[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.

Viral and Mycoplasma pneumoniae community-acquired pneumonia and novel clinical outcome evaluation in ambulatory adult patients in China

Few studies have addressed the etiology and clinical outcomes of community-acquired pneumonia (CAP) treated in an ambulatory setting. We investigated the etiology by the culture of Mycoplasma pneumoniae, urine antigen testing of Streptococcus pneumoniae and Legionella pneumoniae, and DNA or RNA determination of eight kinds of respiratory virus DNA or RNA. An etiological diagnosis was made in 51.8% of 197 patients. The most common pathogens were M. pneumoniae (29.4%) followed by influenza virus A, parainfluenza virus, adenovirus, human metapneumovirus (9.6%), and S. pneumoniae (4.1%). Patients with mycoplasma infections were younger, less likely to have comorbidities, and less likely to have adequate sputum for gram stain and culture. Patients with viral infections were older and more likely to have poorly defined nodules on chest X-ray (CXR) or computed tomography (CT) scan. Among patients infected with M. pneumoniae, those with quinolones as initial prescriptions had shorter duration of fever after the initiation of antibiotics than patients with β-lactams, macrolides, or β-lactams + macrolides (p < 0.05). This study suggests that M. pneumoniae and respiratory viruses were the most frequent pathogens found in ambulatory adult CAP patients and quinolones were better than β-lactams, macrolides, or β-lactams + macrolides in the resolution of fever of M. pneumoniae pneumonia.