Microbiology of Hafnia alvei

Hafnia alvei is a Gram-negative facultatively anaerobic bacillus that constitutes part of the human gut flora. Until recently, H. alvei strains could be mistakenly identified by conventional methods, miniaturisation or automatic systems as members of the Serratia, Escherichia, Citrobacter, Yokenella, Obesumbacterium or Salmonella genera. Consequently, molecular techniques were required for their definitive identification in the clinical laboratory. In addition, a new Hafnia species, H. paralvei, has recently appeared, which undoubtedly includes many of the strains reported in the literature as H. alvei. Alrhough H. alvei isolation from human clinical specimens remains uncommon, the development of drug resistance due to this species is emerging and it is likely that this organism will gain increasing importance in the future. Moreover, although H. alvei shares some virulence mechanisms with other Gram-negative enteropathogens, little is known about the factors that contribute to its pathogenesis in humans. The present article reviews the current identification methods, antimicrobial resistance and virulence factors of this bacterium.