HIV and ID Observations

Why do many clinically important microorganisms change names?

They haven’t married and taken their spouse’s name or gone to Hollywood and adopted a stage name.

Instead, through the tireless work of microbiologists, taxonomists, and geneticists, they have undergone sufficient reclassification so that their old name just doesn’t make sense anymore.

Or more graphically:

Why do clinical microbiologists love taxonomy? https://t.co/BdgGEUOFlh @ASMicrobiology #ASMClinMicro pic.twitter.com/fL3qgemYea

— JClinMicro EIC (@JClinMicro) May 17, 2019

What we gain in accuracy, alas, is accompanied by an increase in confusion, and a heavy taxation on our memory reserves. Even we ID types can barely keep the names straight; imagine how non-ID clinicians feel?

Our colleagues in clinical microbiology recognize this problem — really they do. But spend a little time reading Name Changes for Fungi of Medical Importance, and pretty soon you get deep into the weeds with no available machete to hack your way out. How’s this for an example?

The Ajellomycetaceae contains the teleomorph species Ajellomyces dermatitidis, Ajellomyces capsulatus, and Ajellomyces duboisii, the anamorphs of which are the genera Blastomyces and Histoplasma. The Ajellomycetaceae also contains some genera that have no known teleomorphs, including Paracoccidioides and the newly described genus Emergomyces.

Well, I’m sure glad we cleared that up!

So if you’re looking for an in-depth, detailed review of some recent name changes, take a look at the references section in this editorial, kindly sent to me by ID doctor and medical microbiologist Kim Henson. Warning — they are not for the faint of heart!

But here is a more subjective list of name changes that I’ve weathered over the years, along with a few miscellaneous comments:

Clostridium difficile became Clostridioides difficile. This recent change will take a while to get used to, as it’s such a common infection that Clostridium is pretty hardwired in our neural circuits. Also, the ubiquitous abbreviation “C. diff” still works fine, so there’s not much motivation to learn how to write, or to say, Clostridioides — in fact, I just had to teach my spell checker not to flag it.

Pneumocystis carinii became Pneumocystis jirovecii. It’s now quite clear that pneumocystis is a fungus (and not a protozoan, as originally thought). It’s also widely accepted (finally) that the species encountered in corticosteroid-treated rats is different from the one infecting humans — the rat gets Pneumocystis carinii, and humans Pneumocystis jirovecii. What’s still a matter of substantial debate is how to abbreviate the pneumonia caused by Pneumocystis jirovecii, as demonstrated by this hotly-contested poll:

What's the current preferred abbreviation for Pneumocystis jirovecii pneumonia? cc @UpToDate #IDtwitter https://t.co/uIq2dJEb1S

— Paul Sax (@PaulSaxMD) May 11, 2019

Haemophilus aphrophilus became Aggregatibacter aphrophilus. I attended a meeting a few years back which included several other ID geeks like myself, and we were discussing various aspects of our work. One mentioned she had just seen a case of endocarditis due to the wonderfully named Cardiobacterium hominis, which is of course the “C” in the HACEK group of organisms. I then mentioned that Haemophilus aphrophilus had been renamed Aggregatibacter aphrophilus — and suddenly there was a palpable sadness in the room. How could anyone be so heartless as to change the name of this whimsical and mellifluous-sounding microbe? Such a deep injustice, we’re still in mourning.

Streptococcus milleri became Streptococcus anginosus, intermedius, and constellatus. The name change to these abscess-forming streptococcal infections happened so long ago that many youngsters out there might not have even heard of Strep milleri. But trust me, it was tricky enough that for a while these three species were called “Strep milleri group” to help bridge the pain; now they’re called “Streptococcus anginosus group,” and milleri is no more. For the record, streptococcal taxonomy is mega-complicated and confusing — but if you think that is bad, wait until you start getting into the fungi!

Pseudallescheria boydii became Scedosporium boydii. Big improvement — Scedosporium is a wonderful word, replacing the strange and unspellable Pseudallescheria. I remember attending an ID conference during medical school that had two cases, both of which included details that caused me great confusion. The first was a streptococcal endocarditis case complicated by a “mycotic aneurysm.” Aren’t fungal infections called “mycoses”? So how did the strep cause a fungal complication — isn’t it a bacterial infection? (Turns out any infectious aneurysm is called “mycotic” — who knew?) The second was a post-traumatic fungal infection due to Pseudallescheria boydii, which I heard as “Pseudo …” which of course means “not genuine” or “sham” — you know, like “pseudo-intellectual.” So, if Pseudallescheria is the fake one, what’s the real one? I guess the real one is Scedosporium. Or not — fungal taxonomy is a total mess, right Andrej?

