Management of Streptococcal Pharyngitis: Role of the Laboratory and POC Testing Arthur E. Crist, Jr., Ph.D. Director, Clinical Microbiology York Hospital

Outline n Organism n Nomenclature n Pathogenesis & Spectrum of Disease n Clinical Diagnosis n Laboratory Diagnosis –Culture –Rapid Antigen Testing –Molecular Methods

Gram Stain – Blood Culture

Structure

Extracellular products: Pyrogenic exotoxin = erythrogenic toxin scarlet fever, toxic shock lysogenic bacteriophage, Spe-A,B,C,F, Ssa. Hemolysins streptolysin Ostreptolysin S O 2 sensitiveO 2 resistant antigenic (AST) non antigenic Enzymes DNases A-DHyaluronidase Streptokinase NADase

Classification

Beta hemolysis on SBA

Ignaz P. Semmelweiss

Joseph Lister

Why Diagnose Streptococcal Pharyngitis? Treatment Prevents Sequelae Treatment Prevents Sequelae - Rheumatic Fever - Rheumatic Fever - Scarlet Fever - Glomerulonephritis - Invasive Streptococcal Disease - (Flesh-eating Strep)

Local Infections n Pharyngitis - Winter-Spring months - School aged child, esp years - Abrupt onset n Pyoderma (Impetigo) n Otitis Media n Sinusitis

Streptococcal Sore Throat

Impetigo

Invasive Infections n Erysipelas n Cellulitis n Necrotizing Fasciitis n Puerperal Fever n Sepsis n Endocarditis n Scarlet Fever n Toxic Shock Syndrome

Erysipelas

Cellulitis

Necrotizing Fasciitis

Nonsuppurative Sequelae n Acute Rheumatic Fever –1 to 5 weeks following acute pharyngitis –6 to 15 years of age –Attack rate 0.4% (civilian) to 3% (military) –M types 1,3,5,6,12,18,19,24 –Inflammation of the heart (heart valves), joints, blood vessels, and subcutaneous tissues –Probably immunological (autoimmune?) –Recurrences are common

Nonsuppurative Sequelae n Acute Glomerulonephritis –Approx. 10 days following acute pharyngitis; (3 weeks following pyoderma) –Winter/Spring (Summer/Fall-pyoderma) –6 to 15 years of age (preschool-pyoderma) –Attack rate 10-15% with known neph. strain –Limited M types involved –Probably immunological (immune complex) –Recurrences are rare

Which Streptococci Cause Sore Throat? n Group A streptococcus (S. pyogenes) n Group C streptococcus (S. dysgalactiae subsp. equisimilis) n Group G streptococcus (S. dysgalactiae subsp. equisimilis)

Signs of Streptococcal Tonsillopharyngitis n Characteristic signs -Tonsillopharyngeal erythema -Tonsillopharyngeal exudate -Soft-palate petechiae (doughnut lesions) -Beefy red, swollen uvula -Anterior cervical lymphadenitis -Scarlatiniform rash n Uncharacteristic signs -Conjunctivitis -Anterior stomatitis -Discrete ulcerative lesions

Symptoms of Streptococcal Tonsillopharyngitis n Characteristic symptoms -Sudden onset of sore throat -Headache -Pain on swallowing -Abdominal pain -Fever -Nausea and vomiting n Uncharacteristic symptoms -Coryza -Cough -Hoarseness -Diarrhea (Bisno, NEJM)

Clinical Diagnosis of Streptococcal Pharyngitis n Based on signs and symptoms n Not very accurate n 50% of patients with pharyngitis will be treated but will not be infected with Group A Streptococci n 30% of patients with pharyngitis will not be treated but will be infected with Group A Streptococci

Microbial Causes of Acute Pharyngitis (Bisno, NEJM) Pathogen Estimated Percentage of Cases Viral Rhinovirus (100 types and 1 subtype)20 Coronavirus (3 or more types) 5 Adenovirus (types 3, 4, 7, 14, and 21)5 Herpes simplex virus (types 1 and 2)4 Parainfluenza virus (types 1-4)2 Influenzavirus (types A and B)2 Coxsackievirus A (types 2, 4-6, 8, and 10)<1 Epstein-Barr virus<1 Cytomegalovirus<1 Human immunodeficiency virus type 1<1

