Streptococcal Diseases

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Streptococcal Diseases

• Streptococcus pyogenes

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Streptococcus pyogenesPyogenes means pus
producing

• One of the most important pathogens
• Gram positive cocci in chains
• Lancefield Serological Group A
• Beta Hemolytic on blood agar

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Gram Stain of S. pyogenes
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Hemolysis on Blood Agar Plates

• Alpha hemolysis-organism excretes hemolysins
  which partially break down rbc (incomplete
  hemolysis) thus a greenish zone appears around
  colony. S. pneumoniae
• Beta hemolysis-organisms excretes potent
  hemoysins which completely lyse rbc (complete
  hemolysis) thus a clear zone appears around
  colony. S. pyogenes

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S.pyogenes
S. pneumonia
Beta hemolysis
Alpha hemolysis
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Diseases caused by S. pyogenes

• Strep throat
• Impetigo
• Erysipelas
• Cellulitis
• Invasive Strep A infections
• Necrotizing fasciitis
• Myositis
• Toxic shock-like syndrome

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Erysipelas

• Acute infection and imflammation of the dermal
  layer of skin.
• Painful red patches which enlarge and thicken
• Treatment -penicillin or erythromycin

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Erysipelas
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Strep Throat

• Most common of all Strep diseases
• Spread by saliva or nasal secretions
• Incubation period 2-4 days
• Sore throat, slight fever (101)
• Important to treat immediately to avoid post
  strep diseases

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Diagnosis and treatment of Strep Throat

• Tell tale symptoms are slight fever associated
  with sore throat and visual of pus in back of
  throat
• Quick diagnostic tests (Molecular) available but
  must be confirmed by throat swab and growth on
  blood agar (beta hemolysis)

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Diagnosis and treatment of Strep Throat

• If the strain of S. pyogenes is lysogenic for a
  particular phage which expresses an erythrogenic
  toxin the result is Scarlet fever
• Rash appears and characteristic is the strawberry
  colored tongue

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Strawberry Tongue
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Treatment of Strep

• Penicillin G or Erythromycin are drugs of choice
• Although the disease is self-limiting it is
  important to treat immediately to avoid post
  strep complications

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Poststreptococcal diseases

• Rheumatic Fever-autoimmune disease involving
  heart valves,joints, nervous system. Follows a
  strep throat
• Acute glomerulonehritis or Brights
  Disease-inflamatory disease of renal glomeruli
  and structures involved in blood filter of
  kidney. Due to deposition of Ag/Ab complexes

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Rheumatic Fever

• Most common cause of permanent heart valve damage
  in children
• Exact cause not yet known but there appears to be
  some antibody cross reactivity between the cell
  wall of S. pyogenes and heart muscle

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Rheumatic Fever

• Diagnosis is based on symptoms and is difficult
• Occurs most frequently between ages of 6 and 15
• US it is about 0.05 of pop having strep
  infections
• 100x more frequent in tropical countries

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Rheumatic Fever

• Treatment is via salicylates (aspirin
  derivatives) and corticosteroids to decrease
  inflammation and fever.

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Glomerular Nephritis

• Diagnosis based on history of Strep throat and
  clinical findings.
• Symptoms include fever, malaise,edema,
  hypertension and blood or protein in urine
• Occurs in 0.5 of those having strep throat.

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Glomerular NephritisTreatment and Recovery

• Penicillin or erythromycin to eradicate and
  residual strep infection
• 80-90 of cases recover with bed rest lasting for
  months
• Kidney damage in the remainder is often permanent
  resulting in chronic glomerular nephritis

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Streptococcus Pneumonia

• Caused by infection with Streptococcus pneumoniae
  
• Gram positive, alpha hemolytic, not of lancefield
  serotype A
• Often part of normal flora of respiratory track
  and becomes infective once hosts resistance is
  lowered. Classified as an endogenous infection.
  

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Strep Pneumonia
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Strep Pneumonia
S. pneumoniae Alpha hemolysis
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Strep pneumonia

• Predisposing factors upper respiratory viral
  infection, diabetes, alcoholism
• 60-80 of all pneumonias

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Strep Pneumonia
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Cause of strep pneumonia

• Primary virulence factor is the capsular
  polysaccharide which protects the organism
  against phagocytosis
• Pathogenesis is due to rapid growth of bacteria
  in alveolar spaces

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Symptoms of Strep Pneumonia

• Onset abrupt
• Chest pains
• Chills
• Labored breathing

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Diagnosis of Strep pneumonia

• Chest Xray
• Culture and staining
• Biochemical tests of isolated organism

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Treatment of Strep Pneumonia

• Typically treated with Penicillin G cefotaxime,
  oflaxacin or for those allergic to penicillins
  can be treated with erythromycin or tetracycline
• Pneumococcal vaccine (Pneumovax 23 or Pnu-immune
  23) is available for the elderly

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Staphylococcal infections

• One of the most common of all infections
• Staphylococcus are divided into pathogens and non
  pathogens based on possession of the enzyme
  coagulase
• Coagulase are usually S. aureus and pathogenic
• Coagulase - are organisms like S. epidermidis are
  less invasive

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Diseases of Staphylococcus
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Toxic Shock Syndrome

• Most in women using superabsorbant tampons
• Staphylococcus aureus-Gram positive cocci
• Low blood pressure, fever, diarrhea, skin rash
  can be fatal

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Toxic Shock Syndrome

• Symptoms mainly caused by toxic shock syndrome
  toxin 1(TSST1)
• Several other enterotoxins also involved

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Staph skin infections

• Most common cause of acne, boils, furuncle and
  cabuncles
• Treatment can be difficult because of antibiotic
  resistance.Usually can be treated with
  methicillin, cephalosporins,or vancomycin
• Methicillin resistant strainsMRSA

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Staph skin infections
Furuncle (infected hair follicle
Deep folliculitis
superficialfolliculitis
Carbuncle Multiple abcesses Around many
hair follicles
Scalded skin syndrome
Staph impetigo
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Scalded Skin Syndrome

• Due to strains of S. aureus containing a special
  toxin-exfoliatin

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Diagnosis

• Culture and stain-gram positive in grape-like
  clusters
• Catalase and coagulase tests
• DNA fingerprinting

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S. aureus