AAs that displayed statistically significant higher loads in winter than in summer included MTZ, SLZ, LEX, TET, OTC, CIP, TMP, and the metabolites hMTZ and AMXa (table ). The AAs with some of the highest variabilities across the three seasons in Bath and Keynsham were the macrolides CLR and ERY. Statistically significant differences were observed when loads peaked in winter 2018/19 at an average load of 32.8 ± 8.7 and 2.4 ± 2.0 g/day for Bath and Keynsham respectively, compared to summer loads of 14.5 ± 4.2 and 0.8 ± 0.4 g/day (p≤0.05). Similar observations could be observed for CLR and ERY's major metabolites dmCLR and dmERY. As mentioned previously, CLR and ERY are known to have higher prescribing in winter months, when respiratory illness peaks in the UK.