Microbio Techniques

Davin C. Enigl enigl at aol.com
Sun Jun 2 13:34:20 EST 2002

On Wed, 29 May 2002 14:50:44 GMT, JEDilworth
<bactitech at nospamhortonsbay.com> wrote:

>Why? What difference will the sensitivities make?

I am one of the first research microbiologists who developed anaerobic
sensitivity tests back in the 1970s (An-sheepBA plates in BBL's jar,
then broth-disc method of the isolates).  They are not easy to perform
and can be highly misleading.  For instance, tetracycline is aften
used for treament of acne.  Anaerobe in vitro sensitivities to
tetracycline are the most highly misleading of all the antibiotics (in
vitro results did *not* match its performance when in vivo) -- so, I
think you might be wasting your time and misleading yourself ever if
you could perform the tests.  (However the research was fun to
perform, at least for me back in the 1970s.)

While doing research at the Neutrogena Corporation, I found
formulations that could help acne problems without the use of
antibiotics, by using  1.0% salicylic acid (look for that active
listed of the product container).  The products took years to develop
with extensive use of computer modeling for the D-values and hundreds
forulations were tested (by me personally, plus my senior and junior
microbiolgists).  Keep in mind, acne is *not* just "caused" by
bacteria, nor even esp. by P. acnes, so you must look further that.  

>You definitely need anaerobic conditions. Proprionibacteria only come up
>after 2-3 days incubation. They are tedious to identifify. We use a
>Rapid ANA methodology and half the time the ID's don't work very well
>and we end up ID'ing from gram stain morphology. Performing antibiotic
>sensitivity testing on these slow growers will be expensive and tedious. 
>Do you happen to have access to a lot of cash? You will need anaerobic
>primary isolation agar of some sort, anaerobic baggies (BBL makes them -
>I'm sure they're expensive), an incubator capable of reaching 35 degrees
>C, inoculation loops, lots of slides and gram stain reagents, some sort
>of antibiotic for sensi testing (our Ph.D. uses predispensed microtiter
>plates [expensive] when running antibiotic sensis - I don't perform them
>so I don't know what's all involved. As John said, there are also E-Test
>strips, but they are not cheap either and must be stored in a freezer
>until used, as they are fussy). Our aerobic microtiter setup includes
>the plates, the inoculation media, a calibrated 100 ul pipette.
>I don't understand, I guess, why you would worry about this. P. acnes
>isn't really considered a pathogen, unless it gets into a shunt or
>invasive catheter tip inserted when a patient is in the ICU. P. acnes is
>normal skin flora. I've found that most normal skin flora is fairly
>resistant to antibiotics as it's exposed to the rigors of the
>environment on a daily basis.
>You may want to investigate clinical laboratory resources if you really
>want to pursue this. In a clinical lab, as I've said, we don't get too
>excited about this organism as it usually shows up as a skin contaminant
>and rarely as a pathogen.
>Judy Dilworth, M.T. (ASCP)
>Lorren wrote:
>> I wish to culture P. acnes. You see, I've been cycled through several
>> antibiotics over the years and I would like to culture the strains specific
>> to my skin and determine resistance characteristics. I have access to a
>> community college lab, though I don't belive they have an anerobic
>> incubation chamber. Perhaps something could be inprovised... and anaroebic
>> culture bag or so forth. The college doesen't have the literature resources
>> that are essential for this project, which is why I am inquiring here.

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