Posted by: loungekitten | April 22, 2009

Even More Microbes

We had a series of labs in Pathogenic Microbiology dealing with bacteria that infect the genitourinary tract.  Mostly, we dealt with bacteria that are found in the urinary tract, and we prepared a slide with Neisseria gonorrheae for viewing under the microscope.  We got to play with gonorrhea!

We collected our own bacterial samples, and pictured below are the two TSA plates that I inoculated with my own bacteria.


Two TSA Plates streaked with urine sample

Two TSA Plates streaked with urine sample

Despite all that bacteria you see growing there, I do not have a urinary tract infection.  There is a normal amount of bacteria that should be present in your bladder, and accounting for dilutions I had 25,000 colony forming units per milliliter.  A UTI is indicated by greater than 100,000 c.f.u./mL.

Then we inoculated a bunch of triple sugar iron (TSI) tubes and a bile esculin (BEA) tube with bacteria standards we were provided with.  I also inoculated a BEA tube with bacteria from my own urine sample, based upon the fact that my sample was shown to be a gram positive coccus shaped bacteria with a negative result from the catalase test.

Here is a picture of what inoculating a TSI tube with E. coli looks like:

E. coli in TSI agar tube

E. coli in TSI agar tube

E. coli was able to ferment all the sugars in this tube – you can tell because all of the agar turned yellow.  There is no back color, so the bacteria cannot produce Hydrogen sulfide.  Also, the force from the accumulation of gas as a by-product of fermentation split the agar!

Enterobacter aerogenes was also inoculated in TSI agar, and here are the results:

Enterobacter aerogenes in TSI agar

Enterobacter aerogenes in TSI agar

The bacteria was able to ferment glucose, because the bottom of the agar is yellow.  It appears that Enterobacter aerogenes cannot ferment sucrose or lactose, because the slant color (the top) is red.  Notice also how this agar is split!

This is the result we got of Proteus vulgaris when inoculated in the TSI tube:

Proteus vulgaris in TSI agar

Proteus vulgaris in TSI agar

I did not inoculate this tube, so I don’t know if the results relate back to the inoculation of the tube itself.  The results of this test are atypical of Proteus vulgaris in TSI agar.  The top should have a yellow color, not a red color.  The fact that most of the agar turned black is correct.

And the final inoculation on TSI agar was for the bacterium Enterococcus faecalis.  It’s not a test that would be performed on TSI agar in normal circumstances, but here is the result:

Enterococcus faecalis on TSI agar

Enterococcus faecalis on TSI agar

The red color on the bottom of the tube indicates that the bacteria cannot ferment glucose, and the yellow color on the slant indicates the bacteria can ferment sucrose or lactose.  Since this test is not normally performed with bacteria, the test results don’t mean much to me – in fact if I think about it a little bit, I think the results seen indicate the effect of the availability of oxygen on the ability to ferment any of these sugars.

We inoculated the bile esculin agar (BEA) tube with Enterococcus faecalis only.  It’s hard to see if this result is positive or not.  Again, I did not inoculate this tube, so I have no idea how much bacteria was used to inoculate the tube, and that may have affected the results:

Enterococcus faecalis on BEA

Enterococcus faecalis on BEA

This could be a positive result (as it should be) because the agar does appear to be a darker brown that the original agar color.  Or it could look darker because of my crappy camera. . .

I also inoculated a BEA slant with bacteria from my own urine.  Here is the result:

Urine sample bacteria on BEA slant

Urine sample bacteria on BEA slant

This is definitely a negative result for a BEA test – the agar in the tube is the same color as the pre-inoculation color.  You can compare this result with the result from the test above, to determine if the test above is positive.

Abrupt topic change alert

And here is a special note for the ladies from my knitting group:

Dear maroon Honda Pilot driver who was driving on 202 South around Rt. 29 at about 8 AM this morning:

So, did you kill someone or something?  Because when that State Trooper entered the highway you just slowed down and would not pass that cop no matter how slow he was going in the right hand lane.  It would have been O.K., you know, if you passed him at a speed of 55 mph, the legal speed limit.  You did not need to slow down to 45 mph in the left hand lane just so you wouldn’t pass him.  Unless you are one of America’s 10 most-wanted criminals or something, then I wouln’t blame you for not wanting to get caught.




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