4CPS-008 Is linezolid penetration in the mediastinum adequate? A case report

<h3>Background and Importance</h3> Mediastinitis is a relatively uncommon infection that affects structures within the mediastinum and can result from various underlying etiologies, including oesophageal perforation. Antibiotic penetration into mediastinal space is typically low due to its separation from the bloodstream. It’s been demonstrated that linezolid’s diffusion into tissues is superior to vancomycin. Given that linezolid has good tissue penetration (mediastinum/plasma ratio=1.32), it may be an effective treatment for mediastinitis. However, there is limited evidence regarding its penetration into the mediastinum. <h3>Aim and Objectives</h3> Determine linezolid levels in plasma and mediastinum and confirm their correlation with existing literature. <h3>Material and Methods</h3> 71-year-old woman presented to emergency department with sensation of foreign body in oesophagus, accompanied by pain and feeling of dyspnoea. A rigid esophagoscopy revealed oesophageal perforation caused by a foreign body in Killian’s mouth, leading to her hospitalisation. On day+2, a computed tomography (CT) scan showed pneumomediastinum. The patient began to experience dysphagia and chest pain. After a febrile peak, piperacillin-tazobactam (P/T) was initiated. On day+4, patient’s respiratory condition worsened, requiring CPAP support. CT scan revealed extensive mediastinitis with a retroesophageal collection and left pleural effusion. An urgent surgical intervention with drainage placement were performed. S.anginosus and S.merionis, multisensitive, were isolated, leading to de-escalation to amoxicillin/clavulanic. The patient showed good progress but several febrile peaks. On day+23, CT scan revealed significant worsening of collections. Antibiotic treatment was changed to meropenem+vancomycin+caspofungin, and a drainage of the collections were performed. In new cultures grew N.favescens and S.epidermidis, initiating targeted treatment with P/T+linezolid 600mg/12h, resulting in radiological and analytical improvement. On day+7 of linezolid, plasma levels were determined by High-Performance Liquid Chromatography(HPLC-UV). <h3>Results</h3> After obtaining subtherapeutic levels of linezolid (0.88mcg/mL, therapeutic range=2–7mcg/mL), it was decided to adjust the dosage to 600mg/8h. Additionally, new levels were requested two days after, both in plasma and mediastinum, to assess whether the concentrations in the mediastinum were adequate: 5.06 and 7.64mcg/mL in plasma and mediastinum, respectively (mediastinum/plasma ratio=1.51). Given patient‘s favourable progress and levels within therapeutic range, it was recommended to maintain current regimen. <h3>Conclusion and Relevance</h3> These values align with ranges published in literature, confirmed by a series of cases, and demonstrate good tissue penetration of linezolid in mediastinum and pleural tissue. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest