When inoculated on tryptic soy agar plates, both bacterial types show growth. Yes, it can ferment lactose. Most non-pathogenic staphylococci will not ferment mannitol. This may lead to false positives for Non-staphylococcus that can ferment mannitol. Mannitol salts agar is differential since it will detect acid production as a result of fermentation of mannitol (a sugar in the medium) in species that can ferment mannitol to produce acid. What bacteria does mannitol salt agar inhibit? Bacillus subtilis does not grow on MacConkey Agar. However, you may visit "Cookie Settings" to provide a controlled consent. c. It kills the bacteria. While there are numerous known species in the genus Bacillus, only two,B. Cells retain their natural size and shape What color will human cells stain when doing a gram stain? b. The microrganisim B. Subtilis tested positive for catalase, lipase, and amylase. An antimicrobial chemical used to sanitize a lab bench is called a(n) ________________. Instead, you observe pink bacilli and pink cocci. It contains a high concentration (about 7.510%) of salt (NaCl) which is inhibitory to most bacteria making MSA selective against most Gram-negative and selective for some Gram-positive bacteria (Staphylococcus, Enterococcus and Micrococcaceae) that tolerate high salt concentrations. Bile salts and crystal violet inhibits the growth of most Gram positive, non-enteric bacteria. Bacillus species are rod-shaped, endospore-forming aerobic or facultatively anaerobic, Gram-positive bacteria; in some species cultures may turn Gram-negative with age. Bacillus cereus is a Gram-positive, rod-shaped, facultatively anaerobic, motile, beta-hemolytic, spore forming bacterium commonly found in soil and food. Boil to dissolve the medium completely. We demonstrate that the sugar alcohol has a . e. microbial motility. These cookies ensure basic functionalities and security features of the website, anonymously. Staphylococcus species, which commonly inhabit human skin, can grow on this high salt concentration (left plate in picture below). If a bacterial growth medium is selective, that means that it grows only certain types of microbes while inhibiting the growth of other types of microbes. Bacillus subtilis is not able to ferment mannitol and yet the Mannitol test yielded a positive result. subtilis is able to complete glycolysis and the TCA (tricarboxylic acid) cycle because of its aerobic cellular respiration. d. Safranin does not penetrate Gram-positive cell walls. Why should negatively stained slides be handled with extra precaution? c. fibrin This cookie is set by GDPR Cookie Consent plugin. c. Add decolorizing agent. c. Soft soap (Antimicorbial) It selects organisms that can survive in areas of high salt concentration (sodium chloride). What type of organisms grow in mannitol salt agar? It is mostly found in soil and vegetation with an optimal growth temperature from 25-35 degrees Celsius. e. Bacteria, Based solely upon its name, what type of shape and arrangement should the cells of Streptococcus pyogenes demonstrate? Inactivation of the gene mtlD, encoding Mtl-1-P dehydrogenase was found to markedly reduce survival in the presence of the antimicrobial fatty acid, linoleic acid. If the bacteria is able to grow then it is a halophilic bacteria, due to its ability to grow in a high salt environment. epidermidis grow well on MAC. 1. Using mannitol salt agar helps demonstrate the ability of bacteri a to grow in a 7.5% salt . Mannitol Salt Agar (MSA) is used to determine if the bacteria is halophilic (salt loving) and if the bacteria can ferment mannitol. Will Bacillus Grow on . The Gram-positive rod, Bacillus subtilis is lipase positive (pictured on the left) The plate pictured . It does not store any personal data. b. c. Add safranin. The decolorizing agent forms a complex with the peptidoglycan. Would Bacillus cereus Grow on mannitol agar? a. colorless; purple What is the lowest concentration of a substance that prevents bacterial growth? identify S.aureus. MANNITOL SALT AGAR. After performing a Gram stain, gram-negative cells appear, After performing a Gram stain, gram-positive cells appear. True/False Which is the best chromogenic medium for Bacillus cereus? d. None of the above. d. Cells retain their natural size and shape, and are not distorted by the effects of chemicals or heat. If you forget to add the decolorizing agent when performing a Gram stain, what color will the gram-negative cells be? Bacillus subtilis is not able to ferment mannitol and yet the Mannitol test yielded a positive result. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. These cookies track visitors across websites and collect information to provide customized ads. Be sure to perform a catalase test before you proceed with the salt tolerance broth test. 2 What bacteria does mannitol salt agar inhibit? Enterococcus faecalis does not go on the synthetic medium but does grow on the tryptic soy broth and the SF broth. c. 520 nm Objective 2: To do a simple streak of an E. coli culture on a nutrient agar plate. b. Phenol red inhibits the growth of gram-positive organisms. c. Age will not affect decolorization. Contrast allows the cells to stand out from the background. We also use third-party cookies that help us analyze and understand how you use this website. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. c. evaporation of the media a. Staphylococcus aureus e. It makes the bacteria easier to see. a. chloroxylenol b. c. Clusters of gram-negative bacilli When the Bacillus subtilis was isolated on the Mannitol Salt Agar plate, the color of the plate also changed from red to yellow. MacConkey agar is a selective and differentiating agar that only grows gram-negative bacterial species; it can further differentiate the gram-negative organisms based on their lactose metabolism. e. Capsule, Four-way quadrant streak plates are useful in microbiology to __________________. 7 Will Bacillus Grow on mannitol salt agar? You also have the option to opt-out of these cookies. EMMY NOMINATIONS 2022: Outstanding Limited Or Anthology Series, EMMY NOMINATIONS 2022: Outstanding Lead Actress In A Comedy Series, EMMY NOMINATIONS 2022: Outstanding Supporting Actor In A Comedy Series, EMMY NOMINATIONS 2022: Outstanding Lead Actress In A Limited Or Anthology Series Or Movie, EMMY NOMINATIONS 2022: Outstanding Lead Actor In A Limited Or Anthology Series Or Movie. Which of the following represents an incorrect association regarding the reagents used during the Gram Staining procedure? If there is no growth after adding salt, it means that . a. What are the differential ingredients in MacConkey Agar? Which of the following objective lenses is the ONLY lens that should be used with oil immersion? 4 What kind of bacteria can grow on mannitol salt agar? e. Mueller Hinton agar, Kirby Bauer tests provide ______________ results. Begin typing your search term above and press enter to search. Staphylococci other than S. aureus (e.g. Blood agar is an enriched medium that provides an extra rich nutrient environment for microbes. c. Bacillus subtilis Mannitol Salt Agar (MSA) This is a medium that is both selective and differential. True/False Which of the following basic stains is used in the Gram staining procedure? You performed the Gram stain. This . A microscope with a resolving power of 1 cm is superior to one with a resolving power of 1 mm. Crystal violet agar: inhibits the growth of gram-negative organisms, used to isolate gram-positive organisms Mannitol salt agar has 7.5% salt. Add crystal violet. What Agar does Bacillus megaterium grow on? d. The counterstain, If you forgot to add the counterstain to the mixed culture sample at the end of the staining procedure, gram-negative cells would appear __________ and gram-positive cells would appear __________. b. chlorhexidine True/False Mannitol is not fermented by isolate if growth and surrounding medium are eosin pink. A dog loses a lot of heat through panting. a. coagulase . hydrogen peroxide Necessary cookies are absolutely essential for the website to function properly. What test is used to differentiate between Staph aureus and Staph epidermidis. b. Psuedomonas aeruginosa (Gram negative) - no growth. If desired, sterile Egg Yolk Emulsion (E7899) can be added to a final concentration of 5% v/v after autoclaving. As the name suggests, it contains cetrimide, which is the selective agent against alternate microbial flora. Bacara is a chromogenic selective and differential agar that promotes the growth and identification of B. c. Over time, gram-negative cells gain the ability to retain the crystal violet stain after decolorization. What is the purpose of mannitol salt agar? The cookie is used to store the user consent for the cookies in the category "Analytics". E coli is facultatively anaerobic with a type of metabolism that is both fermentative and respiratory. Preparation of Mannitol Salt Agar (MSA) Suspend 111 grams of Mannitol Salt Agar in 1000 ml of distilled water. Mannitol Salt Agar (MSA) is Used to determine if the bacteria is halophilic (salt loving) and if the bacteria can ferment mannitol.If the bacteria is able to grow then it is a halophilic bacteria, due to it's ability to grow in a high salt environment. b. Safranin penetrates the cell wall, but not enough of it is retained to cause a color change. Can gram-negative bacteria grow on mannitol salt agar? 7 Can You ferment