Types of Pathogens

Types of Pathogens

1. Bacteria

• Structure: Single-celled organisms with cell walls but no nucleus
• Size: 1-5 micrometers (relatively large for microorganisms)
• Reproduction: Can reproduce independently through binary fission
• Treatment: Can be killed by antibiotics
• Examples:
  • Tuberculosis (TB) - affects lungs, spreads by airborne droplets
  • Pneumonia - lung infection, can be life-threatening
  • Salmonella food poisoning - causes vomiting and diarrhea
  • Gonorrhoea - sexually transmitted infection caused by Neisseria gonorrhoeae; symptoms include yellow/green discharge and pain when urinating (may be asymptomatic); treated with antibiotics, but antibiotic resistance is a growing concern

2. Viruses

• Structure: Not complete cells - just genetic material (DNA/RNA) in a protein coat
• Size: 20-300 nanometers (much smaller than bacteria)
• Reproduction: Must hijack host cells to reproduce
• Treatment: Cannot be killed by antibiotics; some can be prevented by vaccination
• Examples:
  • Influenza (flu) - spreads through airborne droplets
  • Measles - highly contagious, spreads through respiratory droplets
  • HIV/AIDS - damages immune system, spreads through bodily fluids

3. Fungi

• Structure: Can be single-celled (yeasts) or multicellular with thread-like structures
• Reproduction: Produce spores that can spread through air or contact
• Growth conditions: Prefer warm, moist environments
• Examples:
  • Athlete's foot - affects skin between toes, spreads by direct contact
  • Rose black spot - plant disease that causes black spots on rose leaves
  • Chalara ash dieback - caused by the fungus Hymenoscyphus fraxineus; affects ash trees across the UK and Europe; symptoms include leaf loss, crown dieback, and bark lesions; spreads by wind-borne spores and movement of infected nursery stock; no effective treatment and affected trees usually die

4. Protists

• Structure: Single-celled organisms with a nucleus (eukaryotic)
• Transmission: Often require vectors (other organisms) to spread
• Examples:
  • Malaria - caused by Plasmodium protist, transmitted by Anopheles mosquitoes