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Upper respiratory tract infection:

Upper respiratory tract infection:. Streptococcus pyogenes . Neisseriae meningitidis . Haemophilus influenzae , and H parainfluenzae . Bordetella pertussis Corynebacterium diphtherium. Streptococcus pyogenes infection:. Microscopy : Gram positive cocci in chains, capsulated and

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Upper respiratory tract infection:

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  1. Upper respiratory tract infection: Streptococcus pyogenes. Neisseriae meningitidis. Haemophilus influenzae, and H parainfluenzae. Bordetella pertussis Corynebacteriumdiphtherium

  2. Streptococcus pyogenes infection: Microscopy: Gram positive cocci in chains, capsulated and non-motile. Cultural characteristics: Facultative anaerobic bacterium , beta-hemolytic on blood agar, and bacitracin sensitive.

  3. a Virulence factors and clinical picture: Streptococcuspyogeneshas several virulence factors : 1- capsule and M protein: anti-phagocytic activity. 2- Streptolysin-O exotoxin: the Beta-hemolysin. 3- Streptolysin-S exotoxin: a cardiotoxic exotoxin with beta- hemolytic activity. Clinical picture: Transmission: aspiration of airsoles (inhalation). Primary infection: tonsillitis, pharyngitis, and follicular tonsillitis. Secondary infection: Scarlet fever and septic shock. ( toxigenic strains in blood stream). Long term Streptococcuspyogenes infection: It could be complicated with Rheumatic fever and postinfectious glomerulonephritis.

  4. Clinical picture of Streptococcuspyogenes: Scarlet fever is characterized by: 1-Sore throat 2-Fever 3-Bright red tongue with a "strawberry" appearance 4-Characteristic skin rash.

  5. Neisseriae meningitidis infection: Microscopy: Gram negative cocci 0.8 µm in diameter, Kidney-shaped, occur in pairs. In clinical specimens: present in neutrophils (intracellular). Cultural characteristics: All species grow best on chocolate agar or Thayer-Martin medium at A microaerophilic conditions of 5-10%CO2. It is a fastidious bacterium Show an optimum growth at 37C.

  6. Virulence factors and clinical picture: Neisseriaemeningitidis virulence factors include: 1- The outer membrane lipo-oligosaccharide. 2- The polysaccharide capsule. 3- The adhesion pili. Clinical picture: Transmission: inhalation of airsoles. Primary infection: upper respiratory: pharyngitis, epiglottitis, Secondary: bacteremia, and septicemia. Meningococcemia(cause disseminated intravascular coagulation (DIC), a condition where blood starts to clot throughout the body) causing ischemic tissue damage. Meningoencephalitis.

  7. The characteristic skin rash (purpura) (DIC) of meningococcal septicemia, caused by Neisseria meningitidis A

  8. Haemophilus influenzae, and H. parainfluenzae: Haemophilusinfluenzae: Microscopy: Gram’s negative coccobacilli, rod-shaped pleomorphic bacteria. Some strains are capsulated. Non-motile, and non-spore forming. Cultural characteristics: Aerobic or facultative anaerobic bacteria that isolated on chocolate agar, which supplies special growth factors namely, factorX (haemin) and factorV (NAD). They can grow on blood agar around Staph aureus (satellitism phenomenon). H. parainfluenzaerequires factor V only.

  9. Haemophilusinfluenzae and H.parainfluenzae: a

  10. Clinical picture: Transmission: inhalation of droplets. Primaryinfection: upper respiratory epiglottitis. sinusitis in children. Secondary: bacteremia, could cause septicemia (toxigenic strains). The infection is extended to cause meningoencephalitis. Haemophilusinfluenzae is associated also with a specific bacterial pneumonia, if aspirated into lower respiratory tracts.

  11. Clinical picture: a

  12. Bordetella pertussis: Microscopy and culture: Gram’s-negative non-motile, non-sporing capsulated short bacilli. Bordetella pertussis is the most important pathogenic strain that causes whoopingcough. They are strict aerobe and growth best on selective and enrichment media such as charcoalcephalexinbloodagar for 4-6 days, colonies are shiny small and pearly grey (mercury drop).

  13. Cultural characteristics and clinical picture: A child complaining of whooping cough. Shiny small pearly grey (mercury drop) colonies of Bordetella pertussison Charcoal Cephalexin blood agar.

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