The incidence of necrotizing changes in adults with pneumococcal pneumonia

Necrotizing pneumonia is generally considered a rare complication of pneumococcal infection in adults. We systematically studied the incidence of necrotizing changes in adult patients with pneumococcal pneumonia and examined the severity of infection, role of causative serotypes, and association with bacteremia.

We used a database of all pneumococcal infections identified at our medical center between 2000 and 2010. Original readings of chest X-rays (CXR) and computerized tomography (CT) were noted. Images were then independently reevaluated by 2 radiologists. The severity of disease at admission was assessed using SMART-COP and Pneumonia Outcomes Research Team (PORT) scoring systems.

In 351 cases of pneumococcal pneumonia, necrosis was reported in no (0%) original CXR readings and in 6 of 136 (4.4%) CTs. With rereading, 8 of 351 (2.3%) CXR and 15 of 136 (11.0%) CT had necrotizing changes. Overall, these changes were identified in 23 of 351 (6.6%) patients. The incidence of bacteremia and the admitting SMART-COP and PORT scores were similar in patients with and without necrosis (P = 1.00, P = .32, and P = .54, respectively). Type 3 pneumococcus was more commonly isolated from patients with necrosis than from patients without necrosis (P = .05), but 10 other serotypes were also implicated in 16 cases for which the organism was available for typing.

Necrotizing changes in the lungs were seen in 6.6% of a large series of adults with pneumococcal pneumonia but were often overlooked on initial readings. Patients with necrosis were not more likely to have bacteremia or more severe disease. Type 3 pneumococcus was the most commonly identified serotype.