Characteristics of Enterobacteriaceae Clinical Microbiology Review 176
Gram stain Non–spore-forming gram-negative rodsGrowth characteristics Facultative anaerobesColonies on sheep blood agar Most are large, dull, gray, nonhemolyticColonies on MacConkey Lactose fermenters pink
Non–lactose fermenters colorlessBiochemicals Ferment glucose
Oxidase neg
Most reduce nitrates to nitrites
Most are catalase pos