Patients with phagocyte disorders develop bacterial pneumonias at high frequency. Other common infections include skin abscesses, osteomyelitis, and lymphadenitis. Patients with CGD are at highly susceptible to catalase positive organisms. Patients with severe phagocyte defects can also be at high risk for gram negative bacterial sepsis.Patients with early complement component deficiencies can present with recurrent sinopulmonary infections. C3b is a key opsonin that facilitates the phagocytosis of encapsulated bacteria such as H. influenzae and S. pneumoniae.