eMedicine Specialties > Infectious Diseases > Bacterial Infections

Escherichia Coli Infections

Author: Tarun Madappa, MD, MPH, Attending, Department of Pulmonary and Critical Care Medicine, Elkhart General Hospital, Elkhart, Indiana
Coauthor(s): Chi Hiong U Go, MD, Assistant Professor, Department of Internal Medicine, Texas Tech University Health Science Center at Odessa
Contributor Information and Disclosures

Updated: Feb 19, 2009

Introduction

Background

Escherichia coli is one of the most frequent causes of many common bacterial infections, including cholecystitis, bacteremia, cholangitis, urinary tract infection (UTI), and traveler's diarrhea, and other clinical infections such as neonatal meningitis and pneumonia.

The genus Escherichia is named after Theodor Escherich, who isolated the type species of the genus. Escherichia organisms are gram-negative bacilli that exist singly or in pairs. E coli is facultatively anaerobic with a type of metabolism that is both fermentative and respiratory. They are either nonmotile or motile by peritrichous flagella. E coli is a major facultative inhabitant of the large intestine.

Pathophysiology

Acute bacterial meningitis

The vast majority of neonatal meningitis cases are caused by E coli and group B streptococcal infections (28.5% and 34.1% overall, respectively). Pregnant women are at a higher risk of colonization with the K1 capsular antigen strain of E coli. This strain is also commonly observed in neonatal sepsis, which carries a mortality rate of 8%; most survivors have subsequent neurologic or developmental abnormalities. Low birth weight and a positive cerebrospinal fluid (CSF) culture result portend a poor outcome. In adults, E coli meningitis is rare but may occur following neurosurgical trauma or procedures or complicating Strongyloides stercoralis hyperinfection involving the CNS.

Pneumonia

E coli respiratory tract infections are uncommon and are almost always associated with E coli UTI. No virulence factors have been implicated. E coli pneumonia may also result from microaspiration of upper airway secretions that have been previously colonized with this organism in severely ill patients; hence, it is a cause of nosocomial pneumonia. However, E coli pneumonia may also be community-acquired in patients who have underlying disease such as diabetes mellitus, alcoholism, chronic obstructive pulmonary disease, and E coli UTI. E coli pneumonia usually manifests as a bronchopneumonia of the lower lobes and may be complicated by empyema. E coli bacteremia precedes pneumonia and is usually due to another focus of E coli infection in the urinary or GI tract.

Intra-abdominal infections

E coli intra-abdominal infections often result from a perforated viscus (eg, appendix, diverticulum) or may be associated with intra-abdominal abscess, cholecystitis, and ascending cholangitis. Patients with diabetes mellitus are also at high risk of developing pylephlebitis of the portal vein and liver abscesses. Escherichia coli liver abscess is seen in the image below.

Intra-abdominal abscesses are usually polymicrobial and can be caused by spontaneous or traumatic GI tract perforation or after anastomotic disruption with spillage of colon contents and subsequent peritonitis. They can be observed in the postoperative period after anastomotic disruption. Abscesses are often polymicrobial, and E coli is one of the more common gram-negative bacilli observed together with anaerobes.

Cholecystitis and cholangitis result from obstruction of the biliary system from biliary stone or sludge, leading to stagnation and bacterial growth from the papilla or portal circulation. When bile flow is obstructed, colonic organisms, including E coli, colonize the jejunum and duodenum. Interestingly, partial obstruction is more likely than complete obstruction to result in infection, bacteremia, bactibilia, and gallstones.

