medical bacteriology - powerpoint 2

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Questions and Answers

What is the primary function of mucous membranes in the immune response?

To trap debris and microorganisms (correct)

To promote cell turnover and regeneration

To facilitate absorption of substances

To produce antibodies for pathogens

Which feature of the skin provides a significant defense against pathogenic bacteria?

The moisture level of the epidermis

The stratification of epidermal cells (correct)

The presence of capillaries

The mucus production in skin layers

What type of cells are primarily found in the mucous membranes that serve a defensive role?

Adipocytes

Muscle cells

Fibroblasts

Epithelial cells (correct)

Which of the following components is NOT included in the cellular defenses of nonspecific immunity?

Basophils Signup and view all the answers

How does the skin contribute to innate immunity?

Through physical barriers and desquamation Signup and view all the answers

Which characteristic of endothelia is crucial for their defensive function?

Tight packing of cells Signup and view all the answers

What role do Langerhans cells play in the skin’s defense mechanisms?

They are a type of immune cell. Signup and view all the answers

What is the primary mechanism by which mucus contributes to pathogen defense?

It traps and neutralizes microbes. Signup and view all the answers

Which statement best describes the composition of the skin as a barrier?

It consists of several layers of tightly packed cells. Signup and view all the answers

Which of the following best describes the term 'chemical defenses' in nonspecific immunity?

Non-specific proteins and enzymes secreted to fight pathogens. Signup and view all the answers

What role do antimicrobial peptides (AMPs) primarily play in the body?

They are produced in response to the presence of pathogens. Signup and view all the answers

How do resident microbiota contribute to host defense?

They occupy binding sites and compete for nutrients with pathogens. Signup and view all the answers

Why are mechanical actions like peristalsis important for the removal of microbes?

They help to mechanically dislodge and remove trapped microbes. Signup and view all the answers

What is the primary characteristic of opportunistic pathogens like S.epidermidis?

They can cause disease only in compromised hosts. Signup and view all the answers

Why is lysozyme considered more effective against growing bacteria?

Growing bacteria have a weaker cell wall structure. Signup and view all the answers

Which antimicrobial peptide is produced on the skin and plays a role in pathogen defense?

Dermcidin Signup and view all the answers

What function do muco-ciliary sweeping actions serve in host defense?

They transport and expel mucus containing trapped microbes. Signup and view all the answers

Which of the following best describes the nature of chemical mediators in the immune response?

They exhibit nonspecific antimicrobial functions. Signup and view all the answers

What mechanism is primarily employed by the body to eliminate microbes through bodily fluids?

Flushing by urination and tears Signup and view all the answers

Which antimicrobial peptide competes with pathogens by disrupting their membranes?

Cathelicidin Signup and view all the answers

What role do resident microbiota play in the body?

They act as a first-line defense against pathogens. Signup and view all the answers

What is the function of bile in the digestive system?

It initiates digestion of lipids and emulsifies membranes. Signup and view all the answers

How does lactoperoxidase contribute to microbial defense?

It produces superoxide that destroys microbial linkages. Signup and view all the answers

What effect do antibiotics have on the resident microbiota?

They can disrupt the balance, allowing pathogens to thrive. Signup and view all the answers

What is a significant consequence of a breach in physical barriers in innate immunity?

Potential establishment of infection by pathogens. Signup and view all the answers

Which condition can lead to a pathogenic shift in resident flora?

Antibiotic treatment. Signup and view all the answers

Which type of immunity primarily relies on resident microbiota?

Innate immunity. Signup and view all the answers

What is a primary function of mucins in the context of microbial defense?

To facilitate the removal of microbes from the eye surface. Signup and view all the answers

What characteristic of the gut environment aids in the defense against pathogens?

Rapid transit of contents. Signup and view all the answers

How do tight cell junctions contribute to physical immunity?

They prevent microbes from passing through epithelial layers. Signup and view all the answers

What role do antimicrobial peptides (AMPs) primarily serve in the body?

They act as a first line of cellular defense against bacteria. Signup and view all the answers

Which of the following statements is true about defensins?

Defensins can be produced by epithelial cells and cellular defenses. Signup and view all the answers

What is the mechanism by which lysozyme acts on bacterial cells?

