Pyogenic liver abscess: Changes of Organisms and Consequences for Diagnosis and Therapy

Liver abscess is a rare but potentially fatal disease with mortality rates of 2-12%. The spectrum of causative microorganisms varies across the world and is changing due to increasing worldwide travel activity. As a result, previously less frequent pathogens must increasingly be considered in the differential diagnosis. The most common pathogens of liver abscess are so-called abscess streptococci, anaerobes and Gram-negative bacteria such as Escherichia coli and Klebsiella pneumoniae. Certain clones among the Gram-negatives, typically among Klebsiella spp., harbour specific virulence factors and are therefore referred to as hypervirulent clones which spread worldwide. In any case, the causative agent should be identified before anti-infective treatment is initiated. Several pathogens such as Candida spp., Pseudomonas aeruginosa or Staphylococcus aureus are uncommon and only detected in a specific context. Various therapeutic regimens are available for anti-infective therapy. Usually an empirical therapy is started, combining mostly β-lactam antibiotics or quinolones with anaerobically active substances.