The Impact of Environmental Contamination with Antibiotics on Levels of Resistance in Soil Bacteria
- Magdalena Popowska *,
- Antoni Miernik,
- Marzenna Rzeczycka and
- Agnieszka Łopaciuk
This study examined the effects of tetracycline and streptomycin on microorganisms in three different soil habitats: forest soil, agricultural soil, and compost. These antibiotics are commonly used in both medical and veterinary therapy as well as in the production of plant biomass and until quite recently, the production of animal biomass. Microcosms were used as model systems in which the number of microorganisms in environments containing different amounts of antibiotics was analyzed. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of tetracycline and streptomycin were determined. The MIC and MBC values of tetracycline against the tested strains were 20 to 180 μg/mL and 30 to 300 μg/mL, respectively, and of streptomycin, 360 to 500 μg/mL and ≥500 μg/mL, respectively. Resistant bacterial strains were identified and their physiological profiles assessed. Streptomycin and tetracycline were found to reduce the number of bacteria in the studied soils by between 50 and 80%. Soil bacteria were found to be more resistant to streptomycin than to tetracycline. The bacterial species showing the highest resistance to tetracycline were Rhizobium radiobacter, Burkholderia cepacia, Brevundimonas vesicularis, and Pasteurella multocida Most soils with high concentrations of streptomycin (5 mg/kg) contained Rhizobium radiobacter, Burkholderia cepacia, and Sphingomonas multivorum, among others. The strains most resistant to tetracycline were isolated from agricultural soil that is constantly subjected to tetracycline pressure from animal manures and biosolids. Among resistant strains, opportunistic pathogens were identified.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2010. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America