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Streptococcal Diseases
Streptococcus pyogenes
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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
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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 zoneappears around colony. S. pneumoniae
Beta hemolysis-organisms excretes potent
hemoysins which completely lyse rbc
(complete hemolysis) thus a clear zoneappears around colony. S. pyogenes
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S.pyogenes S. pneumoniaBeta
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 andthicken
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 avoidpost 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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Strawberry Tongue
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Treatment of Strep
Penicillin G or Erythromycin are drugs
of choice
Although the disease is self-limiting it isimportant 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 inblood 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 thereappears 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 agesof 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 strepthroat.
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Glomerular Nephritis
Treatment and Recovery
Penicillin or erythromycin to eradicate
and residual strep infection
80-90% of cases recover with bed restlasting for months
Kidney damage in the remainder is
often permanent resulting in chronicglomerular nephritis
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Streptococcus Pneumonia
Caused by infection with Streptococcuspneumoniae
Gram positive, alpha hemolytic, not oflancefield serotype A
Often part of normal flora of respiratorytrack and becomes infective once hostsresistance is lowered. Classified as anendogenous 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 witherythromycin or tetracycline
Pneumococcal vaccine (Pneumovax 23
or Pnu-immune 23) is available for theelderly
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Staphylococcal infections
One of the most common of allinfections
Staphylococcus are divided intopathogens and non pathogens basedon 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 positivecocci
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 ofantibiotic resistance.Usually can betreated with methicillin,cephalosporins,or vancomycin
Methicillin resistant strains=MRSA
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Staph skin infections
superficialfolliculitis
Deep folliculitis
Furuncle
(infected hair
follicle
Carbuncle
Multiple abcesses
Around many hair
follicles
Staph impetigoScalded skinsyndrome
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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