Respiratory Pathogens Detected among Pediatric Hospitalizations for Pneumonia: A Multicenter Study from Saitama, Japan

Routine in-hospital testing may not detect the full range of respiratory pathogens in children hospitalized with pneumonia. We conducted a prefecture-wide multicenter retrospective cohort study at four hospitals in Saitama, Japan, from July 2023 to March 2024 to describe detected respiratory pathogens and assess the additional findings obtained by multiplex polymerase chain reaction (PCR) beyond routine in-hospital testing. Among 1,170 pediatric hospitalizations for acute respiratory infections (ARIs), 457 (39.1%) were complicated by pneumonia. Human metapneumovirus (hMPV; n=124, 27.1%) and respiratory syncytial virus (RSV; n=85, 18.6%) were the most frequently detected pathogens. Multiplex PCR was performed in 199 hospitalizations. Among 123 hospitalizations in which at least one in-hospital respiratory pathogen test was performed and all results were negative, multiplex PCR detected at least one pathogen in 85 (69.1%). In an exploratory unadjusted comparison excluding 16 group A Streptococcus-positive hospitalizations, antibiotic initiation was associated with older age, higher C-reactive protein levels, and absence of a positive in-hospital test. Among 210 antibiotic-treated hospitalizations without a positive in-hospital test, 110 underwent multiplex PCR and a viral pathogen was detected in 74/110 (67.3%). Multiplex PCR frequently identified pathogens after negative routine testing and broadened the detectable pathogen spectrum beyond targeted in-hospital tests.