Touring the Microbiology Lab

This is my second post about shadowing general medical residents, and talks about our tour of the Microbiology lab.

If you don't like reading about blood, feces, or dissections, you might not enjoy this post.

In addition to seeing patients and attending a lecture on kidney development, the residents I shadowed went on a tour of the Microbiology lab to learn how they did blood cultures. Blood cultures are run when a clinician suspects sepsis (blood bacterial infection). The first step is to find if the blood has anything growing in it. The lab does this using an automated machine which incubates the blood samples and lights up if one of them reaches a certain level of growth (the blood sample bottle has an indicator of some sort). This way, only the blood which has detectable bacterial growth is put on culture plates, saving the lab time, money, and labor.

If a blood sample sets off the alarm, the lab tech disinfects the bottle top with iodine and then extracts a small sample, putting a drop of blood on each culture plate. The plates have different varieties of agar (a gel made from algae), including blood agar (which has sheep blood added to show bacteria that can break down blood cells) and chocolate agar (in which the blood cells are heated to break them up - these plates show bacteria that cannot break down blood cells - there is no actual chocolate). I wish I had taken pictures of the plates; they were oddly beautiful. Even though some of them had nasty bugs growing on them, seeing the different shapes of the bacterial colonies (some looked like snowflakes) against the red and brown agar was fascinating.

For those who are curious:
http://en.wikipedia.org/wiki/Agar_plate
http://en.wikipedia.org/wiki/Chocolate_agar

The most amusing takeaway from the lab was hearing which type of sample the lab techs despised most. I thought there would be widespread detest for fecal samples, given the smell factor. Acknowledging that working in a lab may desensitize one to strong smells (they used acetone to do Gram stains), I also wondered if there was a diversity of opinions about body fluids. After all, many of the nurses I have worked with admitted that even though they could deal with (name a list of body fluids) pretty well, there was still one fluid that made them nauseous or uneasy.

I know that I am much more tolerant of blood than of fecal matter. Watching an open prostatectomy during my tour of the surgical wing (through a window to an OR) did not phase me. Oh, look at all those red sponges, I thought. They almost looked pretty in the periwinkle blue organizer that had individual pockets for each used sponge.  I attribute my comfort with blood to watching my dad do fingersticks (for blood sugar tests) for 23+ years and being a blood donor for 6 years.

When I did a fetal pig dissection in anatomy and we had to examine a portion of the large intestine, though, I stepped back after feeling the intestine between my fingers.  I can't explain why cutting into a sheep brain or looking at a cow heart didn't phase me, but fetal pig intestinal contents did. It is mostly the smell, I think. There are definitely serious pathogens that are transmitted in both blood and feces, but my automatic reaction to the latter is that it is dirty and nauseating. While a stranger's blood is a disease risk, I don't look at it as an inherently dirty substance.

But the most hated sample category among the lab techs was not blood or stool. It wasn't urine, either, which they process a lot of as well. It was foot wound samples (i.e. diabetics with infected foot sores), simply because of the number of organisms in each sample. One tech's quote was: "where do people put their feet?"

On that lovely note, enjoy the rest of the weekend and cover your foot blisters!