Microbiology Chapter: Streptococci and Glomerulonephritis

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Questions and Answers

What is a hallmark symptom of acute proliferative glomerulonephritis?

Albuminuria and haematuria (correct)

Itching

Painful joints

Tiny bumps

What is the primary role of Viridans group streptococci in the human microbiome?

Contributing to the development of autoimmune diseases

Causing infections in immunocompromised individuals

Producing toxins that damage tissue

Inhibiting colonization of pathogens (correct)

Which of the following characteristics distinguishes Viridans streptococci from pneumococci?

Catalase-negative

Optochin resistance (correct)

Alpha-hemolytic on blood agar

Gram-positive cocci arranged in chains

Which of the following is NOT a major group of Viridans group streptococci?

Streptococcus pneumoniae (C) Signup and view all the answers

What is the characteristic rash associated with rheumatic fever?

Erythema marginatum (B) Signup and view all the answers

What is the typical time frame for the development of rheumatic fever after a streptococcal throat infection?

Two to four weeks (B) Signup and view all the answers

Which of the following is NOT a sign or symptom of rheumatic fever?

Itching rash (D) Signup and view all the answers

Which bacterial component is responsible for attachment to the surface of epithelial cells?

Fimbriae (C) Signup and view all the answers

What type of fimbriae are associated with strains of E. coli causing meningitis?

S fimbriae (A) Signup and view all the answers

What is the main mechanism by which Viridans streptococci inhibit the growth of other pathogens?

Production of bacteriocins and hydrogen peroxide (C) Signup and view all the answers

Which of the following is a virulence factor associated with Neisseria gonorrhoeae?

Microcapsule (B) Signup and view all the answers

Which of the following enzymes is NOT a hydrolytic enzyme?

Hemolysin (B) Signup and view all the answers

Which type of toxin is secreted by bacteria into their surroundings?

Exotoxins (D) Signup and view all the answers

What is the key property that differentiates exotoxins from endotoxins?

Exotoxins are proteins, while endotoxins are lipopolysaccharides. (A) Signup and view all the answers

Which of the following enzymes is secreted by both Staphylococcus aureus and group A Streptococcus?

Hyaluronidase (A) Signup and view all the answers

Which of the following is NOT a mechanism of bacterial mobility?

Fimbriae (C) Signup and view all the answers

What is the main function of the reticular-endothelial system cells and lymphocytes during inflammation?

To initiate immune responses. (D) Signup and view all the answers

Which of the following is NOT a clinical sign of inflammation?

Numbness (A) Signup and view all the answers

What is the main purpose of local capillary vasodilatation during inflammation?

To increase blood flow to the affected area. (D) Signup and view all the answers

What are chemotactic stimuli?

Signals that attract leukocytes to the site of inflammation. (D) Signup and view all the answers

Which type of leukocyte arrives first at the site of inflammation?

Polymorphonuclear leukocytes (PMNs) (C) Signup and view all the answers

What is the main difference between healing restitutio ad integrum and healing with sequelae?

Healing restitutio ad integrum leads to complete tissue restoration. (D) Signup and view all the answers

What is leukocyte diapedesis?

The migration of leukocytes into the interstitial space. (A) Signup and view all the answers

Which of the following is NOT a factor influencing the outcome of an inflammatory reaction?

The effectiveness of antibiotic therapy. (D) Signup and view all the answers

Which of the following is NOT a characteristic typically used to identify enterococci?

Production of coagulase (A) Signup and view all the answers

What is the most common infection caused by enterococci?

Urinary Tract Infections (A) Signup and view all the answers

Which of the following enterococci species is known for producing a yellow pigment?

Enterococcus sulfureus (A) Signup and view all the answers

Enterococci are typically found as part of the normal flora in which part of the body?

Intestinal tract (D) Signup and view all the answers

What percentage of infectious endocarditis cases are estimated to be caused by enterococci?

5-15% (A) Signup and view all the answers

Which of the following is TRUE about enterococci causing lower urinary tract infections?

They occur more frequently in older men. (B) Signup and view all the answers

How are enterococci typically identified in the lab?

Through a combination of conventional biochemical tests and DNA analysis (C) Signup and view all the answers

What is the role of leucine aminopeptidase in Enterococcus identification?

It is a commonly used enzyme for rapid identification of Enterococci. (A) Signup and view all the answers

What is the process called where phagocytes migrate towards bacteria or other particles?

Chemotaxis (A) Signup and view all the answers

Which of the following is NOT a mechanism by which opsonization can be achieved?

The release of lysosomal enzymes (A) Signup and view all the answers

What is the name of the vacuole formed when a phagocyte engulfs a particle?

Phagosome (D) Signup and view all the answers

What is the process called where the phagosome merges with lysosomes?

Phagolysosome formation (C) Signup and view all the answers

Which of the following is NOT a compound formed during the 'respiratory burst' in oxygen-dependent mechanisms of microbial destruction?

Lysosome (A) Signup and view all the answers

What is the name given to the enzymes involved in oxygen-independent mechanisms of microbial destruction?

All of the above (D) Signup and view all the answers

What is the process called where phagocytes leave capillaries and enter tissues?

Diapedesis (B) Signup and view all the answers

What is the function of the Fc fragment of an antibody in opsonization?

It binds to the phagocyte. (C) Signup and view all the answers

Which of the following is NOT a mechanical barrier to infection?

Lysozyme in saliva (D) Signup and view all the answers

What is the primary function of the low pH on the skin surface?

To directly kill bacteria (A) Signup and view all the answers

How does lysozyme act as a chemical barrier against bacteria?

It breaks down components of the bacterial cell wall (D) Signup and view all the answers

Which of the following statements about the acidic pH of the vagina is TRUE?

