Updated: 10/23/2019

Introduction to Bacteria

Review Topic
  • A 25-year-old woman presents to the emergency room with dsyuria and frequency of urination. She reports that she has had these symptoms for about 2 days now. Despite drinking copious amounts of water and cranberry juice, the symptoms have worsened. On physical exam, she has dry mucous membranes and suprapubic tenderness to palpation. There is no costovertebral tenderness. A urine dipstick test is positive for leukocytes and nitrates. The physician explains that she has a bacterial infection. (Urinary tract infection E. coli)
  • Bacteria
    • prokaryotic microorganisms that can cause disease in humans
      • i.e., pneumonia, urinary tract infections, meningitis, cellulitis, etc.
    • bacteria also exist as part of normal human flora
    • do not contain a nucleus in the cell 
  • Classification
    • bacteria are often classified via their morphology and chemical properties
    • morphologies
      • cocci
      • rods/bacilli
      • vibrio (comma-shaped)
      • spirochetes (spiral-shaped)
    • chemical properties
      • Gram stain
        • gram-positive bacteria have a thick cell wall 
        • gram-negative bacteria often have a thin cell wall
        • some bacteria Gram stain variably
      • other stains are summarized here
    • aerobic vs anaerobic
    • may produce pigment
    • may produce certain enzymes
  • Treatment
    • antimicrobial medications (antibiotics) either kill or inhibit the bacteria from causing further damage
    • mechanisms differ but may involve preventing bacterial protein synthesis, disrupting the cell membrane or cell wall, disrupting DNA or RNA synthesis, or inhibition of other key bacterial enzymes

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