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Introduction
1. Anatomy
2. Microbiology
2.1 General bacteriology
2.2 Introduction to systemic bacteriology
2.3 Gram positive cocci
2.4 Gram negative cocci
2.5 Gram positive bacilli
2.6 Gram negative bacilli
2.6.1 Introduction
2.6.2 E.coli
2.6.3 Klebsiella pneumoniae
2.6.4 Proteus
2.6.5 Vibrio cholerae
2.6.6 Other Vibrios
2.6.7 Salmonella
2.6.8 Pseudomonas
2.6.9 Minor pathogens
2.7 Other important bacteria
2.8 Virology
2.9 Parasitology
2.10 Mycology
3. Physiology
4. Pathology
5. Pharmacology
6. Immunology
7. Biochemistry
8. Cell and molecular biology
9. Biostatistics and epidemiology
10. Genetics
11. Behavioral science
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2.6.4 Proteus
Achievable USMLE/1
2. Microbiology
2.6. Gram negative bacilli

Proteus

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This organism is usually easy to recognize because it has characteristic morphological features. It’s associated with UTIs and sepsis.

Human pathology

Pili and urease production are key to pathogenicity.

Urease alkalinizes the urine, which helps the organism cause upper urinary tract infections such as pyelonephritis. Urease activity also promotes the formation of struvite (magnesium ammonium phosphate) stones in individuals with Proteus UTIs.

Laboratory diagnosis of Proteus infections

  • Gram stain shows Gram-negative bacilli.
  • Culture on blood agar shows swarming.
  • Culture on MacConkey agar shows non-lactose-fermenting colonies with a fishy or seminal smell.
  • Indole test is positive in P. vulgaris and negative in P. mirabilis.
Proteus swarming
Proteus swarming

Pathogenicity of Proteus

  • Pili and urease are main virulence factors
  • Urease alkalinizes urine, aiding pyelonephritis
  • Promotes struvite stone formation in UTIs

Laboratory diagnosis

  • Gram-negative bacilli on Gram stain
  • Swarming growth on blood agar
  • Non-lactose fermenter on MacConkey agar
  • Characteristic fishy/seminal odor
  • Indole test:
    • Positive: P. vulgaris
    • Negative: P. mirabilis

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Proteus

This organism is usually easy to recognize because it has characteristic morphological features. It’s associated with UTIs and sepsis.

Human pathology

Pili and urease production are key to pathogenicity.

Urease alkalinizes the urine, which helps the organism cause upper urinary tract infections such as pyelonephritis. Urease activity also promotes the formation of struvite (magnesium ammonium phosphate) stones in individuals with Proteus UTIs.

Laboratory diagnosis of Proteus infections

  • Gram stain shows Gram-negative bacilli.
  • Culture on blood agar shows swarming.
  • Culture on MacConkey agar shows non-lactose-fermenting colonies with a fishy or seminal smell.
  • Indole test is positive in P. vulgaris and negative in P. mirabilis.
Key points

Pathogenicity of Proteus

  • Pili and urease are main virulence factors
  • Urease alkalinizes urine, aiding pyelonephritis
  • Promotes struvite stone formation in UTIs

Laboratory diagnosis

  • Gram-negative bacilli on Gram stain
  • Swarming growth on blood agar
  • Non-lactose fermenter on MacConkey agar
  • Characteristic fishy/seminal odor
  • Indole test:
    • Positive: P. vulgaris
    • Negative: P. mirabilis