It cleaves the bonds in peptidoglycan, weakening the cell wall. Signup and view all the answers

What is the primary function of lactoferrin in the context of microbial growth?

It sequesters iron to inhibit microbial growth. Signup and view all the answers

Which of the following describes mechanical defenses in the body?

They provide non-specific physical removal of pathogens. Signup and view all the answers

The flushing action of which bodily process is an example of a mechanical defense?

Urination Signup and view all the answers

Which type of antimicrobial peptides are produced by resident microbiota?

Bacteriocins Signup and view all the answers

What is the key function of mucin produced by goblet cells?

It traps bacteria on sticky surfaces. Signup and view all the answers

Which of the following is NOT a component of the mechanical defense system?

Phagocytosis by immune cells Signup and view all the answers

Which feature distinguishes gram-positive bacteria in relation to lysozyme activity?

They lack a protective outer membrane. Signup and view all the answers

Study Notes

Microbial Defense Mechanisms

Microbes trapped in dead skin cells or mucus are expelled through mechanical actions: skin shedding, muco-ciliary sweeping, coughing, peristalsis, and bodily fluid flushing.
Antimicrobial peptides (AMPs) such as dermcidin, cathelicidin, defensins, histatins, and bacteriocins combat pathogens and are produced in response to their presence.
The resident microbiota provide physical defense by occupying binding sites and competing for nutrients with pathogens.

Opportunistic Infections

Staphylococcus epidermidis is an opportunistic pathogen that exploits changes in human practices (e.g., medical devices) increasing infection risks.
Opportunistic pathogens like Staphylococcus epidermidis can cause infections primarily in immunocompromised hosts, highlighting the importance of host defenses.

Mucin in Host Defense

Mucin, a glycoprotein secreted by epithelial cells, forms a protective mucus layer that traps debris and microbes, shielding underlying cells.

Lysozyme Effectiveness

Lysozyme demonstrates heightened effectiveness against growing bacteria due to its ability to cleave peptidoglycan bonds, compromising bacterial integrity during active cell division.

Non-specific Immunity

Non-specific innate immunity provides a multi-faceted defense against pathogens, categorized into physical, chemical, and cellular defenses.

Physical Barriers

Epithelial cells, linked by tight junctions, form an effective barrier (98% exclusion rate), with the skin being a primary defense structure.
Skin Structure: Epidermis consists of stratified layers, producing dry, inhospitable conditions for pathogens, aided by keratin and continual cell turnover.

Mucous Membranes

Mucous membranes, with tight junctions and epithelial cells, secrete mucus to protect and trap pathogens, containing various antimicrobial components.

Endothelial Defenses

Endothelial cells line blood vessels and glands, acting as barriers against pathogens, with specialized structures like the blood-brain barrier protecting the CNS.

Antimicrobial Peptides (AMPs)

AMPs, including defensins, are produced in response to pathogens and exhibit broad-spectrum antimicrobial properties, generated by various body cells and resident microbiota.

Mechanical Defenses

Mechanical actions like urination and tearing physically remove pathogens, preventing their establishment within the body.

Chemical Defenses

Secretions from glands, including lysozyme and lactoferrin, in tears and mucus prevent pathogen colonization by degrading bacterial structures and limiting essential nutrients like iron.

Microbiome's Role

Resident microbiota act as a first-line defense, occupying niches and depleting resources, thus preventing pathogen proliferation.
Disruptions to the microbiome (e.g., through antibiotics) can lead to opportunistic infections, such as C. difficile overgrowth.

Gastrointestinal Tract Defenses

The gastric environment (pH 1-2) and rapid transit times serve as robust defenses against pathogens, assisted by resident microbiota.

Consequences of Barrier Breaches

Breaches in physical barriers can lead to serious infections, emphasizing the necessity of intact innate immune defenses.

Summary of Innate Immunity

The innate immune system incorporates physical barriers, mechanical removal of microbes, and the competitive interactions of the microbiome to thwart pathogen establishment across various body sites.

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Description

This quiz explores the various microbial defense mechanisms, including the role of antimicrobial peptides and the protective functions of mucin. Additionally, it examines opportunistic infections caused by pathogens like Staphylococcus epidermidis, particularly in immunocompromised individuals. Test your knowledge on how the body defends against microbes and the implications of opportunistic infections.