[Molecular epidemiology and clinical characteristics of six cases of CA-MRSA pneumonia after influenza].

Objective: To summarize and analyze the strains' molecular epidemiology and clinical characteristics of 6 strains of post-influenza community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) pneumonia. Methods: Six cases of CA-MRSA pneumonia after influenza from 2014 to 2022 were retrospectively collected and CA-MRSA strains from each patient were cultured. Then, SCCmec typing, MLST typing, and spa typing were performed on the samples, which also included the procedures for the detection of virulence factors. Antibiotic susceptibility test was then performed on all 6 strains. Results: ST59-t437-Ⅳ was the predominant type in all the strains of CA-MRSA(2/6). Leukocidin (PVL) was detected in 5 cases, and hemolysin α (HLAα) and phenol soluble regulatory protein α (PSMα) were detected in 6 cases. Five of the cases included in this study were diagnosed with severe pneumonia. In terms of treatment, 4 cases received antiviral therapy, and 5 patients with severe pneumonia received anti-infection treatment with vancomycin as the first choice and were discharged after improvement of their condition. Conclusions: The molecular types and virulence factors of CA-MRSA after influenza infection could vary considerably. Our experiments also showed that secondary CA-MRSA infection after influenza was more common in young people with no underlying diseases and could cause severe pneumonia. Vancomycin and linezolid were the first-line drugs for treating CA-MRSA infection and were highly effective in improving the condition of diagnosed patients. We highlighted the importance of referring patients with severe pneumonia after influenza for etiological tests to determine whether they had CA-MRSA infection, so that they could be properly treated with anti-influenza agents and receive appropriate anti-CA-MRSA infection treatment.