WILTIMS #190: Raise shields!

Today was a very lab/practical heavy day, so I didn't learn much in the way of interesting factoids, but rather reinforced things from previous days. But in preparation/procrastination for tomorrow, I did learn something:

TIL: One of the ways of describing the bacterial colony feature of elevation, or the raised/flattened appearance of the colony, is the term umbonate. Umbonate comes from the latin root umbo which describes a "boss," or raised bump on a shield. This is the same ultimate root as the modern word emboss, which took a detour through French before becoming part of the English lexicon.

A boss on a shield

WILTIMS #189: Nutritional facts

TIL: Kwashiorkor, which literally means "first-second" disease, or disease of the displaced child. The name describes how it is seen in the first child in a family when a second child is born. Suddenly there isn't enough food for everyone and the older child is often the one left to suffer through malnutrition.

Malnourished children can look merely unremarkably thin due to the masking effect of swelling (edema) from diminished albumin production. Albumin is the most important protein for controlling the osmotic pressure of blood. Its low rate of production would cause more water to leak out of the circulation into the surrounding tissues.

Flag sign of malnutrition

Relatedly, malnutrition can also manifest as a "flag sign" from lack of protein. This is when long hair changes color and/or texture for the period of the malnutrition, leading to a broad stripe in the hair.

Pseudomonas is naturally resistant to most antibiotics by living in the soil, which contains many other organisms that have learned to combat these organisms just like we have over the eons.

Haemophilus influenzae does not cause influenza (the flu virus does). H. influenzae does cause similar symptoms, though. 

Legionnaires disease, and the bacterium found to cause it, is named for a conference of the American Legion at which the first outbreak was reported.

WILTIMS #188: The Importance of TB-ing Dermis

TB-associate lesions in a
 3000-3500 year old egyptian mummy

We have entered that part of the year where, thanks to our affiliation with a predominantly Jewish institution, we get three four-day weekends in the next month. To make up for this, it seems like our classes have tried to put as much material as possible in our reduced class time. Unless I'm feeling unusually motivated, all of this means there will be a few fewer posts in the coming month. But today's is good enough to make up for the next couple days:

TIL: Though we've only been exposed to viruses like ebola and HIV for the last half-century, we have, as a species, been battling bacterial infections like tuberculosis (TB) since ancient times. Leprosy has been explicitly mentioned in historical and religious texts, and TB has been diagnosed both macro- and microscopically in mummified remains from ancient Egypt. Only now, 3-4,000 years later are we finally turning the tide.

Armadillo PSA: There's no
armor for leprosy; get tested.

Mycobacterium leprae, the bacterium that causes leprosy, is the slowest growing pathogen known. It doubles every 14 days (that's in comparison to every 20 minutes for E. coli). It also only grows in humans, mouse footpads and armadillos. Because M. leprae prefers the cooler tissues of the body (similar to the normal temperature of armadillos) it often causes lesions on the skin and in peripheral nerves. Untreated, this disease is gruesome. And because of the resilient ancient stigma associated with it, there has been a campaign to rename it Hansen's disease so that people will come get treatment before suffering the more deadly and debilitating consequences of the infection.

Lady Windermere syndrome is caused by an opportunistic infection of mucous buildup in the lungs by Mycobacterium avium-intracellulare. The name comes from an Oscar Wilde character who was a very proper English lady. Though, as defensive librarians have pointed out, her character was never actually sick in her eponymous play, the reference hints at the cause in real people. A proper lady is not supposed to cough in front of company, and the only otherwise healthy people who develop this syndrome are older women who, it is hypothesized, learned to always suppress their cough reflex and thus built up collections of mucus in their lungs for this obscure bacterium to grow in.

M. marinum a fresh and salt-water bacterium that causes "fish tank granuloma."

WILTIMS #187: Pre-med-achu, I choose you!

This evening I had the fun and freaky opportunity to learn how to interview applicants to our medical school. Our school uses the Multiple Mini-Interview (MMI) format which allows for students to sometimes participate in interviewing the applicants for future classes. Each interviewee completes eight, six-minute interviews on any of a number of usually ethical prompts with members of the school's academic community. This MMI system reduces bias and has been shown to be a fairer and truer judge of communication skills and predictor of clinical excellence than the old one-on-one long-form interviews. It was a nice break from dealing with our own comparatively petty second-year problems, to remember how stressful it was interviewing for the privilege of having our current problems.

TIL: When giving an oral patient summary, it's just as important to give pertinent negative diagnostic findings as pertinent positive ones. On the flip-side, it's important to omit positive as well as negative findings when they are not pertinent to the case at hand. The trick with this being that you have to know what is and is not likely to be pertinent, accepting your medical inexpertise as compared to the person to whom you are presenting the patient. Of course if your mentor wants to know any information that you didn't report, they can always ask.

WILTIMS #186: Shooting starter colonies

Listeria comet

TIL: Listeria comets are super cool (if you don't have them streaking through your intestinal epithelium). This bacterium likes to live inside the cells of the lining of the gut. It uses a potent one-two punch of toxins to burst through the vesicles that cells use to scoop up and destroy offensive organisms. Once in the cell, listeria hijacks some of the cell's scaffolding machinery and redirects it to quickly polymerize in the direction of the cell membrane. This streak is called a listeria comet and it's so strong that it can puncture the adjacent cell's membrane. From there, the bacterium needs only to reactivate its toxic tools to degrade the lipid layers surrounding it and start the process all over again.

This process allows listeria to spread completely unseen by the body's adaptive immune response, by never needing to exit its cellular hiding place to spread or replicate.