It is primarily due to the activity of lactic acid bacteria (D) Signup and view all the answers

What role do commensal flora play in the body's defense system?

They compete with pathogens for resources (D) Signup and view all the answers

Which of the following is a characteristic of specific resistance against infection?

It is acquired throughout life (D) Signup and view all the answers

Which of the following examples best illustrates the concept of species-specific resistance?

Humans are susceptible to malaria while mosquitoes are not (A) Signup and view all the answers

Which of the following is NOT a component of innate (non-specific) resistance?

Antibodies (C) Signup and view all the answers

Study Notes

Infectious Process*
Infectious process is the pathophysiological and clinical responses resulting from the conflict between a microorganism and the human body.
Infection involves all biological changes in the human body triggered by the penetration of an infectious agent. A key characteristic of infection is its specific etiology; a particular infectious agent causes a specific infectious disease.
Basic Mechanisms of Infectious Process*
Infection is achieved through the antagonistic combined actions of pathogenicity factors of bacteria and the resistance factors of the infected body.
Pathogenicity refers to the ability of bacteria to cause disease, expressed through virulence and toxigenicity.
Virulence Factors of Bacteria*
Virulence is the ability of bacteria to penetrate, adapt, multiply, invade, and elicit specific tissue lesions. This is driven by:
- Corpuscular Factors: Related to bacterial cell structure components providing protection against host defenses and facilitating tissue penetration.
  - Capsule: Inhibits phagocytosis, promoting microbial invasion. Examples include pneumococcus, Klebsiella pneumoniae, some strains of staphylococci and streptococci.
  - Components of bacterial cell wall: Located in superficial bacterial layers, these components play an anti-phagocytic role. Examples include M protein in Streptococcus beta-hemolytic group A, virulence factors in Staphylococcus aureus and Koch bacillus, factors of attachment to intestinal mucus in pathogenic E. coli and Shigella, and Vi antigen in Salmonella typhi.
  - Mobility: Mobile bacteria tend to have higher virulence compared to non-mobile bacteria. Mobility is achieved through cell body movements (e.g., corkscrew motion in leptospires), cilia (flagella), an attribute of species.
  - Fimbriae: Involved in germ attachment, aiding in invasion. Common pili (adhesion pili) allow strong attachment to epithelial cells. Different types of fimbriae are associated with specific infections (e.g., P fimbriae and pyelonephritis, S fimbriae and meningitis, K88 and K89 fimbriae and diarrhea in newborns).
- Enzymatic Factors (Exoenzymes): Substances produced and released by bacteria that break down tissues facilitating bacterial invasion and spread.
  - Coagulase, fibrinolysin, hyaluronidase, nucleases (DN-ase and RN-ase), collagenases, lecitinases, neuramidases, lipases, proteases, are examples.
Toxigenicity*
Toxigenicity is the ability of bacteria to produce toxins (soluble substances inducing toxic effects on infected tissues).
- Exotoxins: Toxic substances released by living Gram-positive bacteria in their environment (e.g., in culture media or infected organisms).
  - Physical-chemical properties: Thermostable, transformed by aging and formalin, and sensitive to radiation and pH variation. Toxoids are inactivated toxins that preserve their immunogenicity.
  - Biological properties: Appear after latency, high toxic power, and small minimum lethal dose.
- Endotoxins: Toxic substances found in the Gram-negative bacterial cell wall, released after the bacteria's death.
  - Physical-chemical properties: Heteroproteins (complex proteins), typically carbohydrate-lipid-polypeptide complexes, are soluble but released at the same time of bacterial cell lysis. They are thermostable, resistant to treatment with alcohol, and do not turn into toxoids under the action of formalin.
  - Biological properties: Lower toxicity compared to exotoxins, the minimum lethal dose is high, the toxic effects occur without latency.
Host Defense Mechanisms Against Infection*
Non-specific (Natural, Innate) Resistance: A resistance state present in individuals of a species against certain pathogens.
- Mechanical barriers: Skin and mucous membranes. Epidermis, cilia, cilia movement, and mucous secretions limit bacterial penetration.
- Chemical barriers: Low pH, lysozyme, hydrochloric acid. These substances are present in mucous and on the skin, preventing bacterial growth.
- Biological barriers: Commensal flora. Competing microbes inhibit the colonization of pathogens.
Specific (Acquired): Immunologic defense develops over time through exposure to various infectious agents.
Specific Inflammatory Processes*
Febrile reaction (inflammation with fever) often accompanies bacterial infections. Pyrogens (interleukin-1, tumor necrosis factor) trigger this response.
Phagocytosis: Cells (e.g., neutrophils, macrophages) engulf and destroy invading microbes. Phagocytosis involves chemotaxis, cellular adherence, ingestion, and intracellular digestion.
Inflammation: A response aimed at localizing an infection, caused mainly by infectious agents. Inflammation manifests with symptoms like redness, swelling, heat, pain, and reduced function in the affected area. Inflammatory processes are essential for immune defense. Inflammation can result in tissue damage if persistent. The outcome depends on the inflammatory process's extent, the invading microorganisms, and the host's reaction.
Infections/Diseases Caused by the Different Microbial Species*
Detailed descriptions of diseases caused by Staphylococci, Streptococci, S. Viridans, Enterococci, and Streptococcus pneumonia - Various infections of the skin, oral cavity, urinary tract, tissues, and other areas are described.

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Description

Test your knowledge on the key concepts related to acute proliferative glomerulonephritis and the role of Viridans group streptococci in the human microbiome. This quiz covers symptoms, characteristics, and virulence factors associated with these bacteria. Understand their implications in infections and diseases such as rheumatic fever and meningitis.