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Questions and Answers
What is the primary mode of transmission for Corynebacterium diphtheriae?
Which of the following statements is true regarding the pathogenicity of Corynebacterium diphtheriae?
What disease is predominately caused by Mycobacterium leprae?
What is the primary reservoir for Mycobacterium leprae?
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What characterizes the speed of growth of Mycobacterium tuberculosis?
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What type of toxin produced by Staphylococcus specifically lyses leukocytes?
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Which of the following diseases is NOT associated with Staphylococcus?
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Which toxin produced by Staphylococcus is heat stable and remains active at 100 degrees C for 30 minutes?
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What is the main pathogenicity factor produced by Streptococcus that can stimulate fever and shock?
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Which of the following treatments is commonly used for Methicillin-resistant Staphylococcus aureus (MRSA)?
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Which of the following best describes alpha hemolysis in blood agar tests?
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What disease caused by Streptococcus can lead to irreversible kidney damage?
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Bacillus anthracis is primarily associated with which of the following diseases?
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Which type of anthrax is characterized by a high mortality rate near 100%?
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What is the most common form of anthrax, which can be fatal in 20% of untreated patients?
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Which Clostridium species is known for causing the deadliest known toxins?
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What is the recommended prevention method for Clostridium tetani infections?
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How does Clostridium difficile infections typically resolve in patients with minor infections?
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What is a unique characteristic of Listeria that allows it to thrive in stored food?
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Which method is NOT a transmission route for Listeria monocytogenes?
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Which species is the smallest free-living microbe known to cause significant human disease?
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What process did the Chinese use to induce immunity in children against smallpox?
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Which type of immunity provides immediate protection against disease?
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What is a characteristic of attenuated vaccines?
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What distinguishes Gram-positive bacteria from Gram-negative bacteria?
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What is the role of Staphylococcus epidermidis in human infections?
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Which feature contributes to the pathogenicity of Staphylococcus aureus?
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What is the principal component of the Gram-positive bacterial cell wall?
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Which vaccine is considered the safest and consists of inactivated viruses?
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Study Notes
History of Immunization
- Variolation was the first method of inducing immunity by infecting individuals with material from a smallpox scab.
Success of Vaccines
- Polio vaccine introduced in the 1950s and 1960s significantly reduced cases.
- Measles vaccine introduced in the 1960s, resulting in a gradual decrease in cases.
Active and Passive Immunity
- Active immunity: Achieved by administering antigens, stimulating an adaptive immune response.
- Passive immunotherapy: Acquired by transferring antibodies from an immune individual or animal.
Vaccine Types
-
Attenuated (modified live) vaccines:
- Produce a mild infection, potentially resulting in disease.
- Provide lasting protection, often without boosters.
- Examples: chickenpox, measles, mumps
-
Inactivated (killed) vaccines:
- Considered the safest type of vaccine.
-
Toxoid vaccines:
- Use chemically or thermally modified toxins to stimulate active immunity.
Gram-Positive Bacteria
-
Distinguishing features:
- Thicker peptidoglycan layer in the cell wall, appearing purple during Gram staining.
-
Main groups:
- Low G+C bacteria (Firmicutes)
- High G+C bacteria (Actinobacteria)
Staphylococcus
- Nonmotile.
- Salt-tolerant.
- Catalase-positive.
-
Key organisms:
- Staphylococcus aureus: More virulent strain.
- Staphylococcus epidermidis: Opportunistic infections.
Staph Aureus Pathogenicity
-
Factors enabling evasion of phagocytosis:
- Capsule
- Protein A
-
Production of enzymes:
- Coagulase
- Hyaluronidase
- Staphylokinase
-
Production of toxins:
- Cytolytic toxins: Lyse cell membranes.
- Exfoliative toxins: Cause skin cell separation.
- Toxic-shock syndrome (TSS) toxin.
- Enterotoxins: Cause food poisoning symptoms.
Staph Aureus Diseases
- Food poisoning: Fast onset (4 hours), typically lasts 24 hours.
- Skin infections: Scalded skin syndrome, impetigo, folliculitis.
- Toxic-shock syndrome: Affects blood pressure, leading to organ failure.
- Other infections: Bacteremia, endocarditis, pneumonia, osteomyelitis.
- Treatment: Methicillin; Vancomycin for MRSA infections.
