1 Department of Infectious Diseases, National Naval Medical Center, 8901 Wisconsin Avenue, Bethesda, MD 208895600, USA; 2 Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 40 Convent Drive, Bethesda, MD 20892, USA
Keywords: nosocomial meningitis , post-neurosurgical meningitis , ventriculostomy
Sir,
Acinetobacter calcoaceticus-baumannii complex is a common cause of nosocomial infections, including post-neurosurgical meningitis. Multidrug-resistant (MDR) Acinetobacter is increasingly common worldwide, presenting a therapeutic challenge. Non-traditional antibiotics, including sulbactam, colistin and polymyxin B, have been used for MDR Acinetobacter meningitis.
Rifampicin demonstrates a bactericidal effect against Acinetobacter baumannii both in vitro as well as in animal models. Rifampicin monotherapy for MDR Acinetobacter pneumonia in a mouse model achieves a superior survival rate (94%) to other antibiotics1 and has superior bactericidal activity to colistin.2 Rifampicin is also additive or synergistic with sulbactam against MDR A. baumannii,3 and with carbapenems for Pseudomonas aeruginosa, Serratia marcescens and Enterobacter species.4 To our knowledge, this is the first published report of the use of rifampicin in Acinetobacter meningitis in humans. We describe our use of rifampicin, in combination with meropenem, in the treatment of post-neurosurgical Acinetobacter meningitis.
A 34-year-old female suffered a subarachnoid haemorrhage while on military service in Iraq and underwent emergency ventriculostomy in Kuwait 18 days prior to admission to our hospital. She was transferred after coiling of two intracranial aneurysms and replacement of the ventriculostomy. On arrival, she was receiving vancomycin for ventriculostomy prophylaxis and phenytoin for seizure prophylaxis. Cerebrospinal fluid (CSF) at admission was normal. On hospital day 7, she developed fever and became obtunded. Gram staining of the CSF demonstrated Gram-negative coccobacilli. Culture of the CSF grew both A. calcoaceticus-baumannii complex and Enterobacter aerogenes. Blood cultures also grew Acinetobacter. Antibiotic susceptibility testing by Vitek revealed both Acinetobacter isolates were susceptible to imipenem, ticarcillin/clavulanic acid and ampicillin/sulbactam. Meropenem, gentamicin and metronidazole were empirically added to the vancomycin. The ventriculostomy was required for increased intracranial pressure and was replaced at an adjacent site. On day 9 the patient remained febrile and obtunded. CSF cultures grew A. calcoaceticus-baumannii resistant to ampicillin/sulbactam, ceftazidime, ceftriaxone, gentamicin, imipenem, piperacillin/tazobactam, tobramycin and trimethoprim/sulfamethoxazole, with intermediate susceptibility to ticarcillin/clavulanic acid.
On hospital days 11 and 13 the CSF Gram stains and cultures demonstrated persistent Acinetobacter, with susceptibility to imipenem, ampicillin/sulbactam and ticarcillin/clavulanic acid. Rifampicin susceptibility testing by disc diffusion (5 µg disc on MuellerHinton agar with a 0.5 McFarland inoculum incubated for 24 h at 3236°C in ambient air) revealed an 11 mm zone of inhibition. On hospital day 13, rifampicin at a dose of 600 mg intravenously daily was added to the meropenem, and gentamicin and metronidazole were stopped. On hospital day 16, the patient defervesced, and CSF analysis demonstrated marked improvement with negative cultures (Table 1). Rifampicin and meropenem were continued for 2 more weeks. The ventriculostomy was removed on hospital day 23. The patient was discharged from the hospital ambulating with minimal assistance 30 days after admission.
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References
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