Errors in First Aid for the USMLE (2007): Microbiology

March 24, 2007

As always, comments are welcome. I’m sorry to say that I did not do a good job reviewing the section on viruses as this is my weakest subject.

Microbiology

  1. P.137, Bugs with exotoxins
    1. Bordetella pertussis does not stimulate adenylate cyclase, it instead inhibits GTPase. This differentiates its action from that of cholera toxin and the LT toxin of E.coli, whose actions stimulate adenylate cyclase.
  2. P.140, Intracellular bugs
    1. For facultative intracellular, I offer the following:

i. My Liege, Your Niece Lists Frank, Bruce and Sam.

ii. Mycobacterium, Leigonella, Yersinia, Neisseria, Listeria, Francisella, Brucella, Salmonella.

  1. P.144, Lactose-fermenting enteric bacteria
    1. After including Serratia, change the mnemonic from “lactose is KEE” to:

i. “Test lactose with MacConKEE’S”.

ii. Citrobacter, Klebsiella, E.coli, Enterobacter, Serratia.

  1. P.145, Bugs causing diarrhea
    1. O157:H7 should refer to Enterohemorrhagic E.coli (EHEC), not Enteroinvasive E.coli.
  2. P.150
    1. The heading “Microbiology-Mycology” is on the wrong page, and should be on P.151.
  3. P.152, Pneumocystis carinii
    1. This microbe is now referred to as Pneumocystis jeroveci.
  4. P.154, Medically important helminths
    1. There should be some mention that Schistosomiasis can cause granulomas in the bladder and has a role in Squamous cell carcinoma of the bladder.
  5. P.163, HIV diagnosis
    1. A test with high sensitivity has low false-positives, not high. A sensitive test with high false-positives indicates that there is low prevalence of the tested disease in the population. It is more appropriate to use NPV for this type of statement.
    2. A test with high specificity has low false-negatives, not high. A specific test with high false-negatives indicates that there is a low prevalence of the tested disease in the population. It is more appropriate to use PPV for this type of statement.

i. You may not think that these distinctions are important, but they are. Sensitivity and specificity are qualities of a test and do not change depending on the population tested, but a test conducted in Africa (where prevalence of HIV is high) versus the same test conducted in the US (where the prevalence is low) will have different PPVs and NPVs, i.e., different numbers of false-positive and false-negative results.

  1. P.164, Prions
    1. Fatal Familial Insomnia should be included in this list of Prion diseases.
  2. P.169, Bactericidal antibiotics
    1. I think that Rifampin, daptomycin, the combination treatment SMX/TMP and the polymyxins should be included in the list of cidal drugs
  3. P.169, Methicillin….
    1. “Don’t need MeNDing: Methicillin, Nafcillin, Dicloxacillin”
  4. P.170, Cephalosporins
    1. The MTT group responsible for the disulfiram-like reaction is only found in 2nd generation cephalosporins cefotetan and cefamandole. I think it’s worth changing to “(in 2nd generation cephalosporins with a methylthiotetrazole group, e.g. cefamandole and cefotetan)”.
  5. P.172, Macrolides
    1. I think it’s worth mentioning that Erythromycin is a potent inhibitor of P450, that Azithromycin is used in prophylaxis of MAC, and that their clinical use is for atypical pneumonias.
  6. P.172, Clindamycin
    1. Lincomycin is listed on P.171 as one of the 50S inhibitors, but it is not mentioned that this drug belongs to the same family as Clindamycin. I think this should be changed to “Clindamycin, Lincomycin
  7. P.173, Trimethoprim
    1. I think that the following grouping is interesting:

i. Methotrexate – inhibits human Dihydrofolate reductase

ii. Trimethoprim – inhibits microbial Dihydrofolate reductase

iii. Pyrimethamine – inhibits parasitic Dihydrofolate reductase

  1. P.176, Antifungal therapy
    1. The antimicrobials were listed as being either cidal or static, but this is not done for the antifungal drugs. I think this should be included with each description.

i. Polyenes (Amp B and Nystatin) – cidal

ii. Azoles – static

iii. Flucytosine – cidal

iv. Caspofungin – cidal

v. Terbinafine – static

vi. Griseofulvin – static


How to Prepare for the USMLE: Learning from Mistakes

January 26, 2007

I have always insisted on making my own mistakes. I often have to repeat my mistakes. This eats up a lot of my time.