Streptococcus Pathogenicity Factors
- Hyaluronidase: Enables streptococcus to spread in tissues.
- Pyrogenic (erythrogenic) toxins: Induce fever, rash, and shock.
- Streptolysins: Lyse red blood cells, white blood cells, and platelets.
Streptococcus Diseases
- Pharyngitis (strep throat).
- Rheumatic fever: Damages heart valves and muscle.
- Scarlet fever: Chest rash.
- Pyoderma and erysipelas.
- Streptococcal TSS: Organ failure, shock, and death.
- Necrotizing fasciitis (flesh-eating bacteria).
- Glomerulonephritis: Irreversible kidney damage.
- Treatment: Penicillin.
Other Streptococcal Groups
-
Group B streptococcus (Streptococcus agalactiae):
- Neonatal bacteremia, meningitis, and pneumonia.
-
The Viridans Group (Streptococcus mutans):
- Opportunistic pathogens causing dental caries (cavities) and dental plaques.
-
Streptococcus pneumoniae:
- Causes disease when it reaches the lungs.
Hemolysis Patterns
- Beta hemolysis: Complete lysis of red blood cells.
- Alpha hemolysis: Partial lysis of red blood cells.
- Gamma hemolysis: No lysis of red blood cells.
Bacillus
- Bacillus anthracis causes anthrax.
Anthrax
- Transmission: Inhalation of spores, inoculation through skin breaks, ingestion of spores.
-
Types:
- Gastrointestinal anthrax.
- Inhalation anthrax (high mortality).
- Cutaneous anthrax (most common; fatal in 20% of untreated cases).
Clostridium
- Key species:
- Clostridium perfringens: Produces gas gangrene.
- Clostridium difficile: Causes severe diarrhea.
- Clostridium botulinum: Produces potent neurotoxin, causing botulism.
- Clostridium tetani: Causes tetanus.
Clostridium Diseases and Mechanisms
-
Clostridium perfringens:
- Treatment: Hyperbaric chamber to oxygenate tissues.
- Prevention: Proper wound cleaning.
-
Clostridium difficile:
- Treatment: Discontinuation of causative antimicrobial drug.
- Prevention: Proper hygiene to prevent nosocomial infections.
-
Clostridium botulinum:
- Prevention: Safe canning of food; infants under 1 year should not consume honey.
-
Clostridium tetani:
- Prevention: Tetanus toxoid immunization.
Listeria
- Reservoir: Humans, animals, soil, water.
- Entry: Contaminated food and drink.
- Unique characteristic: Growth at refrigeration temperatures.
-
Diseases:
- L. monocytogenes: Intracellular pathogen, often found in the gallbladder.
Listeria Transmission
- Contaminated food.
- Mother to fetus.
- Contact with infected birds/animals.
- Contaminated equipment/materials.
Mycoplasma
- Unique characteristic: Smallest free-living microbes.
-
Diseases:
- Mycoplasma pneumoniae: Causes atypical pneumonia, common in children 5-15 years old.
Corynebacterium
-
Diseases:
- Corynebacterium diphtheriae: Causes diphtheria.
- Transmission: Respiratory droplets or skin contact.
-
Signs and symptoms:
- Diphtheria toxin: Inhibits polypeptide synthesis in eukaryotes.
- Non-toxigenic bacteria are not pathogenic.
- Prevention: DTaP toxoid vaccine.
Mycobacterium
-
Diseases:
- Tuberculosis.
- Leprosy (Hansen's disease): Armadillos are hosts.
-
Transmission and reservoirs:
- Leprosy: Person-to-person contact or skin breaks; armadillos are the primary reservoir.
- Tuberculosis: Airborne transmission; humans are the primary reservoir.
- S&S (Signs and Symptoms): Vary depending on the specific disease.
- Prevention: BCG vaccine for tuberculosis.
-
Growth rate:
- Tuberculosis: Slow growth, making it drug-resistant.
- Leprosy: Long incubation periods; 12-day generation time.
Propionibacterium
- Propionibacterium acnes: Causes acne.
- Treatment: May not always be necessary, but antimicrobial drugs can help control the bacterium.
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Description
Explore the fascinating history of immunization, from the origins of variolation to the introduction of significant vaccines like those for polio and measles. Learn about the different types of vaccines, including attenuated, inactivated, and toxoid vaccines, as well as the concepts of active and passive immunity.
