Klebsiella pneumoniae liver abscess with metastatic complications is an emerging infectious disease in Taiwan. To identify genes associated with liver infection, we used a DNA microarray to compare the transcriptional profiles between three strains causing liver abscess and three strains without liver infection. There were 14 clones that revealed higher RNA expression levels in the three liver infection strains and three of these 14 clones contained a region that was absent in MGH 78578. The strain of K. pneumoniae MGH 78578 was isolated from a patient without liver abscess and was chosen for full genome sequencing by the Genomic Sequencing Center at Washington University (St. Louis, MO) (http//genome.wustl.edu/gsc). Sequencing of the clones revealed the replacement of 149 bp of MGH 78578 with a 21,745 bp fragment in a liver infection strain, NTUH-K2044. This 21,745-bp fragment contained 19 open reading frames, 14 of which were proven to be associated with allantoin metabolism. The K2044(