Primary lung infection is affected by volume in the intranasal challenge mouse model.

(A-B) Groups of 5–9 C57Bl/6J mice were challenged by intranasal instillation with 2,000 (circles) or 500 (squares) colony forming units (CFU) in 10μL (black), 20μL (grey), or 30μL (white) of Yersinia pestis KIM6+pCD1Ap, a wild type strain. (A) Survival was monitored for 14 days; n = 16–21 per group, collected in 3 independent trials. Data were combined and analyzed by Mantel-Cox log rank test, survival curves with the same letter are not significantly different. (B) Mice were euthanized at 6 hours post infection (HPI) and CFU in the lungs or at 48 HPI and CFU in the lungs and spleen determined. Dashed line indicates the lower limit of detection, with numbers below that line representing undetected animals for that group; light grey line indicates the upper limit. Data were collected in two independent experiments and each tissue analyzed individually, 2,000 CFU challenge groups by Kruskal-Wallis test with Dunn’s multiple comparisons test and 30μL 500 vs 2,000 CFU groups by Mann Whitney test, *P<0.05, **P<0.01.