Microbiology: Bacterial Pathogenesis

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Questions and Answers

What is a common way for microbes to gain access to the body?

Through the digestive system

Through the respiratory system

Through openings in the skin, such as hair follicles and sweat gland ducts (correct)

Through the circulatory system

Which of the following can establish a parenteral route of entry?

Punctures, injections, or wounds (correct)

Inhalation of contaminated air

Natural shedding of skin cells

Consumption of contaminated food

Why is the portal of entry important for microbes?

Because it allows microbes to avoid the host's immune system

Because it affects the type of disease that will occur (correct)

Because it determines the number of microbes that can enter

Because it determines the severity of the disease

Which of the following mucous membranes is most susceptible to microbial penetration due to its delicacy?

Conjunctiva Signup and view all the answers

What determines the likelihood of disease when microbes enter the body?

The number of microbes that enter Signup and view all the answers

What is the primary mechanism by which microorganisms bypass host defenses in the skin?

Through cuts and wounds Signup and view all the answers

How can microbes infect the skin?

By infecting the keratin in skin Signup and view all the answers

Which of the following routes of infection is also known as the parenteral route?

Direct deposition beneath the skin or membranes Signup and view all the answers

What is required for microbes to cause disease?

A large number of microbes must enter the body Signup and view all the answers

Which portal of entry is specific to sexually transmitted infections?

Genitourinary tract Signup and view all the answers

What is the primary mechanism by which microorganisms damage host cells?

Production of toxins that disrupt cellular function Signup and view all the answers

Which of the following is a characteristic of mucous membranes that makes them prone to microbial penetration?

Delicate membrane structure Signup and view all the answers

What is the primary function of the M protein produced by Streptococcus pyogenes?

To mediate attachment and resist phagocytosis Signup and view all the answers

Which of the following mechanisms is used by some pathogens to obtain free iron from the host?

Secretion of siderophores to bind iron Signup and view all the answers

What is the primary function of capsules in bacterial pathogens?

To impair phagocytosis and resist host defenses Signup and view all the answers

Which of the following enzymes is involved in the breakdown of fibrin and facilitation of bacterial movement?

Kinase Signup and view all the answers

What is the primary function of mycolic acid in Mycobacterium tuberculosis?

To resist digestion by phagocytes Signup and view all the answers

Which of the following mechanisms is used by some pathogens to damage host cells?

Direct damage through the production of toxins Signup and view all the answers

Study Notes

Portals of Entry

Microorganisms can enter the body through: mucous membranes, skin, and direct deposition beneath the skin or membranes (parenteral route)
Mucous membranes are a common portal of entry, including: respiratory tract, gastrointestinal tract, genitourinary tract, and conjunctiva
Skin is the largest organ in terms of surface area and weight, and can be penetrated by microorganisms

Protecting Against the Host's Defenses

Bacterial capsules can resist phagocytosis, a process by which certain cells engulf and destroy microorganisms
Examples of bacteria with capsules include: Streptococcus pneumoniae
Cell wall components can also contribute to virulence, such as:
- Streptococcus pyogenes producing M protein, which mediates attachment and resists phagocytosis
- Mycobacterium tuberculosis producing waxy lipid (mycolic acid), which resists digestion by phagocytes

Enzymes and Toxins

Some bacteria produce extracellular enzymes (exoenzymes) that aid in virulence
Examples of enzymes include:
- Coagulases, which coagulate fibrinogen into fibrin to protect the bacterium from phagocytosis
- Kinases, which break down fibrin and allow bacteria to move further

How Pathogens Damage Host Cells

Pathogens can damage host cells by:
- Using the host's nutrients, such as iron, by producing siderophores
- Directly damaging host cells
- Producing toxins

Number of Invading Microbes

The likelihood of disease increases as the number of pathogens increases
A small number of microbes may be overcome by the host's defenses, but a large number can set the stage for disease

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Description

This quiz covers the mechanisms of bacterial pathogenesis, including the role of capsules in resisting host defenses and cell wall components that contribute to virulence.