starlathornhill

Hm, #2 might be it. I don't think its contamination because I definitely flamed the inoculating loop and the colony I chose was on the streak line. Here's a picture of the two gram stains next to each other. Left (diplococci) is definitely a gram positive, and right (staph) is what I have identified as gram negative. It looks like my usual gram negative stain (it always comes out a really deep pink for me, not sure why). Is it possible I just over decolorized? Looking at the results of the other tests it looks to me like this should be S. aureus (coagulase positive) except that it stained pink.

For my path micro lab I had to swab certain places of my body (nose, ears, hands), plant them on MSA, chose a colony, streak isolate it on TSA, then gram stain it (in addition to performing a catalase and coagulase test). When I did the gram stain of an isolated colony from my nose, I got gram negative staphylococci. I know the gram stain wasn't wrong because I redid it. I did a gram stain of another colony from the ear and it was gram positive, and the color was definitely purple, and definitely different, so it's not a problem with my interpretation. How could I have gotten a gram negative colony? Since the samples were first grown on MSA I should have only isolated gram positive bacteria. Is it possible that the gram negative was surrounded by gram positives and was able to survive the night on the TSA, then was isolated during the streak plating and was able to grow? I am thinking it is Neiserria sp. since they are common commensals on mucus membranes but I am unsure of how it would have survived being plated on MSA overnight!