August 4th, 2020

Carbapenems and Pseudomonas, Lyme and Syphilis Testing, a Bonus Point for Doxycycline, and Some Other ID Stuff We’ve Been Talking About on Rounds

As noted multiple times, many of us ID doctors attend on the general medical service. This offers us a chance to broaden our patient care activities and to work with medical students, interns, and residents.

Boy, that’s fun!

Yes, those of us who attend on medicine enjoy it enormously, though the experience humbles us on a daily basis about what we need to learn in cardiology, nephrology, gastroenterology, rheumatology, hematology, endocrinology — you name it.

Fortunately, the smart trainees (and subspecialty consultants) teach us tons.

Plus, at our hospital we have a co-attending system, meaning my knowledge can be amplified by another experienced doctor — this month an endocrinologist, who has fortunately for all of us never encountered a metabolic disturbance (electrolytes, minerals, glucose) he can’t solve.

So this week we take a partial break from the COVID-19 coverage, and summarize some ID stuff we’ve chatted about on rounds.

The patient lived in New England and installed air-conditioning equipment. He owned a ferret and five snakes, to which he fed frozen rabbits and live or frozen rats that he obtained from a pet supply store. His brother owned a healthy puppy. The patient had returned 27 days earlier from a 10-day trip to Hawaii, where he had cut himself on coral while scuba diving. Several of the hotels that he visited had caged parrots in their lobbies.

  • The ratio of trimethoprim to sulfamethoxazole in the combination tablets is 1:5. A single strength has 80 mg/400 mg, and a double-strength twice that — hardly anyone knows these arcane facts (except for pediatricians and pharmacists). And aren’t my math skills impressive?  Here’s a tip:  Since no one on rounds wants to say “trimethoprim sulfamethoxazole” (too long), go with “trim-sulfa.” It’s a better abbreviation than the brand names “Bactrim” or “Septra” (both of which should be retired), and it makes more sense than “co-trimoxazole.” Oh, and this is one of several antibiotics with excellent oral absorption.
  • Anaerobic bacteria can cause urinary tract infections. Consider these organisms when your standard urine culture is negative, especially in patients with anatomic abnormalities. And trim-sulfa (commonly used for UTIs) won’t be active against these organisms. Check with your microbiology laboratory about how to evaluate further.

All this antibiotic talk! On the first day of rounds this week, during introductions, one of the residents asked us to say our name and our favorite antibiotic.

Good time to replay the antibiotic draft I did with my friend Dr. Rebeca Plank!

15 Responses to “Carbapenems and Pseudomonas, Lyme and Syphilis Testing, a Bonus Point for Doxycycline, and Some Other ID Stuff We’ve Been Talking About on Rounds”

  1. Jesse Couk says:

    Another indication for aztreonam:

    Aztreonam-Avibactam Combination Restores Susceptibility of Aztreonam in Dual-Carbapenemase-Producing Enterobacteriaceae

  2. Elliott Wolfe, MD says:

    Dr. Sax, Another simple abbreviation for trimethoprim sulfamethoxazole: TMP-SMZ.

    • Paul Sax says:

      Or is it … TMP-SMX.

      Not easy to say!

      • Jesse Couk says:

        I picked up “TSX” somewhere. I liked it. Used it as a recently graduated fellow. Told by a colleague: “What is TSX? I don’t think anyone abbreviates it like that.” So I stopped.

  3. Catherine G. Ratliff says:

    T2 Biosystems Lyme test has been at FDA since February. It should bring improvement to “the mess.”

  4. Rebecca Baranowski says:

    Lots of red herrings in the C. psittaci scenario!

  5. Sophia Cardwell says:

    Fun! Also not causing similar IgE mediated type-1 hypersensitivity reactions in patients with *penicillin* allergy are most cephalosporins (except cephalexin) and antistaphylococcal penicillins, due to structural dissimilarity. Using any structurally dissimilar beta lactam in this circumstance, as opposed to alternatives (vancomycin, clindamycin, fluoroquinolones, aztreonam, etc.) can spare affliction generally and C. difficile, SSIs, MRSA, AKI, etc. specifically.; 10.1016/j.jaip.2017.08.027

  6. Roberto Esposito says:

    Inhaled aztreonam is very useful for the eradication of newly acquired Pseudomonas aeruginosa infection and for long-term suppressive therapy of chronic infection in patients with cystic fibrosis.

  7. Loretta S says:

    I learned a new word: “hypermucoviscosity”… I’m going to try to figure out how to use that word in a conversation soon.

    I happen to like the way trimethoprim/sulfamethoxazole rolls off my tongue when I am teaching my nursing students about antibiotics. And (ahem) I did know the ratio of trimethoprim to sulfamethoxazole in the combination tablets. Do I get a prize? 🙂

  8. Diego Escarramán says:

    A high guality gave us a great teaching

  9. Bernard Hirschel says:

    Practice your French:
    Lyme serology is problematic
    Problème à tiques

  10. Les Linares-Hengen says:

    What about checking followup CSF VDRL as test of cure in AIDS and immunocompromised? This is what always got me. But then again I would not want to repeat LP unless there was inadequate response.

  11. C. Kelley Tibbels MD says:

    I also would choose doxycycline as number one on my list of preferred antibiotics, I loved the discussion in the audio webcast. Thank you. I recall also that “doxy” was virtually forgotten as a choice for therapy in the anthrax scare a few years back, and also remember it is used for malaria prophylaxis. In the next world wide apocalypse, I’ll be sure a big bottle of “doxy” is in my bag.

HIV Information: Author Paul Sax, M.D.

Paul E. Sax, MD

Contributing Editor

NEJM Journal Watch
Infectious Diseases

Biography | Disclosures | Summaries

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