123. Moulds: Dermatophytes

Alyssa and Callum talk all things dermatophytes and Tinea:

• Tinea capitis – scalp, hair
• Tinea corporis – trunk, limbs (ringworm)
• Tinea manuum/pedis - palms and soles (athlete’s foot)
• Tinea cruris - groin (jock itch)
• Tinea barbae - beard area and neck
• Tinea faciale - face
• Tinea unguium / onychomycosis - nails

What does  Anthropophilic mean and how do you pronounce it? Tune in to find out.

Show notes for this episode here: https://idiots.notion.site/12-Moulds-Dermatophytes-3e6b963f48db46808f67985884be5794?source=copy_link

Transcript

Hi everyone. Welcome to the Idiots Podcast. That's infectious disease insights of these specialists. I'm Callum, and that's Alyssa. And we're going to tell you everything you need to know about fungal infection. Soon, may the Aine come to discontinue Caspo Fung gun one day. When the BD done. We'll take our leave and go.

Hi, Callum, how are you? I'm great actually. Although actually something bad did happen the other day to me. Oh, no. I saw this terrible thing happen. Uh, so a couple of my neighbors had this altercation and they were out in the street, and then they were like looking, it looked like a fight was gonna kick out and went and picked up their doormats and used them as weapons.

So I was like shouting. I was like, oh, no. They're metal fighting. That's really interesting because coincidentally today, okay, yeah, yeah. We're gonna continue talking about molds and we're gonna talk about Dema [00:01:00] fights. Oh, I thought you were gonna say, coincidentally, something happened to you. It did actually.

I was coming down on the train from Bristol this morning, and I was just about to sit down in my seat, really busy train, and I asked the ticket conductor something and the next thing I knew. Someone sat in my seat and I was like, ask, oh my seat.

Oh, that is much better. Yes. That, that sounds terrible. It was coincidence. 'cause all these molds we are gonna cover today are asking my seats. That was, that was very smooth. So, yes, what we're talking about today, we're continuing in the, the vein of the molds and we're gonna talk about Dermatophytes.

Okay. I guess at this stage we've done a couple of mold episodes, so we've already talked about mu and rare invasive molds, and you'll [00:02:00] remember from our fungal overview episode that the Dermatophytes are molds star in asco, my Cota order. Yes, that's right. Yep. So what, what is a phy fights, uh, essentially a group of molds that have the ability to invade the dead keratinized tissue, say skin, hair, and nails.

And they cause the disease known as dermatosis or more commonly teeny. And they're. A several species that infect humans and they're in three distinct genre. Your trichophyton, your micro spor, and your epidermis. The main way that people think about Dify infection is. This site of the body that's involved.

So Tenia cactus is scalp and hair infection. Corpus is your trunk and limbs, so commonly [00:03:00] known as ringworm and Tanium. Manum and PDUs involves your hands and feet. So PDUs is known as a athlete's foot tenia careers involving the groin. It's known as Jock, and then Tenia Barbie can involve the beard and neck area.

Tenia, I think it's fale, involves the face and Tenia er more. Oncom. Mycosis involves the nails I'd never heard by half of those terms before, which is interesting. Yeah. Tinia, Barberry. I didn't, I didn't even know that was a thing. I are sort of naming maybe be a historical thing. Is that a useful differentiator in terms of the organisms that cause these diseases are slightly different?

Yes. So certain species have a tendency to cause certain clinical manifestations like Triton in predominantly causes tenored. That makes sense. And I guess those are the. Body sites [00:04:00] and then the organisms themselves in terms of how they, they spread so they can be anthrop ilic. So that's when it's primarily or exclusively infecting humans.

So when we're talking about PCP, that was anthrop, paraphilic, uh, and then they can be, uh, phi or coming from animals or biophilic, where they come from. Soil. And then as a result of that, their transmission routes will depend on which they, they grow in the environment. So they can be either transmitted from human to human direct contact, not always necessary.

