Which medium can best differentiate Kingella kingae from Eikenella corrodens?

Sheep blood agar is the medium that can best differentiate Kingella kingae from Eikenella corrodens due to its ability to support the growth of both organisms while revealing important colony characteristics.

Kingella kingae typically shows small, non-hemolytic, or weakly beta-hemolytic colonies on sheep blood agar and can sometimes display a characteristic “twitching” motility. Meanwhile, Eikenella corrodens generally produces colonies that may appear more moist or may cause a slight greenish discoloration around them due to their ability to decompose red blood cells differently. The differences in colony morphology and hemolytic patterns on sheep blood agar make it easier to distinguish between these two organisms, which may not be as effectively differentiated on other types of media.

Other media, such as chocolate agar, are more supportive for the growth of fastidious organisms without providing clear differentiation based on colony characteristics. MacConkey agar is selective for gram-negative bacteria and would not provide the necessary conditions to differentiate between these two types of bacteria, as both are gram-negative but can grow poorly on this medium. XLD agar, primarily aimed at differentiating enteric gram-negative bacteria, is not suitable for isolating and distinguishing these species due to