Microbiology Chapter on Virulence Factors
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Questions and Answers

What defines the virulence of a bacterial organism?

  • The extent of damage caused by the organism (correct)
  • The type of serologic tests conducted
  • The geographic location of the infection
  • The number of bacteria in the infection

Which of the following correctly classifies virulence factors?

  • Only cellular components are considered virulence factors
  • Bacterial toxins are always structural components
  • Virulence factors can be structural components or extracellular substances (correct)
  • Virulence factors are exclusive to viral pathogens

What is a plasmid in bacteria?

  • An intracellular pathogen
  • A self-replicating extrachromosomal DNA molecule (correct)
  • A type of viral DNA
  • A self-replicating piece of chromosomal DNA

Which method can lead to the conversion of an avirulent bacterial strain into a virulent one?

<p>Acquisition of exogenous DNA coding for virulence factors (D)</p> Signup and view all the answers

What is the purpose of serologic tests in relation to diseases?

<p>To diagnose diseases based on antibody detection (A)</p> Signup and view all the answers

What may be included in the standard reporting format for serologic results?

<p>Interpretation of results and testing methodologies (C)</p> Signup and view all the answers

In the context of immunology, what is considered an extracellular substance?

<p>Exotoxin (B)</p> Signup and view all the answers

Which of the following is NOT a category of diseases discussed?

<p>Mechanical diseases (C)</p> Signup and view all the answers

What is the primary mechanism by which streptokinase promotes its effect?

<p>Converts plasminogen to plasmin (A)</p> Signup and view all the answers

Which of the following statements is true regarding Streptolysin S?

<p>It produces surface hemolysis on blood agar plates (A)</p> Signup and view all the answers

Which condition is NOT typically associated with Group A Streptococci infections?

<p>Pneumonia (A)</p> Signup and view all the answers

What is a clinical test that helps determine susceptibility to scarlet fever?

<p>Dicks test (A)</p> Signup and view all the answers

What is a characteristic of Impetigo caused by Group A Streptococci?

<p>Lesions that itch, eventually crust and heal (C)</p> Signup and view all the answers

What type of hemolysis does Streptolysin O produce on blood agar plates?

<p>Subsurface hemolysis (A)</p> Signup and view all the answers

What is the primary advantage of the Anti-DNAse test over the ASO test?

<p>It is better in diagnosing glomerulonephritis cases. (B)</p> Signup and view all the answers

What is the pathogenic significance of DNases and NADase in Group A Streptococci?

<p>Their significance remains largely unknown (D)</p> Signup and view all the answers

What happens to the methyl green in the presence of DNase?

<p>It turns colorless when hydrolyzed. (B)</p> Signup and view all the answers

Which symptom is commonly associated with pharyngitis due to Group A Streptococci?

<p>Severe sore throat (A)</p> Signup and view all the answers

Which bacterial infection is most associated with gastric ulcers?

<p>Helicobacter pylori (C)</p> Signup and view all the answers

What mode of transmission is associated with Helicobacter pylori?

<p>Oral–oral and fecal–oral routes (B)</p> Signup and view all the answers

Which virulence factor of Helicobacter pylori acts as a toxin precursor?

<p>VacA (D)</p> Signup and view all the answers

What is a consequence of untreated Helicobacter pylori infection?

<p>Development of gastric carcinoma (D)</p> Signup and view all the answers

What is the typical result of a peptic ulcer's formation?

<p>An ulcer in the stomach or duodenum (D)</p> Signup and view all the answers

What is the role of urease in the infection process of Helicobacter pylori?

<p>To provide buffering against stomach acid (A)</p> Signup and view all the answers

Which group of Rickettsial infections spreads the rash from the extremities to the trunk?

<p>Spotted fever group (A)</p> Signup and view all the answers

What is the main pathogen responsible for Rocky Mountain Spotted Fever?

<p>Rickettsia rickettsii (D)</p> Signup and view all the answers

Which tick is NOT a known vector for Rocky Mountain Spotted Fever?

