Enterobacteriaceae, Infections

Key Features

Essentials of Diagnosis

• Diarrhea by several different mechanisms due to E coli

• Hemorrhagic colitis and hemolytic-uremic syndrome

• Neonatal sepsis or meningitis

• Urinary tract infection

• Opportunistic infections

• Diagnosis confirmed by culture

General Considerations

• Enterobacteriaceae

  • Family of gram-negative bacilli that are normal flora in the gastrointestinal tract and are also found in water and soil

  • Cause gastroenteritis, urinary tract infections, neonatal sepsis and meningitis, and opportunistic infections

  • E coli is the organism in this family that most commonly causes infection in children

• Klebsiella, Morganella, Enterobacter, Serratia, Proteus, and other genera are also important, particularly in the immunocompromised person

• Klebsiella, Enterobacter, Serratia, and Morganella are normally found in the gastrointestinal tract and in soil and water

• Klebsiella may cause a bronchopneumonia with cavity formation

• Klebsiella, Enterobacter, and Serratia

  • Often hospital-acquired opportunists associated with antibiotic usage, debilitated states, and chronic respiratory conditions

  • Frequently cause urinary tract infection or sepsis

Clinical Findings

Symptoms and Signs

• E coli gastroenteritis

  • May cause diarrhea of varying types and severity

  • Enterotoxigenic E coli (ETEC)

    • Usually produce mild, self-limiting illness without significant fever or systemic toxicity, often known as traveler's diarrhea

    • May be severe in newborns and infants, and occasionally an older child will have a cholera-like syndrome

  • Enteroinvasive E coli (EIEC)

    • Cause a shigellosis-like illness, characterized by fever, systemic symptoms, blood and mucus in the stool, and leukocytosis

    • Uncommon in the United States

  • Shiga toxin-producing E coli (STEC)

    • Cause hemorrhagic colitis

    • Diarrhea initially is watery; progresses to blood streaking or grossly bloody stools

    • Fever usually is absent

    • Abdominal pain and cramping occur

    • Hemolytic-uremic syndrome occurs within a few days of diarrhea in 2–5%; characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure

• Neonatal sepsis

  • Jaundice, hepatosplenomegaly, fever, temperature lability, apneic spells, irritability, and poor feeding

  • Respiratory distress develops when pneumonia occurs; it may appear indistinguishable from respiratory distress syndrome in preterm infants

  • Meningitis is associated with sepsis in 25–40% of cases

  • Other metastatic foci of infection may be present, including pneumonia and pyelonephritis

  • Sepsis may lead to severe metabolic acidosis, shock, disseminated intravascular coagulation, and death

• Neonatal meningitis

  • High fever

  • Full fontanelles

  • Vomiting

  • Coma

  • Convulsions

  • Pareses or paralyses

  • Poor or absent Moro reflex

  • Opisthotonos

  • Hypertonia or hypotonia

  • Sepsis coexists or precedes meningitis in most cases

• Acute urinary tract infection

  • Dysuria, increased urinary frequency, and fever in the older child.

  • Nonspecific symptoms such as anorexia, vomiting, irritability, failure to thrive, and unexplained fever are seen in children younger than age 2 years

  • Young infants may have jaundice

Differential Diagnosis

• Enteropathogenic E coli (EPEC) infection may resemble salmonellosis, shigellosis, or viral gastroenteritis

Diagnosis

• Serotyping, biochemical and nucleic acid tests for enterotoxin production or invasiveness, and tests for P-fimbriae are performed in research laboratories

• STEC

  • MacConkey agar with sorbitol substituted for lactose (SMAC agar) is useful

  • Serotyping ...