123. Moulds: Dermatophytes

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. May the additive come to discontinue Caspo Funga. 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 neighbours had this altercation and they were out on the street and then they were like looking it looked like a fight was gonna kick out. and went and picked up their door mats and used them as weapons. So I was like shouting, I was like, oh no.

Thermatophyting. That's really interesting, cause coincidentally, today we're gonna continue talking about molds and we're gonna talk about dermatophytes. 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 then 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 a coincidence, because all these molds we're gonna cover today are ascamyces. That was it 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 dramatophytes to count. Okay, I guess at this stage we've done a couple of of mould episodes, so we've already talked about Mucarales and Rare Invasive Mold.

and you'll remember from our fungal overview episode that the dermatophytes are Mold star in Ascomycota order. Yeah. So what what is a domatophyte? Fights are essentially a group of moulds that have the ability to invade the dead. yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n. And there are several species that infect humans and they're in three distinct genera, so your tricophyton, your microsporum, and your epidermophyton.

See the main way that people think about Dematify infection is the sight of the body that's involved. So tinea cactus is scalp and hair. Infection, corporis is your trunk and limbs, so commonly known as ringworm. Tiniumanum and PDS involves your hands and feet. So pedis is known as athlete's foot. Tina Cruiris involving the groin, it's known as jocket. And then Tinia Barbie can involve the beard and neck area. Tinia I think it's Baziale involves the face.

Antenia ungium or onicomycosis involves the nails. I'd never heard behalf those terms before. Which is interesting. Yeah. Yeah, Tina Barbary. I didn't I didn't even know that was a thing. I didn't sort of naming that might 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 tricophyton and predominantly causes tineopedith.

That makes sense. And I guess those are the the body sites and then the organisms themselves in terms of how they they spread. So They can be anthropophilic, so that's when it's primarily or exclusively infecting humans. So when we were talking about PCP, that was anthropophilic.

uh and then they can be uh zoophilic so coming from animals or geophilic 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, athlete's foot from walking barefoot in the changing rooms, so you get those little weird foot covers that you get when you go swimming. Or animal to human from close contact or soil to human. I think all of them, they like that moist, humid environment and skin, and that's a feature.

of all of them really. Um and then in the UK it's trichophyte and rubrum that's the most commonly isolated dermatophyte. So that accounts for about seventy percent. of isolations. So I was talking to some of the lab staff about their processing 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 on to the diagnostics in a bit. So of those infections in the UK, is it onchomycosis is the is the most common fungal It's rare that these infections are going to do you any serious damage, though an immunocompromised individual. Mae'n gallu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael eu cael Interesting.

The disease itself isn't that severe, but when we're assessing people with, say, cellulitis, one of the things you might say is something called oncomycosis or tineopedia. 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 m other more severe diseases, I guess. So what about worldwide? How does that differ?

Conditions, obviously, with the zoophilic, if you've got contact with animals, and then things like the anthropophilic, communic, communal battery. So yeah, e everyone listening I'm sure will either have had or have seen lots of these conditions. I guess they're a common thing, but maybe less I dunno, we can just speak into 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, I think that's a really good point. I think a lot of this is gonna be dealt with in primary care. Rydyn ni'n gyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf neu'r cyntaf 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.

But I think the laboratories that we work in are going to be processing all of these samples and we'll come on to the laboratory diagnostics later. But so I think it you know, it's good to have a a good understanding of of what we actually do with them as well. Yeah, definitely. These are transmitted by Hardy Arphros.

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

then then germinate and invade. And as Alyssa mentioned earlier on, the risk factors for this happening really are is is a moist condition, communal baths. Things that either allow the the fungus to move out of that spore state, they give us some moist environment.

or transmit or things where there's like abrasions, so athletic activity and finally A to B. And then invasive infections are, as we mentioned earlier, rare, but they can happen in an immune compromised individual where they have defective cellular immunity.

