Most commonest agent for Early Onset Nosocomial pneumonia is

Early Onset Nosocomial pneumonia which manifest within the first 4 days of hospitalization,is most often caused by community acquired pathogens such as Streptococcus pneumoniae and Hemophilus species Hospital-acquired pneumonia (HAP) or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48-72 hours after being admitted. It is thus distinguished from community-acquired pneumonia. It is usually caused by a bacterial infection, rather than a virus . Ref Harrison 19th edition pg 915