<p>Lone star tick (A)</p> Signup and view all the answers

Which of the following is a common symptom associated with Rickettsial infections?

<p>Gastrointestinal complaints (D)</p> Signup and view all the answers

What type of bacteria are Rickettsiae categorized as?

<p>Gram negative coccobacilli (B)</p> Signup and view all the answers

Which of the following statements is true regarding the Weil-Felix Test?

<p>It is insensitive and nonspecific. (D)</p> Signup and view all the answers

What effect does the invasion of Rickettsiae have on endothelial cells?

<p>Enhanced permeability and edema (C)</p> Signup and view all the answers

Which of the following Rickettsial species shares antigens with Proteus vulgaris OX-19 in the Weil-Felix Test?

<p>Rickettsia prowazekii (C), Rickettsia conorii (D)</p> Signup and view all the answers

What is the primary purpose of a CLOtest in diagnosing Helicobacter pylori?

<p>To detect urease activity in gastric mucosal biopsies (A)</p> Signup and view all the answers

Which test is considered the most invasive method for diagnosing Helicobacter pylori?

<p>Endoscopy with biopsy (B)</p> Signup and view all the answers

What occurs to the gel in a CLOtest if urease is present in the biopsy specimen?

<p>It changes to a hot-pink color due to increased pH (B)</p> Signup and view all the answers

How does the urea breath test indicate the presence of Helicobacter pylori?

<p>By measuring radioactive carbon dioxide exhaled in the breath (B)</p> Signup and view all the answers

What is indicated by elevated IgG antibody levels in untreated individuals?

<p>Chronic infection with Helicobacter pylori (B)</p> Signup and view all the answers

Which of the following is a noninvasive method for detecting Helicobacter pylori?

<p>Urea breath test (C)</p> Signup and view all the answers

What substance is measured during the urea breath test to diagnose Helicobacter pylori?

<p>Carbon dioxide (D)</p> Signup and view all the answers

What is the role of the rapid EIA test in diagnosing Helicobacter pylori?

<p>To identify the presence of H.pylori antigen in stool samples (D)</p> Signup and view all the answers

What is the causative agent of Yaws?

<p>T.pallidum subspecies pertenue (A)</p> Signup and view all the answers

Which condition is primarily characterized by scaly psoriasiform plaques?

<p>Pinta (B)</p> Signup and view all the answers

What is the mode of transmission for Bejel?

<p>Direct contact and sharing of utensils (C)</p> Signup and view all the answers

Which microscopy method is not recommended for oral lesions due to the presence of commensal treponemes?

<p>Darkfield Microscopy (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of T.pallidum seen in Darkfield Microscopy?

<p>Exhibits high flexibility (D)</p> Signup and view all the answers

What percentage sensitivity does Darkfield Microscopy have in diagnosing syphilis?

<p>80% (C)</p> Signup and view all the answers

What are the primary lesions seen in the late stages of Bejel?

<p>Destructive lesions of skin and bone (A)</p> Signup and view all the answers

Which Treponema species is known as the causative agent of Rabbit syphilis?

<p>Treponema cuniculi (A)</p> Signup and view all the answers

Flashcards

Virulence

The extent of damage or pathology caused by an organism.

Bacterial Virulence Factors

Features that determine whether an organism is pathogenic and can cause disease.

Structural Components of Bacterial Virulence Factors

Components of bacteria's cell walls.

Extracellular Substances of Bacterial Virulence Factors

Substances produced by bacteria, like toxins.

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Plasmid

Self-replicating DNA molecules found in a bacteria's cytoplasm.

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Plasmid

Mobile genetic elements that can transfer between bacteria.

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Acquisition of Exogenous DNA

Transfer of DNA from a donor bacterium to a recipient bacterium.

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Conversion of Avirulent Strain into Virulent Strain

Conversion of an avirulent strain into a virulent strain.

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Streptokinase

Converts plasminogen to plasmin, breaking down fibrin clots and promoting bacterial spread.

