Dose–response in early treatment with tetracycline i.p. of body weight and clinical score of C57BL/6J mice after lung infection with C. trachomatis serovar D and early treatment with different dosages of tetracycline i.p. (Tet_E). Mice were intranasally (i.n.) infected with 8 × 10⁶ IFU (of a new preparation) of C. trachomatis (CtrD) or mock material (Mock) and subsequently monitored until they were euthanized on day 6 p.i. Tetracycline was applied once a day on days 1–3. In this experiment 20 (Tet_E High), 5 (Tet_E Medium), and 1.25 (Tet_E Low) mg kg⁻¹ body weight tetracycline or buffer (NaCl) were used. (A) Body weight is depicted as means ± standard errors of the means. (B) Clinical score values are depicted as medians ± interquartile ranges. Asterisks indicate (for day 4 p.i. as example) significant differences between the infected groups: *P = 0.05; **P = 0.01; ***P = 0.001; n.s. = not significant. On days 3 and 5, and partially also on day 6 p.i., depending on the varying dosages of tetracycline there were also significant differences between the body weights of several CtrD-infected groups (see also Table S1, Supporting Information).