Thrombocytopenia causes PC-dependent impaired survival and enhanced bacterial growth during Klebsiella-induced pneumonia. Survival (A) and clinical observation score (B) of very low-PC (open dots), low-PC (half-open dots), and control (closed dots) mice infected with K pneumoniae via the airways. For bacterial quantification, very low-PC (open dots), low-PC (half-open dots), and control (closed dots) mice were again infected with K pneumoniae via the airways and euthanized at the indicated time points. Bacterial counts were determined in lungs (C), blood (D), spleen (E), and liver (F). (G) Correlation of platelet counts and Klebsiella CFU recovered from blood 44 hours after infection. Data are expressed as scatter dot plots with the median. n = 20 mice per group in the survival experiment and n = 8 mice per group for bacterial quantification. ***P < .0005 for all comparisons in survival and clinical observation score graphs; *P < .05, **P < .005, and ***P < .0005 vs control; #P < .05 and ##P < .005 vs low-PC.