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Hyaluronidase

Degrades hyaluronic acid, a component of connective tissue, facilitating bacterial spread.

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Streptolysin O

Oxygen-labile streptococcal hemolytic exotoxin. Active in its reduced form, it can cause lysis of red blood cells and white blood cells.

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Streptolysin S

Oxygen-stable enzyme that produces surface hemolysis on blood agar plates. Smaller in size and non-antigenic.

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Pharyngitis

A major site of Group A Streptococcal infection characterized by sore throat, fever, and tonsillar exudates.

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Scarlet Fever

A common childhood disease caused by Group A Streptococci, characterized by a rash, fever, and sore throat.

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Impetigo

A superficial skin infection caused by Group A Streptococci, characterized by itchy, crusted lesions.

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Cellulitis

A deeper skin infection caused by Group A Streptococci, characterized by redness, warmth, tenderness, and swelling.

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What is Helicobacter pylori?

A bacterium that is a major cause of gastric and duodenal ulcers, often associated with 90% of duodenal ulcers and nearly all gastric ulcers. If left untreated, it can lead to gastric carcinoma.

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What is the structure of Helicobacter pylori?

A Gram-negative bacterium with a spiral shape that thrives in low-oxygen environments.

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How is Helicobacter pylori transmitted?

Oral-oral (sharing food/drinks) and fecal-oral (contamination from feces) routes.

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What is CagA?

A major virulence factor of Helicobacter pylori, highly immunogenic (triggers an immune response).

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What is VacA?

A virulence factor of Helicobacter pylori known as a toxin, responsible for forming vacuoles (small compartments) in cells.

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What is the role of Urease in Helicobacter pylori?

An enzyme produced by Helicobacter pylori that neutralizes stomach acid, creating a protective layer that makes the bacteria resistant to the acidic environment.

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What is a Peptic Ulcer?

An ulcer located in the lining of the stomach or duodenum, caused by the breakdown of the mucous membrane by gastric fluids.

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What is the Urea Breath Test?

A common test for Helicobacter pylori infection, using a breathalyzer to analyze the amount of carbon dioxide produced by the bacteria in the stomach.

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Gastric Ulcer

A condition caused by the digestive action of gastric juice on the mucous membrane when it's susceptible to its action.

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Helicobacter pylori

A spiral-shaped bacterium that is a common cause of gastritis, peptic ulcers and stomach cancer.

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Endoscopy with biopsy

The most expensive and invasive method to diagnose Helicobacter pylori infection.

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Urea breath test

A non-invasive test to diagnose Helicobacter pylori infection used in clinical practice.

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CLOtest

A test that detects the presence of urease in biopsy specimens, leading to a change in color based on the presence of urease.

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Rapid urease test

A rapid method to diagnose Helicobacter pylori infection by placing a biopsy specimen in urea broth.

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Antigen detection in stool

A non-invasive method to detect the presence of Helicobacter pylori antigens in stool samples.

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Anti-H.pylori Antibody test

An immunoassay that measures the presence of antibodies against H.pylori in blood.

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Rickettsia

A group of Gram-negative coccobacilli that are obligate intracellular parasites, meaning they can only survive and reproduce inside a host cell.

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Spotted Fever Group (SFG)

A category of Rickettsial infections characterized by a rash that starts in the extremities and then spreads towards the trunk.

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Typhus Group (TG)

A category of Rickettsial infections characterized by a rash that appears first on the trunk and then spreads to the extremities.

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Rocky Mountain Spotted Fever

A tick-borne illness caused by Rickettsia rickettsii, known for a characteristic spotted rash.

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Endothelial Cell Damage

The primary mechanism of Rocky Mountain Spotted Fever, involving damage to blood vessel linings, leading to leakage, fluid accumulation, and reduced blood volume.

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Weil-Felix Test

A serological test used to diagnose rickettsial infections based on the sharing of antigens between Rickettsia and Proteus bacteria.

