Abstract
The ecological and human health impact of antibiotic use and the related antimicrobial resistance (AMR) in animal husbandry is poorly understood. In many countries, there has been considerable pressure to reduce overall antibiotic use in agriculture or to cease or minimise use of human critical antibiotics. However, a more nuanced approach would consider the differential impact of use of different antibiotic classes; for example, it is not known whether reduced use of bacteriostatic or bacteriolytic classes of antibiotics would be of greater value. We have developed an ordinary differential equation model to investigate the effects of farm practice on the spread and persistence of AMR in the dairy slurry tank environment. We model the chemical fate of bacteriolytic and bacteriostatic antibiotics within the slurry and their effect on a population of bacteria, which are capable of resistance to both types of antibiotic. Through our analysis, we find that changing the rate at which a slurry tank is emptied may delay the proliferation of multidrug-resistant bacteria by up to five years depending on conditions. This finding has implications for farming practice and the policies that influence waste management practices. We also find that, within our model, the development of multidrug resistance is particularly sensitive to the use of bacteriolytic antibiotics, rather than bacteriostatic antibiotics, and this may be cause for controlling the usage of bacteriolytic antibiotics in agriculture.
Highlights
Antimicrobial resistance (AMR) has long been recognised as a threat to environmental, animal and human health
Two scenarios were considered: a simulation with no tank emptying regime, and one with seasonal tank emptying. In both cases the system is most sensitive to the relative costs of multidrug and bacteriolytic resistance αu and αl, and to the inflow rate of bacteriolytic antibiotic, θl. This brings about another possible implication for farm practice, indicating that reduced usage of bacteriolytic antibiotics would decrease the number of multidrugresistant bacteria much more effectively than reducing the quantity of bacteriostatic antibiotics used on farms
We have developed a model of the spread and persistence of antimicrobial resistance in an E. coli population in a dairy farm slurry tank
Summary
Antimicrobial resistance (AMR) has long been recognised as a threat to environmental, animal and human health. Human use of antibiotics means that AMR is highly prevalent in agriculture and the environment. In the case of colistin, a so-called last-line or last-resort antibiotic (Nation and Li 2009; Chaudhary 2016), there is evidence that the resistance gene mcr-1 has been transferred to human populations as a result of agricultural use (Liu et al 2016). This prompts the need for more in-depth research into the effects of farm practice and antibiotic usage on the development of AMR in the farming and recipient environments
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