FIG 4.

Imipenem treatment cures M. abscessus-infected embryos. (A to E) From 1 dpi, embryos were exposed for 5 days to imipenem concentrations corresponding to 0.5×, 5×, or 28× the MIC. (A) Survival of R-M. abscessus-infected embryos treated at various doses of imipenem and compared to untreated infected embryos (≈300 CFU, n = 20, representative of three independent experiments). Survival of treated R-M. abscessus-infected embryos is dose dependent. Significant increased survival was observed in infected embryos exposed to 5× and 28× MIC of imipenem. The red bar indicates the start and duration of treatment. (B) Bacterial loads of untreated or imipenem-treated embryos (≈400 CFU). Results are expressed as mean log₁₀ CFU per embryo from three independent experiments. A significant decrease of bacterial load was observed after 3 dpi in the 28× MIC imipenem-treated embryos. (C) Spatiotemporal visualization of the infection by R-M. abscessus expressing tdTomato (≈300 CFU) in untreated or imipenem-treated embryos. The representative fluorescence and transmission overlays of whole embryos are shown. (D) Frequency of abscesses in whole untreated or imipenem-treated embryos over 13 dpi (≈300 CFU, average of three independent experiments). Only the 28× MIC imipenem-treated embryos developed significantly fewer abscesses than untreated-infected embryos. (E) Average localization of abscesses of the infected embryos in panel D. Five times and 28× MIC of imipenem-treated embryos infected by M. abscessus developed fewer abscesses within the brain than untreated infected embryos. For panel B, statistics were calculated using one-way ANOVA; for panels D and E, Fisher's exact test was used, comparing each category of imipenem-treated embryos to untreated controls. Error bars represent the SEM. *, P = 0.02; **, P < 0.01; ***, P < 0.001.