Snapshot A 35-year-old woman presents to the emergency room for an ulcer on her arm. She reports that she recently completed a travel program in Africa, where she worked on the farms in exchange for room and board. She reports coming into contact with farm animals every day. She said she accidentally cut her left forearm on some wooden post a few days ago. Yesterday, she noticed a painless but pruritic lesion. On physical exam, there is a 4-mm papule with a dusky-looking central vesicle and surrounding edema. There is also axillary lymphadenopathy. She is started on antibiotics. Introduction Classification Bacillus anthracis spore- and exotoxin-forming gram + rod capsule protects against phagocytosis the only bacteria with a polypeptide capsule (poly-D-glutamate) transmission inhalation of spores introduction of spores into a skin break ingestion of spores Epidemiology incidence more common in areas where animal vaccination rates are low bioterrorism risk factors intravenous drug use (e.g., heroin) occupational exposure to unvaccinated animals occupational exposure to animal hides Pathogenesis anthrax toxin composed of 3 components protective antigen binds cell surface and mediates entry of edema and lethal factor edema factor binds calmodulin and performs the same function as adenylate cyclase, ↑ cAMP and resulting in black eschar’s edematous borders vasodilation and hypotension lethal factor a protease that cleaves the amino terminus of mitogen-activated protein kinase kinases (MAPKK), inhibiting this signalling pathway, and resulting in macrophage apoptosis infection may spread via lymphatics Associated conditions cutaneous anthrax most common pulmonary anthrax “woolsorter’s disease” gastrointestinal anthrax Prevention post-exposure prophylaxis 3 doses of anthrax vaccine 60 days of a single antibiotic ciprofloxacin or doxycycline are first line Prognosis biphasic nature of pulmonary anthrax prodromal symptoms fulminant bacteremic phase often leads to death within days Presentation Symptoms pulmonary anthrax flu-like syndrome with non-productive cough nausea and vomiting hemoptysis chest pain gastrointestinal anthrax nausea and vomiting dysentery abdominal pain Physical exam cutaneous anthrax initial lesion is a painless and pruritic papule with a central vesicle or bulla this progresses to painless and necrotic black eschar surrounded by edema eschar sloughs off at day 14 pulmonary anthrax mediastinitis shock hypoxia dyspnea lymphadenopathy Imaging Chest radiography indication pulmonary anthrax findings pleural effusion pulmonary consolidation widened mediastinum Studies Labs multiple methods of detection “medusa head” appearance on microscopy halo of projections culture of blood, pleural fluid, or eschar positive Gram stain of affected tissue polymerase chain reaction anti-protective antigen immunoglobulin G on enzyme-linked immunosorbent assay biopsy with immunohistochemistry staining marked hemoconcentration Making the diagnosis most cases are diagnosed clinically and confirmed with positive culture, serology, or immunohistochemistry detection of Bacillus anthracis DNA in tissue Differential Community-acquired pneumonia distinguishing factor less likely to have nausea, vomiting, pallor, or unexplained mediastinal widening on chest radiography Treatment Management approach antibiotics should be given in the prodromal phase of the disease cutaneous anthrax can be treated with 1 antibiotic systemic anthrax can be treated with 2 antibiotics Medical ciprofloxacin or doxycycline indication all patients protein synthesis inhibitor indications systemic anthrax combination therapy with fluoroquinolone or doxycycline mechanism reduces toxin production drugs clindamycin linezolid antitoxins indication all patients drugs monoclonal antibodies raxibacumab anthrax immunoglobulin Complications Bacteremia from cutaneous anthrax Death
QUESTIONS 1 of 3 1 2 3 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 You have 100% on this question. Just skip this one for now. Take This Question Anyway (M1.MC.17.4754) A 61-year-old male presents to the emergency department complaining of malaise. He reports a two-day history of rapidly progressive fatigue, malaise, fever, and dyspnea. The patient immigrated from Finland five years ago and works on a large farm. His past medical history is notable for diabetes mellitus and emphysema. He takes metformin, salmeterol, and tiotropium. He has a 40 pack-year smoking history. His temperature is 102.3°F (39.1°C), blood pressure is 90/50 mmHg, pulse is 130/min, respirations are 30/min, and oxygen saturation is 92% on room air. Physical examination is notable for rales at the bilateral lung bases. Chest radiography reveals a widened mediastinum and bilateral pulmonary infiltrates. He is subsequently admitted and started on broad-spectrum antibiotics and fluid resuscitation. However, his fever rapidly progresses and he perishes the following day. Results from a blood culture taken on admission are shown in Figure A. The pathogen responsible for this patient’s condition produces a toxin with which of the following mechanisms of action? Review Topic | Tested Concept QID: 108945 FIGURES: A Type & Select Correct Answer 1 Directly activates adenylyl cyclase 28% (72/259) 2 Mimics adenylyl cyclase 24% (62/259) 3 Inhibits 60S ribosomal subunit 15% (38/259) 4 Binds Fc portion of immunoglobulin 12% (32/259) 5 Depolymerizes actin cytoskeleton 16% (41/259) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 You have 100% on this question. Just skip this one for now. Take This Question Anyway (M1.MC.15.75) A 65-year-old farmer presents for evaluation of a lesion on his arm. The lesion originally started as a painless pruritic papule, but enlarged over the last several days. The current appearance of the lesion is shown in Figure A. Which of the following is the most likely cause of the lesion? Review Topic | Tested Concept QID: 106723 FIGURES: A Type & Select Correct Answer 1 Autoimmune disorder against hemidesmosomes 0% (0/24) 2 S. aureus infection 4% (1/24) 3 B. anthracis infection 83% (20/24) 4 Squamous cell carcinoma 0% (0/24) 5 Basal cell carcinoma 8% (2/24) L 2 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3