chilli

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Ok all you microbiologists- I want to take a poll. I like MacConkey, but my
supervisor will hear nothing of it. It's EMB or the highway. What do you guys
like, and why? (I'm hoping for a groundswell of support to buoy my position.)

Eric-
A lab in California

jedilworth

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I personally have never used EMB in the 29 years I've been in
microbiology. Oh wait - we used to sub yeasts to EMB to look for
pseudohyphae back in the 70's. I don't know whether that was a
legitimate use either then or now. We looked under a dissecting scope to
see the pseudohyphae.

What is his/her reasoning for EMB? Does he/she just like to be different
or is there some microbiological reason? Yeah, I know that E. coli is
supposed to be iridescent and all that good stuff, but other than that,
what's the point?

BTW, the labs I've worked in have all been headed by Ph.D's in
microbiology, and were large institutions. The lab I currently work for
does the work for four hospitals in our area including a medical school.
The smallest lab I ever worked at back in 1977 (for one year) even used
Mac. I would venture to say that in our service area of over 400,000+
population, not one lab is using EMB for gram negatives. There are only
four labs doing micro in our area. I've worked at two of them, a
co-worker moonlights at the third (big outfit also) and I used to work
for the supervisor of the 4th one and we used Mac then (back in the
1974-77 era), so I would suspect he still uses it now. I am in the North
Central midwest.

Maybe it's one of those California things......:-)

Judy Dilworth, M.T. (ASCP)
Microbiology 29 years

john gentile

in article KqGdnUj-W4fzAxndRVn-vg@comcast.com, EJ at chilli@lightspeed.net


I've always used MacConkey's agar. I did try EMB a while ago, but never
really took to it. I can see discrete colonies and subtle differences
between them better on the Mac. Since I never used it a lot, does NLF E.
coli still "shine", how about some of the inactive E. coli's like A-D?

I did use a variant called Levine's EMB for water testing - the typical E.
coli colonies were counted, but the agar was much clearer than regular EMB.


--
John Gentile Editor, Rhode Island Apple Group
yjgent@cox.net RIAG Web page: www.wbwip.com/riag/
"I never make mistakes, I only have unexpected learning opportunities!"

lynn gerber

I will admit that I use EMB. I work in an outpatient laboratory and for us,
it's more a matter of tradition than anything. 3 of the 5 employees in the
lab have used EMB for 15-20 years. There didn't seem to be any overwhelming
reason to change. As with most labs, the majority of the enterics that we
isolate are E. coli and the EMB seems to work for us. But, like I said,
it's more tradition than science.

chilli

In article <F6idnfK5Y79h-hjd4p2dnA@buckeye-express.com>,
bactitech@nospamhortonsbay.com says...


Yea, it's the E.coli thing. I'm thinking of preparing an objective evaluation
of both media, at least it will give me some purpose for a couple of weeks.
BTW, the weirdest thing happened today: Everybody knows that I'm lobbying for
MacConkey. On Monday I placed the media order, and was specifically told "No
MacConkey". It arrived today and it contained 10 sleeves of MacConkey! They're
not on the invoice but nobody will believe that I didn't order them. I think
there must have been some unspoken, psychic connection between girl at Hardy
and me.

Eric- a lab in California

jedilworth

E. coli is "lactose positive/purple/flat," Klebsiella is "lactose
positive/pink-purple/mucoid," Enterobacters are "pink/mucoid/yellowish
sometimes" etc. In other words, you just get used to how they look. I
probably would have a hard time at first distinguishing colonies on EMB
but I would adjust eventually.

If you hold Mac up to the light you can see subtle differences in shades
of purple and pink, and also see differences with non-lac fermenters.
EMB is a darker medium. I don't know if you'd get the same effect. In
mixed cultures this is a really helpful thing to do.

Even if E. coli has an iridescent sheen, you don't call it from that, do
you? Don't you run some sort of biochemical to prove it? We use GNI+
cards and get an ID in 3-5 hours. We set up positive urine ID/sensis
first thing on day shift AND second shift (we also read urines arriving
after 3 p.m. on second shift) so we sign out positives by the end of the
shift (if we're lucky and if they're pure). So, how does the sheen come
into play when reporting and identifying? I've been told the reason we
do full biochemicals is that one cannot charge an ID code unless one
does at least three tests to prove an organism is what it is. Indole and
sheen, indole and citrate (what we used to do at another employer)
doesn't cut it for charging a full ID any more. You can, I suppose, call
it presumptive EC on a report with a sheen.

So, it's just because of old habits? I'll admit, my old habit is using
Mac.

Judy Dilworth, M.T. (ASCP)
Microbiology


weeks.