General Microbiology Infection Question And Answers

Infection Important Notes

1. Types of infection

2. Sources of infection

3. Exotoxin

• Generally formed by Gram-positive bacteria
• Heat labile, highly antigenic, highly specific
• Inactivated by formalin
• Converts toxins into toxoids

4. Endotoxin

• Produced by Gram-negative bacteria
• Heat stable, less potent, nonspecific
• Cannot be toxoided

Infection Short Essays

Question 1. Modes of transmission of infection.
Answer:

Modes of transmission of infection

1. Contact:

• It may be direct (or) indirect
• Infections spread by direct contact are sexually transmitted diseases such as syphilis, AIDS, and gonorrhea.
• A contagious disease is a term used for the disease acquired by direct contact
• Indirect contact may be through the agency of fomites which are inanimate objects such as clothing, toys, etc.

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2. Inhalation:

• Respiratory infections such as the common cold, influenza, and T.B. are acquired by inhalation.
• These organisms are shed into the environment by patients in secretions from the nose (or) throat during sneezing, coughing (or) speaking.

3. Inoculation: In some instances, pathogens may be directly inoculated into the tissues of the host For Example: Tetanus spores in deep wounds, and rabies virus directly by bite of a rabid animal.

4. Ingestion: Intestinal infections like cholera, dysentery, food poisoning, and most of parasitic infections are acquired by ingestion of food (or) drink contaminated by pathogens.

5. Vectors:

• Vectors are anthropods or other invertebrate hosts Examples: are flies, ticks, and mosquitoes.
• Transmission by vector may be either mechanical or biological.

6. Transplacental transmission: Some pathogens can cross the placental barrier and infect the fetus in utero. This is known as vertical transmission.

Example. Teratogenic infections like rubella.

7. Iatrogenic and laboratory infections:

• If meticulous care in asepsis is lacking certain infections like AIDS and hepatitis B may sometime be transmitted during procedures such as injections, lumbar punctures, blood transfusions, and surgery. These are known as iatrogenic infections.
• Laboratory personnel handling infectious material are at risk of infection transmission.

Question 2. Sources of infection?
Answer:

Sources of infection

Sources of infection may be endogenous (or) exogenous sources.

1. Endogenus sources: Organisms of normal flora are usually non-pathogenic but occasionally they behave as pathogens outside their habitat.

Example: Virtdians streptococci (normal flora of mouth) can cause infective endocarditis.

2. Exogenous sources:

• Most of the infections are exogenous In origin.
• Exogenous sources include.
  • Human cases and carriers.
    • Humans themselves are the most common source of infection.
  • Animals.

• • Insects
    • Blood-sucking insects such as mosquitoes, ticks mites, and flies may transmit several pathogens to man.
    • Anopheles mosquito – malaria.
  • Soil and water
    • Spores of tetanus and gas gangrene bacilli remain viable in the soil for decades and serve as a source of infection.
  • Food:
    • Contaminated food acts as a source of infection in cases of food poisoning, diarrhea, and dysentery.
    • Example: Food poisoning by staphylococcus.

Question 3. Differences between Exotoxin and endotoxin.
Answer:

Differences between Exotoxin and endotoxin

Question 4. Nosocomial or hospital-acquired infections?
Answer:

Nosocomial or hospital-acquired infections

• Cross-infection acquired in hospitals is called hospital-acquired hospital-associated or nosocomial infection.
• They may manifest during their stay in the hospital or sometimes after the patient is discharged.
• They may spread through droplets infection, dust, skin scales, in animate sources.
• Direct spread through contact and indirectly through equipment and materials.

Nosocomial Infections and Causative Organisms

Prevention or Control of Hospital-Acquired Infections:

• Proper sterilization and disinfection of the inanimate objects.
• Control of route of transmission by regular washings of hands, and disinfection of equipment.
• Isolation of an infectious patient
• Administration of antibiotics and antiseptics to the carrier staff (or) source patient
• Vaccination to susceptible hosts.