Microbial Infection Routes and Mechanisms

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Questions and Answers

What is the major local defense for the skin?

Ciliated epithelium

Mucous membrane

Immune cells

Epidermal barrier (correct)

Which of the following pathogens can be introduced through needle sticks?

Human immunodeficiency virus (correct)

Staphylococcus aureus

Vibrio cholerae

Schistosoma spp.

What is a basis for the failure of local defense in the gastrointestinal tract?

Attachment and local proliferation of microbes (correct)

Bacterial replication in blood

Mechanical defects

Chemical burns

Which pathogen is associated with arthropod and animal bites?

Yellow fever Signup and view all the answers

What type of infection does direct penetration typically involve?

Eukaryotic infections like schistosomiasis Signup and view all the answers

Which pathogen is primarily eliminated by the gastrointestinal epithelial barrier?

Shigella spp. Signup and view all the answers

What type of infection is typical for mechanical defects in the skin defense?

Bacterial infections like staph Signup and view all the answers

Which pathogen is transmitted through the uptake of M cells in the gastrointestinal tract?

Poliovirus Signup and view all the answers

What is a consequence of burns or ulcers on the skin's defense?

Higher susceptibility to pathogens Signup and view all the answers

What is the role of normal gut microbiota in preventing infections?

Competing for resources with potential pathogens Signup and view all the answers

What mechanism primarily protects the urinary tract from infection?

Regular emptying during micturition Signup and view all the answers

How do organisms like Staphylococcus aureus cause gastrointestinal disease?

By producing a powerful exo-toxin Signup and view all the answers

Which of the following infections is primarily associated with systemic immunodeficiency?

Respiratory infections from fungal agents Signup and view all the answers

What condition can lead to superinfection by bacteria in the respiratory tract?

Impaired mucociliary clearance Signup and view all the answers

What is a characteristic of Norovirus?

It spreads easily in crowded spaces Signup and view all the answers

Why do women have more urinary tract infections than men?

Women have shorter urethras Signup and view all the answers

What characteristic of intestinal protozoa allows them to survive harsh conditions?

Formation of acid-resistant outer coats Signup and view all the answers

What type of organism is primarily responsible for acute food poisoning in contaminated food?

Staphylococcus aureus Signup and view all the answers

What can result from mechanical ventilation and smoking in terms of respiratory health?

Weakening of local defenses Signup and view all the answers

What is a major factor in susceptibility to urinary tract infections?

Obstruction of urinary flow or reflux of urine Signup and view all the answers

What role do lactobacilli play in vaginal health?

They suppress the growth of pathogens Signup and view all the answers

What is a potential consequence of antibiotics on vaginal flora?

They kill lactobacilli, allowing for yeast overgrowth Signup and view all the answers

Which organisms invade the intestinal mucosa and can cause dysentery?

Shigella spp. Signup and view all the answers

What is vertical transmission of infectious agents?

Transmission from mother to fetus or newborn Signup and view all the answers

Which factor can lead to infections affecting fetal development during pregnancy?

Pathogen infection during pregnancy Signup and view all the answers

What type of development issues can occur if a mother contracts rubella virus during the first trimester?

Heart malformations Signup and view all the answers

What happens to microorganisms trapped in large particles in the respiratory tract?

They are caught in the mucociliary blanket and cleared Signup and view all the answers

What is a potential outcome of chronic HBV infection?

Cirrosis of the liver Signup and view all the answers

What is the effect of rubella virus infection during the third trimester?

Little effect on fetal development Signup and view all the answers

Which agent is primarily responsible for the damaging symptoms in infections caused by certain bacteria?

Exotoxins Signup and view all the answers

Which virus is primarily associated with bronchiolitis?

Respiratory syncytial virus Signup and view all the answers

What is a major cause of dysfunction in liver due to exuberant scarring?

Pipestem fibrosis Signup and view all the answers

Which of the following viruses can lead to conjunctivitis in its hosts?

HSV Signup and view all the answers

What is a common complication associated with the mumps virus?

Pancreatitis Signup and view all the answers

Influenza viruses are most commonly associated with which type of infection?

Upper respiratory tract infection Signup and view all the answers

What characterizes granulomatous inflammation?

Accumulation of activated macrophages Signup and view all the answers

Which organisms are known to cause granulomatous inflammation?

M.tuberculosis and Histoplasma capsulatum Signup and view all the answers

What type of cell formation occurs due to certain viral infections, such as those caused by measles or herpesviruses?

Formation of polykaryons Signup and view all the answers

What is a characteristic feature of the lesions produced by viruses?

Cell necrosis or cellular proliferation Signup and view all the answers

What type of necrosis is associated with rapid and severe tissue damage caused by certain organisms?

Gangrenous necrosis Signup and view all the answers

What type of cells are formed by the fusion of epithelioid macrophages in granulomatous inflammation?

Giant cells Signup and view all the answers

Which virus is specifically mentioned as causing epithelial cell proliferation?

HPV Signup and view all the answers

The presence of inclusion bodies can often be associated with which type of organism?

Viruses Signup and view all the answers

What type of immunity is strongly stimulated during granulomatous inflammation?

T cell-mediated immunity Signup and view all the answers

Which of the following may be present in granulomas as a central feature?

Caseous necrosis Signup and view all the answers

Study Notes

Routes of Microbial Infection

Skin:
- Major defense: Epidermal barrier
- Failure mechanisms:
  - Mechanical defects (punctures, burns, ulcers)
  - Needle sticks
  - Arthropod and animal bites
  - Direct penetration
- Pathogens: Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa, Human immunodeficiency virus, hepatitis viruses, Yellow fever virus, plague bacteria, Lyme disease spirochete, malaria parasite, rabies virus, Schistosoma spp.
Gastrointestinal Tract:
- Major defense: Epithelial barrier
- Failure mechanisms:
  - Attachment and local proliferation of microbes
  - Attachment and local invasion of microbes
  - Uptake through M cells (Peyer's patches)
- Pathogens: Vibrio cholerae, Giardia duodenalis, Shigella spp., Salmonella spp., Campylobacter spp., Poliovirus
Respiratory Tract:
- Major defense: Mucociliary clearance
- Failure mechanisms:
  - Damage to mucociliary clearance (influenza, mechanical ventilation, smoking, cystic fibrosis)
  - Systemic immunodeficiency
- Pathogens: Pneumocystis jirovecii (AIDS), Aspergillus spp. (neutropenia), a plethora of viruses, bacteria, and fungi
Urogenital Tract:
- Major defense: Urine flow and low pH in women
- Failure mechanisms:
  - Obstruction of urinary flow
  - Urinary reflux
  - Antibiotic use (disrupts vaginal microbiota)
- Pathogens: Escherichia coli, Candida albicans
Vertical Transmission (mother to child):
- Failure mechanisms:
  - Placental-fetal transmission during pregnancy
- Pathogens: Rubella virus

Pathogenic Mechanisms and Effects

Toxin Production:
- Some organisms produce gastrointestinal disease without necessarily establishing an infection
- Example: Staphylococcus aureus (food poisoning)
Bacterial Colonization and Toxin Production:
- Bacteria establish an infection and produce toxins
- Examples: Vibrio cholerae and enterotoxigenic Escherichia coli
Adhesion and Mucosal Invasion:
- Pathogens invade the intestinal mucosa and cause ulceration, inflammation, and hemorrhage
- Examples: Shigella spp., Salmonella enterica, Campylobacter jejuni, Entamoeba histolytica (dysentery)
Viral Effects:
- Cytopathic effects (CPE): Cell necrosis or proliferation, often with sparse inflammation
  - Inclusion bodies: Visible viral aggregates within cells
  - Polykaryons: Fusion of infected cells into multinucleated cells
  - Blisters: Cell detachment in skin
  - Epithelial proliferation: Warts (HPV) or umbilicated papules (poxviruses)
  - Oncogenesis: Viral contribution to cancer
Tissue Necrosis:
- Rapid and severe necrosis caused by toxins
- Examples: Clostridium perfringens, Corynebacterium diphtheriae

Inflammatory Responses

Chronic Inflammation and Scarring:
- Many infections lead to chronic inflammation, which can cause scarring
- Examples:
  - Cirrhosis of the liver (HBV infection)
  - "Pipestem" fibrosis of the liver
  - Fibrosis of the bladder wall (schistosomal eggs)
  - Constrictive fibrous pericarditis (tuberculosis)

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Description

This quiz explores the various routes of microbial infection in the human body, including skin, gastrointestinal tract, and respiratory tract. It covers major defense mechanisms, failure mechanisms, and the pathogens associated with each route. Test your knowledge of how infections can occur and the body's defenses against them.