Next, C. difficile infections are almost entirely caused by antibiotics. And by that I don't mean that we are injecting people with bacteria or anything, but rather that a side effect of even the most appropriate antibiotic usage can be a gastrointestinal infection from this annoying (and sometimes deadly) bug. It's weird looking back at incidence rates from before and after widespread antibiotic use, because the correlation is very apparent. In fact, scientists originally hypothesized that the antibiotics themselves were the cause of the diarrhea sometimes seen upon their administration.

C. diff is commonly found in small numbers in a large percentage of the population, but it can never really get a foothold thanks to our existing gut microbiota. The problem arises when we wipe out the healthy bacteria while treating some other infection elsewhere in the body with antibiotics. This gives c. diff the chance it needs to assume a bigger and more pathogenic role in the intestines. 

Lastly, most STDs grew in prevalence from the 60s through the 70s. Then the rates of new infections stopped abruptly in 1980. The reason? Fear of the growing AIDS epidemic forced people into practicing safer sex.

WILTIMS #185: Revenge of the outcasts!

After seven hours of three horrific tests yesterday, we started up again bright and early this morning. Thankfully, in my humble opinion, we are starting the actual microbiology portion of our microbiology course, having wrapped up the immunology section. So, to celebrate the end of ridiculous detail (I'm looking at you, cytokines!), this post will be about a fairly broad idea.

Why do bacteria cause diseases? This may seem obvious, but hear me out. Viral diseases make sense: viruses depend on infecting and lysing cells for reproduction. But bacteria can live without our cellular machinery, so why evoke the wrath of the immune system by picking a fight with the local cells?

Well, first of all, many bacteria don't! These are the commensal bacteria that make up 90% of the cells in "our" bodies*. We love these guys because they do a couple important things for us. Some bacteria help us digest and/or absorb things that we can't easily digest and/or absorb on our own. But more importantly, all commensal bacteria help us out by outcompeting pathogenic bacteria from their niches. And this is the big hint as to why other bacteria need to cause disease.

Essentially, these other bacteria know (evolutionarily, not literally) that they can't win when playing by the same rules as those other extremely well adapted commensal bacteria. So, they change the rules. What do these bugs need to flourish? Water, nutrients, and hopefully a route to move on to other organisms. A great way to get these things is to make the body bring it to you through the well-intentioned but often overzealous actions of the immune system.

In broad terms, the immune system frequently starts it's fight by bringing in reinforcements in the form of immune cells riding a wave of fluid through leaky blood vessels. This fluid gives the bacteria the water it's hoping for, while the damaged cells of the surrounding tissue leak nutrients providing a great environment for the critters to multiply and thrive. If they flare up big enough to cause coughing, sneezing, diarrhea, sores, bleeding, or death, then they can spread to other people and start the cycle anew.

So bacteria often cause disease because all the peaceful positions are usually taken and you either die by the system or break the system in order to survive. 

TIL: Streptococci like to grow in chains, pneumococci in pairs, staphylococci like clusters, and enterococci can do pairs or small clusters.

* They make up 90% of the number of cells not the volume of cells; most prokaryotic cells are very small compared to those of eukaryotes. To give perspective, some bacteria can live inside our cells and some eukaryotic organelles, like mitochondria and chloroplasts, are thought to be very old intracellular commensal organisms that were so symbiotic that we essentially annexed them.

WILTIMS #184: It's actually lupus!

Apparently, today is one of two days during our preclinical years that we are taught by the dermatology department. In case you are somehow unfamiliar with the weird place that dermatology holds in the medical specialty hierarchy, the head of dermatology had this to say about training in that specialty: "Dermatology is very hard to get into, but your life is very easy after that." [everyone laughs], not at his message, but at his candor.

When you ask the average person what the most prestigious medical specialty is, you are likely to hear some impressive sounding area of medicine like neurosurgery. Dermatology is, in fact, the most competitive and highest paid specialty. Though poking at people's rashes and scraping away moles might not seem like the most desirable work, the lifestyle, hours, and pay have made it, far and away, the most hotly contested field to enter every year.

One of the weird flukes of this arrangement is that, though most would admit one doesn't need to be the top of one's class in med school to treat diseases of the skin, only the most intelligent and talented graduates become dermatologists. This trend was driven home again for me today in a small group session where my module was taught by the senior dermatology resident at our hospital. She was quite the imposing and intelligent instructor. Though only a few years older than us, she was easily an expert on today's topics and absentmindedly bossed around our normally high-and-mighty physician instructor.

TIL: Hemophiliacs are like summer squashes... Stick with me on this one. You know how each individual squash can look dramatically different in size, shape and color from one another regardless of the seed from which it grown? The way they can modify their appearance, even with the same DNA is through epigenetics. Epigenetics is the suppression or augmentation of genetic information through processes like methylation and X-inactivation. This is the same mechanism that diseases like hemophilia use to present with completely different symptoms and severity between directly related family members.

IT'S NEVER LUPUS (at least on House MD)! Ever wonder why lupus is always in the differential diagnosis for the patients on House, even though it almost comedically was never actually lupus causing the symptoms? The reason for this is that lupus has very broad, variable diagnostic criteria. It only requires 4 of the following 11 symptoms to diagnose lupus, often remembered by the mnemonic 

DOPAMINE RASH:

Discoid rash
Oral ulcer
Photosensitivity
Arthritis
Malar rash
Immunologic criterias
Neurological symptoms-(lupus cerebritis)
Elevated ESR
Renal disease
ANA+ve
Serositis
Hematological abnormality