Whether atypical enteropathogenic E. coli (aEPEC) causes disease in adults is yet not clear. It is usual to trace aEPEC in symptomatic and asymptomatic individuals. AEPEC, in contrast to typical EPEC, lacks bundle forming pili, altering its pathogenicity. 

A recent study defined for the first time the clinical manifestations of sporadic aEPEC infection in U.S. children and adults and determined if EPEC load correlates with the disease.

This retrospective case-control study included 380 in/outpatients of all ages. It determined the EPEC load in stools by quantitative PCR.

The findings were as follows-

• The study found more cases of diarrhea, vomiting, abdominal pain, and fever in EPEC-positive cases than in EPEC-negative controls.
• Common presentations of aEPEC infection were acute, mild diarrhea lasting for 6-13 days. However, some had severe diarrhea with 10-40 B.M.s/day or persistent/chronic diarrhea.
• Fever, vomiting, and abnormal serum sodium levels were more common in children, while abdominal pain and a longer duration of diarrhea were more common in adults.
• 24% of Symptomatic aEPEC infections had leukocytosis.
• EPEC load >0.1% showed an association with symptomatic infection. However, loads varied greatly.
• Co-infecting pathogens showed no effects on diarrhea severity or EPEC load.
• Longitudinal data showed that some are colonized for months to years or repeatedly infected.

Thus, aEPEC causes a spectrum of symptoms in adults ranging from asymptomatic carriage to severe diarrhea. Higher EPEC loads lead to the occurrence of symptoms. However, it does not predict disease or severity. 

Future studies explaining bacterial and host factors contributing to aEPEC pathogenicity are warranted to improve diagnostic tools and clinical care.

Source: Kralicek SE, Sitaraman LM, Kuprys PV, et al. Gastroenterology. 2022 Aug 7;S0016-5085(22)00893-9. doi: 10.1053/j.gastro.2022.07.064.