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Colonial morphology serves as the first step in the identification of microbial species from clinical samples. [10] Based on the visual appearance of the colonies, microbiologists can narrow down the list of possible organisms, allowing them to select appropriate tests to provide a definitive diagnosis.
The growth rate is the length of time required to form mature colonies visible without magnification on solid media. Mycobacteria forming colonies visible to the naked eye within seven days on subculture are known as rapid growers, while those requiring longer periods are termed slow growers.
The total number of living aerobic bacteria can be determined using a plate count agar which is a substrate for bacteria to grow on. The medium contains casein which provides nitrogen, carbon, amino acids, vitamins and minerals to aid in the growth of the organism. Yeast extract is the source for vitamins, particularly of B-group. Glucose is ...
In microbiology, a colony-forming unit (CFU, cfu or Cfu) is a unit which estimates the number of microbial cells (bacteria, fungi, viruses etc.) in a sample that are viable, able to multiply via binary fission under the controlled conditions. Counting with colony-forming units requires culturing the microbes and counts only viable cells, in ...
An MSA plate with Micrococcus sp. (1), Staphylococcus epidermidis (2) and S. aureus colonies (3). Mannitol salt agar or MSA is a commonly used selective and differential growth medium in microbiology. It encourages the growth of a group of certain bacteria while inhibiting the growth of others. [1]
The catalase test tests whether a microbe produces the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide. Smearing a colony sample onto a glass slide and adding a solution of hydrogen peroxide (3% H 2 O 2) will indicate whether the enzyme is present or not. Bubbling is a positive test while nothing happening is a negative result.
Beta-hemolysis (β-hemolysis), sometimes called complete hemolysis, is a complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent. [1] Streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells. There are two types of ...
Virtual colony count procedure. A 2 mL bacterial culture is inoculated from a single colony and grown overnight in Phosphate Mueller Hinton (PMH) or Phosphate Mueller Hinton Tryptic Soy Broth (PMHT) media. PMH is a 1:1 mixture of Mueller Hinton Broth and 10 mM sodium phosphate pH 7.4. Either cation-adjusted or non-cation-adjusted MHB may be used.