MEDI 3104 Bacterial Pathogenesis

Questions and Answers

What defines strict pathogens in terms of virulence?

They are less virulent than opportunistic pathogens.

They do not cause diseases in healthy individuals.

They can cause diseases in normal individuals. (correct)

They can cause diseases only in the immunocompromised.

Which of the following correctly describes opportunistic pathogens?

They rarely coexist with the human microbiota.

They are exclusively airborne pathogens.

They typically arise from normal flora and affect immunocompromised individuals. (correct)

They always cause disease in healthy individuals.

Which stage of bacterial pathogenesis follows adherence to cell surfaces?

Transmission.

Invasion, Inflammation, & Intracellular Survival. (correct)

Toxin Production.

Evasion of the host immune system.

What is the primary mode of transmission for pathogens like Salmonella and Shigella?

Ingestion through contaminated food or water. Signup and view all the answers

Which pathogen is associated with tuberculosis transmission?

Mycobacterium tuberculosis. Signup and view all the answers

Which of the following statements accurately reflects the impact of respiratory pathogens?

They can lead to significant mortality, killing around 2 million people annually. Signup and view all the answers

What is the first stage of bacterial pathogenesis?

Transmission. Signup and view all the answers

What type of transmission does Clostridium tetani primarily involve?

Trauma related transmission Signup and view all the answers

In the context of bacterial infections, what does evasion of the host immune system accomplish?

Enables prolonged survival and infection within the host. Signup and view all the answers

What defines a commensal in the context of human microbiota?

Harmless microbes that live on the host without causing harm. Signup and view all the answers

Which bacterial infection is associated with blood borne transmission?

HIV Signup and view all the answers

What is the infective dose of Shigella required to cause disease?

10 bacilli Signup and view all the answers

Which term describes the growth and multiplication of a microbe in the body without necessarily causing disease?

Infection Signup and view all the answers

How is virulence best defined?

The measure of the pathogenicity of a microorganism. Signup and view all the answers

Which of the following bacteria requires a large infective dose to cause cholera?

Vibrio cholerae Signup and view all the answers

What role do pili (fimbriae) play in bacteria?

They help bacteria to adhere to cells. Signup and view all the answers

What distinguishes opportunistic pathogens from other pathogens?

They primarily cause disease in immunocompromised individuals. Signup and view all the answers

Which of the following is NOT part of vertical transmission?

Gonorrhea Signup and view all the answers

What characterizes nosocomial infections?

Infections that are hospital-acquired. Signup and view all the answers

What is meant by invasiveness in the context of pathogenic bacteria?

The ability of a pathogen to penetrate and multiply within host tissues. Signup and view all the answers

Which factor does NOT contribute to a bacterium's ability to colonize tissue?

Environmental conditions Signup and view all the answers

Which of the following is NOT a means of vector borne transmission?

HIV via blood transfusion Signup and view all the answers

Which of the following best describes the difference between pathogenicity and virulence?

Pathogenicity refers to the potential to cause disease, while virulence measures the severity of the disease caused. Signup and view all the answers

What type of infection is categorized as iatrogenic?

Infections that are a result of physician intervention or treatment. Signup and view all the answers

What is the primary function of leukocidins?

Destroy neutrophilic leukocytes and macrophages Signup and view all the answers

What role do plasmids play in bacteria?

They confer additional properties like drug resistance Signup and view all the answers

What is the function of bacteriophages?

To infect bacteria and add DNA to them Signup and view all the answers

How do transposons contribute to bacterial virulence?

By moving DNA sequences within the genome Signup and view all the answers

What is the significance of diphtheria and tetanus vaccines?

They are bacterial toxins rendered non-toxic to produce antitoxins Signup and view all the answers

What is a key characteristic of exotoxins as compared to endotoxins?

Exotoxins can be released before or after bacterial lysis. Signup and view all the answers

Which of the following is a correct example of a bacterium that produces an exotoxin?

Clostridium botulinum Signup and view all the answers

What makes endotoxins distinct from exotoxins in terms of stability?

Endotoxins are heat stable. Signup and view all the answers

Which statement is true regarding the immunogenicity of exotoxins compared to endotoxins?

