381 likes | 1.26k Views
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.
E N D
Streptococcal Diseases Streptococcus pyogenes
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 • 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.pyogenes S. pneumonia Beta hemolysis Alpha hemolysis
Diseases caused by S. pyogenes • Strep throat • Impetigo • Erysipelas • Cellulitis • Invasive Strep A infections • Necrotizing fasciitis • Myositis • Toxic shock-like syndrome
Erysipelas • Acute infection and imflammation of the dermal layer of skin. • Painful red patches which enlarge and thicken • Treatment -penicillin or erythromycin
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 • 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 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 • 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 • 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 • 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 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 Fever • Treatment is via salicylates (aspirin derivatives) and corticosteroids to decrease inflammation and fever.
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 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 • 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 Pneumonia S. pneumoniae Alpha hemolysis
Strep pneumonia • Predisposing factors: upper respiratory viral infection, diabetes, alcoholism • 60-80% of all pneumonias
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 • Onset abrupt • Chest pains • Chills • Labored breathing
Diagnosis of Strep pneumonia • Chest Xray • Culture and staining • Biochemical tests of isolated organism
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 • 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 • Most in women using superabsorbant tampons • Staphylococcus aureus-Gram positive cocci • Low blood pressure, fever, diarrhea, skin rash can be fatal
Toxic Shock Syndrome • Symptoms mainly caused by toxic shock syndrome toxin 1(TSST1) • Several other enterotoxins also involved
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 Furuncle (infected hair follicle Deep folliculitis superficialfolliculitis Carbuncle Multiple abcesses Around many hair follicles Scalded skin syndrome Staph impetigo
Scalded Skin Syndrome • Due to strains of S. aureus containing a special toxin-exfoliatin
Diagnosis • Culture and stain-gram positive in grape-like clusters • Catalase and coagulase tests • DNA fingerprinting