Enteric Gram Negative Rods
- The Enterobacteriaceae are a loose collection of gram negative rods that can infect the GI system in humans and animals. Although they hold in common their capacity to infect the GI system, a variety of species can infect other organs and cause significant pathology. Additionally, enterobacteriaceae produce a wide variety of powerful exotoxins.
- Selective Media: All enterobacteriaceae usually grow well on MacConkey Agar which inhibits growth of gram positive bacteria
- Lactose Fermentation: Enterobacteriaceae are often sub-classified by their capacity to ferment lactose which can be visualized rapidly on EMB medium by the development of pigmented colonies when fermentation is positive. Consequently, organisms can be categorized as lactose fermenters and lactose non-fermenters
- Indole Production: Enterobacteriaceae are often sub-classified by their capacity to produce indole from tryptophan leading to categorization as indole positive and indole negative organisms.