So for example, athletes food from walking barefoot in the changing rooms. So you get those little weird food covers that you get when you go swimming or animal to human from close contact or soil to human. And I think all of them, they like that moist, humid sort of environment in skin. And that's a feature of, of all of them, really.

Um hmm. And then in the UK it's Trico fight and br, that's the most commonly isolated DMA fight. So [00:05:00] that counts for about 70%. Of isolation. So I was talking to some of the lab staff about their processing of skin and nail and hair samples for dermatophytes, and they're like, it's always rubrum. I think that's mainly what what we see.

Yeah. Yeah. And we'll come onto to the diagnostics in a bit. So of those infections in the uk, is it oncom? Mycosis is the, is the most common fungal. PHY in the uk? Yeah, so generally phy infections are hugely common worldwide and in the uk so huge burden of of morbidity. And fungal nail infections probably affect about 5% of adults in the uk.

So it is a big problem. It's rare that these infections are going to do you any serious damage, though in immunocompromised individuals with cellular defects, they can cause more invasive infections, but predominantly [00:06:00] they're not able to invade beyond that dead keratinized tissue. Interesting. And I guess the other thing.

The disease itself isn't that severe, but when we're assessing people, say, cellulitis, one of the things you might say is something called onco mycosis, orial pd. You might say, actually that could be the portal of entry because you get this sort of disruption of your normal, um, barrier immunity, which can lead to entry of, of bacteria.

It, it can be a risk factor for, for other more severe diseases, I guess. So what about worldwide? How does that differ? So again, it's very common and I think it's particularly seen with higher incidences in hot and humid regions of the world. So main risk factors are, are moist conditions, obviously with the phi, if you've got contact with animals, and then things like the anthrop, paraphilic, commun communal baths and sporting activities that.

Where you're sharing changing rooms and things like that. [00:07:00] And I think A to P also can predispose ut to these infections. So yeah, everyone listening I'm sure will either have had or have seen lots of these conditions. I guess a common thing, but maybe less, I dunno, we can just speak to myself here. Not something that I get consulted on that much, and when I do, I'm often, oh, I should probably know more about this than I actually do.

Yeah, so I think that's a really good point. I think a lot of this is gonna be dealt with in primary care. Kids with teen capitalists or ringworm or athlete's foot that either things that you can manage yourself at home or that you might see the GP about. It's rare that that we get consulted and I think when we do, because we don't have as much day-to-day experience of it, then it can be.

Hard to think. Daunting. Yeah. Yeah. But I think the laboratories that we work in are gonna be processing all of these samples and we'll come onto the laboratory diagnostics later. But, so I think it, you know, it's good to [00:08:00] have a, a good understanding of what we actually do with them as well. Definitely these are transmitted by hardy aro spores.

Now, I think aro means in Latin joint, so basically it's joint spore maybe, or, uh, not sure why it's named by that, but it's basically you have fungal spores that are fragmentation of the hyphy, which are the sort of longer growing parts of the molds. Those then adhere to keratinocytes, which are the cells which produce the keratin in nail and skin.

They then germinate and invade. And as Alyssa mentioned earlier on, the risk factors for this happening really are, is a moist condition. Communal baths, things that either allow the the fungus to move out of that spore state, that give it some moist environment or transmit, or things where there's like abrasions, so athletic activity.

And finally atop P. And then invasive infections are, as we mentioned earlier on rare, but they can happen in an immune compromised individual where they have defective cellular immunity. [00:09:00] So as the pathogenesis and a little bit about the background, what about the clinical features? Do you wanna take this bit?

Yes. I think the appearance really varies if these infections varies depending on several things. So the fungal site involved. And also the immune response that the host has to the pathogen. And also if, if some of them have been treated, um, with topical steroids, then they might have a more atypical, um, appearance.

