Introduction Classification bacteria gram-negative bacilli the enterics facultative anaerobes lactose fermenting Escherichia E. coli Pathogenesis Transmission endogenous fecal-oral contaminated food undercooked meat Reservoir normal colonic flora cow feces Molecular biology normal flora acquires virulence factors pili P-fimbrae virulence factor is most important for colonization of urinary tract exotoxin LT ST shiga-like endotoxin lipid A part of LPS K capsule K-1 capsular antigen allows meningeal infection iron-binding siderophore molecular mechanism of virulence depends on strain (see below) Laboratory Oxidase negative Most E. coli ferment sorbitol except EHEC which usually does not Distinguish pathogenic strains via immunoassay serotyping DNA probes PCR Clinical Conditions Diarrhea severity of diarrhea depends on strain ("PITcH") virulence factors are shared between Vibrio, E. coli, and Shigella EPEC ("pediatric") second most common cause of diarrhea in infants adherence to M cells prevents absorption no Shiga toxin produced, but some strains may produce Shiga-like toxin developing countries EIEC ("inflammatory") bacteria invade epithelial cells invasion and toxin act synergistically virulence factor is shared by Shigella blood and WBC in stool like Shigellosis ETEC ("traveler") LT (heat labile) toxin similar to cholera toxin ↑ cAMP ST (heat stable) toxin secretion of Cl- and HCO3- into intestinal lumen results in rice-water stools resembling those seen in cholera EHEC ("hamburger") Shiga-like toxin (verotoxin) inhibits protein synthesis by inhibiting 60S ribosome no invasion of epithelium virulence is only toxin-mediated blood in stool but no WBCs because no invasion hemolytic uremic syndrome (HUS) O157:H7 strain associated classic triad anemia thrombocytopenia acute renal failure swelling of endothelium narrows lumen leading to hemolysis ↓ renal blood flow ↓ platelets as damage is repaired O157:H7 strain does not ferment sorbitol nor does it produce glucuronidase (vs. most other E. coli strains) EAEC enteroaggregative E. coli has the ability to adhere to intestinal cells cause of traveler's diarrhea to less-developed countries UTI most common cause of UTI acquisition of pili allows motility up the GU tract ascending infection can cause pyelonephritis Neonatal meningitis second most common cause (vs. group B strep) acquisition of K capsule inhibits phagocytosis to allow spread to meninges Sepsis most common cause of Gram-negative sepsis hospitalized patients Pneumonia hospital acquired in neonates Cystitis Pyelonephritis Treatment for Common Clinical Conditions Caused by E.Coli EPEC diarrhea Supportive EIEC diarrhea ----- ETEC diarrhea Rehydration with TMP/SMX EHEC diarrhea Supportive (do not use antibiotics - they may cause HUS) UTI Fluoroquinolones or sulfonamides Neonatal meningitis Ceftriaxone Sepsis Fluoroquinolones or 3rd generation cephalosporins
QUESTIONS 1 of 7 1 2 3 4 5 6 7 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 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.75) A 23-year-old woman goes to a walk-in clinic while on the fourth day of her honeymoon. She is very upset saying that her honeymoon is being ruined because she is in severe pain. She states that yesterday she began to experience severe pain with urination and seems to be urinating more frequently than normal. She does admit that she has been having increased sexual intercourse with her new husband while on their honeymoon. The physician diagnoses the patient and prescribes trimethoprim-sulfamethoxazole. Which of the following virulence factors is most likely responsible for this patient's infection? Review Topic QID: 106731 1 LPS endotoxin 5% (9/180) 2 K capsule 9% (16/180) 3 P fimbriae 70% (126/180) 4 Flagella 8% (14/180) 5 Exotoxin 7% (12/180) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 3 (M1.MC.13) A 27-year-old male suddenly develops severe abdominal cramping and bloody diarrhea. The patient reports consuming undercooked ground beef four days prior to the onset of the symptoms. Which of the following best describes the toxin-mediated mechanism of this disease process? Review Topic QID: 101472 1 Depolymerization of actin filaments in gastrointestinal mucosal cells, leading to mucosal cell death 11% (27/248) 2 Increased pH of gastrointestinal lumen resulting in reduced mucosal absorption 0% (1/248) 3 Increased intracellular cAMP in gastrointestinal mucosal cells, resulting in decreased absorption and increased secretion in the digestive tract 20% (49/248) 4 Inhibition of elongation factor-2 (EF-2), resulting in decreased protein synthesis in gastrointestinal mucosal cells 17% (42/248) 5 Inhibition of the 60S ribosomal subunit, resulting in decreased protein synthesis in gastrointestinal mucosal cells 50% (124/248) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 5 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK