Upper Respiratory Tract Infections

What is the classification of streptococci based on C carbohydrate antigen called?

Lancefield classification.

Name the medically important Lancefield groups of streptococci.

Groups A, B, C, D.

What is the characteristic of alpha-hemolytic streptococci?

Green, partial hemolysis.

Give examples of alpha-hemolytic streptococci.

Streptococcus pneumoniae and Viridans (mutans, sanguis).

What is the characteristic of beta-hemolytic streptococci?

Clear, complete hemolysis.

Provide examples of beta-hemolytic streptococci.

Streptococcus pyogenes (Group A) and Streptococcus agalactiae (Group B).

What defines gamma-hemolytic streptococci?

No hemolysis.

Which bacteria are classified as gamma-hemolytic streptococci?

Enterococcus (E. faecalis, E. faecium).

What is Group A Streptococci also known as?

Group A Streptococcus (GAS) or Streptococcus pyogenes.

How is Streptococcus pyogenes differentiated?

By M-protein, which has more than 124 serotypes.

Where is Streptococcus pyogenes commonly found?

On skin and mucous membranes of the nasopharynx.

What are the key virulence factors of GAS?

Adhesion molecules, toxins, and immune system interference.

What are pore-forming toxins in GAS?

Streptolysin O and Streptolysin S.

What is the significance of Spe toxins in streptococci?

They are exotoxins that can overstimulate the immune system.

Which illnesses are associated with Streptococcus pyogenes?

Streptococcal pharyngitis, tonsillitis, scarlet fever, and rheumatic fever.

What causes rheumatic fever?

Cross-reactivity between Streptococcal antigens and heart muscle antigens.

What type of toxin does Corynebacterium diphtheriae produce?

A-B type (binary) toxins.

How does diphtheria toxin affect host cells?

By ADP ribosylation of elongation factor 2 (EF2), halting protein synthesis.

What does a pseudomembrane consist of in diphtheria?

Necrotic fibrin, leukocytes, erythrocytes, epithelial cells, and bacterial organisms.

What are the key virulence factors of Bordetella pertussis?

Filamentous hemagglutinin (FHA) and pertussis toxin (PT).

How is the pertussis toxin categorized?

As a binary (A-B) toxin.

What is a major symptom during the paroxysmal stage of pertussis?

Repetitive coughing with whoops.

What do the symptoms of acute bacterial meningitis result from?

The inflammatory response to bacteria and bacterial products in the brain.

What bacterium is most commonly associated with meningitis?

Neisseria meningitidis.

What is the role of polysaccharide capsules in meningitis bacteria?

They block phagocytosis by immune cells.

How are bacterial meningitis agents primarily transmitted?

By respiratory droplets.

Which age group is most commonly affected by Haemophilus influenzae?

Children aged 0-5 years.

What happens in meningococcemia caused by Neisseria meningitidis?

Purpura or petechial lesions appear, giving a rash-like appearance.

What are bacterial avoidance mechanisms of phagocytosis?

Capsules can cover bacterial molecules recognized by phagocytes.

What can lead to secondary infections of the upper respiratory tract?

Less virulent strains associated with milder upper respiratory infections.