B

Stool leukocytes and mucus indicate an invasive, dysentery-type colitis. Entamoeba histolytica causes amoebic dysentery with mucus-laden, sometimes bloody, thin stools and abdominal pain, whereas Giardia causes non-inflammatory, greasy diarrhea; Staphylococcus aureus and Clostridium perfringens produce toxin-mediated watery diarrhea without fecal leukocytes. [Espinosa-Cantellano, 2000, PMID 10756002; Salles, 2007, PMID 17914922]