Microbial Causes of Acute Pharyngitis (Bisno, NEJM) Pathogen Estimated Percentage of Cases Bacterial Streptococcus pyogenes (Group A -hemolytic streptococci) Group C -hemolytic streptococci 5 Neisseria gonnorrhoeae <1 Corynebacterium diphtheriae <1 Arcanobacterium haemolyticum 1 Chlamydial Chlamydia pneumoniae Unknown Mycoplasmal Mycoplasma pneumoniae <1

Laboratory Diagnosis n Culture –Specimen Collection (10% FN) –Gold Standard ?? –Selective vs. non-selective medium –Aerobic, 5-10% CO 2, anaerobic atmosphere –1 or 2 day incubation –Broth enhancement

CP Total positive cultures (%) Days SXT plus blood agars Blood agar plate only Aggregate antigen detection tests n=261 n=189 n=106 n=151 n=187 Cockerill Mayo Clinic Data. AACC Internet Presentation

Culture Methods Roddey, et al JAMA 274:

Presumptive Identification

Definitive Identification (Biochemical or Serological) Definitive Identification (Biochemical or Serological)

Positive PYR Test

Rapid Antigen Tests n Extract (acid) cell wall antigen from organism on throat swab n Detect presence of extracted antigen by –Latex agglutination (LA) –Enzyme immunoassay (EIA) –Optical immunoassay (OIA)

Rapid Antigen Test

FDA Approved Kits n 40 CLIA High Complexity ( ) Effective Date –Abbott TestPack Plus Strep A –BD Directogen Group A Strep –J & J CDI SureCell –Gen-Probe Group A Strep Direct n Almost all are used to type organisms from culture n Gen-Probe most frequently used direct specimen test in this group

FDA Approved Kits n 77 CLIA Moderate Com. ( ) Effective Date –Abbott Signify Strep A –Quidel Quickvue Strep A Test –Abbott TestPack Plus Strep A w/OBC II –Binax Strep A Test –J & J CDI SureCell –Abbott TestPack Plus Strep A –Baxter MicroScan Cards O.S –BD Directogen Grp A Strep –Binax Equate Strep A –BioStar Strep A OIA –Hybritech ICON Strep A –Meridian Diagnostics ImmunoCard –Quidel Group A Strep –Wampole Bactigen Group A Strep

FDA Approved Kits n 24 CLIA Waived ( ) Effective Date –Genzyme OSOM Ultra Strep A Test –Quidel Quickvue In-Line Strep A –Acon Strep A Rapid Test Strip –Beckman Coulter ICON DS Strep A –Quidel Quickvue Dipstick Strep A –ICON DS Strep A –Beckman Coulter ICON FX Strep A –Wyntek Diagnostics OSOM Ultra Strep A –Fisher Sure -Vue Strep A –Meridian ImmunoCard STAT Strep A –Abbott Signify Strep A Test –Biostar Acceava Strep A Test –Binax NOW Strep A Test

Factors Affecting ADT Sensitivity n Culture methods selected in a study influence the calculated ADT sensitivities n Studies are likely to report higher ADT sensitivities when cultures are performed in physician offices n When culture methods result in identification of very small numbers of GABHS, the calculated sensitivity of an ADT will be lower than that calculated when a less rigorous culture method is used because ADTs are likely to fail to detect low numbers of GABHS

Comparison of a CLIA Waived & Moderately Complex Test Mod. Complex ADT Mod. Complex ADT Sens. (%) Spec. (%) Sens. (%) Spec. (%) Waived ADT91 93 Gold Standard Gold Standard Sens. (%) Spec. (%) Sens. (%) Spec. (%) Waived ADT80 95 Gold Standard Gold Standard Sens. (%) Spec. (%) Sens. (%) Spec. (%) Mod. Com ADT82 100

Comparison of the Abbott Signify Group A Test to Culture – York Hospital Dec to Mar (n=397) n Study Sens. (%) Spec. (%) PVP (%) PVN (%) __________________________________________________________________ n YH* n PI** ND ND *York Hospital *York Hospital ** Package Insert ** Package Insert