So that's the pathogenesis and a little bit about the background. What about the clinical features? Yeah, so I think the appearance really varies of these infections varies depending on several things. So the fungal site involved and also the immune response that the host has to the pathogen. Rydyn ni'n ymwneud â llawer o'r pethau sy'n ymwneud â llawer o'r pethau sy'n ymwneud â llawer o'r pethau sy'n ymwneud â llawer o'r pethau.

I think that's because it usually clears once people reach puberty, because the fatty acids and grease in the scalp area inhibits their growth. So these are mainly caused by your anthropophilic organisms, can be caused by some zoophilic organisms. Infection's generally divided into ectothrit So that's where the arthrospores are found on the hair and the hair that causes the hair to break a few millimetres above the skin, or endothrix, where the arthrospores develop within the hair shaft.

And the main sort of clinical findings, scaling of the scalp, associated hair loss. So it might look like dandruff. And some of these species can cause carrion. Have you I don't know if you've come across carrion before. So this is where you get more of an abscess. yw'n ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud.

So we had a really nice case in Brist 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 the around the cattle and had been rubbing the top of his head on these railings and then developed this big pushy abscess thing that yw'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n ymwneud â'i'n

Trichophyton, Tonsorans, Tricophyte and Vericosim, and Trit Trichophyton Mentacrophyte. Yeah, they've you've put some excellent show notes together for this episode and uh there's an image there from Dermett. 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, so Tina Capitus, Exophrix, Endophrix and Carrion.

So next one is Tiniacarporis or ringworm. So I feel like this is the sort of thing that historically grannies would have diagnosed. Your granny would say, Yeah, that's clearly ringworm. So this can be either an anthropophilic or zoophilic and the antropophilic um result in less inflammation or less well defined lesions compared to those formed from zoophilic cases.

Uh 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 as an image, but it's a pretty classic thing. Once you've seen it once you'll you'll recognise it well. Tinia imbricata is another is that a clinical disease, and that's a variant caused by trichophytis. Concentricum, and that is lesion with concentric scaled ring. Yeah, there's an image at the bottom of the episode notes. It's like a

A really interesting variant of Tinia corporis where yeah you get instead of just a single scaled ring, you get these concentric scaled rings. So it's quite a fancy kind of patterned wrap. Interesting. I'd 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 Tineocorporus, but it's got these concentric scaled rings. Yep.

Teinio pedis, sy'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n ymw'n. It's usually caused by trichophytin rubrum or trichophytin in interdigitale, and it causes fissures within the toe rep web. sy'n cael ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud â'r ymwneud. And next we've got Tinia Curis. So Tinia Curus, this is the one that happens in the groin, and you get erfematous lesions with central clearing and raised border.

So I guess quite similar to Tina corporis, but maybe a bit more central clearing, and generally caused by tricophiton rubrum or e flucosum. So one is Tina Indotinii that I think first emerged in India and it Rydyn ni'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd i'n mynd

Mae'n gweithwyr yn gweithwyr yn gweithwyr yn gweithwyr. Mae'n gweithwyr yn gweithwyr yn gweithwyr. Mae'n gweithwyr yn gweithwyr. Mae'n gweithwyr yn gweithwyr yn gweithwyr. ac mae wedi bod wedi'i defnyddio sefydliadau sefydliadau. Felly mae'n ymwneud â'r hyn sy'n ymwneud â phobl sy'n ymwneud â phobl sy'n ymwneud â phobl sy'n ymwneud â phobl sy'n ymwneud â phobl sy'n ymwneud â phobl.

And another one is tiny mentagrophytes type seven. So this is another emerging domatophyte that also causes tinea cruis or genitalis affecting the genitals. And this one also has evidence of sexual transmission. Interesting. And there's mentogrophitis. Does that have any intrinsic resistance that we're worried about? Not that I know of. I think it's more that it's been quite well documented now as the sexual transmission element.

Okay, so uh an emerging 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 tinea unguum. So this is common in the older in older age of diabetic And event essentially it's a 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 oncolysis, so the nail bed that's lifting up. And you get these sort of fit.

discoloured, dystrophic nails. I think this is more common on the feet because in a moisture environment, you've got socks, you've maybe got your slippers, you're your feet by the fire. Um sounds comfortable but see then you get your fungal nail infection. Majority of these are caused by dermatophytes, most commonly trichophytes and rubrum, but so about ten percent are caused by other molds, so things like Aspergillus scopular Scopliaropsis, Acrimonium and Fusarium.