Enteric infections

As a cause of enteric infections, 6 different mechanisms of action of 6 different varieties of E coli have been reported. Enterotoxigenic E coli (ETEC) is a cause of traveler's diarrhea. Enteropathogenic E coli (EPEC) is a cause of childhood diarrhea. Enteroinvasive E coli (EIEC) causes a Shigella -like dysentery. Enterohemorrhagic E coli (EHEC) causes hemorrhagic colitis or hemolytic-uremic syndrome (HUS). Enteroaggregative E coli (EAggEC) is primarily associated with persistent diarrhea in children in developing countries, and enteroadherent E coli (EAEC) is a cause of childhood diarrhea and traveler's diarrhea in Mexico and North Africa. ETEC, EPEC, EAggEC, and EAEC colonize the small bowel, and EIEC and EHEC preferentially colonize the large bowel prior to causing diarrhea.

Urinary tract infections

The urinary tract is the most common site of E coli infection, and more than 90% of all uncomplicated UTIs are caused by E coli infection. The recurrence rate after a first E coli infection is 44% over 12 months. E coli UTIs are caused by uropathogenic strains of E coli. E coli causes a wide range of UTIs, including uncomplicated urethritis/cystitis, symptomatic cystitis, pyelonephritis, acute prostatitis, prostatic abscess, and urosepsis. Uncomplicated cystitis occurs primarily in females who are sexually active and are colonized by a uropathogenic strain of E coli. Subsequently, the periurethral region is colonized from contamination of the colon, and the organism reaches the bladder during sexual intercourse.

Uropathogenic strains of E coli have an adherence factor called P fimbriae, or pili, which binds to the P blood group antigen. These P fimbriae mediate the attachment of E coli to uroepithelial cells. Thus, patients with intestinal carriage of E coli that contains P fimbriae are at greater risk of developing UTI than the general population. Complicated UTI and pyelonephritis are observed in elderly patients with structural abnormalities or obstruction such as prostatic hypertrophy or neurogenic bladders or in patients with urinary catheters. Escherichia coli right pyelonephritis is seen in the image below.

E coli bacteremia is usually associated with UTIs, especially in cases of urinary tract obstruction of any cause. The systemic reaction to endotoxin (cytokines) or lipopolysaccharides can lead to disseminated intravascular coagulation and death. E coli is a leading cause of nosocomial bacteremia from a GI or genitourinary source.

Other infections

Other miscellaneous E coli infections include septic arthritis, endophthalmitis, suppurative thyroiditis, sinusitis, osteomyelitis, endocarditis, and skin and soft-tissue infections (especially in patients with diabetes).

Frequency

United States

E coli is the leading cause of both community-acquired and nosocomial UTI. Up to 50% of females eventually experience at least one episode of UTI. E coli causes 12-50% of nosocomial infections and 4% of cases of diarrheal disease.

International

In tropical countries, EPEC is an important cause of childhood diarrhea. ETEC causes 11-15% of cases of traveler's diarrhea in persons visiting developing countries and 30-45% of cases of traveler's diarrhea among those visiting Mexico. EAggEC causes 30% of cases of traveler's diarrhea.

Mortality/Morbidity

• E coli neonatal meningitis carries a mortality rate of 8%, and most survivors have neurological or developmental abnormalities.
• The mortality and morbidity associated with E coli bacteremia is the same as that for other aerobic gram-negative bacilli.

Race

• E coli infections have no recognized racial predilection.

Sex

• E coli UTI is more common in females than in males because of differences in anatomic structure and changes during sexual maturation, pregnancy, and childbirth.
• Men older than 45 years with prostatic hypertrophy are at an increased risk of UTI due to related bladder stasis.
• Among neonates, E coli UTI is more common in boys than in girls, but circumcision reduces the risk.

Age

• E coli is an important cause of meningitis in neonates.
• In adults, E coli meningitis is due only to open CNS trauma or neurosurgical procedures.

