What is the clinical significance of Enteroaggregative Escherichia coli (E. coli) in a Gastrointestinal (GI) stool culture panel?

From the Guidelines

Enteroaggregative E. coli (EAEC) found in a GI stool culture panel is clinically relevant and requires careful interpretation, as it can cause persistent diarrhea in both children and adults, particularly in immunocompromised patients or those with severe symptoms 1. When EAEC is identified in a symptomatic patient, treatment with fluoroquinolones like ciprofloxacin (500 mg twice daily for 3-5 days) or azithromycin (500 mg once daily for 3 days) is recommended, along with hydration and electrolyte replacement as essential components of management. The presence of EAEC in an asymptomatic individual may represent colonization rather than active infection, so clinical correlation is necessary when interpreting results 1. Some key points to consider when interpreting EAEC results include:

• Clinical correlation is necessary to determine the significance of EAEC in a patient's symptoms
• Antibiotic resistance is increasingly common in EAEC strains, so susceptibility testing can guide optimal therapy in cases that don't respond to initial treatment
• EAEC can cause persistent diarrhea through its unique ability to adhere to intestinal mucosa in a "stacked-brick" pattern and produce enterotoxins that damage the intestinal lining
• Immunocompromised patients or those with severe symptoms require prompt and effective treatment to prevent complications and reduce morbidity and mortality 1. It is essential to consider the patient's clinical presentation, medical history, and other laboratory results when interpreting EAEC findings to provide appropriate management and prevent unnecessary antibiotic use 1.

From the Research

Enteroaggregative E. coli (EAEC) Characteristics

• EAEC is a heterogeneous category of emerging enteric pathogens associated with cases of acute or persistent diarrhea worldwide in children and adults 2
• EAEC infection is an important cause of diarrhea in outbreak and non-outbreak settings in developing and developed countries 2, 3
• EAEC is defined by its characteristic aggregative adherence (AA) to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa with a "stacked-brick" adherence phenotype 2, 4

Pathogenesis and Clinical Relevance

• EAEC pathogenesis involves adherence to the intestinal mucosa, increased production and deposition of a mucus biofilm, and mucosal toxicity due to inflammation and cytokine release 3
• EAEC infection can cause intestinal inflammation, growth impairment, and interleukin-8 release from intestinal epithelial cells 5
• EAEC is a significant cause of protracted diarrhea in children and may cause diarrhea in adults 4
• EAEC infection can be treated with antimicrobial agents such as ciprofloxacin, which can shorten the course of diarrhea 3, 6

Diagnosis and Detection

• EAEC is identified by cell adhesion tests or DNA-based tests involving gene probes or polymerase chain reaction (PCR) for detecting the genes encoding cell adhesion 4
• The HEp-2 cell adherent assay allows identification of EAEC's characteristic aggregative or "stacked brick" adherence pattern 3
• Serotyping alone cannot identify strains of E. coli expressing an EAEC phenotype 4

Relevance in GI Stool Culture Panel

• The presence of EAEC in a GI stool culture panel may indicate an emerging enteric pathogen that can cause diarrhea, intestinal inflammation, and growth impairment 2, 5
• The detection of EAEC in a GI stool culture panel can guide antimicrobial treatment and management of diarrhea 3, 6