Exotoxins can be made into toxoids, while endotoxins cannot. Signup and view all the answers

Which of the following correctly distinguishes the effects of exotoxins and endotoxins on the host?

Endotoxins can cause fever and have various effects. Signup and view all the answers

Which statement about the bacterial origin of exotoxins is correct?

Exotoxins can be produced by both Gram-positive and Gram-negative bacteria. Signup and view all the answers

What is true regarding the toxic component of endotoxins?

Lipid A is the toxic component of endotoxins. Signup and view all the answers

How would an exotoxin response differ from an endotoxin response in a host?

Endotoxins induce more severe systemic effects. Signup and view all the answers

Study Notes

Bacterial Pathogenesis and Virulence

Commensals vs. Pathogens: Commensals are harmless microbes (normal flora) that coexist with the host, while pathogens are capable of causing disease.
Infection vs. Colonization: Infection occurs when a microbe grows in/on the body, potentially causing disease. Colonization is when bacteria multiply without invading tissues.
Pathogenicity vs. Virulence: Pathogenicity is the ability to cause disease; virulence is a measure of pathogenicity, reflecting the severity of the disease produced.
Opportunistic Pathogens: Cause disease primarily in immunocompromised individuals, such as those with HIV or undergoing chemotherapy.
Nosocomial Infections: These are infections acquired in a hospital setting, while iatrogenic infections are caused by medical treatment.

Stages of Bacterial Pathogenesis

Transmission: The initial stage involves the entry of bacteria into the host.
Adherence: Bacteria adhere to cell surfaces using structures like pili and adhesins.
Invasion and Survival: This includes tissue invasion, triggering inflammation, and surviving intracellularly.
Toxin Production: Pathogens produce toxins that can damage host cells and tissues.
Evasion of Immune System: Pathogens employ strategies to avoid detection and destruction by the host's immune system.

Modes of Transmission

Ingestion: Example pathogens include Salmonella and Shigella, which can cause severe gastrointestinal issues.
Inhalation: Airborne pathogens such as Mycobacterium tuberculosis and Streptococcus pneumoniae are significant causes of respiratory tract infections.
Direct Contact: Transmissions can occur through unclean hands or breaks in the skin, with Staphylococcus aureus and Pseudomonas aeruginosa being common culprits.
Sexual Transmission: Pathogens like Neisseria gonorrhoeae and Treponema pallidum are transmitted through sexual contact.
Blood Borne Transmission: Pathogens like HIV can be transmitted through needlestick injuries and unsterile practices.
Vector Borne: Insects like mosquitoes can spread diseases such as malaria; mechanical vectors include flies transmitting bacteria like Salmonella.
Vertical Transmission: Involves transmission from mother to fetus (TORCH infections include Toxoplasma and Rubella).

Infective Dose

Low Infective Dose: Shigella requires as few as 10 organisms to cause disease.
High Infective Dose: Vibrio cholerae needs an estimated 10^6 to 10^8 organisms for infection.

Colonization Factors

Adherence Mechanisms: Bacteria attach to host tissues via pili, which bind to specific receptors.
Adhesins: Proteins like M protein in Streptococcus pyogenes aid in the adherence process.

Toxin Production

Exotoxins vs. Endotoxins:
- Exotoxins are proteins released by bacteria and can provoke strong immune responses; they can be vaccine candidates (e.g., toxoids).
- Endotoxins, particularly lipopolysaccharides (LPS) from the Gram-negative bacteria cell wall, induce general immune responses, such as fever.

Genotypic Virulence Factors

Plasmids: Circular DNA molecules that can confer traits like antibiotic resistance or toxin production.
Bacteriophage: Viruses that infect bacteria, influencing bacterial characteristics and virulence.
Transposons: Segments of DNA that move within the genome, altering bacterial properties and enhancing virulence.

Additional Factors in Pathogenesis

Leukocidins: Substances produced by some bacteria (e.g., PVL by MRSA) that can kill immune cells like neutrophils and macrophages, enhancing bacterial survival.

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Description

Explore the intricacies of bacterial pathogenesis and virulence in this MEDI 3104 quiz. Delve into the differences between commensal organisms and pathogenic bacteria along with their modes of action. Enhance your understanding of microbiology and immunology concepts essential for medical studies.