entro and nesseria

• Enterobacteriaceae classification


  • Escherichia
  • Shigella
  • Edwardsiella
  • Salmonella
  • Citrobacter
  • Klebsiella
  • Enterobacter
  • Hafnia
  • Serratia
  • Proteus
  • Providencia
  • Morganella
  • Yersinia
  • Erwinia
  • Pectinobacterium

  
• Enterobacteriaceae


  • Gram-negative, non-sporing, rod shaped bacteria
  • Oxidase -
  • Ferment glucose
  • Reduce nitrate to nitrite
• Enterobacteriaceae are found worldwide in soil, water, vegetation, and microbial flora of animals and humans
• Some Enterobacteriaceae are always associated with disease, e.g. Shigella, Salmonella, Yersinia pestis
• Some Enterobacteriaceae are normal flora that can become opportunistic pathogens, e.g. E. coli, K. pneumoniae, P. mirabilis
• Enterobacteriaceae are facultative anaerobes
• If motile, Enterobacteriaceae motility is by flagella in general

  
• Many Enterobacteriaceae are normal inhabitants of the intestinal tract of man and other animals
• Some Enterobacteriaceae are enteric pathogens and others are urinary or respiratory tract pathogens
• Differentiation of Enterobacteriaceae is based on biochemical reactions and differences in antigenic structure

  
• Escherichia coli


  • Gram-negative, rod shaped bacteria
  • Part of the Enterobacteriaceae family
  • Normal inhabitant of the G.I. tract
  • Some strains cause gastroenteritis
  • Major cause of urinary tract infection and neonatal meningitis and septicemia
  • May have a capsule
• Key tests for "normal" E. coli strain


  • Urea -
  • Indole +
  • Citrate -
  • Motility +
• Shigella


  • Gram-negative, rod shaped bacteria
  • Part of the Enterobacteriaceae family
  • Urea -
  • Motility -
  • All ferment mannitol except S. dysenteriae
  • Pediatric disease (1-4 years)
  • Associated with day-care centers, nurseries
  • Spread by fecal-oral route (hands)
  • 200 bacilli can establish disease

  
• Salmonella


  • Gram negative, rod shaped
  • Part of the Enterobacteriaceae family
  • Urea -
  • Motility +
  • Citrate +/-
  • Indole -
  • Source of most infections is ingestion of contaminated water or food, e.g. poultry, eggs, dairy products
  • Need to ingest large number of organisms
• Klebsiella


  • Gram negative, rod shaped bacteria
  • Part of the Enterobacteriaceae family
  • Normal flora of GI tract, but potential pathogen in other areas
  • Urea +
  • Citrate +
  • MR-, VP+
  • Motility -

  
• Enterobacter

  • Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the Enterobacteriaceae family
  • Normal flora of GI tract
  • Urea gives variable result depending upon species
  • Citrate +
  • Causes nosocomial infections

  
• Serratia


  • Gram-negative, rod-shaped bacterium in the Enterobacteriaceae family
  • A free-living saprophyte
  • Citrate +
  • Motility +
  • Urea +/-

  
• Proteus


  • Part of the Enterobacteriaceae family of gram-negative bacilli
  • Are all part of the normal flora of the GI tract
  • Are motile
  • Urea +
  • Oxidase -
  • Catalase -
  • Nitrate +

  
• Neisseria


  • Gram negative diplococci that are coffee-bean shaped
  • Neisseria and their relatives can be isolated from animals, and some species are pathogenic, e.g. N. gonorrheae and N. meningitidis
  • Some of the most naturally competent bacteria known

  
• Nonfermenters


  • Gram-negative bacilli or coccobacilli
  • Most are nonfastidious and are isolated by the same means used to isolate the Enterobacteriaceae
  • They are obligate aerobes and most will not grow or will grow poorly under anaerobic conditions

  
• Pseudomonas aeruginosa


  • Straight or slightly curved Gram-negative bacteria
  • Pigmentation: green
  • Odor: sweet, grape-like
  • Oxidase+
  • Motile
  • Is a major cause of nosocomial infections