So tenia, capitalists talk about first. So this is worldwide disease that predominantly affects childhood. And I think that's because it usually clears once people reach puberty. Because the fatty acids in, in Greece, in the scalp area inhibits their growth. Um, so these mainly caused by your anthropo ilic organisms can be caused by some, uh, zoophilia organisms.

Infections generally divided into ect ahr, so that's where [00:10:00] the arthro boards are found on the hair. And the hair that causes the hair to break a few millimeters above the skin. Or Endot where the arthro spores develop within the hair shaft and that causes the hair to break at the skin surface. And the main sort of clinical findings, scaling of the scalp associated hair loss.

So it might look like dandruff. And again, there's variable degree of inflammation depending on the host response. So you can get pustules and more crusting and exudate and some of these species can cause carry on. Have you, I don't know if you've come across, carry on before. So this is where you get more of an abscess that mainly occurs on the scalp area.

That can occur on the face or, or limbs as well. And that's really due to a, a dramatic. Immune response to the Dema fight. So he had a really nice case [00:11:00] in Bris in Exeter a couple of years ago of a kid who lived on a farm and I think he used to like poking his head through the railings around around the cattle and had been rubbing the top of his head on these railings and then developed this big pussy.

Abscess thing that on his head he had to treat him for, for weeks with, with antifungals. Um, and also he can get some secondary bacterial infection in those and the main species. Micro sporin, canis trico and tons tritin ose. And try to try to fight one. Minify. Yeah. You've put some excellent show notes together for this episode, and there's an image there from Derm Net.

Uh, odd Skin Lesions are one of those diagnostic conundrums, which can be really tricky to unpick, um, particularly if you've not seen it, the, the condition before. So it's good to have an example there. Okay. Tenia Capita [00:12:00] Rex Endof Rx and Carry on. So the next one is Tinia, porus or ringworm. So I feel like this is a sort of thing that historically grannies would've diagnosed.

Granny would say that's clearly ringworm. So this can be either anrophilia or zoophilia. And the amphiphilic, um, result in less inflammation or less well-defined lesions compared to those formed, uh, from zoophilia cases. And it's that classic appearance of a slightly raised, slightly scaly red rash, which is in a, a circle and broadens out from that.

Again, there's an image, but it's a pretty classic. I think once you've seen it, once you, you'll recognize it. Well, tinia IATA is another, is that a clinical disease? And that's a variant caused by Trico concentric. And that is lesion with concentric scaled rings. Is that Yeah. There's an image at the [00:13:00] bottom of the episode notes.

It's like a, a really interesting variant of Teen Ess where. Yeah, you get, instead of just a single scaled ring, you get these concentric scaled rings. So it's quite fancy, kind of patterned rash, and it's very specifically localized to certain geographic areas. So it's found in the Pacific Island, Southeast Asia, and South America.

Interesting. I've never heard of that before. I guess thinking about that with, if you've got a patient with a travel history and they've got something that looks a bit like tin porus, but it's got these concentric scaled rings. Yep. So 10 PDUs, uh, which most people are familiar with is Athletes'. Foot mainly affects young adults, but I think it can affect any, anybody really.

It's usually caused by Titin, rubrum, or Titin in into digit, and it causes fishes within the toe. Webs can call scaling and [00:14:00] maceration of the feet, and as Callum said earlier, it's then acts as a portal of entry for other, um, skin pathogens. And next we've got Tenia, curus. Um, so Tenia Curus, this is the one that happens in the groin, and you get emus lesions with central clearing and raised borders.

So I guess quite similar to Tenia, porus, but maybe a bit more central clearing, um, generally caused by Trico and rum or e for. Yeah, epiderm Phy quite a big area in the Mycology news at the moment because there's a couple of novel phy species which are causing. Outbreaks of of 10 careerists. So one is tenia ini that I think first emerged in India and it's anthropos.

They spread human to human and really worryingly. It's to ine resistant. It's now really common in India and Southeast Asia and cases are starting to be [00:15:00] seen in the UK as well. So it causes quite severe and difficult to treat. REITs can also affect the body and the face. And you get a lot of inflammation and, and itchiness and there has been evidence of sexual transmission.

