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The hemolysis of some weakly beta-hemolytic organisms is enhanced when streaked close to certain beta hemolytic strains of Staphylococcus aureus. This phenomenon is the mechanism behind the CAMP test, [2] a test that was historically used for the identification of Streptococcus agalactiae and Listeria monocytogenes. [3]
Staphylococcus aureus produces yellow colonies with yellow zones, whereas other coagulase-negative staphylococci produce small pink or red colonies with no colour change to the medium. [4] If an organism can ferment mannitol, an acidic byproduct is formed that causes the phenol red in the agar to turn yellow. [1]
Staphylococcus aureus is a gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe, meaning that it can grow without oxygen. [1]
Vogel–Johnson agar is a type of agar growth medium selective for coagulase-positive staphylococci. It is used to isolate Staphylococcus aureus from clinical specimens and food. It was first described by Vogel and Johnson, who modified the Tellurite Glycine Agar recipe by Zebovitz et al. by doubling the mannitol concentration to 1% (w/v) and ...
Phenylethyl alcohol agar selects for Staphylococcus species while inhibiting Gram-negative bacilli (e.g., Escherichia coli, Shigella, Proteus, etc.). R2A agar, a nonspecific medium, imitates water, so is used for water analysis. Tryptic (trypticase) soy agar (TSA) is a general-purpose medium produced by enzymatic digestion of soybean meal and ...
Streak a beta-lysin–producing strain of aureus down the center of a sheep blood agar plate. The test organism streak should be 3 to 4 cm long. Streak test organisms across the plate perpendicular to the S. aureus streak within 2 mm. (Multiple organisms can be tested on a single plate). Incubate at 35°-37°C in ambient air for 18-24 hours.
CLED agar (cystine–lactose–electrolyte-deficient agar or medium) is a valuable non-inhibitory growth medium used in the isolation and differentiation of urinary microbes. It contains cystine and lactose and is electrolyte -deficient; the latter trait prevents the swarming of Proteus species.
Staphylococcus species are facultative anaerobes (capable of growth both aerobically and anaerobically). [15] All species grow in the presence of bile salts. All strains of Staphylococcus aureus were once thought to be coagulase-positive, but this has since been disproven. [16] [17] [18] Growth can also occur in a 6.5% NaCl solution. [15]