strep staph(1)

8/12/2019 Strep Staph(1)

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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

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