Throat Infections

Sore Throat Pathogens

• Sore throat, medically known as pharyngitis, can range in severity.
• Many sore throats are symptom parts of other respiratory infections (e.g., cold, flu).
• Focus is on three pathogens causing pharyngitis: Adenovirus, Corynebacterium diphtheriae, and Streptococcus pyogenes.

Adenovirus

• Over 30 serotypes (groups) of Adenovirus can infect humans.
• Serotypes 1-7 are linked to upper respiratory tract and eye infections (colds, pharyngitis, conjunctivitis).
• Symptoms include fever, sore throat, red/inflamed throat/conjunctiva, and potentially photophobia.
• Treatment involves easing symptoms rather than curing the virus (e.g., eye drops, lozenges).
• Usually, the infection is mild and resolves within 1-2 weeks on its own.

Corynebacterium diphtheriae and Diphtheria

• Corynebacterium diphtheriae is a Gram-positive bacillus arranged in palisades.
• It contains metachromatic granules (stain iridescent red with methylene blue), giving a club shape appearance.
• Diphtheria is a disease caused by C. diphtheriae.
• Initial symptoms are localized throat infection, fever, sore throat, and severe inflammation.
• A hallmark is a thick, leathery pseudomembrane on the back of the tongue (made of dead tissue, bacteria, immune byproducts).
• The membrane can enlarge and block the airway, causing asphyxiation.
• Many C. diphtheriae strains are lysogenic (carrying viral DNA).
• The lysogenic bacteria produce a potent exotoxin that blocks eukaryotic ribosome translation.
• The exotoxin causes systemic effects due to the disruption of cellular function, with possible dangerous complications like nerve damage and heart failure leading to paralysis and death.
• Diphtheria is transmitted by respiratory droplets, direct contact, and fomites.
• Treatment includes antibiotics and antisera, with careful monitoring of the heart and respiratory system.
• Vaccination (DTaP) is highly effective in preventing diphtheria.
• Outbreaks can occur if herd immunity wanes.

Streptococcus pyogenes and Strep Throat

• Streptococcus pyogenes is a Gram-positive coccus in chains.
• It's part of the normal flora in 15% of humans.
• Transmitted through respiratory droplets and direct contact.
• Virulence factors include C-carbohydrate and M-protein (attachment and phagocytosis defense), hemolysin toxins (beta-hemolysis), and erythrogenic toxin (bright red rash and fever- only in lysogenic strains).
• Strep throat is characterized by extreme throat pain with a bright red, pus-covered throat and potentially a foul smell.
• Diagnosis of strep throat is crucial due to potential complications.

Complications of Strep Throat

• Scarlet Fever:
  • Lysogenic S. pyogenes causes erythrogenic toxin, resulting in a bright red rash, high fever, and a characteristic sandpaper-like rash.
  • May include "strawberry tongue" (dark red tongue with white bumps).
  • Requires prompt treatment to avoid complications.
• Rheumatic Fever:
  • Antibodies against S. pyogenes M-protein cross-react with heart tissue causing immune reaction.
  • Can lead to permanent heart valve damage; treatment is vital.
• Glomerulonephritis:
  • Immune complexes (antibodies and antigens) deposit in the kidneys.
  • Causes kidney inflammation (nephritis/glomerulonephritis).
  • Symptoms include swelling, lowered urine output, blood in urine, increased blood pressure, and possible heart/kidney failure.
  • Urgent antibiotic treatment is crucial.