mannitol with Bacillus subtilis? c. Mannitol Salt Agar (MSA) Hence, blood agar supports the growth of fastidious microorganisms which are not easy to grow in culture media. Phenylethyl alcohol inhibits gram ____________ bacteria. e. catalase hydrogen peroxide, It would be appropriate to screen mothers and nursery workers in the "case of the newborn nightmare" for Staph. E. coli When it ferments D-mannitol, it produces an acid which turns the agar yellow from red. By clicking Accept All, you consent to the use of ALL the cookies. The decolorizing agent forms a complex with the lipopolysaccharide in the outer membrane. The differential ingredient in MSA is the sugar mannitol. d. Streptococci Bacillus subtilis is a typical germ, which is rod-shaped and Gram-positive. These data reveal that we now have rapid, cost effective ways to identify enterococci to the species, and not just genus, level and have significance for patient treatment in hospitals. It kills the bacteria. a. b. Although these organisms grow well on nutrient agar, they are not halophiles so will not grow on mannitol salt agar. What would be the effect on decolorization? TimesMojo is a social question-and-answer website where you can get all the answers to your questions. Which category of bacteria do not grow on MSA? b. e. catalase . rabbit plasma, What reagent is used to do a coagulase test? a. Safranin cannot pass through the outer membrane. Acidic stains have a positively charged chromogen and are repelled by the negative charges on bacterial surfaces. You forgot the safranin step. d. Take a dropful of nigrosin. Mannitol Salt Agar (MSA) is used as a selective and differential medium for the isolation and identification of Staphylococcus aureus from clinical and non-clinical specimens. B. cereus food poisoning may occur when foods are prepared . subtilis cannot ferment either glucose or pyruvate efficiently (unlike E. coli) and why pyruvate enhances glucose fermentation are unknown. Gram-negative bacteria like E. coli and P. Staphylococcus aureus is also able to ferment mannitol, because this bacterial species has the enzyme coagulase required for the process. Can You ferment lactose on mannitol salt agar? B. cereus colonies are usually lecithinase-positive and mannitol-negative on MYP agar. You forgot the decolorizing step. What is the purpose of adding phenol red to mannitol salt agar? The disk diffusion method is the most reliable method to test the effectiveness of disinfectants and antiseptics, What media was used for antibiotic susceptibility testing in lab? Examples of sterile MSA as well as plates with growth of . Which ELISA looks for specific antibodies and has the known antigen to trap the antibody you're seeking? Can Bacillus megaterium ferment mannitol? True/False Staphylococcus species are halotolerant, whereas Streptococcus species and many other organisms are inhibited by high concentrations of NaCl. b. Staph. Which step must be done first? MSA contains a high concentration of salt (NaCl), and therefore, selects for the growth of microbes that can tolerate high salt concentrations. Which of the following organisms is gram-negative? . d. Archaea It's a site that collects all the most frequently asked questions and answers, so you don't have to spend hours on searching anywhere else. a. Yes, it can ferment lactose. What is the purpose of mannitol salt agar? a. Staph. Crystal violet agar: inhibits the growth of gram-positive organisms, used to isolate gram-negative organisms 1)The pictured bacteria produce endotoxin (also known as lipopolysaccharide, LPS). The MSA will select for organisms such as Staphylococcus species which can live in areas of high salt concentration (plate on the left in the picture below). All cells will decolorize. However, it will also allow growth of Staphylococcus so further identification work must be conducted to form a strong identification of Micrococcus presence. It is both differential and selective agar. metabolize the sugar lactose) to grow in pink colonies, whereas Gram-negative non-lactose fermenting bacteria will grow in colorless colonies. Mannitol Salt Agar (MSA) is used to determine if the bacteria is halophilic (salt loving) and if the bacteria can ferment mannitol. Mannitol salt Mannitol salt agar is a selective and differential medium used for differentiating between different stapylococci Staphylococcus aureus changes medium to yellow Staphylococcus epidermidis will not change the medium Why does S. aureus change the color of this medium? But the genus Staphylococcus has a protective slime layerthat protects it in a harsh, salty environment. The high concentration of salt (7.5%) selects for members of the genus Staphylococcus , since they can tolerate high saline levels. This medium only grows salt-loving bacteria (so it is selective). The red colour is due to production of acid from lactose, absorption of neutral red and a subsequent colour change of the dye when the pH of medium falls below 6.8. The other colony, from unknown #102, was determined to be Gram positive rods (bacillus). When . ; In spite of the diversity, the colonies of Bacillus species can be recognized on agar plates quite easily. Cetrimide agar is a type of agar used for the selective isolation of the gram-negative bacterium, Pseudomonas aeruginosa. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. The MSA agar will retain its initial red color and will not change to yellow. c. Hydrogen peroxide (H2O2) A positive result for mannitol fermentation would be the formation of a yellow halo around . Crystal violet is attracted to the negatively-charged components of the cell wall; safranin is attracted to the positively-charged components of the cell wall. From this determination, a mannitol test was performed and the organism was inoculated onto a Mannitol Salt Agar plate (MSA). of bacteria. c. Safranin penetrates cell walls and causes the walls to become pink. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. d. liquefaction of the agar c. The ability of an organism to mutate in the presence of an antibiotic Uses citrate as its sole carbon source also positive for carbohydrate . What specific bacterial species can MSA identify? Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. MacConkey agar contains four key ingredients (lactose, bile salts, crystal violet, and neutral red) that make it a selective and differential media. d. Isolated colonies are all white in color and about the same size. c. Isolated colonies are all white in color, but some colonies are noticeably larger than others. a. Low-power lens (10X) d. The smear preparation is too light. 2022 - 2023 Times Mojo - All Rights Reserved It is recommended for the detection and enumeration of coagulase-positive Staphylococci in milk, food and other specimens. INSTAGRAM | @thecatalystuniver. Adding which of the following substances between the slide and the lens acts to decrease the refraction of light? Pathogenic gram-positive Staphylococcus aureus salt-tolerant (halophilic) and will produce colonies on MSA. c. All would be purple. True/False In this experiment, the presence of yellow halos around colonies growing on mannitol salt agar indicates that the microbe ___________. a. Escherichia coli When the Bacillus subtilis was isolated on the Mannitol Salt Agar plate, the color of the plate also changed from red to yellow. Analytical cookies are used to understand how visitors interact with the website. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. Stress and starvation are common in this environment, therefore, Bacillus subtilis has evolved a set of strategies that allow survival under these harsh conditions. __________________ media incorporate chemical compounds that produce characteristic changes in the appearance of the bacterial colonies. What bacteria does mannitol salt agar inhibit? e. measure turbidity. I used to carry a mannitol non-fermenting Staph. aureus. c. The contrast allows you to differentiate between gram-negative and gram-positive cells by observing the color of the organism. The cookie is used to store the user consent for the cookies in the category "Analytics". If the color is red, it is the bacteria is basic. Which of the following media would be MOST appropriate for this purpose? ___________________ media incorporate chemical substances that inhibit the growth of one type of bacteria while permitting the growth of another. By definition, all have the capacity to form spores, but they vary widely in motility, colony morphology, and nutritional requirements. Organisms that ferment lactose will form colorless colonies on MAC. Why Do Cross Country Runners Have Skinny Legs? a. rabbit plasma Most known bacteria that have been cultured from human skin are Gram-positive. c. dilution on a solid surface a. By clicking Accept All, you consent to the use of ALL the cookies. b. High-power lens (100X) a. c. The decolorizing agent forms a complex with the peptidoglycan. streptococcus faecilis Cultural Characteristics of Bacillus subtilis. c. NaCl (sodium chloride) agar: inhibits the growth of a non-halophilic organisms, often used to isolate Staphylococcus Can a mannitol isolate be fermented by isolate? The high salt concentration (7.5%) is the selective ingredient. Image Based Life > Uncategorized > can bacillus grow on mannitol salt agar subtilis) is a Gram-positive, aerobic bacterium. b. Yeast The acidic stain is