Just when you thought you understood Scetosporium. It gets more complicated, more difficult to treat, and like all of fungus, a taxonomic mess. #MSGERC2018 #MedEd pic.twitter.com/xZ7J0XABlv

— Andrej Spec, MD, MSCI (@FungalDoc) September 27, 2018

I am a cutie-bacterium.

Propionibacterium acnes became Cutibacterium acnes. Of all the recent name changes, this is easily my favorite! I have already thoroughly embraced this new name, and even pedantically correct people stuck on the old one — making me excellent company on rounds. Maybe Cutibacterium will give greater attention to this under-appreciated pathogen, infamous for causing prosthetic joint (especially shoulder) and neurosurgical infections. And why do I like it? First, Propionibacterium is a devil to say, good riddance. Second, Cutibacterium is adorable, especially if you pronounce it “Cutie-bacterium.”

Xanthomonas maltophilia became Stenotrophomonas maltophilia. This problematic, highly antibiotic-resistant gram-negative rod changed names long ago — so as with Streptococcus milleri, many might not even have heard of Xanthomonas. I first learned about this bug when imipenem had just been FDA-approved (yes, I’m that old), as it is one of the rare gram negatives intrinsically resistant to carbapenems. Two other points worth emphasizing:  1) Xanthomonas sounds very cool, could almost be the name of a science fiction series, “The Galactic Empires of Xanthomonas”; 2) Stenotrophomonas is real mouthful. Takes a while to learn how to say that comfortably — which is why, to many cystic fibrosis clinicians and patients, it’s just known as “steno.”

Enterobacter aerogenes became Klebsiella aerogenes. C’mon, that’s just mean, flipping one enteric gram-negative rod name to another. I suppose we’ll get used to it eventually, grumble grumble.

Rochalimaea henselae became Bartonella henselae. These agents of cat scratch disease, endocarditis, bacillary angiomatosis, and peliosis hepatis haven’t been Rochalimaea for many years. But my friend Joel Gallant used to call my other friend Rochelle Walensky “Rochalimaea” long ago when they were at Johns Hopkins together — which just goes to show that we ID doctors have a very strange sense of humor, one that may be difficult to explain to others.

Diphyllobothrium latum became Dibothriocephalus latus. This fish tapeworm of gefilte fish fame wasn’t easy to learn in medical school, so I’m going to resist this change for as long as possible. Note that even CDC hasn’t updated their page, taxonomy notwithstanding, so I appear to be on safe ground holding out at least for now. Dibothriocephalus indeed, hmmph. Try saying that three times fast.

Penicillium marneffei became Talaromyces marneffei. This dimorphic fungus, endemic to Southeast Asia, causes disseminated disease in severely immunocompromised hosts. I always liked that we had a clinically important fungus that included the name Penicillium, reminding us of the source of our first beta lactam antibiotic. Oh well. This Talaromyces name is taking a while to get used to, probably because it’s not a common infection here.

Pseudomonas cepacia became Burkholderia cepacia. It hasn’t been Pseudomonas cepacia for ages. But did you know that Burkholderia cepacia is really at least two different species, Burkholderia multivorans and Burkholderia cenocepacia? Isn’t microbiology fun?

Streptococcus bovis became Streptococcus gallolyticus — and a whole host of other things. Medical school curricula indelibly impart certain ID facts to every student — three of them are 1) daptomycin is inactivated by lung surfactant; 2) listeria and its various dietary associations; and 3) endocarditis due to Streptococcus bovis should prompt a look for colon cancer. However, they haven’t yet gotten around to updating the species name, perhaps because hardly anyone remembers it. And did I mention that streptococcal taxonomy is confusing, irrational, and complicated? Sure I did, many times — and further reviewed the whole clinical world of clinical streptococcal infections here.

And last, but not least …

Ixodes dammini became Ixodes scapularis. Hey, no fair — I have enough trouble with microorganism taxonomy, do I have to start keeping track of insects arthropods too? All I know is that Gustave Dammin was an esteemed pathologist here at the Brigham for many years, and studied both Lyme Disease and babesiosis. Which begs the question — is it an honor, or a curse, to have such a nasty little critter named after you? Let the debate begin.

Any other name changes that deserve highlighting?