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Proteus vulgaris (OX-2 & OX-19), Proteus mirabilis (OX-K)

The different types of Proteus bacteria used in the Weil-Felix test, each associated with a different OX antigen.

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Disadvantages of the Weil-Felix test

The Weil-Felix Test is a simple, cost-effective serological test used for diagnosing rickettsial infections, however it lacks sensitivity and specificity, making it less reliable.

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Yaws

A chronic skin and bone disease found in tropical regions, caused by the bacterium Treponema pallidum subspecies pertenue. It is characterized by granulomatous lesions resembling raspberries and can lead to bone, cartilage, and tissue damage in severe cases.

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Pinta

A skin infection caused by Treponema carateum, primarily affecting the skin, hands, feet, and scalp. It manifests as scaly, psoriasis-like plaques and does not usually affect other organs.

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Bejel

A non-venereal form of syphilis caused by Treponema pallidum subspecies endemicum, spread through direct contact or shared eating utensils. It starts in the mouth and can progress to involve bones, cartilage, and the nasopharynx.

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Rabbit Syphilis

A sexually transmitted infection in rabbits caused by Treponema cuniculi, leading to genital lesions.

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Darkfield Microscopy (DFM)

A microscopic technique used to diagnose syphilis, where the organism is visualized in material from lesions. A thin, tightly wound, rigid spiral shape is observed under the microscope.

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Treponemal Test

A diagnostic test for syphilis that uses antibodies to detect the presence of specific treponemal antigens in the blood.

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Nontreponemal Test

A non-treponemal test used to diagnose syphilis by detecting antibodies produced by the body in response to syphilis, rather than the bacterium itself.

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Immunohistochemical Microscopy

A type of microscopic technique that involves introducing labeled antibodies to target specific antigens, enabling visualization of the organism in the material from lesions.

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Study Notes

Central Philippine University

  • Located in Iloilo City, Philippines
  • Established in 1905

MLS 3103 Lecture: Clinical Immunology and Serology

  • Course focused on clinical immunology and serology
  • Prepared by Rodolph C. Lagarto, RMT
  • Additional notes by Mario Ivan G. Gonzales, RMT

Module Five: Diseases and Serologic Tests

  • Learning Outcomes

    • Enumerate different bacterial, viral, parasitic, and fungal diseases
    • Enumerate serologic detection methods for each disease
    • Relate serological tests to clinical diagnosis
    • Report serology results using standard format
    • Explain pathophysiology of bacterial, viral, parasitic, and fungal diseases

  • Module Topics

    • Bacterial Diseases
      • Group A Streptococci
      • Helicobacter pylori
      • Mycoplasma pneumoniae
      • Rickettsial infections
      • Spirochete infections (includes syphilis, yaws, pinta, bejel, rabbit syphilis)

Group A Streptococci

  • Streptococcus pyogenes

    • Gram-positive, beta-hemolytic
    • Spherical, ovoid, or lancet-shaped cocci
    • Seen in pairs or chains
    • Lancefield groups (A-H, K-V) based on carbohydrates

  • Virulence Factors

    • M protein: inhibits phagocytosis, limits complement activation
    • F protein: enhances adherence to host cells
    • Lipoteichoic acid: facilitates bacterial adherence
    • Exoantigens (enzymes, pyrogenic/erythrogenic toxins)

  • Clinical Manifestations

    • Acute infections: pharyngitis, skin infections (impetigo, pyoderma)
    • Severe infections: necrotizing fasciitis, toxic shock syndrome

  • Complications/Sequelae

    • Acute rheumatic heart fever, poststreptococcal glomerulonephritis

  • Laboratory Diagnosis

    • Culture (plated on blood agar)
    • Susceptibility to bacitracin
    • Positive PYR test
    • Growth in trimethoprim/sulfamethoxazole
    • Detection of Group A Streptococcal Antigens (lateral flow immunoassays and molecular methods)
    • Detection of Streptococcal Antibodies (anti-streptolysin O [ASO], anti-DNase B, anti-NADase, anti-hyaluronidase)

