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Snapshot
  • A 76-year-old woman presents to the emergency department for altered mental status. She currently lives in a nursing home and was brought to seek treatment by her daughter. She was noted to be more confused over the course of a few days and developed a fever. Her temperature is 101°F (38.3°C), blood pressure is 133/99 mmHg, pulse is 101/min, and respirations are 20/min. Physical examination is notable for being alert and oriented to self but not time or place and suprapubic abdominal pain. A urinalysis is remarkable for being leukocyte-esterase positive. Urine culture grows Escherichia coli.
Introduction
  • Classification
    • a gram-negative bacilli
  • Epidemiology
    • incidence
      • the most common cause of UTI in women
  • Microbiology
    • reservoir
      • gastrointestinal tract
    • transmission
      • fecal-oral
      • urethral ascension
      • catheter
      • aspiration
    • properties
      • enterotoxins
        • heat labile
          • increases cAMP
        • heat stable
          • increases cGMP
        • shiga-like toxin
          • inhibits the 60s ribosomal subunit, impairing protein synthesis 
      • fimbriae  
      • K-antigen (capsule) 
      • H-antigen (flagella)
  • Associated conditions
    • enterotoxigenic (ETEC)
    • enterohemorrhagic (EHEC)
      • can result in hemolytic uremic syndrome
    • enteroinvasive (EIEC)
    • neonatal meningitis
    • urinary tract infection (UTI)
Presentation
 
E. coli Clinical Presentation
Condition
Presentation
Diagnostic Studies Treatment
Enterotoxigenic (ETEC) 
  • Symptoms
    • watery diarrhea that occurs after returning from a resource-limited area
  • Clinical diagnosis and no diagnostic studies are required
  • Supportive treatment
Enterohemorrhagic (EHEC)
  • Symptoms
    • bloody diarrhea with no pus
    • no fever
  • Physical exam
    • abdominal tenderness
  • Hemolytic uremic syndrome (HUS)
    • associated with the strain O157:H7 
    • triad
      • acute renal failure
      • microangiopathic hemolytic anemia
      • non-immune mediated thrombocytopenia
  • Sorbitol-MacConkey agar
    • O157:H7 ferments sorbitol slowly
  • Enzyme-linked immunosorbent assay (ELISA)
  • Polymerase chain reaction (PCR)
  • Supportive care
  • Antibiotics are generally not beneficial and its use has been associated with the development of HUS
Enteroinvasive (EIEC)
  • Symptoms
    • begins as watery diarrhea and can lead to bloody diarrhea with pus
      • the organism invades the intestinal cells to multiply intracellularly and then invade adjacent intestinal cells
  • Sereny test
  • Supportive care
Neonatal meningitis 
  • Symptoms
    • irritability
    • lethargy
    • poor tone
    • seizures
  • Physical exam
    • temperature instability
      • fever or hypothermia
    • bulging fontanelle
  • Lumbar puncture
  • Ampicillin
  • Cefotaxime or ceftazidime in ampicillin-resistant strains
Urinary tract infection (UTI)
  • Symptoms
    • dysuria
    • urinary frequency and urgency
  • Urinalysis and urine culture
  • Trimethoprim-sulfamethoxazole
  • Fosfomycin
  • Nitrofurantoin
 
 

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Questions (6)
Lab Values
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/L
Female: 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/mL
Female: 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/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative 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/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 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/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 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/min
Female: 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 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 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
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(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

6%

(12/202)

2

K capsule

9%

(19/202)

3

P fimbriae

68%

(138/202)

4

Flagella

8%

(17/202)

5

Exotoxin

6%

(13/202)

M1

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PREFERRED RESPONSE 3
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(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%

(31/280)

2

Increased pH of gastrointestinal lumen resulting in reduced mucosal absorption

0%

(1/280)

3

Increased intracellular cAMP in gastrointestinal mucosal cells, resulting in decreased absorption and increased secretion in the digestive tract

22%

(61/280)

4

Inhibition of elongation factor-2 (EF-2), resulting in decreased protein synthesis in gastrointestinal mucosal cells

17%

(47/280)

5

Inhibition of the 60S ribosomal subunit, resulting in decreased protein synthesis in gastrointestinal mucosal cells

48%

(135/280)

M1

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PREFERRED RESPONSE 5
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