Clinical

History

• Acute bacterial meningitis
  • Newborns with E coli meningitis present with fever and failure to thrive or abnormal neurologic signs. Other findings in neonates include jaundice, decreased feeding, periods of apnea, and listlessness.
  • Patients younger than 1 month present with irritability, lethargy, vomiting, lack of appetite, and seizures.
  • Those older than 4 months have neck rigidity, tense fontanels, and fever.
  • Older children and adults with acute E coli meningitis develop headache, vomiting, confusion, lethargy, seizures, and fever.
  • In rare cases, persons with a history of open CNS trauma or multiple neurological procedures develop S stercoralis hyperinfection.
  • Because patients who have undergone neurosurgery frequently have headaches, nuchal rigidity, and a decreased level of consciousness secondary to the surgery, signs may be difficult to interpret.
  • The differential diagnoses of acute E coli meningitis include sepsis, seizure disorder, brain abscess, ruptured aneurysm, and neonatal tetanus.
• Pneumonia
  • Patients with E coli pneumonia usually present with fever, shortness of breath, increased respiratory rate, increased respiratory secretions, and crackles upon auscultation.
  • Findings include bronchopneumonia on chest radiography, commonly in the lower lobes. Many patients are intubated and have fever, an increased respiratory rate, and increased respiratory secretions.
  • The differential diagnoses of E coli pneumonia include congestive heart failure and pulmonary embolism. Other pneumonias caused by gram-negative bacilli are difficult to distinguish clinically.
• Intra-abdominal infections
  • Patients with E coli cholecystitis or cholangitis develop right upper quadrant (RUQ) pain, fever, and jaundice. In severe cases, hypotension and confusion also develop. Cholecystitis manifests with fever (>102°F). Cholangitis manifests with fever (>102°F), shaking chills, and RUQ pain and can be complicated by hepatic abscess. Amebic liver abscess, Echinococcus cyst, and Klebsiella and Enterococcus infections are difficult to distinguish clinically. Anaerobes are observed in patients with diabetes and acute acalculous cholecystitis.
  • Patients with E coli intra-abdominal abscesses may have low-grade fever, but the spectrum of clinical presentations ranges from nonspecific abdominal examination findings to frank septic shock. Peritonitis manifests as localized pain with rebound and fever. The presentation ranges from low-grade fever with abdominal tenderness, weakness, malaise, and anorexia to hypoxemia and hypotension. The infection is usually polymicrobial with E coli and other gram-negative bacilli and anaerobes. The differential diagnoses include retroperitoneal hematoma and septic thrombophlebitis.
• Enteric infections
  • Patients with E coli traveler's diarrhea (ie, watery nonbloody diarrhea; caused by enterotoxigenic E coli [ETEC] or enteroaggregative E coli [EAggEC]) may appear to be dehydrated. Traveler's diarrhea is observed in young healthy travelers to tropical countries and is watery diarrhea without polymorphonuclear (PMN) leukocytes. The differential diagnoses of E coli traveler's diarrhea include rotavirus infection, Norwalk virus infection, Salmonella infection, and Campylobacter diarrhea.
  • Patients with E coli childhood diarrhea (ie, watery nonbloody diarrhea; caused by EAggEC, enteroadherent E coli [EAEC], or enteropathogenic E coli [EPEC]) may also appear to be dehydrated. These infections produce a noninflammatory watery diarrhea observed especially in children. The differential diagnoses of E coli childhood diarrhea include Vibrio cholerae infection and Rotavirus infection.
