Introduction Classification bacteria Gram-positive cocci Streptococcus S. pyogenes (Group A strep, or "GAS") Pathogenesis transmission direct contact respiratory reservoir throat skin molecular biology M protein main virulence factor inhibits phagocytosis inhibits complement activation mediates bacterial attachment antigenic antibodies to M protein can give rise to rheumatic fever hyaluronic acid capsule non-immunogenic streptolysin O immunogenic lyses erythrocytes and PMNs ASO titer reveals the presence of this antigen streptolysin S non-immunogenic streptokinase dissolves clot hyaluronidase dissolves connective tissues erythrogenic toxin (SPE-A) anti-DNase antibody stays elevated for longer - useful for diagnosis Presentation GAS is pyogenic, toxigenic, and immunogenic pyogenic pharyngitis acute onset sore throat, fever, malaise, and headache "exudative tonsillitis" however, 70% of exudative tonsilitis is caused by viruses don't assume GAS solely based on finding of exudative tonsilitis tonsillar abscesses tender anterior cervical lymph nodes cellulitis impetigo honey-crusted lesions toxigenic scarlet fever sandpaper rash sparing palms and soles strawberry tongue toxic shock syndrome immunogenic rheumatic fever antibodies to heart tissue type II hypersensitivity symptoms include subcutaneous plaques polyarthritis erythema marginatum chorea carditis occurs following pharyngitis does NOT occur following skin infection (impetigo) post-streptococcal glomerulonephritis (PSGN) immune deposits in glomeruli type III hypersensitivity associated with M12 serotype occurs following either pharyngitis or impetigo "PHaryngitis can result in rheumatic PHever and nePHritis" Studies Diagnosis rapid strep test is ELISA based misses 25% of infections → culture all negative tests ASO (anti-streptolysin O) titer detects recent infection >200 indicates rheumatic fever Evaluation bacitracin sensitive β-hemolytic PYR (pyrrolidonyl arylamidase) positive Treatment Pharmacologic beta-lactam medications penicillin derivatives cephalosporins macrolides if penicillin allergy consider prophylactic antibiotics post acute rheumatic fever prompt treatment prevents rheumatic fever but does NOT affect likelihood of developing post-streptococcal glomerulonephritis
QUESTIONS 1 of 9 1 2 3 4 5 6 7 8 9 Previous Next Lab Values Blood Hematologic Cerebrospinal Sweat, Urine, and BMI Blood, Plasma, Serum Reference Range ALT 8-20 U/L Amylase, serum 25-125 U/L AST 8-20 U/L Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL Calcium, serum (Ca2+) 8.4-10.2 mg/dL Cholesterol, serum Rec: < 200 mg/dL Cortisol, serum 0800 h: 5-23 μg/dL //1600 h: 3-15 μg/dL 2000 h: ≤ 50% of 0800 h Creatine kinase, serum Male: 25-90 U/LFemale: 10-70 U/L Creatinine, serum 0.6-1.2 mg/dL Electrolytes, serum Sodium (Na+) 136-145 mEq/L Chloride (Cl-) 95-105 mEq/L Potassium (K+) 3.5-5.0 mEq/L Bicarbonate (HCO3-) 22-28 mEq/L Magnesium (Mg2+) 1.5-2.0 mEq/L Estriol, total, serum (in pregnancy) 24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL 28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL Ferritin, serum Male: 15-200 ng/mLFemale: 12-150 ng/mL Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL Female: premenopause: 4-30 mIU/mL midcycle peak: 10-90 mIU/mL postmenopause: 40-250 pH 7.35-7.45 PCO2 33-45 mmHg PO2 75-105 mmHg Glucose, serum Fasting: 70-110 mg/dL2-h postprandial:<120 mg/dL Growth hormone - arginine stimulation Fasting: <5 ng/mLProvocative stimuli: > 7ng/mL Immunoglobulins, serum IgA 76-390 mg/dL IgE 0-380 IU/mL IgG 650-1500 mg/dL IgM 40-345 mg/dL Iron 50-170 μg/dL Lactate dehydrogenase, serum 45-90 U/L Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL Female: follicular phase: 5-30 mIU/mL midcycle: 75-150 mIU/mL postmenopause 30-200 mIU/mL Osmolality, serum 275-295 mOsmol/kd H2O Parathyroid hormone, serume, N-terminal 230-630 pg/mL Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L Phosphorus (inorganic), serum 3.0-4.5 mg/dL Prolactin, serum (hPRL) < 20 ng/mL Proteins, serum Total (recumbent) 6.0-7.8 g/dL Albumin 3.5-5.5 g/dL Globulin 2.3-3.5 g/dL Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h Thyroxine (T4), serum 5-12 μg/dL Triglycerides, serum 35-160 mg/dL Triiodothyronine (T3), serum (RIA) 115-190 ng/dL Triiodothyronine (T3) resin uptake 25%-35% Urea nitrogen, serum 7-18 mg/dL Uric acid, serum 3.0-8.2 mg/dL Hematologic Reference Range Bleeding time 2-7 minutes Erythrocyte count Male: 4.3-5.9 million/mm3Female: 3.5-5.5 million mm3 Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/hFemale: 0-20 mm/h Hematocrit Male: 41%-53%Female: 36%-46% Hemoglobin A1c ≤ 6 % Hemoglobin, blood Male: 13.5-17.5 g/dLFemale: 12.0-16.0 g/dL Hemoglobin, plasma 1-4 mg/dL Leukocyte count and differential Leukocyte count 4,500-11,000/mm3 Segmented neutrophils 54%-62% Bands 