Selective Change in the Bacteria Cultured and Isolated in Respiratory Sputum from Elderly Patients during the SARS-CoV-2 Pandemic

The SARS-CoV-2 pandemic has affected social patterns and consequently the prevalence of infections, such as seasonal influenza. It has been reported that invasive pneumococcal infection has markedly decreased worldwide. Method: We retrospectively investigated the bacteria cultured and isolated from 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. Results: 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 detection ratio of former pathogens in the good-quality respiratory sputum had decreased significantly since April 2020 by 60–80%, while that of P. aeruginosa and S. aureus had increased by 40–50%. Conclusions: The SARS-CoV-2 pandemic reduced the detection ratio of H. influenzae, M. catarrhalis, and S. pneumoniae but increased that of P. aeruginosa and S. aureus in the good-quality respiratory sputum from elderly patients. The influence of this selective change in isolated bacteria on the health and comorbidity of elderly patients remains to be investigated.