MICROBIOLOGY

• Aerobic, Gram-negative rod, 2-4 x 0.4-0.6µm.
• Grows on standard media from a stool source but needs a fresh specimen.
  • Enrichment broth (tetrathionate or selenite) may help growth when organisms present in low numbers.
• Salmonella enterica serovars typhi and paratyphi cause enteric fever; see separate module for details.
• Salmonella genus (non-typhoidal) can be divided into species (S. enterica and S. bongori) based on their phenotypic profile.
  • S. enterica comprises six subspecies based on phenotypes.
    • The most frequently seen subspecies causing human infection are S. enteritidis, S. typhimurium, S. newport, and S. javiana.
    • Salmonella enterica serotype Dublin causes more bloodstream infections and hospitalizations than other Salmonella serotypes. It is also much more likely to be isolated in metastatic foci of infection secondary to bacteremia[7].