So that's one to sort of, if you're seeing cases that GPS might refer to where the resistant treatment. And another is 10 Es type seven. So this is another emerging phy that also causes teen reus or genitals affecting the genitals. And this one also has, um, evidence of sexual transmission. Interesting.

And does Menes, uh, does that have any intrinsic resistance that we're worried about? Not that I know of. I think it's more that it's quite, been quite well documented now of the sexual, um, transmission element. Yeah. Okay. So an emerging [00:16:00] space and something to, to keep on top of, to be aware of what's happening with the epidemiology.

And then finally we've got tenia. So this is common in the older, in older age of diabetics and event. Essentially it's our. Fungal infection of the nails. So essentially the nails are embedded from the distal and lateral aspects, and it grows into the middle. And that can lead to on oncolysis. So the nail bed that's lifting up and you get these sort of thick.

Discolored Dystrophic nails, and I think this is more common on the feet because of moisture environment. You've got socks, you've maybe got your slippers, you, your feet by the fire. Um, so it's comfortable. But see, then you get your fungal nail infection. Majority of these are caused by dermatophytes, most commonly trico fight and rubrum.

But so about 10% are caused by other molds. So things like aspergillus, scapular. Scully ais, acrimonious and fusarium and rarely caused by at least including Canada. So we come onto to this lab diagnostics, but this is something where you [00:17:00] get your nail sample and the lab staff are saying it's usually phy and rubrum, but actually they are doing tests to look for these other things.

Um, and when you see them, it's quite interesting to, to look at them under the microscope. Talking of which we're now onto lab diagnostics. Although before we move there, we've mentioned a couple of them there. Like what organisms cause the clinical syndromes and in the show notes is a large table that this was put together, which has each species classification, clinical manifestation, and the key points.

So if you are wanting a bit more detail on that, more so than we've gone over there could do that. And then we haven't done an alternate saying the organism name one by one, which is a sort of podcast classic. But you can always read that and do that in your head yourself if you want. So actually you talk about the lab diagnostics.

Yeah. So yeah, coming onto lab diagnostics. So I think the main document that is used for this is the U-K-S-M-I, uh, B 39. That covers diagnosis of organisms causing skin, hair, and, and [00:18:00] nail infection. So samples are skin or scalp scrapings, nail clippings, or plucked hair. Um, firstly they're treated with KOH and then examined by direct microscopy.

And the lab staff are gonna be looking for the presence of hyphy and arthro spores and also the presence of, of yeasts, which can rarely cause these diseases. And the main thing that they'll, that will help them see that there's a Dema fight is that these have Sept eight branching hyphy that fairly even diameter along so they don't taper, which may develop these chains of rectangular spores.

So the art spores. And for hair specimens, they'll also be looking to see if it's ect, so on the outside of the hair shaft or endot, which is on the inside of the hair shaft. Yeah, so the KOH, the testim hydroxide just basically is breaking down the sample, allowing you to get that single cell layer. So when you click a [00:19:00] microscope, it's a bit easier to see and then you're going through the whole slide looking for, and it's quite difficult to see sometimes because the growth is usually in patches.

On your slide, you might go through the whole slide and only see a couple of small. Small patches. So your sensitivity of microscopy really depends on the, the expertise of the person doing it. But that said, I think that is the gold standard for diagnosis is microscopy. Uh, and seeing that the Hy feet, and you can also see, I can't remember what they're called, but there's the round areas as well.

What's that? Symia Sports. Yeah, chlamydia spor. So you see, they, they actually refract the light pretty well, so they, they're quite obvious to see. So yeah, it's definitely a skilled, uh, role for the biomedical scientist. And then you can use these fluorescence microscopy. You can do fluorescence microscopy with optical brightness like calor, which can really, which will light up the fungal elements and will really help enhance the sensitivity of your microscopy.