especially toxic. b. purple; red or pink What would be the likely consequences of omitting the NaCl in Mannitol Salt Agar? c. mycobacteria d. Stunted, robust, or intermediate, Which of the following media will be used for culturing your skin in lab? Analytical cookies are used to understand how visitors interact with the website. What test is used to differentiate between Staphylococci and Streptococci? It contains 7.5% sodium chloride which selects for organisms that are halotolerant. Do Men Still Wear Button Holes At Weddings? aureus strains will not ferment mannitol. This medium can detect the destruction of erythrocytes by growing bacteria. Inclusion bodies 2)The indicated bacterium is Gram-negative. c. Phenol red permits the differentiation of bacteria based on their ability to ferment mannitol. Welcome to Catalyst University! Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. c. Heat fixation is recommended when staining with an acidic stain, but not when staining with a basic stain. As its name suggests, mannitol salt agar (MSA) contains 1% mannitol (sugar), 7.5% salt, and agar as a solidifying agent. aureus in my anterior nares - last . What is most likely true if your negative stain is dark black with lots of clear cracks present? ; The growth on a simple medium like nutrient agar might result in . Mannitol Salt is a selective bacterial growth medium because it has a very high concentration of NaCl (7.5%). When the Bacillus subtilis was isolated on the Mannitol Salt Agar plate, the color of the plate also changed from red to yellow. These cookies will be stored in your browser only with your consent. Similar, reversion, or indeterminate What is likely to happen to E. coli cells on the TSA + 15% NaCl medium? Crystal violet and bile salts in MAC will inhibit the growth of gram negative bacteria. As a rough calculation, assume that one pant causes 0.010 g of water to be evaporated from the respiratory tract. Old Gram-positive cells will be decolorized. a. Kirby Bauer agar It causes the cells to adhere to the slide. What is the rate of heat loss for the dog through panting? A negatively charged chromophore will NOT stain cells. What would be the likely consequences of removing the NaCl from MSA? d. The counterstain used is especially toxic. Lab Assignment about Mannitol Salt Agar (MSA) ali gilblair mannitol salt agar mannitol salt agar is differential and selective indicator medium used to identify . True/False What bacteria can grow on mannitol salt agar? The high concentration of salt (7.5%) selects for members of the genus Staphylococcus, since they can tolerate high saline levels. d. red or pink; purple, Which of the following describes the correct cellular morphology and Gram reaction for Staphylococcus aureus? Mannitol Salt is a selective bacterial growth medium because it has a very high concentration of NaCl (7.5%). Mannitol Salt Agar (MSA) is a selective and differential medium. Lactose non-fermenter colonies on the MacConkeys agar and central black, small size colonies with smooth to rough in appearance on the Salmonella-Shigella agar were identified as Salmonella spp. What grows on mannitol salt agar? d. Illumination, Which of the following microbes cannot be directly seen using our light microscopes? The Staphylococcus aureus ferments mannitol and turns the medium yellow. Bacillus cereus is an aerobic spore-forming bacterium that is commonly found in soil, on vegetables, and in many raw and processed foods. No, enterococci cannot grow on mannitol salt agar because are salt resistant bacteria but they are able to ferment mannitol and produce lactic acid, creating colonies of yellow color on MSA. Such a medium normally consists of a mixture of protein digests (peptone, tryptone) and inorganic salts, hardened by the addition of 1.5% agar. The cookie is used to store the user consent for the cookies in the category "Performance". d. Phenylethyl alcohol agar: inhibits the growth of gram-negative organisms, used to isolate gram-positive organisms. Mannitol Salt Agar contains peptones and beef extract, which supply nitrogen, vitamins, minerals and amino acids essential for growth. b. Mannitol Salt Agar for c. Phenylethyl alcohol agar a. quantify the number of bacteria _________________ media have been supplemented with highly nutritious materials for the purpose of cultivating fastidious organisms, Which of the following associations is INCORRECT regarding selective media? can bacillus grow on mannitol salt agar - did mcdonald's change their chicken nuggets 2021 - Juni 6, 2022 did mcdonald's change their chicken nuggets 2021 - Juni 6, 2022 b. The decolorizing agent dehydrates the peptidoglycan. Prolonged incubation ( 48 hours) may also allow growth of Micrococcus, Bacillus, and some species of Serratia. b. a. Gram-positive cells would be purple, and Gram-negative cells would be colorless. Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol. b. Ultraviolet waves b. Pseudomonas aeruginosa Certain agar's however, are specifically enriched for Staph. b. Additionally, mannitol salt agar contains the sugar mannitol. 4 What bacteria can grow on mannitol salt agar? What is found within MSA media that inhibits the growth of most bacteria? When focusing a microscope, you should always focus by moving the lens away from the slide. June 8, 2022; group homes for adults with mental disabilities; 24x48 polished porcelain tile . grow quickly at 25 to 37C on the usual culture media of the clinical laboratory. Mannitol Salt Agar (MSA) . The program then outputs the windchill factor. a. a. You performed the Gram stain on a smear. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. Organisms capable of using mannitol as a food source will produce acidic byproducts of fermentation that will lower the pH of the media. But the genus Staphylococcus has a protective slime layerthat protects it in a harsh, salty environment. In the streak-plate technique, the intent is to isolate bacteria by dilution in theory by __________. . Bacillus subtilis is not able to ferment mannitol and yet the Mannitol test yielded a positive result. This type of medium is both selective and differential. b. identify bacteria Whats the best temperature to grow Bacillus cereus? B.cereusgrows best in a temperature range of 39F (4C) to 118F (48C). S.epidermidis will grow, but the agar remains red. It is recommended for the detection and enumeration of coagulase-positive Staphylococci in milk, food and other specimens. c. The bacterial cells will grow normally. Staphylococcus species, which commonly inhabit human skin, can grow on this high salt concentration (left plate in picture below). The application of the mordant d. Trypticase soy agar b. Clusters of gram-positive cocci . Both streptococcal organisms are catalase negative and beta-hemolytic on sheep blood agar plates. The acidity of the media will cause the pH indicator, phenol red, to turn yellow. This website uses cookies to improve your experience while you navigate through the website. the agar remains red. The bacteria are commonly found in the environment and can contaminate food. Most of the normal microbiota of the skin are gram, Which of the following wavelengths of electromagnetic radiation is the most lethal to bacteria? Why is chocolate agar used in throat culture? Mannitol Salt Agar is used to 1 What Agar does Bacillus cereus grow on? The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The Staphylococcus aureus ferments mannitol and turns the medium yellow. The MacConkey agar plate and the Mannitol Salt agar plate are both used in the identification of the unknown. b. Does Enterobacter aerogenes Grow on mannitol salt agar? Analytical cookies are used to understand how visitors interact with the website. Photos and narrator interpretation of Mannitol Salt Agar (MSA) specialized bacterial growth medium. Salt tolerance media was intended to differentiate catalase negative gram-positive cocci. The cookie is used to store the user consent for the cookies in the category "Other. Examples of standard general purpose media that will support . It is done on a dried smear. b. catalase..hydrogen peroxide However, you may visit "Cookie Settings" to provide a controlled consent. Non-staphylococcus bacteria would be able to grow on the media. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. Nutrient Agar: Bacillus coagulans: Nutrient Agar Tryptic Soy Agar: Bacillus megaterium: Nutrient Agar; . This cookie is set by GDPR Cookie Consent plugin. pressure (121C) for 15 minutes. Necessary cookies are absolutely essential for the website to function properly. 2 Is Bacillus megaterium mannitol positive or negative? d. Old Gram-negative cells will not be decolorized. can bacillus grow on mannitol salt agarsouthwest cargo phone number. d. isolate bacteria and develop pure cultures NMR analysis showed that fermentation products in B. subtilis include acetate, acetoin, ethanol, lactate, succinate and 2,3-butanediol, indicating a mixed acid fermentation . a. But opting out of some of these cookies may affect your browsing experience. As with the other sugar fermentation tests, we are able to determine the ability of a microbe to metabolize mannitol by observing color changes . Mannitol Salt Agar (MSA) is a selective and differential medium. Mannitol Salt Agar (MSA) is used to . Mannitol Salt Agar is differential due to the presence of mannitol and the pH indicator Phenol Red.