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MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation. [1] Lactose fermenters turn red or pink on MacConkey agar, and nonfermenters do not change color.
The genome of Pseudomonas aeruginosa consists of a relatively large circular chromosome (5.5–6.8 Mb) that carries between 5,500 and 6,000 open reading frames, and sometimes plasmids of various sizes depending on the strain. [11] Comparison of 389 genomes from different P. aeruginosa strains showed that just 17.5% is shared.
It appears as a mucoid lactose fermenter on MacConkey agar. Although found in the normal flora of the mouth, skin, and intestines, [ 1 ] it can cause destructive changes to human and animal lungs if aspirated, specifically to the alveoli, resulting in bloody, brownish or yellow colored jelly-like sputum .
Pseudomonas is a genus of Gram-negative bacteria belonging to the family Pseudomonadaceae in the class Gammaproteobacteria.The 348 members of the genus [2] [3] demonstrate a great deal of metabolic diversity and consequently are able to colonize a wide range of niches and hosts.
Most strains of Acinetobacter, except some of the A. lwoffii strain, grow well on MacConkey agar (without salt). Although officially classified as not lactose-fermenting, they are often partially lactose-fermenting when grown on MacConkey agar. They are oxidase-negative, catalase-positive, indole-negative, nonmotile, and usually nitrate-negative.
Cetrimide also enhances the production of Pseudomonas pigments such as pyocyanin and pyoverdine, which show a characteristic blue-green and yellow-green colour, respectively. [ 3 ] [ 4 ] Cetrimide agar is widely used in the examination of cosmetics, pharmaceuticals and clinical specimens to test for the presence of Pseudomonas aeruginosa .
The laboratory procedure involves making serial dilutions of the sample (1:10, 1:100, 1:1000, etc.) in sterile water and cultivating these on nutrient agar in a dish that is sealed and incubated. Typical media include plate count agar for a general count or MacConkey agar to count Gram-negative bacteria such as E. coli. Typically one set of ...
Pseudomonas oryzihabitans is a nonfermenting yellow-pigmented, gram-negative, rod-shaped bacterium that can cause sepsis, peritonitis, endophthalmitis, and bacteremia. [1] It is an opportunistic pathogen of humans and warm-blooded animals that is commonly found in several environmental sources, from soil to rice paddies.