History
Symptoms of Escherichia coli infection may be subtle and nonspecific in infants and young children. Even in older children, symptoms may resemble those of common viral illnesses, leading to missed or delayed diagnosis. A thorough history, including any history of a prior urinary tract infection (UTI), and thoughtful analysis of the information provided is essential. Pertinent details can guide further diagnostic investigation.
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Neonates and infants with UTIs, bacteremia, or sepsis may present with the following symptoms:
Fever
Hypothermia
Jaundice
Respiratory distress
Apnea
Poor feeding
Vomiting
Diarrhea
Fussiness
Irritability
Lethargy
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Particularly in young infants, meningitis may be present without overt signs attributable to the CNS.
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Infants with histories of prematurity, low birth weight, difficult or prolonged labor, intrapartum maternal fever, or antibiotic administration may have higher risk for serious bacterial infection.
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Older children with bacterial enteritis or UTI may have fever, vomiting, abdominal pain, or diarrhea with or without blood or mucus. In young children with UTI, urinary symptoms (eg, frequency, urgency, dysuria) vary and are often not present; daytime urinary incontinence or new onset of bedwetting may be more suggestive of UTI. Always consider UTI in the differential diagnosis of fever without apparent source. Constipation is not a symptom of UTI but is instead associated with incomplete voiding and urinary stasis. Constipation may predispose a child to UTI and may complicate treatment. In children with recurrent UTI, aggressive treatment of constipation may reduce subsequent UTIs.
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In cases of diarrheal illness, determine stool frequency (ie, number of stools or diaper changes in past 12-24 h), appearance (eg, loose, watery), and presence of blood or mucus. Inquire about a history of exposure to a child with bloody diarrhea or a known local outbreak of hemorrhagic colitis. Specific quantification of stool number and character is important because parents often describe a single loose stool as diarrhea. Also, remember various substances (eg, Kool-Aid, other foods containing red dyes) may tint stools red. Guaiac testing confirms the presence of blood.
Enterotoxigenic E coli (ETEC) diarrhea is watery without blood, mucous, or fecal leukocytes and ranges from mild to severe.
Enterohemorrhagic E coli (EHEC) disease ranges from mild watery diarrhea to severe hemorrhagic colitis, often accompanied by abdominal cramping and vomiting. Diarrhea becomes bloody in 1-2 days in most patients but is usually not associated with fecal leukocytes. Fever is present in about a third of cases.
Enteroinvasive E coli (EIEC) causes watery diarrhea, dysentery, fever, vomiting, painful abdominal cramps, and tenesmus. Stools often contain blood and leukocytes.
Enteropathogenic E coli (EPEC) and Enteroaggregative E coli (EAEC) cause watery diarrhea and dysentery. The resultant acute watery diarrhea may cause dehydration or become chronic and lead to failure to thrive.
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Evaluate the ability of patients who are vomiting or at risk of dehydration to take and tolerate fluids orally. Assess frequency of urination (ie, last void or wet diaper, number of voids in past 8-24 h). Vomiting may occur with ETEC.
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If the patient is experiencing abdominal pain, assess pain for the following features:
Severity and character (eg, sharp, dull, cramplike)
Location
Radiation
Duration
Nature (eg, constant, intermittent)
Aggravating and relieving factors
Physical
The child's overall appearance and behaviors (eg, alert, playful, fussy but consolable, lethargic, irritable, toxic) are valuable because these factors may direct diagnostic and therapeutic choices and influence decisions regarding outpatient management or admission.
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Among the aspects of general appearance to consider are alertness, activity, tone, age-appropriate interaction, and whether the child can be consoled. Observe, for example, whether the child explores the room, clings to the parent, or lies still on the table.
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Evidence of dehydration may be present in patients with bacterial enteritis. Ill appearance, tachycardia, and dry mucous membranes suggest significant volume depletion. Fontanelle and/or eyes may be sunken, but skin turgor change is a late finding and is often not present. If previous weight is known, documented weight loss can help approximate the degree of dehydration.
