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Streptococcal Diseases. Streptococcus pyogenes. Streptococcus pyogenes Pyogenes means pus producing. One of the most important pathogens Gram positive cocci in chains Lancefield Serological Group A Beta Hemolytic on blood agar. Gram Stain of S. pyogenes. Hemolysis on Blood Agar Plates.

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Streptococcal Diseases

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streptococcal diseases

Streptococcal Diseases

Streptococcus pyogenes

streptococcus pyogenes pyogenes means pus producing
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
hemolysis on blood agar plates
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


S. pneumonia

Beta hemolysis

Alpha hemolysis

diseases caused by s pyogenes
Diseases caused by S. pyogenes
  • Strep throat
  • Impetigo
  • Erysipelas
  • Cellulitis
  • Invasive Strep A infections
    • Necrotizing fasciitis
    • Myositis
    • Toxic shock-like syndrome
  • Acute infection and imflammation of the dermal layer of skin.
  • Painful red patches which enlarge and thicken
  • Treatment -penicillin or erythromycin
strep throat
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
diagnosis and treatment of strep throat
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)
diagnosis and treatment of strep throat12
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
treatment of strep
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
poststreptococcal diseases
Poststreptococcal diseases
  • Rheumatic Fever-autoimmune disease involving heart valves,joints, nervous system. Follows a strep throat
  • Acute glomerulonehritis or Bright’s Disease-inflamatory disease of renal glomeruli and structures involved in blood filter of kidney. Due to deposition of Ag/Ab complexes
rheumatic fever
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
rheumatic fever17
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
rheumatic fever18
Rheumatic Fever
  • Treatment is via salicylates (aspirin derivatives) and corticosteroids to decrease inflammation and fever.
glomerular nephritis
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.
glomerular nephritis treatment and recovery
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
streptococcus pneumonia
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.
strep pneumonia23
Strep Pneumonia

S. pneumoniae

Alpha hemolysis

strep pneumonia24
Strep pneumonia
  • Predisposing factors: upper respiratory viral infection, diabetes, alcoholism
  • 60-80% of all pneumonias
cause of strep pneumonia
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
symptoms of strep pneumonia
Symptoms of Strep Pneumonia
  • Onset abrupt
  • Chest pains
  • Chills
  • Labored breathing
diagnosis of strep pneumonia
Diagnosis of Strep pneumonia
  • Chest Xray
  • Culture and staining
  • Biochemical tests of isolated organism
treatment of strep pneumonia
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
staphylococcal infections
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
toxic shock syndrome
Toxic Shock Syndrome
  • Most in women using superabsorbant tampons
  • Staphylococcus aureus-Gram positive cocci
  • Low blood pressure, fever, diarrhea, skin rash can be fatal
toxic shock syndrome33
Toxic Shock Syndrome
  • Symptoms mainly caused by toxic shock syndrome toxin 1(TSST1)
  • Several other enterotoxins also involved
staph skin infections
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 strains=MRSA

Staph skin infections


(infected hair follicle

Deep folliculitis



Multiple abcesses

Around many hair


Scalded skin


Staph impetigo

scalded skin syndrome
Scalded Skin Syndrome
  • Due to strains of S. aureus containing a special toxin-exfoliatin
  • Culture and stain-gram positive in grape-like clusters
  • Catalase and coagulase tests
  • DNA fingerprinting