiotic + SH; and Enrofloxacin 50 mg/kg + SH. Poults received probiotic or Enrofloxacin in the drinking water from days 1 to 5 of age. On day 6, poults received fresh water without any treatment. Poults were orally gavaged with 107 cfu/poult of SH at 7 days of age. Poults were weighed and humanely killed 24 h post-SH challenge to evaluate serum concentration of fluorescein isothiocyanate-dextran to evaluate intestinal permeability, metagenomics, and SH infection. In both trials of Experiment 1, chickens treated with Enrofloxacin were more susceptible to SE organ invasion and intestinal colonization when compared with control non-treated chickens (P < 0.05). In Experiment 2, poults treated with 50 mg/kg of Enrofloxacin showed an increase in body weight, however, this group also showed an increase in SH susceptibility, intestinal permeability, and lower proportion of Firmicutes and Bacteroidetes, but with control group had the highest proportion of Proteobacteria. By contrast, poults that received the probiotic had the highest proportion of Firmicutes and Bacteroidetes, but lowest Proteobacteria. The results of the present study suggest that prophylactic utilization of Enrofloxacin at five times the recommended dose in poultry increases the susceptibility to salmonellae infections, and confirms that probiotics may be an effective tool in salmonellae infections.
Highlights
Fluoroquinolones are the third generation of quinolone development
Chickens treated with 50 mg/kg of Enrofloxacin showed a 3.23 log increased in the incidence of serovar Enteritidis (SE) in cecal tonsils (CCT) as well as total cfu of SE/gram of ceca content when compared with control chickens and 0.45 log
Chickens were humanely killed for culture at 8 days of age. bData of liver and spleen or ceca-cecal tonsils is expressed as positive/total chickens (%). cLog 10 SE/g of ceca-ceca tonsils (CCT) data is expressed as mean ± SD. d,eSuperscripts within columns indicate significant difference at P < 0.05
Summary
Fluoroquinolones are the third generation of quinolone development. Nalidixic acid and pipemidic acid are examples of the first generation and currently have limited activity against Gram-negative bacteria. History has demonstrated that the extensive use of new antibiotics is eventually shadowed by the appearance of resistance to those chemicals that have become a major global problem This was demonstrated by the higher incidence of salmonellae and Campylobacter infections worldwide, and several reports of fluoroquinolone resistance in clinical isolates for these and other enteric pathogens [3,4,5,6,7]. Typical management practices in those countries are to treat or dose healthy neonatal chickens and turkey poults with five times the recommended dose of Enrofloxacin for five consecutive days in the drinking water In those countries, the incidence of Salmonella spp. and Campylobacter spp. rates in both humans and agriculture are high [1, 13,14,15,16].
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