Is Serratia a lactose fermenter?

Asked By: Isabela Behrendes | Last Updated: 12th May, 2020
Category: medical health digestive disorders
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Lactose usually is fermented rapidly by Escherichia, Klebsiella and some Enterobacter species and more slowly by Citrobacter and some Serratia species. Proteus, unlike the coliforms, deaminates phenylalanine to phenylpyruvic acid, and it does not ferment lactose. Typically, Proteus is rapidly urease positive.

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Also know, does Serratia marcescens grown on MacConkey Agar?

Good colony separation will ensure the best differentiation of lactose fermenting and non-fermenting colonies of bacteria. Streak plate of Escherichia coli and Serratia marcescens on MacConkey agar. Both microorganisms grow on this selective media because they are gram-negative non-fastidious rods.

Subsequently, question is, is Serratia marcescens indole positive? The Biochemical identification of Serratia marcescens showed that bacteria were Gram –ve, Rod, Catalase positive, oxidase negative, lactose non- fermenter, motile, Indole negative, citrate utilization positive, TSI y/y, DNase positive and Urease negative as shown in table (1) as [27].

Also question is, what bacteria can ferment lactose?

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

How do I know if I have Serratia marcescens?

marcescens to produce pyruvic acid, thus it can rely on citrate as a carbon source and test positive for citrate utilization. In identifying the organism, one may also perform a methyl red test, which determines if a microorganism performs mixed-acid fermentation. S. marcescens results in a negative test.

38 Related Question Answers Found

Is Serratia marcescens citrate positive or negative?

Biochemical Test and Identification of Serratia marcescens
Basic Characteristics Properties (Serratia marcescens)
Capsule Negative (-ve)
Catalase Positive (+ve)
Citrate Positive (+ve)
Flagella Positive (+ve)

How do you get Serratia?

The major factors that are involved in the development of the Serratia infection include contamination of the respiratory equipment and poor catheterization techniques. Most of the outbreaks have been reported from the paediatrics ward.

How is Serratia marcescens spread?

S. marcescens infections are known to be transmitted through hand-to-hand contact by medical personnel. Patients may also be infected with S. marcescens because this bacterium is known to survive and grow well on disinfectants, antiseptics, and in distilled water.

Does Serratia marcescens ferment sucrose?

Serratia marcescens was able to metabolize mannitol to produce acid, but gas was not produced. Glucose – Positive for the fermentation of glucose to produce acid, but negative for the production of gas.

Is Serratia marcescens aerobic or anaerobic?


Serratia marcescens is short and rod shaped. It is a facultative anaerobe, meaning that it can grow in either the presence of oxygen (aerobic) or in the absence of oxygen (anaerobic).

Does Serratia marcescens ferment mannitol?

Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol. Most non-pathogenic staphylococci will not ferment mannitol. The Staphylococcus aureus ferments mannitol and turns the medium yellow. The Serratia marcescens does not grow because of the high salt content.

What is the colony morphology of Serratia marcescens?

Pinpoint circular colonies which are convex with entire margins. This gram negative spirillum produces a non-diffusable red pigment. Serratia marcescens. These gram negative rods produce mucoid colonies which have entire margins and umbonate elevation.

Does Pseudomonas aeruginosa grown on MacConkey Agar?

Most Gram-negative bacteria grow well on MacConkey. MacConkey agar also contains neutral red (a pH indicator) and lactose (a disaccharide). The reagent is colorless when reduced (oxidase-negative). Pseudomonas species and Aeromonas species are gram-negative bacilli that are oxidase-positive.

How do you know if bacteria ferments lactose?

Enteric bacteria that have the ability to ferment lactose can be detected using the carbohydrate lactose, and the pH indicator neutral red.

Why is MacConkey Agar yellow?


All lactose fermenters on MacConkey agar also ferment sorbitol. The bacteria grew on mannitol salt agar fermenting mannitol, as shown by the change to yellow of the medium. The pH indicator in mannitol salt agar is phenol red, which turns to yellow when the medium is acidified by the products of fermentation.

Is E coli lactose fermenting?

E. coli are facultative anaerobic, Gram-negative bacilli that will ferment lactose to produce hydrogen sulfide. Up to 10% of isolates have historically been reported to be slow or non-lactose fermenting, though clinical differences are unknown.

Why is MacConkey Agar differential?

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. Lactose provides a source of fermentable carbohydrate, allowing for differentiation.

What bacteria can grow on MacConkey Agar?

Crystal violet and bile salts are incorporated in MacConkey agar to prevent the growth of Gram-positive bacteria and fastidious Gram-negative bacteria, such as Neisseria and Pasteurella. Gram-negative enteric bacteria can tolerate bile salts because of their bile-resistant outer membrane.

Can E coli ferment sucrose?

Sucrose is an industrially important carbon source for microbial fermentation. Sucrose utilization in Escherichia coli, however, is poorly understood, and most industrial strains cannot utilize sucrose. However, cscK is not essential for sucrose utilization.

Can salmonella ferment lactose?


Salmonellae are facultative anaerobes and are catalase positive, oxidase negative and ferment glucose, mannitol and sorbotol to produce acid or acid and gas. Whilst S. arizonae is able to ferment lactose, this is the exception rather than the rule.

What bacteria test positive for starch hydrolysis?

Bacillus subtilis is positive for starch hydrolysis (pictured below on the left). The organism shown on the right is negative for starch hydrolysis.

Which bacteria can ferment glucose?

Escherichia coli is capable of fermenting glucose as are Proteus mirabilis (far right) and Shigella dysenteriae (far left). Pseudomonas aeruginosa (center) is a nonfermenter.