Is Shigella indole positive or negative?

In the case of Shigella, the indole reaction is consistently negative only in specific serotypes within each traditional species of Shigella, including 7 of the 10 S. dysenteriae serotypes, 9 of the 15 S. boydii serotypes, 1 of the 6 S.

Does E coli produce indole?

In E. coli, indole is produced by tryptophanase (TnaA; EC 4.1. 99.1) that can reversibly convert tryptophan into indole, pyruvate, and ammonia (Newton and Snell, 1965) in the tryptophan pathway in E.

What bacteria can produce indole?

many pathogenic bacteria such as Bacillus alvei, pathogenic E. coli, several Shigella strains, Enterococcus faecalis, and V. cholerae, can produce indole.

Does Staphylococcus aureus produce indole?

In the Gram-positive Staphylococcus aureus, indole decreased production of the virulence factor staphyloxanthin,33 which confers enhanced oxidant and neutrophil resistance to the bacterium, and has been shown to contribute to virulence in vivo.

Is Salmonella indole negative?

Salmonellae yield negative Voges-Proskauer and positive methyl red tests and do not produce cytochrome oxide. Salmonellae are also unable to deaminate tryptophan or phenylalanine and are usually urease and indole negative. Based on the biochemical tests above, Salmonella can presumptively be identified.

Why is E coli indole positive?

This test demonstrate the ability of certain bacteria to decompose the amino acid tryptophane to indole, which accumulates in the medium. Indole production test is important in the identification of Enterobacteria. Most strains of E. coli, P.

What is indole production?

Indole is generated by reductive deamination from tryptophan via the intermediate molecule indolepyruvic acid. Tryptophanase catalyzes the deamination reaction, during which the amine (-NH2) group of the tryptophan molecule is removed. Final products of the reaction are indole, pyruvic acid, ammonium (NH4+) and energy.

What does indole negative mean?

Indole Spot Reagent Result Positive reaction: The development of a blue colour within 3 minutes. Negative reaction: The development of a pink colour within 3 minutes.

Does Salmonella produce indole?

In contrast to E. coli, Salmonella does not produce indole because it does not harbor tnaA, which encodes the enzyme responsible for tryptophan metabolism.

Is S aureus indole negative?

aureus isolates, 17 (85%) were found as positive for coagulase, catalase, methylene red, Voges-proskauer and hemolysis tests and negative for oxidase and indole tests.

How can you tell if a culture is indole negative?

If a culture is indole negative, the reagent layer will remain yellow or be slightlycloudy. Indole positive bacteria : E. coli, Vibrio cholera Indole negative bacteria : Klebsiella, Salmonella, Shigella spp. Fig. 11.5

How do you test for indole in microbiology?

Additional biochemical testing using pure cultures is recommended for complete identification. The tube test is a more sensitive method of detecting indole than the spot test. When performing a spot test, Kovacs Indole Reagent may be used as a substitute for the spot test reagent.

Is Acinetobacter baumannii Gram positive or negative?

Acinetobacter baumannii complex is a Gram-negative coccobacillus that is oxidase-negative, indole negative, catalase positive, and exhibits twitching motility in wet mount, though it is nonmotile in motility agar. It is a non-fermenter on MacConkey agar but some strains are partial lactose-fermenters.

What is an anaerobic Gram negative bacilli?

Anaerobic Gram-negative bacilli are common elements of the mucous membrane flora throughout the body; they often act as secondary pathogens. They are the most common anaerobes involved in infection and include some of the most antibiotic-resistant species.