Staphylococcus aureus is associated with rapid development of gastroenteritis after consumption of food contaminated with preformed toxin, but it is not usually associated with traveler's diarrhea or persisting illness.

While Giardia lamblia could theoretically cause similar symptoms and is endemic in many parts of Africa, the stool examination would normally show cysts in this case.

Vibrio cholerae can cause severe, life-threatening watery diarrhea, and might be seen in Africa. However, again, the stool examination would usually reveal the organism.

Entamoeba histolytica can cause dysentery, which typically includes bloody diarrhea, but the stool examination in this case was negative.