4Hemolysis on Blood Agar Plates Alpha hemolysis-organism excretes hemolysins which partially break down rbc (incomplete hemolysis) thus a greenish zone appears around colony. S. pneumoniaeBeta hemolysis-organisms excretes potent hemoysins which completely lyse rbc (complete hemolysis) thus a clear zone appears around colony. S. pyogenes
10Strep Throat Most common of all Strep diseases Spread by saliva or nasal secretionsIncubation period 2-4 daysSore throat, slight fever (101)Important to treat immediately to avoid post strep diseases
11Diagnosis and treatment of Strep Throat Tell tale symptoms are slight fever associated with sore throat and visual of pus in back of throatQuick diagnostic tests (Molecular) available but must be confirmed by throat swab and growth on blood agar (beta hemolysis)
12Diagnosis 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 feverRash appears and characteristic is the strawberry colored tongue
14Treatment 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
15Poststreptococcal diseases Rheumatic Fever-autoimmune disease involving heart valves,joints, nervous system. Follows a strep throatAcute 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
16Rheumatic FeverMost common cause of permanent heart valve damage in childrenExact cause not yet known but there appears to be some antibody cross reactivity between the cell wall of S. pyogenes and heart muscle
17Rheumatic Fever Diagnosis is based on symptoms and is difficult Occurs most frequently between ages of 6 and 15US it is about 0.05% of pop having strep infections100x more frequent in tropical countries
18Rheumatic FeverTreatment is via salicylates (aspirin derivatives) and corticosteroids to decrease inflammation and fever.
19Glomerular NephritisDiagnosis based on history of Strep throat and clinical findings.Symptoms include fever, malaise,edema, hypertension and blood or protein in urineOccurs in 0.5% of those having strep throat.
20Glomerular Nephritis Treatment and Recovery Penicillin or erythromycin to eradicate and residual strep infection80-90% of cases recover with bed rest lasting for monthsKidney damage in the remainder is often permanent resulting in chronic glomerular nephritis
21Streptococcus Pneumonia Caused by infection with Streptococcus pneumoniaeGram positive, alpha hemolytic, not of lancefield serotype AOften part of normal flora of respiratory track and becomes infective once hosts resistance is lowered. Classified as an endogenous infection.
26Cause of strep pneumonia Primary virulence factor is the capsular polysaccharide which protects the organism against phagocytosisPathogenesis is due to rapid growth of bacteria in alveolar spaces
27Symptoms of Strep Pneumonia Onset abruptChest painsChillsLabored breathing
28Diagnosis of Strep pneumonia Chest XrayCulture and stainingBiochemical tests of isolated organism
29Treatment of Strep Pneumonia Typically treated with Penicillin G cefotaxime, oflaxacin or for those allergic to penicillins can be treated with erythromycin or tetracyclinePneumococcal vaccine (Pneumovax 23 or Pnu-immune 23) is available for the elderly
30Staphylococcal infections One of the most common of all infectionsStaphylococcus are divided into pathogens and non pathogens based on possession of the enzyme coagulaseCoagulase + are usually S. aureus and pathogenicCoagulase - are organisms like S. epidermidis are less invasive
32Toxic Shock Syndrome Most in women using superabsorbant tampons Staphylococcus aureus-Gram positive cocciLow blood pressure, fever, diarrhea, skin rash can be fatal
33Toxic Shock SyndromeSymptoms mainly caused by toxic shock syndrome toxin 1(TSST1)Several other enterotoxins also involved
34Staph skin infectionsMost common cause of acne, boils, furuncle and cabunclesTreatment can be difficult because of antibiotic resistance.Usually can be treated with methicillin, cephalosporins,or vancomycinMethicillin resistant strains=MRSA
35Staph skin infections Furuncle (infected hair follicle Deep folliculitissuperficialfolliculitisCarbuncleMultiple abcessesAround many hairfolliclesScalded skinsyndromeStaph impetigo
36Scalded Skin SyndromeDue to strains of S. aureus containing a special toxin-exfoliatin
37Diagnosis Culture and stain-gram positive in grape-like clusters Catalase and coagulase testsDNA fingerprinting