3%-5% Eosinophils 1%-3% Basophils 0%-0.75% Lymphocytes 25%-33% Monocytes 3%-7% Mean corpuscular hemoglobin 25.4-34.6 pg/cell Mean corpuscular hemoglobin concentration 31%-36% Hb/cell Mean corpuscular volume 80-100 μm3 Partial thromboplastin time (activated) 25-40 seconds Platelet count 150,000-400,000/mm3 Prothrombin time 11-15 seconds Reticulocyte count 0.5%-1.5% of red cells Thrombin time < 2 seconds deviation from control Volume Plasma Male: 25-43 mL/kgFemale: 28-45 mL/kg Red cell Male: 20-36 mL/kgFemale: 19-31 mL/kg Cerebrospinal Fluid Reference Range Cell count 0-5/mm3 Chloride 118-132 mEq/L Gamma globulin 3%-12% total proteins Glucose 40-70 mg/dL Pressure 70-180 mm H2O Proteins, total < 40 mg/dL Sweat Reference Range Chloride 0-35 mmol/L Urine Calcium 100-300 mg/24 h Chloride Varies with intake Creatinine clearance Male: 97-137 mL/minFemale: 88-128 mL/min Estriol, total (in pregnancy) 30 wks 6-18 mg/24 h 35 wks 9-28 mg/24 h 40 wks 13-42 mg/24 h 17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 hFemale: 2.0-8.0 mg/24 h 17-Ketosteroids, total Male: 8-20 mg/24 hFemale: 6-15 mg/24 h Osmolality 50-1400 mOsmol/kg H2O Oxalate 8-40 μg/mL Potassium Varies with diet Proteins, total < 150 mg/24 h Sodium Varies with diet Uric acid Varies with diet Body Mass Index (BMI) Adult: 19-25 kg/m2 Calculator ( ) xy AC 7 8 9 ÷ 4 5 6 × 1 2 3 - 0 . = + Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.MC.189) A 53-year-old female presents with worsening shortness of breath with activity. Physical exam reveals a diastolic murmur with an opening snap. The patient’s medical history is significant for a left hip replacement 10 years ago, and she vaguely recalls an extended period of illness as a child described as several severe episodes of sore throat followed by rash, fever, and joint pains. Administration of which of the following treatments at that time would have been most effective in reducing her risk of developing cardiac disease? Review Topic QID: 101648 1 Acyclovir 0% (0/22) 2 Penicillin 86% (19/22) 3 Vancomycin 9% (2/22) 4 Aspirin 0% (0/22) 5 Ciprofloxacin 0% (0/22) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 2 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.MC.157) Part of the success of the Streptococcus pyogenes bacterium lies in its ability to evade phagocytosis. Which of the following helps in this evasion? Review Topic QID: 101616 1 M protein 69% (24/35) 2 Streptolysin O 20% (7/35) 3 Streptolysin S 0% (0/35) 4 Pyrogenic toxin 0% (0/35) 5 Streptokinase 6% (2/35) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 1 (M1.MC.152) A 10-year-old male is taken to his physician by his parents due to a sore throat. A throat swab and culture reveal the growth seen in Figure A. The bacteria are gram-positive and bacitracin inhibits their growth. The child is given treatment and sent home. Twenty years later, the patient presents to the emergency department with dyspnea on exertion and CXR showed an enlarged cardiac silhouette and pulmonary edema. The patient's current symptomatology most likely occurred secondary to which of the following? Review Topic QID: 101611 FIGURES: A 1 Type III hypersensitivity reaction 43% (3/7) 2 Coagulase activity 0% (0/7) 3 Leukocidin activity 0% (0/7) 4 Type I hypersensitivty reaction 0% (0/7) 5 Molecular mimicry 57% (4/7) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 5 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.MC.114) A 14-year-old male is brought to the Emergency Department by his mother. She is worried because his face has become puffy and his urine has turned a tea-color. Patient history reveals the child recently suffered from a sore throat. The physician suspects a bacterial infection. Which of the following describes the likely bacteria responsible? Review Topic QID: 101573 1 Coagulase positive 7% (34/464) 2 Catalase positive 10% (46/464) 3 Beta-hemolytic 72% (335/464) 4 Bacitracin insensitive 4% (19/464) 5 Gram negative 5% (25/464) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 3 (M1.MC.15) About two weeks ago, an 11-year-old boy fell from his bicycle into some rose bushes and received superficial lacerations on his hands and arms. His mother bandaged up his wounds, and after a week she noticed that a localized pustular rash with yellow crusts developed on his right forearm (see Figure A). The child was taken to the pediatrician and a wound culture was taken that showed catalase-negative, beta-hemolytic Gram-positive cocci in chains. Which of the following agents is responsible for the infection? Review Topic QID: 101474 FIGURES: A 1 Sporothrix schenckii 14% (2/14) 2 Staphylococcus aureus 0% (0/14) 3 Streptococcus mutans 7% (1/14) 4 Staphylococcus epidermidis 0% (0/14) 5 Streptococcus pyogenes 71% (10/14) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 5