I’ve griped before about not knowing how to handle this period of studying for the USMLE. What I have really meant is that I don’t trust anyone else’s advice and insist on screwing up a little before getting it right.

“You’ve bought too many books, you’ll never read all of those.”
“I never did a single question and got a 99.”
“Just stick with First Aid. It’s all you need.”
“You don’t have to study Emrbyo. There were hardly any Embryo questions on the test.”
“Do nothing but questions. Questions, questions, questions.”
“Man! There were a lot of Emrbyo questions! It’s definitely high yield.”

I still believe now what I believed before: that I have one shot at this test (I have no intention of failing it). In statistical parlance, this means that n=1 and df=0. You cannot draw conclusions from that study. People peddling specific advice to you forget this. Both people that stopped me in the library with their two cents about Emrbyo forgot this. And I will slowly forget this.

Since I broke up the subjects into General and Systems (the organization of the 2007 First Aid), I’ve tried to work on each section a little differently to see what is working. So after Biostats, Behavioral, Embryo, Biochem, Immuno, Autonomic Pharm, Basic Path and Micro, n=8. What follows is a breif chronical of my personal mistakes.

Biostatistics – 1 day

I read through the First Aid section briefly before slowly going through my old notes. I then opened up the Kaplan Lecture notes and read their Biostats section. For the first time, I started to notice that there were disagreements between sources. This sort of thing drives me mad, so I would often waste ten minutes on a piece of minutia to protect the house of cards. I then read the HY Biostatistics by Glaser. It was, by far, the best thing out there. I can’t say enough nice things about this excellent book. Finally, I took out a few pieces of paper and wrote a few pages of notes that I will later use to refresh the week before the test. I spent too much time on this section. I should have just used HY Biostats and taken my notes straight from it. Could have saved half a day.

Behavioral Science – 2 days

Going in, I am less than enthusiastic. Behavioral Science has always felt a little soft and doesn’t lend itself to learning a few core principles and then extrapolating the rest. It’s low yield. I start with Kaplan. It’s overkill. All of the epidemiology is over the top and I am falling asleep. Many of the tables and charts start to conflict with each other (two sentences each claiming different #1 killers for this or that) and I pitch it. After taking a look at the First Aid, I’m desperate to believe that there isn’t much I need to know as I finally turn to the HY Behavioral by Fadem. Everything is compact, well explained, and of a manageable size. This is what I wanted from the beginning. I take all of my notes for later review from this book and move on.

Embryology – 2 days

I wanted to work on Embryo as its own topic, and in the Kaplan notes it is intertwined with each system under Anatomy. Trying to learn from the previous three days, I head straight for the HY Embryo by Dudek (the BRS is also written by Dudek). This book is long, filled with pictures, and weighs in at 177 pages. I really liked this book for its clear explanations. There were several shaky concepts that were finally made clear (meiosis v mitosis, I’m embarassed to say) and it was worth the investment. It was detail heavy, but not to the point of being irrelevant and included plenty of pages devoted to genetic disease. All of this ended up tying in neatly with Biochem, so I consider it time well spent. Two days is a lot to devote to this, but I figured it was worth it on the assumption that it would help me make more connections down the road. I took all my notes onto Post-Its and put them in the First Aid section. I would do this the same way again.

Cell and Molecular Bio – 2 days

At SGU, genetics was a sort of half-assed course. Unfortunate, because I love this stuff and was completely put off at the time. I tried to repeat the success of Embryo with the HY Cell and Molecular Biology book by Dudek.

What trash.

This book has a bizarre number of typographical, illustrative, and conceptual errors. To be sure, there were some bright spots. The first chapter on cell signaling is fantastic and chapter 10: The Human Nuclear Genome was just fascinating, but I spent so much time trying to fact-check this book (after you find one error, you find another, and another) that I reached the point where I just couldn’t trust it any more. It’s largely cobbled together from his other books (almost twenty pages are straight from his HY Embryo) and the patchwork shows. This book was far from high yield and cost me two days before I gave up. I would never recommend it. I decide to cut my losses (Chapter 17 of 27) and go to the next topic.

