Quick Review Cards for Medical Laboratory Science

Characteristics of Nonfermenting

Gram-Negative Rods

Clinical Microbiology Review 189

• Obligate aerobes.


• Don’t ferment carbohydrates. K/K on TSI.


• May be oxidizers or nonoxidizers (asaccharolytic).


• Oxidation-fermentation (OF) medium: either open
  tube pos/closed tube neg (oxidizer) or open tube
  neg/closed tube neg (nonoxidizer).
  
  
  • Grow on SBA & CHOC in 24–48 hr.
  
  
  • Most grow on MAC. Appear as non–lactose fermenter.
  
  
  • Most are oxidase pos. Differentiates from
    Enterobacteriaceae.
  
  
  • Resistant to variety of antibiotics.