Journal article
β-Lactams and Florfenicol Antibiotics Remain Bioactive in Soils while Ciprofloxacin, Neomycin, and Tetracycline Are Neutralized
Applied and environmental microbiology, Vol.77(20), pp.7255-7260
10/2011
Handle:
https://hdl.handle.net/2376/115058
PMCID: PMC3194842
PMID: 21856822
Abstract
It is generally assumed that antibiotic residues in soils select for antibiotic-resistant bacteria. This assumption was tested by separately adding 10 different antibiotics (≥200 ppm) to three soil-water slurries (silt-loam, sand-loam, and sand; 20% soil [wt/vol]) and incubating mixtures for 24 h at room temperature. The antibiotic activity of the resultant supernatant was assessed by culturing a sensitive
Escherichia coli
strain in the filter-sterilized supernatant augmented with Luria-Bertani broth. We found striking differences in the abilities of supernatants to suppress growth of the indicator
E. coli
. Ampicillin, cephalothin, cefoxitin, ceftiofur, and florfenicol supernatants completely inhibited growth while bacterial growth was uninhibited in the presence of neomycin, tetracycline, and ciprofloxacin supernatants. High-performance liquid chromatography (HPLC) analysis demonstrated that cefoxitin and florfenicol were almost completely retained in the supernatants, whereas tetracycline and ciprofloxacin were mostly removed. Antibiotic dissipation in soil, presumably dominated by adsorption mechanisms, was sufficient to neutralize 200 ppm of tetracycline; this concentration is considerably higher than reported contamination levels. Soil pellets from the tetracycline slurries were resuspended in a minimal volume of medium to maximize the interaction between bacteria and soil particles, but sensitive bacteria were still unaffected by tetracycline (
P
= 0.6). Thus, residual antibiotics in soil do not necessarily exert a selective pressure, and the degree to which the pharmaceutical remains bioactive depends on the antibiotic. Efforts to control antibiotic contamination would be better directed toward compounds that retain biological activity in soils (e.g., cephalosporins and florfenicol) because these are the antibiotics that could exert a selective pressure in the environment.
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Details
- Title
- β-Lactams and Florfenicol Antibiotics Remain Bioactive in Soils while Ciprofloxacin, Neomycin, and Tetracycline Are Neutralized
- Creators
- Murugan Subbiah - Departments of Veterinary Microbiology and PathologyShannon M Mitchell - Biological Systems EngineeringJeffrey L Ullman - Washington State University, Pullman, Washington 99164, and Department of Agricultural and Biological Engineering, University of Florida, Gainesville, Florida 32611Douglas R Call - Departments of Veterinary Microbiology and Pathology
- Publication Details
- Applied and environmental microbiology, Vol.77(20), pp.7255-7260
- Academic Unit
- Paul G. Allen School for Global Animal Health
- Publisher
- American Society for Microbiology; 1752 N St., N.W., Washington, DC
- Identifiers
- 99900547337501842
- Language
- English
- Resource Type
- Journal article