Articles

<b>Background</b>: <i>Pseudomonas aeruginosa </i>(<i>P</i><i>.</i><i> aeruginosa</i>)<i> </i>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<i> P</i><i>.</i><i> aeruginosa</i>. <b>Case series</b>: Two cases of <i>P</i><i>.</i><i> aerugi</i><i>n</i><i>osa</i> 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 <i>P</i><i>.</i><i> aeruginosa </i>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. <i>P</i><i>.</i><i> aeruginosa</i> was isolated from his blood, and CTLZ/TAZ was started because the isolated <i>P</i><i>.</i><i> aeruginosa</i> showed resistance to PIPC/TAZ. Although he recovered on Day 28, and CTLZ/TAZ was switched to levofloxacin, his condition worsened again, and<i> P</i><i>.</i><i> aeruginosa </i>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<i> P</i><i>.</i><i> aeruginosa </i>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. <b>Conclusions:</b> These data and cases suggest that CTLZ/TAZ was effective for severe <i>P</i><i>.</i><i> aeruginosa</i> pneumonia although the isolated <i>P</i><i>.</i><i> aeruginosa</i> was resistant to PIPC/TAZ. However, the duration of CTLZ/TAZ administration may need to be considered for pneumonia cases with bacteremia due to <i>P</i><i>.</i><i> aeruginosa</i>.