Mannitol Salt Agar (MSA) is a selective and differential agar medium commonly used in microbiology for the isolation and identification of Staphylococcus aureus, particularly from clinical specimens. It is named after its main components: mannitol (a sugar alcohol) and sodium chloride (salt). Here's how MSA works for the isolation of Staphylococcus aureus. Golden Yellow colonies of Staphylococcus aureus on Mannitol salt agar. Principle of Mannitol Salt Agar Selectivity: MSA is selective because it contains a high concentration of salt (7.5-10% NaCl). This high salt concentration creates an environment that is inhibitory to many bacteria but allows for the growth of staphylococci, particularly Staphylococcus aureus. Staphylococci are salt-tolerant, and this characteristic helps in their isolation. Differential: MSA is also differential because it contains mannitol, a carbohydrate source, and the pH indicator phenol red. Staphylococcus aureus can ferment
Overview Vancomycin-resistant enterococcus (VRE) refers to strains of enterococcal bacteria that have developed resistance to the antibiotic vancomycin. Enterococci are bacteria that are commonly found in the human gastrointestinal tract and are also found in the environment. While most enterococcal infections can be treated with antibiotics, some strains have become resistant to multiple drugs, including vancomycin. Vancomycin is an antibiotic that is often used to treat serious infections, particularly those caused by Gram-positive bacteria. When enterococci become resistant to vancomycin, it limits the treatment options for infections caused by these bacteria, making them more challenging to manage. Types of VRE: There are two main species of enterococci that are commonly associated with vancomycin resistance: Enterococcus faecium: This species is more commonly associated with vancomycin resistance than Enterococcus faecalis. Vancomycin-resistant Enterococcus faecium
Purpose: To enumerate the number of bacteria present in the water by the MPN method. To identify the bacteria present in the drinking water sample. Principle: Water to be tested is diluted serially and inoculated in lactose broth, coliforms if present in water utilizes the lactose present in the medium to produce acid and gas. The presence of acid is indicated by the color change of the medium and the presence of gas is detected as gas bubbles collected in the inverted Durham tube present in the medium. The number of total coliforms is determined by counting the number of tubes giving positive reaction (i.e both color change and gas production) and comparing the pattern of positive results (the number of tubes showing growth at each dilution) with standard statistical tables. Type of container and additives Sterile container Requirements: Equipment: Test tubes, Durham tube, sterile plates, laminar airflow, Incubator. Reagents/ Media: MacConkey broth, Stains, Bioch
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