Pseudomonas pneumonia in infants: an autopsy study.

Pseudomonas pneumonia is an uncommon but serious infection in infants, occurring mainly in infants of low birth weight. In this retrospective clinicopathologic correlation study, we reviewed the clinical records and analyzed postmortem lung pathology in 8 infants with pneumonia due to P. aeruginosa. From the histopathology, 2 different pneumonic patterns emerged: a distinctive paucicellular coagulative confluent bronchopneumonia with perivascular bacillary infiltration (7 cases) and a more usual cellular pneumonia without evidence of perivascular organisms (1 case). Clinically, infants with the first type could be considered immunocompromised and had a precipitous course characterized by signs of sepsis, whereas the infant with the second type (who likely had a more normal immune system) had a relatively protracted course with respiratory failure. We conclude that (1) the pattern of pneumonic inflammation correlates with the immune state of infants, similar to what has been reported in adults; (2) among immunocompromised infants, histopathologic signs of bacteremia are prevalent; and (3) the clinical signs do not correlate with the severity of the pathology at autopsy and may reflect sepsis rather than pneumonia. We speculate that the histopathology in this population reflects the virulence of the organism, as well as the immune status of the host.