Figure 1.

(a) The average frequency of penicillin non-susceptibility in several European countries in 2000 correlates with the average consumption of penicillin in defined daily dose (DDD) in these countries in 2000 (R² = 0.67) (data available on the ECDC website). (b) The seasonal dynamics of penicillin consumption and penicillin non-susceptibility in a Jewish community in Israel [8]. (c) An evolutionary model of seasonal fluctuations in antibiotic prescription (plain line) and resistance frequency (dashed and dotted lines). Grey and white zones highlight the winter and summer months. Resistance frequencies were obtained from equation (2.7), with b = 0.05 and c = 0 (dashed line), and b = 0.05 and c = 50 (dotted line). A stronger stabilizing force reduces the amplitude and the phase difference of fluctuations in resistance frequency.