Fig. 1.

Model of competition between antibiotic sensitive and resistant strains (Eq. 1). $U$ represents uninfected hosts, $I_s$ represents hosts infected with the sensitive strain, $I_r$ represents hosts infected with the resistant strain, $\beta$ is the transmission rate, $\mu$ is the clearance rate, $\tau$ is the population antibiotic consumption rate, and ${\beta }_s=\beta ,{\beta }_r=\frac{\beta }{c_{\beta }},{\mu }_s=\mu ,{\mu }_r=c_{\mu }\mu$, where $c_{\beta }$ and $c_{\mu }$ represent the cost of resistance.