Selective change in the bacterial flora in respiratory sputum from elderly patients during the SARS-CoV-2 pandemic

Abstract The pandemic of SARS-CoV-2 has affected the social lifestyle and consequently the prevalence of infections, such as seasonal influenza. It has been reported that invasive pneumococcal infection is markedly decreased worldwide. We retrospectively investigated the bacterial flora of 23,052 respiratory sputum samples obtained at our hospital from April 2015 to March 2022. The average patient age was 71.8 years old with a standard deviation of 16.0 years old. There was no significant difference in the age of the patients or the female-to-male ratio between each year. The detection ratio of bacteria was analyzed in accordance with sputum quality based on the Geckler classification. The detection ratio of community-acquired pneumonia pathogens such as Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae increased in parallel with the quality of the sputum, while that of hospital-acquired pneumonia pathogens such as Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus was not significantly affected by the quality of the sputum. The former detection ratio decreased significantly since April 2020 by 60–80% for two years in a row, while that of the latter did not change between each year. The pandemic of SARS-CoV-2 reduced the detection ratio of community-acquired pathogens such as Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae but not hospital-acquired pneumonia pathogens such as Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus in the respiratory sputum from elderly patients.