Sensitivity and Specificity of the OIA Study Sensitivity (%) Specificity (%) Harbeck Harbeck Dale Roe Heiter Fries Harris Baker Gerber Hart Pitetti Kuhn Chapin

Comparison of Test Sensitivity Cockerill Mayo Clinic Data. AACC Internet Presentation

Conclusions: Rapid Antigen Kit Analytical Sensitivity Comparison Detection of different isolates by different tests showed no differences Analytical Sensitivities were best for the OIA (3.3 x 10 4 CFU) and worst for Directigen (5 x 10 5 CFU) Cockerill Mayo Clinic Data. AACC Internet Presentation

Molecular Tests for Detection of Group A Streptococcus from Throat Swabs - Not Point-of-Care Group A Streptococcus Direct Test (Gen-Probe) PCR – Conventional or Real Time

Gen-Probe Group A Streptococcus Direct Test Test detects rRNA sequences using a chemiluminescent single-stranded DNA probe Enhanced sensitivity vs. Antigen detection methods

Percent TestSensitivitySpecificity Positive predictive value Negative predictive value Heiter Pakorski Chapin Comparison Of The Gen-Probe Test and Culture

Polymerase Chain Reaction Unamplified DNA Denature and anneal primers Primer extension Denature and anneal primers Cycle 0 Cycle 1 Targeted sequence Cycle 2 Cycle 3 Denature and anneal primers Primer extension Cycles 4-25 At least fold increase in DNA

Comparison of PCR to Other Methods Test Sensitivity (%) Specificity (%) PVP (%) PVN (%) ____________________________________________________________________ OIA Agar culture Both-enhanced cult Combined cult OIA & agar cult PCR Kaltwasser, et al Pediatr. Infect. Dis. J. 16:

Management of Streptococcal Pharyngitis Management of Streptococcal Pharyngitis Hofer, et al Arch. Pediatr. Adolesc. Med. 151:

Management of Streptococcal Pharyngitis Management of Streptococcal Pharyngitis % Physicians Ordering Test _____________________________________________________________________ Private HMO Residents Total (n=50) (n=50) (n=50) (n=150) ____________________________________________________________ % Physicians Ordering Test _____________________________________________________________________ Private HMO Residents Total (n=50) (n=50) (n=50) (n=150) ____________________________________________________________ Case A Throat culture minute ADT hour ADT Case B Throat culture Throat culture minute ADT hour ADT minute ADT hour ADT Berwick, et al Pediatr. Infect. Dis. J. 6: Berwick, et al Pediatr. Infect. Dis. J. 6:

Management of Streptococcal Pharyngitis Management of Streptococcal Pharyngitis % of Physicians Who Believe ADT _____________________________________________________________________ Private HMO Residents Total (n=40) (n=43) (n=36) (n=119) ____________________________________________________________ % of Physicians Who Believe ADT _____________________________________________________________________ Private HMO Residents Total (n=40) (n=43) (n=36) (n=119) ____________________________________________________________ Case A Positive Negative (n=44)(n=45) (n=43) (n=132) (n=44)(n=45) (n=43) (n=132) Case B Positive Positive Negative Negative Berwick, et al Pediatr. Infect. Dis. J. 6: Berwick, et al Pediatr. Infect. Dis. J. 6:

Management of Streptococcal Pharyngitis Effect of ADT Availability on Treatment Management of Streptococcal Pharyngitis Effect of ADT Availability on Treatment Patients Treated (per100) _____________________________________________________________________ Private HMO Residents Total (n=50) (n=50) (n=50) (n=150) ____________________________________________________________ Patients Treated (per100) _____________________________________________________________________ Private HMO Residents Total (n=50) (n=50) (n=50) (n=150) ____________________________________________________________ Case A None minute ADT hour ADT minute ADT hour ADT Case B None None minute ADT hour ADT minute ADT hour ADT Berwick, et al Pediatr. Infect. Dis. J. 6: Berwick, et al Pediatr. Infect. Dis. J. 6:

Conclusions - Rapid Testing for Streptococcal Infection Rapid Antigen Detection (LA, EIA, or OIA-based, point-of-care) - Culture if Rapid Antigen Result Negative Molecular methods, e.g. Real-time PCR, may equal or exceed sensitivity provided by culture (American Academy of Pediatrics) (Infectious Disease Society of America)

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