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Assess peripheral perfusion by observing for extremity mottling, coolness, or delayed capillary refill. Evaluate the quality of central and peripheral pulses.
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Patients may have abdominal pain from either bacterial enteritis or a UTI. Flank pain or costovertebral angle tenderness suggests pyelonephritis. Abdominal pain sometimes is sufficiently severe to mimic appendicitis. Examine the abdomen for distention, increased or decreased bowel sounds, diffuse or localized tenderness, and signs of acute abdomen (eg, rigidity, rebound, guarding).
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Examine anogenital region in children who have urinary or abdominal symptoms or a history of bloody stools. Examination may reveal vulvovaginitis, perianal excoriation, or anal fissures.
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Complete examination should include adequate visualization of all skin surfaces. Subtle findings, such as petechiae or bruising, may be overlooked if the examination is rushed or limited.
Causes
See the list below:
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ETEC infection: ETEC is the primary cause of traveler's diarrhea and the major cause of infantile diarrhea in less affluent countries. ETEC is widespread in areas with poor sanitation and is a ubiquitous contaminant of food and water sources. ETEC's incubation period is 1-3 days. Infection usually is self-limited and persists less than 5 days. [9, 10]
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EHEC infection
EHEC is an emerging cause of food-borne illness, particularly in the northern United States and Canada. [18]
Recent highly publicized outbreaks of hemolytic-uremic syndrome (HUS) that caused fatalities have focused public attention on food safety.
Cattle are the primary reservoir of the EHEC strains that produce diarrhea in humans. Because EHEC is a common inhabitant of the bovine intestine, it may contaminate beef products or foods that contact bovine-exposed soil.
Sources identified in outbreaks include ground beef, apple juice, and alfalfa sprouts, [11, 12] as well as fecally contaminated drinking water and swimming pools.
Most outbreaks have been linked to 0157:H7 strains, although other serotypes have been implicated. [19, 13, 20, 21]
Of particular concern in pediatric populations, E coli 0157:H7 requires a relatively small inoculum for infection and spreads easily from child to child by the fecal-oral route. The incubation period of EHEC is 1-5 days, with illness duration typically 4-10 days.
HUS develops in 10-15% of pediatric patients. Chronic renal failure develops in as many as 10% of patients with HUS, and HUS kills 3-5% of affected patients. [22]
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EPEC infection: EPEC is most often found in developing countries, primarily affecting infants and children. EPEC has been associated with outbreaks of diarrhea in newborn nurseries in the United States, primarily in the 1950s and 1960s.
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EAEC infection: EAEC is similar in geographic distribution, mechanism, and effect to EPEC. The CDC's Traveler's Health Web site provides additional information to physicians and the public.
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UTIs
E coli is the most commonly isolated pathogen in pediatric UTIs. Virulence factors, such as pili, contribute to the pathogenicity of UTIs.
HUS has been reported following UTIs with enterohemorrhagic serotypes of E coli in patients who did not have a diarrheal illness.
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Neonatal infections
E coli infection in neonates may manifest as bacteremia, sepsis, UTI, or meningitis; it rarely manifests as pneumonia, soft tissue, or bone infection.
E coli strains with the K1 capsular polysaccharide antigen cause approximately 40% of the septicemia cases and 80% of the meningitis cases attributed to E coli.
The usual source of E coli in neonatal infections is the maternal GI tract. The organism also may be acquired nosocomially, particularly in infants who are premature or who require mechanical ventilation.
Predisposing factors include maternal perinatal infection, low birth weight, prolonged rupture of membranes, and traumatic delivery. Fetal hypoxia and skin or mucosal defects also increase the risk of gram-negative infection. Infants with galactosemia appear to have an increased susceptibility to serious bacterial infection, particularly E coli sepsis.
In intensive care nurseries, mechanical ventilation, invasive procedures, indwelling catheters, and the frequent use of antimicrobial agents allow selection and proliferation of resistant strains of pathogenic gram-negative bacilli.
