Background: The titers of SARS-COV-2 antigens are frequently used as markers of viral activity and threshold for release from quarantine and treatment. COVID-19 patients were treated with several antiviral agents, including remdesivir (RDV) and ensitrelvir (ESV), which is a novel anti-SARS-CoV-2 agent recently suggested to have strong antiviral activity. Cases: We present the cases of two patients whose SARS-CoV-2 antigens were successfully decreased by oral administration of ESV after they could not be decreased by RDV drip infusion. Case 1 was a 74-year-old man who was admitted with SARS-CoV-2 infection and had been infected by the virus a month earlier and relapsed twice. He had been treated with rituximab for diffuse B cell lymphoma and not received vaccination for SARS-CoV-2. RDV was administered intravenously two weeks earlier and again 4 days earlier, but it failed to control the infection, and he was transferred to our hospital (day 1). Intravenous RDV was restarted on day 1, but viral antigens remained high until day 5. The RDV was then switched to oral ESV, and viral antigen titers were successfully decreased on days 8, 10, and 12. Case 2 was an 81-year-old man who was admitted with SARS-CoV-2 infection on day 0. He had heart failure and diabetes mellitus, and had not received vaccination for SARS-CoV-2. Intravenous RDV was started on day 1, but viral antigens were still high until day 8. He was then switched from RDV to oral ESV, and viral antigen titers were successfully decreased on day 11. Conclusions: These cases suggest that ESV might be more effective than RDV for reducing viral activity, and it is easy to administer orally.

The pulmonary characteristics of Staphylococcus aureus (S. aureus) co-infection with respiratory viruses, such as SARS-CoV-2 and influenza virus, are still unclear. Case series: Two patients with methicillin-susceptible S. aureus (MSSA) infection in the lungs co-infected with either SARS-CoV-2 or influenza virus are reported. Case 1 was a 66-year-old woman who was admitted with SARS-CoV-2 infection. Her chest X-ray and computed tomography (CT) showed multiple cavity formations with infiltration shadows, and MSSA was detected from her sputum and blood, suggesting COVID-19-related bacterial pneumonia and pulmonary embolism. No catheters had been used, but she had skin eruptions and a history of SARS-CoV-2 vaccination. Ampicillin/sulbactam (ABPC/SBT) was administered, and she finally improved. Case 2 was an 87-year-old man with a history of atopic dermatitis who was admitted with moderate pneumonia, and influenza virus co-infection was found. He showed multiple cavitary shadows, and MSSA was isolated from both his sputum and blood. He was diagnosed with influenza-related bacterial pulmonary embolism. No catheters had been used, but he had a history of influenza vaccination. He was also treated by ABPC/SBT and finally improved. Conclusions: These cases suggest that MSSA showed affinity to the lungs when co-infected with either SARS-CoV-2 or influenza virus, and it presented as septic emboli without catheter use. We should consider MSSA infection when patients have SARS-CoV-2 or influenza virus co-infection, and multiple cavity formation and skin disorders are seen, even though they were vaccinated and no catheters were used.

Background: Pseudomonas aeruginosa (P. aeruginosa) is one of the most common pathogens in hospital-acquired pneumonia (HAP) including ventilator-associated pneumonia (VAP). Recently, ceftolozane/tazobactam (CTLZ/TAZ) has been used to treat pneumonia due to P. aeruginosa. Case series: Two cases of P. aeruginosa pneumonia treated by CTLZ/TAZ that had been initially treated by piperacillin/tazobactam (PIPC/TAZ) are presented. (Case 1): A 76-year-old man who underwent esophagectomy developed severe pneumonia caused by P. aeruginosa infection and received oxygen by high-flow nasal canula. PIPC/TAZ was started, and he improved 10 days later. PIPC/TAZ was switched to sulbactam/ampicillin, but on day 14, his respiratory condition worsened, and septic shock developed. P. aeruginosa was isolated from his blood, and CTLZ/TAZ was started because the isolated P. aeruginosa showed resistance to PIPC/TAZ. Although he recovered on Day 28, and CTLZ/TAZ was switched to levofloxacin, his condition worsened again, and P. aeruginosa resistant to CTLZ/TAZ was isolated from his blood on day 32. Finally, he died of septicemia and renal failure. (Case 2) A 51-year-old woman who underwent surgery for a brain tumor developed VAP due to P. aeruginosa and was treated by PIPC/TAZ. Her pneumonia improved, but pneumothorax developed, and she was therefore switched to CTLZ/TAZ on day 7. Her pneumonia improved smoothly without bacteremia 10 days later. Conclusions: These data and cases suggest that CTLZ/TAZ was effective for severe P. aeruginosa pneumonia although the isolated P. aeruginosa was resistant to PIPC/TAZ. However, the duration of CTLZ/TAZ administration may need to be considered for pneumonia cases with bacteremia due to P. aeruginosa.

The initial omicron SARS-CoV-2 subvariants, BA.1 and BA.2 (BA.1.2), were progressively displaced by BA.5in Japan in 2022. In the BA.5-dominant period, there were significantly more healthcare staff infected by nosocomial contact with persons with confirmed SARS-CoV-2 infection than those infected by household contact, compared with the BA.1.2-dominant period. The staff infected via nosocomial contact included non-patient-facing staff, in the BA.5-dominant period, although they did not become infected by SARS-CoV-2 through nosocomial contact in the BA.1.2-dominant period. These data suggest the importance of infection control and care for non-patient-facing staff, in the same way as for patient-facing staff.