What question did this study set out to answer?

This research aims to report the effectiveness of long-term, low-dose macrolide therapy in managing multidrug-resistant Pseudomonas aeruginosa infections.

May 14, 2026Open Access

Recurrent/Refractory Multidrug- and Pre-Multidrug-Resistant Pseudomonas aeruginosa Infection Cases Maintained by Long-Term, Low-Dose Macrolide Administration

MSMasafumi SekiSaitama Medical University

Key Points

This research aims to report the effectiveness of long-term, low-dose macrolide therapy in managing multidrug-resistant Pseudomonas aeruginosa infections.
Reported two case studies involving a 78-year-old man and a 5-year-old girl with pneumonia caused by Pseudomonas aeruginosa.
Managed infections using a combination of meropenem, tazobactam/ceftolozane, and low-dose clarithromycin over a sustained period.
Monitored outcomes over more than six months to assess stability of patient conditions.
Case 1: The adult patient remained stable after initiating clarithromycin therapy post-MDRP isolation.
Case 2: The pediatric patient stabilized following the introduction of half-dose clarithromycin after improving from pneumonia.
Both cases suggest that long-term macrolide therapy may help maintain positive clinical outcomes in drug-resistant infections.

Abstract

Abstract: Multidrug-resistant Pseudomonas aeruginosa (MDRP) is usually induced by inappropriate use of broad-spectrum antibiotics, and pre-multidrug-resistant Pseudomonas aeruginosa (pre-MDRP) is defined as resistance to any two of three antibiotics, such as carbapenems, fluoroquinolones, and aminoglycosides. Two cases of infections with such organisms are reported. Case 1 was a 78-year-old man with esophageal cancer who had pneumonia, treated by meropenem (MEPM) for two weeks because P. aeruginosa , which showed good susceptibility to most antibiotics, was isolated. He improved, but his inflammation status and chest X-ray findings worsened on day 21. MDRP was isolated, and he was treated using tazobactam/ceftolozane (TAZ/CTLZ) for 10 days. After improvement, clarithromycin (CAM) 200 mg once per day was then started as long-term, low-dose macrolide therapy. His condition has remained stable for more than six months. Case 2 was a 5-year-old girl with congenital heart abnormalities. She had pneumonia due to P. aeruginosa that showed good susceptibility to antibiotics and was treated by MEPM for 10 days. However, MDRP was isolated, and then ciprofloxacin (CPFX), to which MDRP showed good susceptibility, with only intermediate susceptibility to levofloxacin (LVFX), was started. Ten days later, her pneumonia improved, and half-dose (5 mg/kg) CAM three times per day was started as long-term, low-dose macrolide therapy. Her condition has remained stable for more than six months. These two cases, one adult MDRP infection and one pediatric pre-MDRP infection, that were maintained by long-term, half-dose macrolide administration, which might have affected pathogen colonization and host immunomodulation, are presented. Keywords: azithromycin, clarithromycin, erythromycin, antimicrobial stewardship, Pseudomonas aeruginosa

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