What is the primary sugar source in Hektoen Enteric Agar?

Hektoen Enteric Agar is a selective differential medium primarily used for the isolation of enteric gram-negative pathogens. Its formulation includes lactose and salicin as the primary sugar sources. Lactose serves as a carbohydrate source that some organisms can ferment, producing acid and leading to a color change in the medium, which helps in differentiating non-lactose fermenters from lactose fermenters. Salicin also provides additional fermentable sugar, contributing to the medium's capacity to identify specific enteric pathogens. The color changes observed on the agar, typically resulting from acid production from fermentation, allow microbiologists to distinguish between pathogen groups, such as Salmonella and Shigella, based on their fermentation abilities.

While other options mention different combinations of sugars, they do not accurately reflect the composition of Hektoen Enteric Agar. The inclusion of salicin alongside lactose is distinctive, enhancing the medium's specificity for isolating and differentiating pathogenic bacteria present in clinical and environmental samples.