Klebsiella pneumoniae brain abscess in adults

Brain abscess is a life-threatening infection caused by hematogenous spread from the remote foci, most commonly of liver abscess, followed by otitic infection and sinusitis. Klebsiella pneumoniae brain abscess metastatic from liver abscess has been reported in Taiwan and has become a globally emerging problem. The K. pneumoniae brain isolates are highly virulent, hypermucoviscous, rmpA-positive and most commonly have capsule serotype K1 or K2. This review focuses on spontaneous K. pneumoniae brain abscess in adults, not related to skull base defect by fracture or surgery. Diabetes mellitus (DM), liver cirrhosis and alcoholic liver disease are the most common underlying diseases, which are all independently associated with increased risk of mortality. All brain abscess patients with DM had K. pneumoniae as the causative pathogen. Procedures of endoscopic injection sclerotherapy or ligation for esophageal varices may predispose to K. pneumoniae brain abscess in cirrhotic patients. The classic triad of brain abscess includes fever, headache and focal neurologic deficit. Endogenous endophthalmitis may be the presenting sign of disseminated infections including abscesses from liver, brain, prostate, kidney and lung. Computed tomographic (CT) scanning and diffusion-weighted magnetic resonance imaging could facilitate early diagnosis and proper management, which usually depends on the size of the brain abscess. On the CT scans, brain abscess manifests as a typical ring pattern of contrast enhancement. K. pneumoniae may sometimes cause a gas-containing brain abscess or pneumocephalus, resulting in a rapidly deteriorated course. Surgical intervention was commonly used together with antibiotics in about 60% of patients in whom the average abscesses diameter was >3.5 cm. The remaining 40% patients whose average abscess diameter of ≤3.5 cm were treated with antibiotics only. Almost all K. pneumoniae brain abscess isolates are susceptible to third-generation cephalosporins. However, some extended-spectrum β-lactamase-producing K. pneumoniae has emerged in the brain abscesses, which may necessity the need of meropenem therapy. An overall mortality rate of 26.7% was reported in adult patients with K. pneumoniae brain abscess. In conclusion, a diagnosis of K. pneumoniae infection should be considered for brain abscesses in diabetic or cirrhotic patients or have a gas-forming appearance, and particular attention should be paid to detection of other metastatic septic abscesses. Early imaging diagnosis, optimal timing of surgery and appropriate use of antibiotics improve the clinical outcome.