This photograph depicts the colonial growth pattern displayed byYersinia enterocolitica bacteria growing on a Xylose Lysine Sodium Deoxycholate (XLD) agar plate.
This Gram-negative bacterium is one of the causes of yersiniosis—an infection found mainly in children that can cause fever, abdominal pain, and diarrhea, which is often bloody. Symptoms typically develop 4 - 7 days after exposure, and may last 1 - 3 weeks or longer. Xylose Lyseine (XL) agar is used when trying to culture and isolate Gram-negative enteric bacilli, i.e., rods. When XL agar is supplemented with sodium thiosulfate, ferric ammonium citrate, and sodium deoxycholate, it is then termed XLD agar, and is then an even more selective medium than XL alone. The presence of any black color indicates the deposition of hydrogen sulfide, (H2S) under alkaline conditions.
Source: CDC
