Lobar pneumonia is pneumonia caused by bacterial infection. The common causative agent is Streptococcus pneumoniae, which accounts for about 90% of the cases. Other bacteria such as Staphylococcus aureus, Haemophilus influenzae, and Streptococcus haemolyticus can also cause lobar pneumonia. Lobar pneumonia is usually common in young adults, with high fever, cough, chest pain after exertion or cold, and some patients may also have symptoms of dyspnea, with elevated leukocyte and neutrophil ratios on ancillary tests, and large dense shadows in segments or lobes visible on CT.