General Classification of medically important pathogens

• What is the main difference between prokaryotic and eukaryotic cells regarding the nuclear membrane?

  Prokaryotic cells lack a nuclear membrane, while eukaryotic cells have one.
• What type of DNA do prokaryotic cells contain?


  Single, closed, circular double-stranded DNA
• How do prokaryotic cells reproduce?

  They reproduce by binary fission.
• What is the composition of the cell wall in prokaryotic cells?

  It contains peptidoglycan, lipid, and protein.
• What is the primary difference in ribosome size between prokaryotic and eukaryotic cells?

  Prokaryotic cells have 70S ribosomes, while eukaryotic cells have 80S ribosomes.
• What organelles are absent in prokaryotic cells?

  Mitochondria, Golgi complex, and endoplasmic reticulum
• What is the function of mitochondria in eukaryotic cells?

  They are the sites of aerobic respiration.
• How are bacteria classified based on Gram staining?

  They are classified as Gram positive or Gram negative based on their cell wall composition.
• What color do Gram positive bacteria appear after staining?

  Blue or purple
• What is an example of a Gram positive bacterium?

  Staphylococcus
• What color do Gram negative bacteria appear after staining?

  Red or pink
• What is an example of a Gram negative bacterium?

  Escherichia coli
• What are the classifications of bacteria based on morphology?

  1. Coccus: spherical or oval

  • Diplococcus: pairs (e.g., Neisseria gonorrhoeae)
  • Streptococcus: chains (e.g., Streptococcus pyogenes)
  • Staphylococcus: clusters (e.g., Staphylococcus aureus)
  • Tetrad: groups of four

  1. Bacilli: rod-shaped

  • Coccobacilli: (e.g., Brucella)
  • Streptobacilli: chains (e.g., Bacillus subtilis)
  • Comma-shaped: (e.g., Vibrio cholerae)
  • Chinese letter shaped: (e.g., Corynebacterium diphtheriae)
• What are the classifications of bacteria based on flagella?

  1. Monotrichous: single flagella at one end (e.g., Vibrio cholera)
  2. Lophotrichous: bundle of flagella at one end (e.g., Pseudomonas fluorescens)
  3. Amphitrichous: flagella at both ends (e.g., Aquaspirillium)
  4. Peritrichous: flagella all over the surface (e.g., E. coli)
  5. Atrichous: no flagella (e.g., Shigella)
• What are the classifications of bacteria based on spore formation?

  1. Spore-forming bacteria:

  • Endospore forming (e.g., Bacillus, Clostridium)
  • Exospore forming (e.g., Methylosinus)

  1. Non-sporing bacteria (e.g., E. coli, Salmonella)
• What are the classifications of bacteria based on gaseous requirements?

  1. Obligate aerobes: require oxygen (e.g., Mycobacterium tuberculosis)
  2. Facultative anaerobes: can use oxygen but do not require it (e.g., E. coli)
  3. Aerotolerant anaerobes: do not require oxygen but can tolerate it (e.g., Lactobacillus)
  4. Microaerophiles: grow in low oxygen concentrations (e.g., Campylobacter)
  5. Obligate anaerobes: can only grow without oxygen (e.g., Peptococcus)
  6. Capnophiles: require carbon dioxide for growth (e.g., Campylobacter)
• What is the smallest known infective agent?

  Viruses
• What do viruses lack that distinguishes them from other pathogens?

  They lack cellular organization and metabolic activity.
• What is the size range of viruses?

  20-300 nm
• What is the term for an extracellular infectious viral particle?

  Virion
• What is mycology?

  • The study of fungi
  • Derived from the Greek word "mykes" meaning mushroom
• Who is regarded as the father of medical mycology?

  Raymond Sabouraud
• How many species of fungi have been described?

  Approximately 80,000 species
• What percentage of fungal species cause more than 90% of infections?

  Less than 50 species
• What is the smallest virus?

  Parvovirus (20 nm)
• What is the largest virus?

  Poxvirus (300 nm)
• What is mycology?

  Mycology is the study of fungi.
• What does the term "mykes" mean?

  "Mykes" means mushroom in Greek.
• When was the first documented animal infection by a fungus made?

  In 1835 by Bassi.
• What disease did Bassi study in silkworms?

  The muscardine disease.
• Who published a comprehensive study of dermatophytic fungi in 1910?

  Raymond Sabouraud.
• What is the role of fungi in relation to animal tissue?

  Fungi can invade plant and animal tissue.
• How many species of fungi have been described?

  Approximately 80,000 species.
• What percentage of fungal infections in humans is caused by less than 50 species?

  More than 90%.
• What is mycelium?

  Mycelium is a mass of branching intercalating filaments.
• What was the trend in reported deaths due to mycoses in the U.S. from 1941 to 1973?

  Reported deaths due to mycoses increased from 324 to 530.
• What is required for fungi to be pathogenic?

  They must tolerate the temperature of the host site and possess an enzymatic system.
• What factors have contributed to the increased incidence of fungal infections in modern times?

  Increased mobility and immunocompromised individuals.
• What are the two major groups of parasites?

  Parasitic protozoa and parasitic helminths.
• How are parasitic protozoa classified?

  Based on their means of locomotion and mode of reproduction.