Appearance of Klebsiella pneumoniae liver abscess syndrome in Argentina: case report and review of molecular mechanisms of pathogenesis.

Klebsiella pneumoniae liver abscess syndrome (KLAS) is an emerging invasive infection caused by highly virulent community-acquired strains of K. pneumoniae displaying hypermucoviscosity. The salient features of this syndrome include the presence of bacteremia, primary monomicrobial liver abscess, and metastatic complications. A previously healthy Argentinean man presented with fever and found to have liver abscess caused by K. pneumoniae with metastatic seeding of gastric wall. Cultures from blood and liver abscess grew hypermucoviscous K1 K. pneumoniae with sequence type (ST) 23 by multilocus sequence typing (MLST), positive for rmpA (regulator of mucoid phenotype A), wzy(KpK1) (capsular polymerase) and aerobactin genes. The hypermucoviscous phenotype of this K. pneumoniae isolate was readily identified by the "string test" (colonies formed a long string when touched with a loop). The patient responded favourably to percutaneous drainage of the abscess and antibiotics. This is the first documented report of KLAS described in Argentina, and may signal the emergence of this syndrome in South America.