Yeah. Yeah, I think they don't tend to do that just 'cause of the volume of the samples and the getting that turnaround time. [00:20:00] So. I guess that's microscopy. And then the other main way that, so you get your nail sample in the lab. Um, certainly locally, ours are sent something called, so we're talking about the pre-analytical phase, just very briefly in the micro trans transport box.

I don't know what you use locally, but we have this sort of like a piece of cardboard that folds over and it's dark material and it allows moisture out and sunlight. It doesn't get in and it means that the, the nail or the he, the sample essentially, uh, suppresses bacterial growth 'cause there's less moisture for it, and it allows the nail to stay brittle, which means it's easier to break up and cut up and do microscopy and stick into your agar plate.

Okay. Yeah, we do stay. Black cardboard packages, but I never knew the, yeah, the, yeah, you can mainly do that. You can also do a tape. So if you're collecting sample from say, tenia Porus, you can basically get a piece of cell tape and stick it on and then lift it off. And you should get the sort of fungal growth if there is any stick onto the cell tape [00:21:00] when you put it in glass side and a special transporter.

So those are the two main sort of specimen types. And then I think just discern that with the hairs as well. You need to like either pluck. Pluck them out or twe them out because if you like cut them, you won't get the bit that's close to the, which is the bit that's being invaded. Oh, yeah, that makes sense.

I, I've never sent here for cultures. So for the culture, you basically get your nail, whatever sample, you cut it into the agar and stick it in. Um, and then you leave it to incubate for, I think it's, yeah, it's 14 days and it's weekly. You do that a lower temperature, so at 26 to 30 degrees. And the reason for that is that other organisms like bacteria and environmental fungi and stuff are less likely to grow.

But phys like that colder temperature. And then once you've grown it, essentially you do identification usually just species level. And that involves, and this is, I have to say, of all the microbiology lab stuff, ology is. I think [00:22:00] probably the coolest I'll say, because a lot of lot of it now is like Maori to you grow the thing, you stick it in the machine, you get the answer of job done.

This feels like real. Oh, you look into the microscope and the analysis of the like shape, and then you look at the agar plate and you say, what's the colony morphology, the color, what's it producing? It feels really like Sherlock Holmesy, you know? Puzzle solving. That's really satisfying. Yeah. Yeah. And look at the color of the colony and then turn the plate over and look at that color on the reverse.

And then, yeah, the microscopic features. Um, and we haven't gone through these, through all the different species. We've got a really good lab, SAP, with pictures and things, and you can refer to things like the identification of pathogenic fungi, a textbook. Yes. Yeah, I think they've got the same one that sits in our ecology lab.

It's quite hard to get a hold of, but there's a newer version, so that's really useful of lots of pictures and diagrams. Yeah. And the other useful thing, I guess we mentioned on Trico and [00:23:00] rubrum is the most common and, uh, useful sort of screening test as the urease test. So whether it breaks down urea and uh, uh, Tricy and Rubrum is uase negative.

Whereas I think a lot of the other organisms like the other dermatophytes are uase positive. So that's quite a quick screening test. And if uh, if you get that as negative and it has the compatible appearance, then you can quite quickly say that's what it is. Yeah. The fact that Tricy and Rubin's Urates negative can help differentiate it from some of the other common Matt fights.

Yeah, and in terms the agar that you put it in, so it's usually saot, so it's a sort of dextrose egg, and then you add in things like Chlor and Nic. Plus or minus Cyclo. Heide and Chlor Pinnacle broadly inhibit bacterial growth and cyclo heide inhibits, I think is it yeasts, another sort of fungi. But because that's a selective agar, you want to use that kinda, uh, an enriched, um, agar.

So you also use 2% multicar and that will allow you to just grow [00:24:00] anything that's going on. Usually we'd set up, certainly in our lab. You get your sample, you do the microscopy, you look for fungal hyphy, you set up your culture plates, and you set up a saro with chloramphenicol, and then you also set up a malt agar, um, is what you would routinely do for those sort of samples.

