Streptococcus Question And Answers

Streptococcus Long Essays

Question 1. Write in detail about the morphology, pathogenesis, laboratory diagnosis, and treatment of streptococcus pyogenes.
Answer:

Streptococcus pyogenes:

• Morphology:
  • Streptococcus pyogenes are:
    • Gram-positive are:
    • Non-sporing.
    • Non-motile.
    • Capsulated.
    • Aerobe and facultative anaerobe organism.
  • Size – 0.5 – 1 micrometer in diameter.
  • Shape – spherical or oval.
  • Arrangement – arranged in a chain.
  • It occurs due to successive cell divisions occurring in one plane only.

Streptococcus Pathogenesis:

• Streptococcus Pyogenos adheres to the pharyngeal epithelium by means of lipoteichoic acid covering the surface epithelial cells.
• The infection may spread to the surrounding tissues leading to suppurative complications.
  • Otitis media.
  • Mastoiditis.
  • Quinsy.
  • Ludwig’s angina.
  • Suppurative adenitis.
  • Rarely meningitis.
• Scarlet fever occurs which leads to sore throat and a generalized erythematous rash.

Streptococcus Laboratory diagnosis:

Streptococcus Treatment:

• Penicillin G – is the drug of choice for all streptococcal infections.
• In the case of a patient allergic to penicillin, erythromycin or cephalexin is used.

Question 2. Classify streptococci. Describe the toxins and lesions produced by β-hemolytic streptococci.
Answer:

Streptococcus Classification:

Streptococci are classified as follows:

1. Based on 0₂ requirement.

• Aerobic and facultative anaerobes.
• Obligate anaerobes
• Example: peptostreptococcus.

Read And Learn More: Microbiology Question and Answers

2. Based on hemolytic property.

Toxins produced by streptococci:

Lesions:

1. Pyogenic infections:

• Respiratory infection.
  • The throat is the primary site of invasion causing a sore throat
    • Tonsilitis – localized in tonsils.
    • Pharyngitis – involves the pharynx.
    • Pyogenic complications like otitis media – are caused by the spread of streptococcal infections to surrounding tissues.
    • Streptococcal pneumonia.
• Skin and soft tissue infections.
  • Cause suppurative infections of the skin. Examples are wounds, burns, cellulitis, and lymphangitis.
  • Typical skin infections include.
    • Erysipelas – It is a diffuse infection involving superficial lymphatics.
    • Impetigo – leads to glomerulonephritis in children.
      • Genital infection includes puerperal sepsis.
• Other infections.
  • Includes sepsis, pyemia, septicemia, and abscess of internal organs.

2. Non-suppurative complication.

It includes:

• Acute rheumatic fever.
  • It is preceded by a sore throat
  • It is characterized by fever, pancarditis, migratory polyarthritis, and sometimes chorea and subcutaneous nodules.
  • Repeated attacks are common.
  • It shows a marked immune response.
• Acute glomerulonephritis.
  • It is preceded by a skin infection.
  • It is self-limiting and resolves without any permanent damage.
  • Pathogenesis may be due to antigenic cross-reaction between glomerular antigens and some components of nephritogenic streptococci.
  • It shows’s moderate immune response.

Question 3. Enumerate the etiology of sore throat. Describe the pathogenesis and complications of streptococcus pharyngitis.
Answer:

Sore throat:

It is an acute tonsillitis/ pharyngitis

Sore throat Etiology

• Bacteria
  • Streptococcus pyogenes
  • Streptococcus groups C and G
  • Corynebacterium diphtheria
  • Haemophilus influenza
  • Bordetella pertussis
  • Treponema vincentii
• Fungus
  • Candida albicans
• Viruses
  • Epstein Burr virus
  • Adenovirus
  • Coxsackie virus A

Streptococcus Pathogenesis:

• Streptococcus is the leading cause of pharyngitis
• Cell surface accounts for its virulence
• It is concerned with colonization and evasion of phagocytosis and host immune responses
• The surface contains capsular polysaccharides, cell wall peptidoglycan, lipoteichoic acid, and surface proteins and cell bound streptokinase
• Cytoplasmic membranes contain antigens that suppresses host immune system

Streptococcus pharyngitis Complications

• A sore throat may lead to rheumatic fever
• It is characterized by inflammation of joints and/or heart following streptococcal pharyngitis

Streptococcus Short Essays

Question 1. Enzymes of streptococci.
Answer:

Enzymes:

Question 2. Cultural characteristics of streptococcus.
Answer:

Streptococcus is an aerobe and facultative anaerobe.

