Friday, January 7, 2011
Fun-a-day 7: Gram Stain
Today I decided to do my "interpretation" of a microbiology Gram Stain. Gram Stains are one of the most common stains in the medical lab, and are used to differentiate different types of bacteria. Almost all bacteria are classifies as "gram positive" (which stain purple), or "gram negative", which stain pink. Furthermore, most bacteria that cause disease in humans are either "rods" (long and thin, like a sausage), or "cocci", (which are little dots or spheres).
I think it was a gram stain that I performed many years ago that was part of my inspiration for my fun-a-day project. I've been a stay-at-home mom for the last 4 years, but recent events have had me spending a great deal of time thinking about gram stains.
You really can't tell from looking at a gram stain what the bacteria is. There are so many that can cause infections in people. We have them living all over and in our bodies, and some of these critter can be "good guys" one day, "bad guys" the next. Staphylococcus aureus is one of these, seen as purple (gram positive) clusters of cocci. They remind me of grape clusters. They normally live happily on the skin, but can infect wounds and other body parts. The chain of purple dots is Streptococcus bacteria. There are multiple types of "Strep", and they can cause Strep throat, as well as many other infections. They remind me of a string of beads. The big long purple rods are my "take" on Clostridium bacteria. Different species of Clostridium can cause botulism and tetanus, among other illnesses. As you may know, they can be found in the soil, and can be very hardy organisms.
Gram negative (pink) bacteria include the rods like E.coli (Escherichia coli) and Salmonella (2 groups at the top), and cocci, like Neisseria, who like to hang out in pairs (far right). E.Coli is another one of those good guy/bad guy bacteria that normally live quite happily in our lower intestine, but can also cause bladder infections (other bacteria can too), among other things. A particular strain of E.coli, the 0157:H7 strain, is the one that can cause severe life-threatening illness in undercooked ground beef. You probably know Salmonella as a cause of "food poisoning". Different species of Neisseria can cause gonorrhea and meningitis.
The last bacteria, lower center, is one that I myself have never seen, that of Vibrio Cholerae, the cause of Cholera. This is what's causing so much misery to those in Haiti right now. It's a curved (like a comma) gram negative rod.
Gram stains can not be used as a sure way to identify the exact species of bacteria that is making someone sick, but can help the doctors know which antibiotic to use, as many are targeted towards these broad classifications. It gives both the doctor and the microbiologist a really good idea of what the bacteria is and additional tests (culture and sensitivity) can further identify the organism and determine further treatment.
Once again, this is all for fun and shouldn't be used in any other way. You really shouldn't believe everything you read on the internet anyway, right?? But hope you're having as much fun reading it as I am sewing and writing it! As a stay at home mom, it's a good way to keep my noodle working, although lately middle school algebra has been using those neurons too :-).