Bacterial Diarrhea

Excerpt

The World Health Organization (WHO) defines diarrhea as loose or liquid stools occurring 3 or more times per day or more frequently than usual for an individual. Dysentery is the invasive form of diarrhea, with visible blood or mucous often accompanied by fever and abdominal pain. Viruses are the main culprits of acute infectious diarrhea in adults and children.

However, identifying clinical features consistent with bacterial infection is critical to prevent morbidity and mortality. A strategic assessment is essential to determine which patients require stool studies, empiric antibiotic therapy, and intravenous fluid (IVF) resuscitation. Distinguishing between viral and bacterial causes of gastroenteritis can be challenging as their symptoms may overlap. However, findings like fever, bloody or mucoid stools, or a history of recent antibiotic use or hospitalization help alert clinicians to the possibility of a bacterial etiology.

Salmonella, Shigella, Campylobacter jejuni, Yersinia enterocolitica, Clostroidies difficile, and Escherichia coli are common bacterial causes of acute diarrhea leading to complications like sepsis, seizures, hemolytic uremic syndrome (HUS), Guillain-Barré syndrome (GBS), and death. Accurately identifying bacterial gastroenteritis and deciding when to investigate less common causes like sexually transmitted infections are essential in avoiding unnecessary testing and antibiotic use and preventing potential complications. While the goal of antimicrobial treatment is to shorten the duration of symptoms and prevent complications, many causes are self-limited and do not require treatment. Antimicrobials may cause more harm in some cases, as in the case of Shiga toxin-producing Escherichia coli (STEC) infection, where antibiotics increase the risk of developing HUS.

Laboratory testing is not usually necessary. However, if available, clinicians should perform stool studies during an epidemic or when patients have severe illness, symptoms persisting for more than 7 days, or risk factors such as pregnancy, older age, or immunocompromised status. Stool studies are also indicated when blood or mucus is present along with fever. Identifying the bacterial pathogen helps inform clinicians about potential complications and treatment decisions. A routine stool culture is the ideal test for identifying Salmonella, Campylobacter, and Shigella. E. coli requires a different medium, but antigen testing or polymerase chain reaction (PCR) of stool are alternative diagnostic options.

Oral rehydration is the mainstay of therapy, with IVF reserved for individuals with severe hypovolemia. Clinicians reserve empiric antibiotic treatment for patients with severe illness, a high likelihood of Clostridioides difficile, high-risk host features, and bloody mucoid stools. A clear understanding of the guidelines regarding empiric antibiotic use will decrease antibiotic misuse and prevent antibiotic resistance.