A 10-Year Retrospective Study of Bacterial Infections in a Japanese Regional Hospital: The Impact of COVID-19 and an Earthquake

Bacterial infections are a leading cause of patient mortality, and antimicrobial resistance continues to pose a growing global health and economic threat. The combined effects of the COVID-19 pandemic and earthquakes may have influenced patterns of bacterial infections. This study analyzed data on antimicrobial-resistant and susceptible bacteria over a 10-year period (2015-2024), encompassing these natural disasters. During the COVID-19 pandemic, the number of positive bacterial cultures declined and continued to decrease following the earthquake. This trend included antimicrobial-resistant bacteria, such as methicillin-resistant <i>Staphylococcus aureus</i> and methicillin-resistant <i>Staphylococcus epidermidis</i> (MRSE). Notably, MRSE cases significantly declined during the pandemic period. In addition, infections caused by drug-sensitive <i>Streptococcus pneumoniae</i> among inpatients and <i>Pseudomonas aeruginosa</i> among outpatients showed a significant reduction, with both continuing to decline in the post-pandemic period. In contrast, <i>Legionella</i> infections significantly increased in both the number and frequency of positive cases, a trend that persisted after the 2024 earthquake. These findings differ from previously reported global data. In Japan, widespread mask usage continued even after the pandemic subsided. The results underscore the importance of improving infection control equipment and promoting individual awareness of infection prevention to reduce the risk of future bacterial infections.