I think the SMI says read it seven to 21 days. Yeah. And then the identification's also important. I understand from like an epidemiological aspect for scalp infection. If you've got an anthrop paraphilic species, then you should probably look at classmates and family of affected children because they might be passing it between, between each other.

Definitely. Okay, so we've got our nail sample, our skin sample in, and we've seen Hy-Fi, let's say, and we've identified, we've cultured something. How do we treat these conditions? So generally your options are either topical therapy or oral systemic, um, therapy. So for things like your [00:25:00] athlete's foot, your teen corpus or your teen careerists, you can use first line topical, um, agents such as ketoconazole.

My conazole or clotrimazole, um, however, more severe disease, um, might need more systemic therapy. And then for some of the other sites, topical therapies that are very rarely effective. So for Tenia capita generally then the treatment would be an oral agent such as Griz tine, or Itraconazole. And for Oncomycosis, there are lots of topical agents out there and, and preparations that you can paint onto the nail, but again, I think these are, are pretty ineffective and to, to clear the infection really are going to need an an oral agent.

Rabine is our first line. You've got to your 80% cure after six weeks for fingernails [00:26:00] and 12 weeks for toenails. It's a very commonly prescribed drug, but it does have quite significant side effects. I think I've seen people getting peripheral neuropathy from it, and it can also affect liver function tests as well to monitor.

So it's one of these drugs that even the, even these non-invasive, non-severe fungal diseases. Have a significant morbidity impact that might be quite distressing for people, and the treatment itself is, is not straightforward, as with with lots of things we're talking in this series. Treatment's not straightforward, is it?

And if you can't use turine, you might be looking at something like systemic econazole and all these sort of AOL drugs that we talk about as we talk about an episode on that specifically. There's pretty significant side effects and risks on these drugs. Again, treating fungal infection is not always that straightforward, and sometimes with these cases it is a way up of do we just not treat them at all, depending on how bothered they are by their symptoms.

Yeah, trying to keep that foot dry and removing the nail involving a [00:27:00] podiatrist. Some of these drugs might be conjugate in the patients, particularly that you're elderly, polypharmacy, other health problems. I guess if you're gonna say, what's the treatment of fights, often the treatment is, no treatment is better than, than treatment.

And having that discussion with your patient can be, I guess, a bit, uh, tricky. And uh, as we mentioned earlier on in the show notes, there's this table that you've produced maybe. Maybe, do you want to just talk through that briefly at the end of this or, yeah. So in the table it's just really to summarize the different species that cause dermatosis.

So grouping them by tra uh, trico, micro spor and epidermic, and then describing if they're predominantly, um, anthro, amphiphilic or biophilic. What are the predominant clinical manifestations that they cause and some key points. And I've also highlighted in red those two that we talked to CI on Es and uh, tri Triton [00:28:00] in that are of public health concern at the moment.

A good reference guide to come back to if you've grown a specific species or vice versa if you're looking at the clinical manifestation and thinking what, what species need to be worried about. And there are these emerging pathogens that you've, you've mentioned, which is I think, useful thing to be keeping tabs on because it will affect our empirical treatments.

But yeah. Okay. That's dramatic phase. This mycology series has been supported by the British Society for Medical Mycology. The BSMM aim to bring together clinicians and academic researchers in the field of medical mycology. For more information, you can find the link to their website in our show notes on notion.

Please consider joining up to become a member. Thank you for listening to The Idiots Podcast, the UK's [00:29:00] premier Infectious Disease podcast. Questions, comments, suggestions. Why don't you send them into Idiots podcasting@gmail.com. Have a five star review in your pocket at ka, and I would love to have it.

Please drop it in your podcast player of choice, and if you want to donate to support the show, there's a link to do so in the description. But until next time, I'm Jane. I'm Callum. See you now. Now that the episode's done, we hope you learn and had lots of fun. So go forth and treat people with some of what you now know.