Gram negative bacteria

Cocci

1. Neisseria
   1. meningitidis (meningococcus)
   2. gonorrhoeae (gonococcus)
2. Moraxella

Rods (Bacilli)

Aerobic

• Lactose fermenting (Lactose positive)
  • Enterobacter spp
  • Escherichia coli
  • Klebsiella spp
  • Citrobacter spp^
  • Serratia spp^
• Non lactose-fermenting (Lactose negative)
  • Oxidase (-)
    • Acinetobacter spp
    • Burkholderia spp
    • E. coli
    • Proteus spp
    • Salmonella spp
    • Shigella spp
    • Serratia spp^
    • Stenotrophomonas maltophilia
  • Oxidase (+)
    • P. aeruginosa
    • Aeromonas spp.

Anaerobic

• Bacteroides spp,
• Fusobacterium spp,
• Prevotella spp.

^Serratia and Citrobacter spp can appear initially as non-lactose fermenting due to slow fermentation

Interpretations of Key Phrases

• “Gram negative coccobacilli” may suggest Haemophilus species
• “Lactose-positive gram negative rods” may suggest Enterobacteriaceae, such as E. coli, Klebsiella, or Enterobacter spp
• “Lactose-negative gram negative rods” may suggest Pseudomonas

See Also

• Microbiology (Main)