Liver abscess caused by Lawsonella clevelandensis in a patient with rheumatoid arthritis: A case report and literature review.

Lawsonella clevelandensis is a recently described anaerobic and partially acid-fast bacterium within the order Corynebacterineae. It is a fastidious microorganism that has been identified as part of the oral microbiota and is rarely associated with human infections. We describe the case of a 70-year-old man with a history of rheumatoid arthritis that developed liver abscesses and pylephlebitis. Gram stain of purulent material obtained by percutaneous drainage of the hepatic collection revealed gram-positive bacilli that stained acid-fast by the Kinyoun method. The patient was initially treated with imipenem, moxifloxacin and clarithromycin for possible Nocardia and/or nontuberculous mycobacterial infection. Cultures failed to grow the organism seen on the stains, and broad-spectrum 16S rRNA PCR gene sequencing analysis identified it as Lawsonella clevelandensis. Treatment was de-escalated to amoxicillin/clavulanic acid. The hepatic abscesses resolved completely after 4 weeks of treatment. There are only 8 documented cases of human infection caused by Lawsonella clevelandensis reported in the literature. Conventional microbiological methods do not reliably detect this bacterium, and the diagnosis relies on molecular methods. Excellent outcomes are obtained with a combined treatment approach that includes abscess drainage and prolonged antibiotic therapy.