What gram-negative rods do not grow on MacConkey agar?

What gram-negative rods do not grow on MacConkey agar?

Long, thin, slowly growing, oxidase-positive, catalase-positive gram-negative rods that do not grow on MacConkey agar should suggest DF-2. Although testing of antimicrobial susceptibility is problematic, DF-2 has been found to be resistant to aminoglycosides.

What bacteria does not grow on MacConkey?

Altogether, MacConkey agar only grows gram-negative bacteria, and those bacteria will appear differently based on their lactose fermenting ability as well as the rate of fermentation and the presence of a capsule or not.

Why there is no growth on MacConkey agar?

MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms. Micrococcus luteus does not grow in the presence of bile salts and crystal violet.

Why does Pasteurella not grow on MacConkey?

They do not grow on MacConkey agar. They are usually oxidase positive and also positive for nitrate reduction, phosphatase, β-galactosidase and acid production from D – Glucose fermentation. They are negative for catalase, indole, urease, Voges-Proskauer and methyl red tests.

What are non lactose fermenting Gram-negative rods?

Non lactose-fermenting (Lactose negative): ● Oxidase (-): Acinetobacter spp, Burkholderia spp, E. coli, Proteus spp, Salmonella spp, Shigella spp, Serratia spp*, Stenotrophomonas maltophilia ● Oxidase (+): P.

Is Pseudomonas Gram-negative?

Pseudomonas species are Gram-negative, aerobic bacilli measuring 0.5 to 0.8, μm by 1.5 to 3.0 μm. Motility is by a single polar flagellum. Species are distinguished by biochemical and DNA hybridization tests.

What Gram negative rods are lactose fermenting?

E. coli are facultative anaerobic, Gram-negative bacilli that will ferment lactose to produce hydrogen sulfide.

How does E coli grow on MacConkey agar?

MacConkey agar not only selects for Gram-negative organisms by inhibiting Gram-positive organisms and yeast but also differentiates the Gram-negative organisms by lactose fermentation. Escherichia coli and other lactose ferments will produce yellow or orange colonies.

What Gram-negative rods are lactose fermenting?

Does yeast grow on MacConkey agar?

Selective and Differential Media MacConkey agar not only selects for Gram-negative organisms by inhibiting Gram-positive organisms and yeast but also differentiates the Gram-negative organisms by lactose fermentation.

Does Brucella grow on MacConkey?

Brucella grows on both BAP and CHOC but not on MAC. Colonies are pinpoint at 24 h and are easily visible as white, non-hemolytic colonies at 48 h.

Is Pasteurella Gram-negative?

Pasteurella are small gram-negative coccobacilli that are primarily commensals or pathogens of animals. However, these organisms can cause a variety of infections in humans, usually as a result of cat scratches, or cat or dog bites or licks.