Biochemistry – 5 days

I spent the first two days doing nothing but looking at the First Aid and reading through the corresponding notes from my first year. At the time, we were using Lipincott’s Illustrated Biochemistry, so having the book next to me made it easy to make sense of my chicken-scratch. I was cruising through the topic, confident, and then an amazing thing happened: I realized how much I didn’t know. You forget about it at the time, but going through Lipincott in first year, every term is alien, every disease and drug tie-in is ignored, and you’re happy to just get a “feel” for what’s going on. The second time around, it’s like seeing the world with new eyes. You understand every reference and all the things that haven’t made sense in other courses are finally connected. It was relevatory. I had originally planned to skim this book but finally decided to reread the whole thing. I didn’t have time to take any formal notes for later review (the Fed-Fast chapters were too engrossing), so I’ll have to carve this out later. This was also the weakest section in the First Aid, and I found myself wasting valuable time fact-checking Lipincott against First Aid against other texts to keep my head on straight.

If I had it to do again, I would have read through my old notes once, and then started on the book. I would have then used the two days that I wasted on Dudek’s HY Cell and Micro to write some review sheets. Oh well. My roommate spent the entire period going through Kaplan’s notes and had positive things to say. I wish I could confirm, but I ran out of time.

Immunology – 2 days

This was another SGU course that fell short for me. Fortunately, you can’t escape it, so that I didn’t learn it formally didn’t stop me from picking it up in Micro, Path, Pathophys, and Pharmacology of Immunosuppression. To get a feel for the scope, I cruised through First Aid and found that I had already covered a great deal of the material in Dudek’s HY Embryo. At this point, I’ve stopped looking at Kaplan all together. I went through the first four chapters of Rapid Review: Immunology and Microbiology. It is bare bones. They make it very obvious what they think is important and I did manage to make some new connections in these chapters, but it was not good enough to be a stand alone. There were several things (like lymph tissue anatomy) that were covered more in depth in the First Aid. I didn’t think that was possible, but there you have it. Between the two of them, I was reintroduced to everything that I saw in Path and my bases are covered. I even had time to take some good review notes for later. For the material I covered, I spent too much time in this book. That said, I didn’t have the time to read a proper text, so, c’est la vie.

Pathology of Neoplasia and Inflammation – 1 day

Path, how I’ve missed you. I’ve been looking forward to cracking open my brand new beautiful Path BRS since the day I bought it, and it was hard to limit myself to these two sections. I like the layout of the book, that the pages are thick enough that highlighter doesn’t bleed through (a previous problem), and the pace. The questions at the end of each chapter are inappropriately easy, which disappoints me. The subject came as a welcome break and I took one page of notes from the BRS and the First Aid.

Pharmacodynamics, kinetics, and ANS – 3 days

I started by reading the sparse entry in the First Aid on dynamics and kinetics before opening my Pharmacology for the Boards and Wards book. It covers these topics in the first 12 pages. It took my three hours. I’m probably just dense, but I didn’t feel this was well presented in either place, so if you already understand the topic, then FA might be enough. I floundered in this, but by the end was happy with my understanding. That left two days to cover autonomic pharmacology. That might have been enough, but the pace to date was too exhausting, and my roommate and I decided to quit for a day and recharge. It was necessary and we felt like a million bucks, but this means that I haven’t covered adrenergic drugs yet and will have to make it up later. If I had this to do over again, I would have traveled back in time and learned it correctly the first time. I also wouldn’t have tried to plow through three weeks of work without a single day off. Live and Learn.

I took a look at the Kaplan pharm section, and they have some very interesting pictures and graphs for conveying difficult topics. There pictures on the effects of cholinergics and adrenergics on the heart rate and BP are amazing, and the picture showing the ionization of drugs in the urine at varying pHs and resulting excretion is one of the most amazing pictures I have ever seen. As Pharm for the Boards and Wards is frustratingly filled with errors, I think I’ll switch over to Kaplan’s pharm when it comes to the systems.

Microbiology – 8 days

This is our first big topic, one of our weakest topics (competing with Pharm), and something I was afraid to begin. I decided to take a completely different approach and this has been the most successful to date.

