From clinical sample we are trying to identify Staphylococcus aureus by using nutrient agar. Based on the appearance of colonies on the nutrient agar plate please describe the characteristics that would suggest the presence of Staphylococcus aureus. Include details about colony shape, color, and Gram stain results.
Old time microbiologists (like me) from the last century could do this - based on colony size, margin, consistency, color (often somewhat yellow), hemolysis on blood agar, smell. This would allow an early report to the docs that drove treatment and we would confirm.
Nutrient agar is not very useful in this application, and I doubt you guys can do it with any validity without avery great lot of experience. Why would you want to do this now?
Typically, it's challenging to isolate Staphylococcus aureus using standard nutrient media. For effective isolation, Mannitol Salt Agar (MSA) is commonly recommended, as it's selective and differential for S. aureus. S. aureus colonies on MSA typically exhibit a yellow color and produce a yellow zone. Following isolation, various biochemical tests, including Catalase and Coagulase tests, are essential for confirming the presence of S. aureus. The coagulase test is particularly effective in this regard.
Tanjim Ishraq Rahaman
I disagree. Any experienced microbiologist should have no problem isolating S. aureus form mixed culture in any context but confluent growth of other bugs. MSA makes it easier by both inhibition of other bugs and the id indicating mannitol fermentation.
Phil Geis
I suggested that MSA might be more effective for isolating S. aureus. Why should I isolate S. aureus using nutrient media when an easier approach exists?
Tanjim Ishraq Rahaman
Isolation from clinical samples would typically involve blood agar (BA), not NA. Any clinical microbiologist would recognize S. aureus on BA and confirm, as they would if they had also used MSA. MSA would make it easier, quicker for some, at added expense.
Agree, Sumia's use of NA is not protocol. Perhaps she can tell us why.
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