Chapter 15: Mechanisms of pathogenicity

What does pathogenicity mean?

The ability to cause disease.

What is the degree of pathogenicity called?

Virulence.

What must microbes do to cause disease?

Gain access to the body through portals of entry, adhere to host cells, evade the immune system, and damage host cells.

What are some common portals of entry for pathogens?

Mucous membranes, skin, and parenteral routes.

What is the most commonly traveled portal of entry for pathogens?

Mucous membranes, particularly the respiratory tract.

How does the number of invading microbes affect pathogenicity?

A larger number of invading microbes increases the likelihood of causing disease.

What does ID50 represent in microbiology?

Infectious dose for 50% of a population.

What does LD50 represent in microbiology?

Lethal dose for 50% of a population.

What role do adherence factors play in pathogenicity?

They help pathogens attach to host tissues, which is crucial for colonization.

What is a biofilm, and why is it significant in infections?

A community of microbes that adhere to surfaces and are protected from the immune system and antibiotics.

What are exotoxins?

Toxins secreted by bacteria that can cause damage to host cells.

How are endotoxins different from exotoxins?

Endotoxins are components of the bacterial cell wall of gram-negative bacteria and are released upon cell lysis, while exotoxins are secreted during growth.

What is toxemia?

The presence of toxins in the blood.

What are the two main categories of toxins?

Exotoxins and endotoxins.

What is antigenic variation, and how do some pathogens use this to evade the immune system?

The ability of pathogens to change their surface antigens to avoid detection by the immune system.

What are inclusion bodies in the context of viral infections?

Aggregates of viral particles or proteins within infected cells that can be used for diagnosis.

What is the significance of superantigens?

They induce a strong immune response that can lead to severe illness or death.

How do pathogens exit the body?

Through the same routes they entered, such as respiratory tract, gastrointestinal tract, urinary tract, and skin.

What types of diseases can be transmitted through saliva?

Diseases like the common cold and flu.

What is meant by the term 'necrosis' in relation to infections?

Tissue death resulting from disturbed blood supply, often caused by endotoxins.