YOUR HEALTH - MEDICINE 101

BACTERIOLOGY

In 1929 a Scottish physician named Alexander Fleming decided to take a holiday. He was working on the isolation of various bacterial species and left his lab, well, in a bit of shambles. When he got back he noticed the bacteria in his petri dishes hadn’t taken a holiday – they'd simply gone about their business, increasing the size of their various colonies. But on one of the petri dishes was something strange – there seemed to be a bit of mold present on the one side of the dish and the bacteria in that dish hadn't multiplied. In fact, in the middle was a clear line of demarcation. It seemed as if the mold had killed the bacteria. You've probably grown this bacteria in your kitchen … it was a common bread mold called Pencillium. You guessed it -- Dr. Fleming eventually isolated the chemical that this mold was producing and called it penicillin. He also picked up the Nobel Prize for that discovery in 1945.

Not much has changed in labs when we test for bacteria and sensitivity to penicillin and other antibiotics.

If you've got a sore throat, it’s very hard for the doctor to tell if it's caused by a virus, or by a bacteria. The doctor takes a swab of the secretions from the back of the throat to pick up some of the bacteria, and sends it to the lab.

The lab technician then tries to grow the bacteria that may be present in a petri dish. Most petri dishes contain agar, a gel-like chemical produced by algae that encourages the growth of bacteria. The swab is spread across the agar and the dish is kept in an incubator with the perfect temperature and humidity to encourage bacterial growth. If the sore throat was caused by a bacteria, the lab technician can read the growth on the petri dish after several hours or sometimes days. Each bacterium produces specific signs and growth patterns. I'm growing some common Streptococcus Type A. This is what the technician would see if you had strep throat. Here’s another one growing Pseudomonas, which produces this light green colour.

Once the bacteria is identified, the next step is to test whether it's sensitive to antibiotics. Small paper discs containing various antibiotics are placed on top of the bacterial growth. If the antibiotic stops the growth of bacteria, a small clear halo appears on the agar .. just like this. Finally, a report is sent back to the doctor saying what bacteria grew and which antibiotic was most effective.

Seventy-five years after Sir Alexander Fleming noticed the strange fungus growing in his petri dish, Pencillin is still a commonly used antibiotic and we have him to thank for that. Not only did he prove that an inquisitive mind is essential in science, he also proved that it’s always a good idea to take a vacation.