Culture Media For Bacteriology

MacConkey agar is a selective and differential medium used in microbiology to isolate and differentiate gram-negative bacteria, particularly those of the Enterobacteriaceae family. The agar contains bile salts, which inhibit the growth of gram-positive bacteria, and peptones, which provide nutrients for the growth of gram-negative bacteria. Additionally, MacConkey agar contains lactose as a carbohydrate source. The ability of bacteria to ferment lactose is indicated by a color change in the agar, allowing for the differentiation of lactose-fermenting (pink/red colonies) and non-lactose fermenting (colorless colonies) bacteria. Therefore, the statement that MacConkey agar contains bile salts, peptones, and lactose is true.

Cystine, lactose electrolyte deficient agar

Stops proteus swarming due to absence of electrolytes.

Can be used to indicate lactose fermentation if bromothylmol blue is added.

Often used in the culture of urine.

Thiosulphate, citrate, bile salt agar.

Also contains sucrose and thymol blue.

Is selective for Vibrio spp.

Vibrio cholerae ferments sucrose and produces yellow colonies.

Vibrio cholerae is a bacterium that causes cholera. It is known to ferment sucrose, which means it can break down sucrose into simpler compounds through a metabolic process. TCBS agar, which stands for Thiosulfate Citrate Bile Salt Sucrose agar, is a selective and differential medium used to isolate and identify Vibrio species, including Vibrio cholerae. The agar contains sucrose as a carbohydrate source, and when Vibrio cholerae ferments sucrose, it produces acid, which turns the media yellow. Therefore, TCBS agar is the correct answer because it allows for the identification of Vibrio cholerae based on its ability to ferment sucrose and produce a yellow color on the agar.

Desoxycholate citrate agar

Differential, selective media for identifying enteric pathogens.

Non-lactose fermentors produce colourless colonies and lactose-fermenters produce pink colonies.

Neisseria is the correct answer because it is a bacteria that requires chocolate agar to grow. Chocolate agar is a type of nutrient agar that contains lysed red blood cells, which provides essential nutrients for the growth of Neisseria bacteria. This type of agar is commonly used for cultivating fastidious bacteria like Neisseria, as it provides the necessary factors for their growth and allows for better isolation and identification of these bacteria. E. coli, Proteus, and Salmonella do not require chocolate agar for growth, therefore they are not the correct answer.

Supportive and selective media for the growth of Yersina enterocolitica is yersinia-selective media Appear as red bull's-eye colonies.

GC media, also known as chocolate agar, is a type of culture medium that is commonly used for the growth of Neisseria species. Neisseria is a genus of bacteria that includes important human pathogens such as Neisseria gonorrhoeae and Neisseria meningitidis. These bacteria have specific nutritional requirements, including the need for factors present in blood, which are provided by GC media. Therefore, it is true that GC media is used for the growth of Neisseria.

Selectively differential agar used to identify enterococcus spp.
Dark brown/black precipitate forms when organism grows.
Can also be used to identify klebsiella-serratio-enterobacter group from other enterobactericiae.

Apeptone containing agar

Used to cultivate fungi

Has a pH of 5.6 to inhibit bacterial growth

A clear zone around the growth indicates the action of DNAse enzymes (i.e. The organism can use DNA for a source of energy).

DNAse positive: Moraxella and Staph aureus

DNAse negative: Coagulase negative staph

Lactose fermenting bacteria are those that have the ability to break down lactose, a sugar found in milk, into lactic acid. E.coli and Klebsiella are both examples of lactose fermenting bacteria. Pseudomonas, Shigella, Salmonella, and Proteus, on the other hand, are not known for their ability to ferment lactose. Therefore, the correct answer is E.coli and Klebsiella.