We present a case of a critically ill patient with severe Legionella pneumonia complicated by morbid obesity (BMI ≥ 40 kg/m²) who was successfully treated with early initiation of veno-venous ECMO (V-V-ECMO) without any sequelae. The patient, a 48-year-old male, initially presented with symptoms of a sore throat, fever, significant fatigue, and decreased appetite. Upon diagnosis of severe pneumonia complicated by morbid obesity, he was transferred to our hospital for further management. Upon admission, he was promptly intubated and placed on mechanical ventilation. Due to a positive urinary Legionella antigen test indicating a risk of deterioration, V-V ECMO was initiated immediately after intubation. During ECMO support, the patient received Levofloxacin Hydrate at 500 mg/day and Prednisolone Sodium Succinate at 100 mg/day. He was successfully weaned off ECMO after 12 days and transferred back to the referring hospital on day 20. While ECMO therapy for morbidly obese patients was traditionally considered relatively contraindicated, this case suggest that obesity alone is not a contraindication to initiating ECMO.

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.