Stool-Based Clues for Enteric Infections  

The presence of fecal leukocytes or pus in the stool is an important indicator of inflammatory diarrhea. In cases of community-acquired diarrhea, the detection of fecal leukocytes suggests infections caused by pathogens such as Campylobacter jejuni, Clostridioides difficile, Salmonella, or Shigella. These leukocytes can be identified using a Gram stain, though the more reliable method is through detection of lactoferrin, a marker of neutrophil activity. A lactoferrin latex agglutination titer of 1:50 or higher typically indicates inflammation. Notably, C. difficile and Entamoeba histolytica may yield positive lactoferrin results even in the absence of intact leukocytes, as they can destroy them. Thus, fecal lactoferrin testing is especially valuable for confirming inflammatory diarrhea and assessing whether further tests, such as for C. difficile toxin, are warranted.