Pneumatocele formation in a fatal adult pneumonia patient coinfected with Streptococcus pyogenes emm-type 3 and influenza A: a case report

BACKGROUND: A pneumatocele is a transient thin-walled lesion and rare complication in adult pneumonia. A variety of infectious pathogens have been reported in children with pneumatoceles. We report the first case of adult pneumonia with pneumatocele formation that is likely caused by Streptococcus pyogenes and coinfection with influenza A virus. CASE PRESENTATION: A 64-year-old Japanese man presented with a one-week history of fever, sore throat, and arthralgia. He was referred to our university hospital for respiratory distress. He required mechanical ventilation in the intensive care unit (ICU). Bacterial culture detected S. pyogenes in the bronchoscopic aspirates, which was not detected in blood. Although a rapid influenza antigen test was negative, an influenza A polymerase chain reaction (PCR) test was positive. Therefore, he was diagnosed with coinfection of influenza A and group A streptococcus (GAS) pneumonia complicated by probable streptococcal toxic shock syndrome. A chest radiograph on admission showed diffuse patchy opacification and consolidation in the bilateral lung fields. Multiple thin-walled cysts appeared in both middle lung fields on computed tomography (CT). On the following day, the bilateral cysts had turned into a mass-like opacity. The patient died despite intensive care. An autopsy was performed. The pathology investigation revealed multiple hematomas formed by bleeding in pneumatoceles. CONCLUSIONS: There have been no previous reports of a pneumatocele complicated by S. pyogenes in an adult patient coinfected with influenza A. Further molecular investigation revealed that the S. pyogenes isolate had the sequence type of emm3.