English: This photograph depicts the colonial morphology displayed by Gram-negative Shigella boydii bacteria on a blood agar plate (BAP). Four species from the genus Shigella, S. boydii, S. dysenteriae, S. flexneri, and S. sonnei, are the etiologic agents of the bacterial infection, shigellosis. Most who are infected with Shigella spp. develop diarrhea, which is often bloody, fever, and stomach cramps starting a day or two after they are exposed to the bacterium. Shigellosis usually resolves in 5 to 7 days.