• It best grows at 37oC and pH – 7.2 – 7.4
• Growth occurs only in media enriched with blood, serum or sugars.

• Virulent strains on isolation produce finely granular colonies.
• Avirulent strains form glossy colonies.
• Strains with well-marked capsules form mucoid colonies.

Question 3. Discuss streptococci under the following heading
-Dental caries
Answer:

Streptococci Dental Caries:

• Dental caries is caused by Str. Mutans.
• It produces enzyme called glucosyltransferase
• This enzyme breaks down dietary sucrose production.

1. Acid

• It leads to the demineralization of the tooth enamel and the initiation of carious lesions.

2. Dextran.

• It binds together with food debris, mucus, epithelial cells, and bacteria to form plaque.
• This plaque leads to dental caries.
• Once the caries process is initiated, it progressed by lactobacilli.
• Other streptococci involved are.
  • Str. Milleri.
  • Str. Sangus.
  • Str. Salivaris.
  • Str. Mitior.

Question 4. Viridans group of streptococci.
Answer:

• Viridans group of streptococci produces alpha hemolysis on blood agar.
• They are commensals of the mouth and upper respiratory tract.

Streptococci included in viridian group:

• Str. Mitis group.
• Str. Anginosus group.
• Str. Bovis group.

Each group contains many species.

Diseases caused by them:

They are usually non-pathogenic but can cause disease.

1. Dental caries.

2. Subacute bacterial endocarditis.

• Predisposing factors are valvular heart diseases, congenital heart diseases, and cardiac surgery.
• Following tooth extraction, transient bacteremia occurs.
• This gets implanted on damaged or prosthetic valves.
• They form vegetation.

Prevention:

• Prophylactic antibiotics should be given before extraction.
• Antibiotic sensitivity must be determined.
• Caries preventive measures should be carried.

Question 5. Antistreptolysin O test.
Answer:

Antistreptolysin O test is a toxin neutralization test used to detect the presence of antistreptolysin O in the patient’s sera.

Antistreptolysin O:

• It is an antitoxin secreted by the body against the exotoxin streptolysin O of streptococci.
• It blocks the hemolysis caused by streptolysin O.

Antistreptolysin O Value:

• Higher than 160 or 200 titer – indicated prior strepto-coccal infection.
• Higher level – indicates acute rheumatic fever.

Antistreptolysin O Uses:

• Aid in the diagnosis of rheumatic fever and acute glomerulonephritis.
• Used for retrospective diagnosis of streptococcal pyoderma.

Streptococcus Short Questions And Answers

Question 1. Streptococcal infections.
Answer:

1. Pyogenic streptococcal infections.

• Respiratory infections.
  • Sore throat
  • Tonsillitis
  • Pharyngitis.
• Skin and soft tissue infections
  • Wounds
  • Burns.
  • Lymphangitis
  • Cellulitis
  • Erysipelas.
  • Impetigo.
• Genital infections – puerperal sepsis.
• Other infections.
  • Septicaemia.
  • Pyaemia
  • Abscess of internal organs.

2. Nonsuppurative complications.

• Acute rheumatic fever
• Acute glomerulonephritis.

Question 2. Virulence factors of streptococci.
Answer:

Question 3. Write briefly on gram-positive cocci.
Answer:

Gram-positive cocci are those that resist decolorization and retain primary stain-appearing violet.

Examples:

Question 4. Alpha hemolytic streptococci.
Answer:

• Produces greenish discoloration with partial hemolysis around colonies
• The zone of lysis is small
• There is the presence of unlysed erythrocytes.
• They are normal commensals in the throat and may cause opportunistic infections rarely
• They are classified into species by physiological and biochemical properties
• Example: viridian’s group of streptococcus