No illustrations for this one. I’ll leave image searching to the hardy, the curious, and the self-punishing.
…Right. So today I’m going to talk about bacteria. For those of you who want to read about interactions with humans, now’s your chance to click away.
I haven’t seen a real patient in a month. Last week during Patient-Doctor we went to an art museum. Before that were videotaped exams during which we interviewed standardized patients. (Best moment: Me: “You mentioned you were hard of hearing. Do you wear a hearing aid?” Patient: “What?”) Next week is our final reflection session, which will have a few Doctors, ~80 Medical Students, and no Patients.
Don’t say I didn’t warn you.
Some interesting things about bacteria that are interesting to me and maybe not to you but hopefully to you too:
1. We are outnumbered 10:1 by bacteria on our own turf, our bodies. (Note: this is by number only. I’m not sure about volume. Most bacteria are only a fraction of the size of human cells.)
2. I used to think “flesh-eating bacteria” (necrotizing fasciitis) were a certain species of superbacteria that you somehow pick up (thanks, Cabin Fever). Actually, they’re normal bacteria species (or certain strains of normal bacteria) gone bad–instead of causing superficial skin infection, they chomp all the way down to the muscle and nerves underneath.
Many kinds of bacteria can be “flesh-eating,” and the scary part is that we’re all harboring them on our skin, in our throats, and in our GI tracts right now. They’re just not in “flesh-eating mode”–and no one knows exactly what factors in the host or the bacteria trigger the often fatal change.
2a. The less scary part is that nectrotizing fascitis is rare. One doctor said he saw two cases in six years.
2b. (Jim Henson, creator of The Muppets, died from it in 1990.)
3. Actually, the whole “normal bacteria turned bad” thing is true for many infections. About a quarter of us have several strains of Strep in our throats… but we don’t have symptoms of the disease. A similar percentage of us have Staph on our skin, in our nose, in our GI tracts, and in our vaginas. Our immune system generally keeps them in check.
4. A vaccine for Lyme disease was developed and made it to the market but was withdrawn because of anti-vaccine sentiment and low public demand. Lyme disease is the only example of a sickness that can be combated with an approved vaccine that is currently not available to the public.
5. We are in a continual arms race against bacteria. We develop an antibiotic that doesn’t let bacteria build their cell wall. Bacteria select for an enzyme that neutralizes our antibiotic. We make an antibiotic that inactivates the enzyme. Bacteria select for modifications of their enzyme that don’t get inactivated by our drugs. And so it goes.
5a. Note the wording: bacteria “select for” traits that evade our weapons. The mutations exist before we introduce our weapons–they don’t develop in response to them. Now the bacteria with previously arbitrary mutations survive, prosper, and share their genes with their friends, lovers, and daughters.
5b. MRSA (methicillin resistant Staph aureus) was first documented in 1961. Now, about one third of people harbor it. Although it used to be found only in hospitals, now it can be acquired in the outside community as well. It is resistant to not only methicillin but many other drugs in similar classes.
Exam on Monday. More facts must come, or I’m not going to pass.