Microbiology - Culture Media and Techniques (GATE)

Campylobacter is inherently resistant to vancomycin and is selectively isolated on addition of vancomycin.

Lactobacillus grows luxuriantly in broth having pH 5.35. This pH is optimum for the growth of Lactobacillus.

Thayer-Martin medium does not contain penicillin as Neisseria is susceptible to it.

Pantoea agglomerans grows luxuriantly in Pikovskaya medium and creates a clear zone indicating phosphate solubilisation.

Shigella produces green colonies on Hektoen enteric agar because it does not produce H2S from thiosulphate or ferric ammonium citrate in the medium.

Pseudomonas selectively grows on cetrimide agar. Cetyltrimethylammonium bromide, a quaternary ammonium and cationic detergent, is the component of cetrimide agar and allows for the selective isolation of Pseudomonas aeruginosa. Cetyltrimethylammonium bromide, when in contact with bacteria, causes the release of nitrogen and phosphorus from the bacterial cell. Organisms other than P. aeruginosa are unable to withstand this germicidal activity. Pseudomonas aeruginosa produces a characteristic fruity or grape juice-like aroma due to the production of an aromatic compound called aminoacetophenone.

This is false. Granada medium is differential for Streptococcus agalactiae. They grow as distinctive red colonies in this medium.

Yellow slant and pink butt (acid slant and alkaline butt) indicate that only glucose is fermented. So, only a glucose fermentor is in the bacterial culture.

Roll tube technique is used for stringent anaerobes. It provides an ideal condition for the cultivation of stringent anaerobes (redox potential below - 300 mV) which can be only achieved by the supplementation of media with reducing agents. This method consists of a roller tube in which the organism to be cultivated is immobilised on the side of the tube by a film of serum or other media.

In cryopreservation, DMSO is used as a cryoprotectant at 10% concentration.

Venkataraman Ramakrishna (VR) medium is a transport medium for the transportation of feces from suspected cholera patients.  These samples contain vibrio cholerae.

Caulobacter naturally lives in dilute aquatic environment. It can grow in the medium with very low levels of carbon and nitrogen. In such minimal media, other bacteria fail to grow and caulobacter grows and produces turbidity.

MSA has a high concentration of sodium chloride that selects for members of the genus Staphylococcus as they can tolerate high saline levels. Organisms from other genera may grow, but very weakly.

Alkaline bile oxalate-sorbosebroth with pH 7.6 is the ideal condition for the enrichment of Yersinia enterocolitica.

Polysorbate 80 increases the growth by dispersing bacilli. It also acts as a surfactant and supplies the essential fatty acids for replication.