Helicobacter pylori

  • Description
    • Gram-negative, microaerophilic spiral bacterium
    • Major cause of gastric and duodenal ulcers
    • May lead to gastric carcinoma
    • Transmission: oral-oral and fecal-oral routes
  • Virulence Factors
    • CagA: highly immunogenic major virulence factor
    • VacA: vacuolating cytotoxin, precursor
    • Urease: providing a buffering zone
  • Laboratory Diagnosis
    • Endoscopy and biopsy
    • CLOtest (detects urease activity)
    • Urease testing (placing biopsy specimens directly into urea broth)
    • Urea breath test (patient ingests urea labeled with radioactive carbon)
    • Antigen detection procedures (rapid EIA of stool samples)
    • Antibody detection (anti-H. pylori detection, best for initial screening)

Mycoplasma pneumoniae

  • Belongs to a unique group (Class Mollicutes, Genus Mycoplasma)

  • Lack of a cell wall

  • Pleomorphic (spherical, pear-shaped, filamentous)

  • Resistant to beta-lactams

  • Lack of Gram stain reaction

  • Colonizes respiratory mucosa, causing primary atypical pneumonia

  • Associated with complications like Stevens-Johnson syndrome and Raynaud syndrome.

  • Laboratory Diagnosis

    • Culture (growth produces mulberry colonies)
    • Detection of Antibodies (IgM immunoglobulin is most useful test, ELISA methods)

Rickettsial Infections

  • Gram-negative coccobacilli, obligate intracellular parasites
  • Genus Rickettsia
  • Spotted fever group (SFG)
  • Spread from extremities to trunk, accompanied by gastrointestinal complains and various symptoms.
  • Typhus group (TG)
  • Rash first appears on the trunk, then spreads to the extremities.
  • Rocky Mountain Spotted Fever (caused by Rickettsia rickettsii)
    • Transmitted through ticks (like American dog tick)
    • Leads to endothelial cell damage (causing inflammation, edema, etc.)
  • Serological Diagnosis
    • Weil-Felix Test (insensitive and nonspecific, uses Proteus vulgaris antigens)
    • Indirect fluorescent assays (IFA), microimmunofluorescent assays (micro-IF), immunoperoxidase assays (IPA), ELISA, immunoblot assays (IBA)
  • Molecular Diagnosis
    • Requires using DNA from skin lesions or similar sources to diagnose and assess potential infection

Spirochete Infections

  • General Information

    • Gram-negative, spiral-shaped bacteria

    • Three key genera: Treponema, Borrelia, Leptospira

    • Clinical Course

      • Proliferation at inoculation site (localized skin infection)
      • Spirochetemia (systemic dissemination)
      • Persistence in tissues ("privileged" sites, latent infection)

    • Syphilis (caused by Treponema pallidum):

    • Stages

      • Primary (hard chancre, initial lesion)
      • Secondary (condylomata lata, generalized rash)
      • Latent (asymptomatic, possibly long-term)
      • Tertiary (gummas, cardiovascular/neurological involvement)

    • Laboratory Diagnosis (Syphilis):

      • Direct (microscopy, darkfield, fluorescence)
      • Indirect (nontreponemal tests like VDRL, RPR; treponemal tests like TPI, FTA-ABS; PCR; Hemagglutination tests)

    • Lyme Disease (caused by Borrelia burgdorferi):

      • Stages
        • Early localized/Stage I (erythema chronicum migrans)
        • Early disseminated/Stage II (systemic involvement)
        • Late disseminated/Stage III (arthritis, neuroborreliosis)
      • Laboratory Diagnosis (Lyme Disease):
        • Culture (difficult to perform)
        • Serological tests (IFA, EIA, Western blot)
        • Molecular tests (PCR)

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Description

Evaluate your understanding of bacterial virulence factors and their classification in this quiz. Topics include plasmids, methods of virulence conversion, serologic tests, and the categorization of diseases. Test your knowledge on the critical aspects of microbiology and immunology.

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