Table 1 Selected studies on the effect of antimicrobials on the cattle microbial resistome
Study | Livestock (animals in study) | Antibiotic tested (class) | Experimental treatment | Sample type | Characterization methodology | Outcome or notable findings |
|---|---|---|---|---|---|---|
Chambers et al. 2015 [165] | Dairy cattle (6 Holstein cows) | Ceftiofur (3rd generation cephalosporin) | Administration of therapeutic ceftiofur over 3 d trial | Fecal | Metagenomic DNA: Illumina HiSeq of total DNA with MG-RAST and ARDB annotation | Increase in bacterial sequences associated with resistance to β-lactam and multidrug resistance |
Benedict et al. 2015 [175] | Beef cattle (>10,000 animals) | Various (5 difference antimicrobial drug classes | Correlation between routine antimicrobial usage in a feedlot system and antimicrobial resistance in non-type Escherichia coli over 3Â yr | Fecal | Bacterial isolation and susceptibility testing. | Exposures to tetracycline, streptomycin, and trimethoprim-sulfamethoxazole were significantly associated with increased abundance of antimicrobial resistance genes |
Kanwar et al. 2014 [164] | Beef cattle (176 steers) | Ceftiofur (3rd generation cephalosporin) Chlortetracycline (tetracycline) | Administration of therapeutic ceftiofur and/or chlortetracycline over 26Â d trial | Fecal | Metagenomic DNA: qPCR of select AMR genes | Increase in ceftiofur resistance genes and decrease in tetracycline resistance genes following ceftiofur treatment Increase in ceftiofur and tetracycline resistance genes following chlortetracycline treatment |
Zaheer et al. 2013 [99] | Beef cattle (40 steers) | Tylosin Tulathromycin Tilmicosin (macrolide) | Administration of either sub-therapeutic tylosin or therapeutic tulathromycin or tilmicosin | Fecal | Bacterial isolation and susceptibility testing. PCR of select AMR genes | Both sub-therapeutic and therapeutic macrolide treatment increased abundance of macrolide resistant Enterococci |
Thames et al. 2012 [219] | Dairy cattle (41 calves) | Neomycin (aminoglycoside) Oxytetracycline (tetracycline) | Administration of either sub-therapeutic or therapeutic neomycin or oxytetracycline over 50Â d milk-replacement trial | Fecal | Metagenomic DNA; qPCR of select AMR genes | Sub-therapeutic antibiotic treatment had no effect on abundance of tested resistance determinants. Therapeutic treatment with oxytetracycline increased abundance of tetracycline resistance genes |