Clinical characteristics and outcome of Klebsiella pneumoniae meningitis in adult patients

Background: Klebsiella pneumoniae meningitis is an uncommon pathology that occurs more often in elderly patients, particularly among those with underlying conditions or neurosurgical problems. K. pneumoniae, however, has been identified as the most common cause of community-acquired meningitis in adults in East Asia. Case reports and small series of K. pneumoniae infections from Korea, Singapore, Japan, India and Thailand have also been reported. In Taiwan, the prevalence rate of Streptococcus pneumoniae meningitis has decreased from 28% to less than 10% in the past 20 years, whereas the prevalence rate of K. pneumoniae has risen to near 30% among all adult meningitis cases. In this review article, we will discuss the protean clinical characteristics and the complexity of the clinical course of this specific K. pneumoniae meningitis. Pathogenesis: The reason for the high prevalence of metastatic septic infections caused by K. pneumoniae in Taiwan remains unclear. High prevalence in this area of serotype K1 and K2 and the expression of magA and rmpA genes conferring an elevated phagocytosis resistance and a capability of active proliferation to bacterium have been suggested. Poor sugar control of diabetes, alcoholism, hepatopathy or neoplastic diseases are also important factors for bacterial virulence, causing an impaired phagocytosis and low immune resistance of host to the bacteria. Clinical Manifestations: Fever, altered consciousness and seizure were the most common clinical features. K. pneumoniae meningitis may cause subdural effusion, empyema, ventriculitis and/or brain abscess and could be rapidly fatal in cirrhotic and diabetic patients. Brain abscess caused by K. pneumoniae can be monoloculated or multiloculated and some (around 13%) may be emphysematous. The leading underlying disease of patients with K. pneumoniae brain abscess was diabetes, and diabetes patients with liver cirrhosis may have a poor prognosis. Concomitant septic metastatic infection is also common in K. pneumoniae infection. Taiwan is the country with the highest frequency of metastatic meningitis or endophtalmitis in 10-13% of cases of K. pneumoniae liver abscess. The common sites of septic metastatic infection include liver, eyes, lung and kidney. Diagnosis: Diagnostic imaging studies are usually required for the detection of multiple septic metastatic lesions. Cerebrospinal fluid analysis and cultures are the cornerstones of diagnosis. For these septic metastatic lesions, an aspiration and/or drainage procedure is also needed for a diagnostic confirmation as well as a more effective therapy. Treatment and Outcome: A timely and effective antimicrobial therapy is essential, as mortality is substantially high (40%-60%) and there is an elevated risk of neurological sequelae. Therefore, guidelines on empirical treatment for K. pneumoniae should be considered in the management of bacterial meningitis of the patient with geographical and demographical risk factors. The K. pneumoniae subdural empyema or brain abscess might need neurosurgical intervention for complications such as abscess rupture into ventricle with subsequent ventriculitis.