Are you performing oxidase off of the Mac? If you are, it is NOT
accurate off of this medium. You MUST perform oxidase on a nonselective
medium like sheep blood agar or TSA plate. The pink color of the
organism and medium renders this plate off-limits for oxidase testing.
Get back to us when you perform the correct oxidase. Can you do indole
testing off of your blood agar plate too while you've got a fresh
isolate? You must have a blood agar plate (tryptophane source) to
perform indole testing directly from plate, or a medium designed to test
for indole. Make SURE you've streaked well for isolation. This is more
important than anything. Make sure you're working with a one colony
isolate. These are basic tests for lactose fermenters and will tell you
where to go after you do these. Bergey's manual is an excellent choice
for reference, but you MUST correctly perform these tests first.
Judy Dilworth, M.T. (ASCP)
Microbiology
"senaatlaw Atlaw Woldeyohanes" <senaatlaw from yahoo.com> wrote in message
news:mailman.120.1211049307.3533.microbio from net.bio.net...
> Dear Sir,
>> I have isolated a Microorganism, Gram-negative Coccobacillus
> Streaked it on MacConkey agar, pink colonies started to grow before
> eight hours.
> Today after 24 hrs, it is Lactose fermenting, good pink colonies,
> and is Oxidase positive too, I thought it would be from
> Enterobactericeae, but it is rare to be Oxidase positive or unless one
> of the rare ?