  • Patients with E coli dysentery (caused by enteroinvasive E coli [EIEC] or enterohemorrhagic E coli [EHEC]) have fever, bloody diarrhea, and dehydration. Intestinal mucosa produces a significant inflammatory response. Clinically, patients with E coli dysentery present with fever and have blood and PMN leukocytes in their stool. The differential diagnoses of E coli dysentery include shigellosis and amebic dysentery.
  • Patients with E coli HUS (caused by EHEC) have fever, bloody diarrhea, dehydration, hemolysis, thrombocytopenia, and uremia requiring dialysis. Symptoms of E coli HUS range from asymptomatic to nonbloody diarrhea to bloody diarrhea, renal failure, microangiopathic hemolytic anemia, thrombocytopenia, and CNS manifestations. The differential diagnoses of E coli HUS include Shigella infections, Clostridium difficile enterocolitis, ulcerative colitis/Crohn disease, ischemic colitis, diverticulosis, and appendicitis.
• Urinary tract infections
  • Acute E coli urethral syndrome manifests as low-grade fever and dysuria. Patients present with dysuria, increased frequency, and urgency, and they have colony counts. S saprophyticus infection is observed in 5-10% of cases, especially in sexually active women, associated with alkaline pH and microscopic hematuria. Less commonly, patients have Proteus mirabilis, Klebsiella, or Enterococcus infections. Approximately 15% of cases are culture-negative; these are due to Chlamydia trachomatis, Ureaplasma urealyticum, or Mycoplasma hominis infection.
  • Patients with symptomatic E coli UTI have dysuria and may have low-grade fever.
  • Patients with E coli pyelonephritis or complicated UTI present with localized flank or low back pain, high fever (>102°F), and urinary frequency and urgency. Findings also include rigors, sweating, headache, nausea, and vomiting. It can be complicated by necrotizing intrarenal or perinephric abscess, which manifests as a bulging flank mass or pyelonephritis that does not respond to antibiotics. Patients with diabetes or urinary tract obstruction can also develop bacteremia and septicemia. The differential diagnoses include psoas abscess appendicitis, ectopic pregnancy, and ruptured ovarian cyst.
  • Patients with E coli acute prostatitis or prostatic abscess have chills, sudden fever (>102°F), and perineal and back pain with a tender, swollen, indurated, and hot prostate. Acute prostatitis also manifests as dysuria, urgency, and frequent voiding. Some patients may have myalgia, urinary retention, malaise, and arthralgia. If the patient does not respond to antibiotics, consider prostatic abscess and confirm it with imaging studies. Treatment consists of open surgical or percutaneous drainage.
  • Patients with E coli prostatic abscess, which manifests as a complication of acute prostatitis, have a high fever despite adequate antimicrobial therapy and fluctuance of the prostate upon rectal examination.
  • The differential diagnoses of E coli acute prostatitis or prostatic abscess can include chronic bacterial prostatitis, which is usually asymptomatic; some patients may have frequency, dysuria, and nocturia with pain and discomfort in the perineal, suprapubic, penile, scrotal, or groin region. Also included are infected prostatic calculi, which can cause recurrent UTIs and should be surgically removed. Finally, nonbacterial prostatitis is also a differential diagnostic possibility and manifests as perineal, suprapubic scrotal, low back, or urethral tip pain.
  • Additionally, patients with E coli renal abscess present with fever, pleuritic chest pain secondary to diaphragmatic irritation, and flank pain, with or without a palpable abdominal mass.