I read the basic information in my main text, the RR: Immuno and Micro. Although it was painful to admit, I had to relearn about gram negative, positive, and the differences therein. After making some very basic notes, I used the FA bacteria-trees for gram positive and gram negative bacteria. I then wrote out all of the toxins for each bug and came up with some mnemonics for them. This would be my base. I spent the rest of the day writing the best notes that I could, trying to combine all the relevant information from the FA and the RR so that I would never have to look at either again. This took all day.

The next day I spent the first two hours trying to recreate the list of toxins from memory and draw the bacteria trees from memory. I accomplished this by noon. For the next two days, I did nothing but read about antibacterial drugs, their mechanisms, targets, and side effects. Every morning I would reread the notes I had made from the previous day until they were almost second nature. I tweaked my mnemonics.

By the time I had to sit down and learn about each bacteria, I found I knew almost everything I needed to simply from the drugs, the bacteria tree, and their toxins. Everything new that I was reading fell neatly into my pre-existing framework and this made everything before and after more solid for me. All in all, I spent four days on the bacteria alone, two days on viruses, and two days covering the remainder (protozoa, helminths, fungi). Nothing I have done has worked out so well.

Because the pharm section in the RR is small, I had to supplement it with the FA (suprisingly complete) and the Boards and Wards book (this section wasn’t too bad).

General Reference Book

Of all my decisions so far, the best one has been to have the Merck Manual with me at all times. It covers Micro, Pharm dynamics and kinetics, Path, Phys, EVERYTHING. It has been the great oracle whenever my review books conflicted and I would be lost without it. Of course, you could always study with your computer on and the internet running, but that would be a disaster for me. Instead, I keep my focus and have this book in front of me at all times

So what have I learned?

Less is more. Some books should generate automatic refunds for all the mistakes in them, and I would have done much more research on reviews before buying many of them (as it was, I went by First Aid’s recommendations alone). Instead of finding one incredibly solid book for each section, I have at least two books for every section (considering Kaplan) and sometimes three (Pharm, Path). This has been a mistake so far and one I’ll try to avoid as we enter systems.

First Aid is not enough. It has errors and will not give you an understanding of the topics. The First Aid is for someone that already knows everything and is looking for reinforcement and an idea of concepts previously tested. While it may be true that most questions you’ll see have their answers in the FA, that’s a far cry from being able to say that the FA helped me answer all the questions. After you read it, you’ll understand what I mean.

Repetition goes a long way. I find that writing out the information and making my own set of notes has worked for every class I have taken in medical school and this is no different. To paraphrase the late Frank Netter, “you can’t lie in a painting.” I feel the same way about writing: the things that are unclear to you become obvious when you try to take notes. It is, however, incredibly time consuming and I’m 3/4 towards my very own carpel tunnel syndrome. I’ve also found that taking notes on a piece of paper folded down the center is helpful, with prompts on the left and the information hidden on the right. It’s an idea stolen from teh Cornell method of note-taking, and it makes it very hard to lie to yourself as you read something that, “yeah, I remember that.”

When the answer is hidden, there’s no way to fake it.

So if you believe my experience, here’s what you keep and what you throw away from my original list:

  • HY Biostatistics (great)
  • HY Behavioral (great)
  • HY Embryo (for the motivated student)
  • HY Cell and Molecular (trash, don’t buy)
  • Lipincott’s Biochem (long, great if it was your text book. Might want to consider Mark’s BRS)
  • Pathology BRS (great)
  • Pharmacology for the Boards and Wards (look for something better)
  • RR: Immunology and Microbiology (Straight to the point, no frills)
  • Kaplan lecture notes (Biochem and Pharm are strong sections. Biostats and Behavioral are weak. A wash).
  • Merck Manual (my rock)

Hope it helps, topher.

Return to USMLE Step 1 page.


Errors in First Aid for the USMLE (2007): Microbiology

January 14, 2007

Until I write this section, please feel free to add any errors that you’ve found in the comments section.

Return to First Aid Errors page.


Errors in First Aid for the USMLE (2007)

January 13, 2007

Apologies to anyone that has been reading this post and wondering why I haven’t done any new work on the First Aid.  This section moved here.  Please change any links that lead you to this page so that you can find the updated version of the errors.

Sorry for any confusion, topher.