A strategy to determine the fate of active chemical compounds in soil; applied to antimicrobially active substances

Potential of ESBL-producing Escherichia coli selection in bovine feces after intramammary administration of first generation cephalosporins using in vitro experiments

“…In the manure slurry, significantly higher levels of tetracycline resistance where observed (16 fold, p = 0.02), and a nonsignificant difference of 210-fold for aminoglycoside resistance ( p = 0.18). The increased levels of tetracycline resistance vs the decreased levels of beta-lactam resistance are potentially caused by the much higher stability of tetracyclines as compared to beta-lactam antibiotics 25 . Overall, no increase in resistance genes was observed in any of the experiments and using different concentrations of the tested antibiotics.…”

A framework to assess the terrestrial risk of antibiotic resistance from antibiotics in slurry or manure amended soils

“…The level of risk depends upon the pH of the soil and the method of application. Both classes of antibiotics also have relatively long half-lives within the terrestrial environment, with values of 8-50 days [54][55][56][57][58][59] being reported for tetracyclines and between 32-100 days for uoroquinolones, 55,57,59,61 meaning there is also the potential that this risk will increase further upon multiple applications of farmyard manure. By contrast, our analysis revealed a minimal risk with respect to the development of environmental antibiotic resistance for lincomycin, where PEC PW values were up to 200-times lower than the PNECr for lincomycin.…”

“…In this framework we predicted the risk based on current scientic knowledge using PNECr for sulfamethoxazole, an antibiotic from the same class as sulfamethazine and only within soils with a pH of 8.7 where sulfamethazine is in its anionic form with PEC PW for sulfamethazine being at least 8 times lower than the PNECr for sulfamethoxazole. Sulfamethazine and lincomycin have relatively short half-lives, 3.5 days and 1.1-82.5 days respectively, 54,59 and therefore are not expected to exceed the concentration required to select for resistance within soil (16 mg L −1 and 4 mg L −1 for sulfamethazine and lincomycin, respectively). The soil properties used within this analysis were based on properties of average worldwide agricultural soils, and these risks will alter as soil properties such as pH, cation exchange capacity and organic matter of the soil changes.…”

“…66) meaning potentially both TET and OXY could exist predominately within soil in their anionic form, which is when these antibiotics are most bioavailable and there is the potential to exceed the PNECr. The half-lives of both TET and OXY are between 8-62 days, 54,55,[57][58][59] suggesting that environmental persistence of these compounds is likely within soil 11 and that concentrations of these antibiotics are unlikely to return to negligible levels between slurry applications. There is therefore potential for concentrations to build over time, highlighting two further research questions that need answering in relation to antibiotics in the terrestrial environment.…”

“…In comparison the PEC PW for both antibiotics within pH 5 soil, ploughed or unploughed, were considerably lower due to the higher K d values for both antibiotics as the soil pH decreased, representing minimal risk for the selection of ABR, with risk quotients of 0.00005-0.01 for CIP and 0.0004-0.05 for ENRO, see ESI Table 4. † As a class of antibiotics, uoroquinolones have some of the longest half-lives in soil with reported DT 50 's ranging between 32-100 days for CIP(61) and 99-696 days for ENRO 55,57,59 meaning that with additional applications of slurry or manure to the land (2 or 3 applications) between 1st February and 15th October (255/6 days per modelled year) there is signicant potential for the accumulation of these antibiotics in the soil environment. As with tetracyclines, there is a clear knowledge gap regarding the potential loading of soils and whether there is a maximum capacity for sorption of antibiotics.…”