|Description:||This photograph depicts the colonies of Proteus mirabilis bacteria grown on a xylose-lysine-deoxycholate (XLD) agar plate.|
P. mirabilis is a Gram-negative bacterium from the family Enterobacteriaceae, and is part of the normal flora of human gastrointestinal tract. However, if this bacterium enters the urinary tract, wounds or lungs it can become pathogenic. 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.