Dissemination of a Highly Virulent Pathogen: Tracking The Early Events That Define Infection
Figure 3
A bottleneck limits dissemination of Y. pestis to the draining LN.
(A and B) Southern dot blot analysis of DNA from bacteria from (A) LNs harvested at 12 hpi and (B) LNs and spleens at 48 hpi. Each row shows results from a single mouse (identified with a number). The number of CFU obtained from each tissue and from which DNA was extracted is also shown. Representative blots are shown for A and B. A dose of 211 CFU was used. Plates that were completely covered with a layer of bacteria (as opposed to isolated colonies) are identified as “lawn”. (C) Number of tagged strains in LNs after ID (black) or SC (white) inoculation at 48 hpi. A dose of 303 CFU and 331 CFU were used for the ID and SC inoculations, respectively. Each symbol represents a value from an individual mouse. Bars indicate medians per group. Results from two combined experiments are shown. (D) Number of tagged strains in ears (triangles) and LNs [circles at 12 hpi (black) and 48 hpi (white)]. A dose of 226 CFU was used. (E) Bacterial burden from LNs 48 h after the first of two consecutive inoculations. Mice were inoculated first with carbenicillin resistant Y. pestis (652 CFU) and, 24 h later, with kanamycin resistant Y. pestis (Yp/Yp, 449 CFU). Another group of mice was mock inoculated with PBS and, 24 h later, inoculated with kanamycin resistant Y. pestis (PBS/Yp, 449 CFU). The dotted line represents the limit of detection. Each symbol represents a value from an individual mouse. Bars indicate medians per group. The Wilcoxon matched-pairs signed-rank test (D) or the Mann Whitney test (C) and (E) was used to determine statistical significance and the p value is shown. Differences between groups were considered to be statistically significant when p < 0.05. Experiments were performed a minimum of 3 times and data from representative experiments are shown.