Physical

• Acute bacterial meningitis
  • E coli is a common cause of meningitis in newborns and is associated most frequently with prematurity.
  • E coli meningitis can be acquired during birth or can develop secondarily after infection in another body site, such as in cases of omphalitis, upper respiratory tract infection, or infected circumcision wound.
  • In adults, E coli meningitis is not uncommon in those who have undergone multiple neurological procedures or who have had open CNS trauma.
  • Immunosuppressed patients receiving corticosteroid therapy and those with S stercoralis hyperinfection are also at risk for E coli meningitis.
• Pneumonia
  • E coli pneumonia is often preceded by colonization of the upper respiratory tract (eg, nasopharynx).
  • Community-acquired E coli pneumonia has been reported in rare cases.
• Intra-abdominal infections
  • Along with Enterococcus faecalis and Klebsiella species, E coli is one of the most common organisms associated with cholecystitis/cholangitis and intra-abdominal abscesses, as part of polymicrobial flora including anaerobes.
  • E coli cholecystitis/cholangitis manifests as the classic Charcot triad of fever, pain, and jaundice in 70% of cases. Fever is the most common finding (95%). RUQ pain and jaundice may be absent if no obstruction is present.
  • In late stages, hypotension, confusion, and renal failure are observed.
  • Liver abscess can develop as a complication of a E coli biliary tract infection.
  • The findings of E coli intra-abdominal abscesses are less conspicuous than those of diffuse peritonitis. The patient may have only low-grade fever, generalized malaise, and anorexia. In the postoperative patient who may have a distended and tender abdomen, clinical diagnosis of E coli intra-abdominal abscess may be difficult.
• Enteric infections
  • Traveler's diarrhea usually occurs in persons from industrialized countries who visit tropical or subtropical regions and develop abdominal cramps and frequent explosive bowel movements 1-2 days after exposure to contaminated food or water.
  • E coli enterotoxin acts on the GI mucosa, leading to an outpouring of copious fluid from the small bowel.
  • The symptoms usually last 3-4 days and are self-limited.
  • Large fluid loss may result in dehydration.
  • EIEC infections are rare and manifest as bloody diarrheal stool containing PMN leukocytes. Patients usually have fever, abdominal cramping, and tenesmus lasting 5-7 days.
  • Childhood diarrhea is due to EPEC strains and usually occurs in underdeveloped countries or nursery outbreaks. The volume of diarrhea is less than that with ETEC strains, and no inflammatory cells are found in the diarrheal fluid. The child may experience fever, and diarrhea lasts longer than 2 weeks in some cases.
  • Infection with EHEC strains of the serotype 0157:H7 begin as watery diarrhea followed by grossly bloody stool without inflammatory PMN cells and results in HUS in 10% of cases, characterized by hemolysis, thrombocytopenia, uremia (possibly requiring dialysis), and death in some cases.
  • EAggEC and EAEC cause clinical illnesses that are not yet well characterized and are associated with persistent diarrhea in children.
• Urinary tract infections
  • E coli is the leading cause of community-acquired and nosocomial UTI.
  • Females are predisposed to UTI because of their anatomy and changes during sexual maturation, pregnancy, and childbirth.
  • Young boys with posterior urethral valves are also predisposed to UTIs, as are elderly men with prostatic hypertrophy.
  • Other risk factors include catheterization or mechanical manipulation, obstruction, or diabetes.
  • Patients with E coli UTI present with a wide spectrum of symptoms, ranging from asymptomatic cystitis to pyelonephritis/perinephric abscess.
  • Urethral syndrome is a term used to describe symptoms of dysuria with colony counts less than 100,000 colony-forming units/mL of urine.
  • Uncomplicated E coli acute cystitis may manifest as low-grade fever, dysuria, and increased urinary frequency.
  • Acute pyelonephritis manifests as high-grade fever (>102°F) and costovertebral tenderness.
  • Acute prostatitis manifests as a sudden onset of fever and chills with perineal and low back pain.
  • Perinephric abscess may manifest as a bulging flank mass. GI symptoms such as nausea and vomiting are more likely in elderly persons. Patients with bacteremia secondary to an obstructed urinary catheter may present with decreased urine output.
  • Prostatic abscess can occur as a complication of acute prostatitis, notably in patients with diabetes mellitus, and should be considered in patients with acute prostatitis or UTI that is not improving with adequate antimicrobial therapy.
• Other infections
  • E coli bacteremia can lead to septic shock, manifesting as hypotension and fever (in some cases, with hypothermia rather than fever). It may be complicated by uremia, hepatic failure, acute respiratory distress syndrome, stupor or coma, and death. Non–life-threatening E coli bacteremia may manifest as a sudden onset of fever and chills, tachycardia, tachypnea, and mental confusion. In cases of E coli UTI with urinary tract obstruction, bacteremia or septicemia may ensue.
  • Several cases of E coli endophthalmitis have been reported in patients with diabetes who have UTI or pyelonephritis.¹

Causes

Differential Diagnoses of E coli Infection

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*Indole
†Glucose fermentation
‡Lactose fermentation
§Sucrose fermentation
||Maltose fermentation
¶Esculin hydrolysis
#Hydrogen sulfite on TSI
**Ornithine decarboxylase
††Lysine decarboxylase
‡‡Oxidative

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