And rarely caused by East including Canada. So we'll come on to this lab diagnostics, but this is something where you get your nail sample and The lab staff are saying it's usually tricophyton 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 mouse.

Talking of which, we're now onto the 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 of Classification, clinical manifestation and the key point.

So if you are wanting a bit more detail on that, more so than we've gone over there, you 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 uh you can always read that and do that in your head yourself if you want. So shall we talk about the lab diagnostics? Yeah, so yeah, coming on to lab diagnostics, so I think the main document that is used for this is the UK SMI uh B thirty nine that covers

diagnosis of organisms causing skin, hair and nail infection. So samples are skin or scalp scrapings, nail clippings or plucked hairs. Mae'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw. Septate branching hyphae that are fairly even diameter along, so they don't taper, which may develop these chains of rectangular spores, so the arthrospores.

And for hair specimens they'll also be looking to see if it's ectothyx, so on the outside of the hair shaft, or endothrix, which is on the inside of the hair shaft. Yeah. potassium hydroxide just basically is breaking down the sample, allowing you to get that single cell layer. So when you could a 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 high 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 the media sports?

Yeah, chlamydia sporores, so you see th 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 science. Rydyn ni'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n. and will really help enhance the sensitivity of your microscopy.

Yeah, I think they don't tend to do that just'cause of the volume of the samples and the the just getting that turnaround time. Um so Guess that's microscopy and then the other main way that so you get your nail sample, the lab.

Um certainly locally ours are sent in something called m so we're talking about the pre analytical phase just very briefly. In the microtrans 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 doesn't get in.

ac mae'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud â'n ymwneud. do microscopy and stick into your agar plate.

black cardboard packages, but I never knew the yeah, the real tape. Yeah, you you can mainly do that. You can also do a tape. So if you're collecting sample from say Tinecorporus, you can basically get a piece of cellar 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 when you put it on glass slide in a special transport.

pluck them out or tweeze them out because if you like cut them, you won't get the bit that's close to the scalp, which is the bit that's being invaded. Well that yeah, that makes sense. I I've never sent hair for culture. It's 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 fourteen days and it's weekly.

And you l do that at lower temperature, so at twenty six to thirty degrees, and the reason for that is that other organisms like bacteria and environmental fungi and stuff are less likely to grow, but dermatophytes like that colder temperature. And then once you've grown it essentially you do identification usually to species level and that involves and this is I have to say, of all the microbiology lab stuff, mycology is

I I think probably the coolest.'Cause a lot of a lot of it now is like moldy tough, you grow the thing, you stick it in the machine, you get the answer of job done. But this feels like real oh you like look under the microscope and you analysis of the like shape. and then you look at the agar plate and you say what's the colony morphology, the colour, what's it producing? It feels really like Sherlock Holmesy, you know,

Puzzle solving. That's really satisfying. Yeah. And look at the colour of the colony and then turn the plate over and look at that colour on the reverse. And then yeah, the microscopic features. Um and we haven't gone through these for 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 uh textbooks.

Yes, yeah, I think I've got the same one that sits in our mycology lab. It's quite hard to get 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 trichophyton rubrum is the most common and uh useful sort of screening test is the urease test. So whether it breaks down urea and uh uh tricophyting rubrum is urea is negative.

Whereas I think a lot of the other organisms like the other dermatophytes are urased positive. So that's quite a quick screening test and if I 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 trichophyton rubrium's ureates negative can help differentiate it from some of the other common termatophytes. Yeah. And in terms of the agar that you put it in, so it's usually Sabaro So it's a sort of dextrasacre and then you add in things like chloramphenicol plus or minus cyclohexamide and chloramphenicol broadly inhibit bacterial growth and cyclohexamide inhibits I think is it yeast?

Another sort of fungi. But because that's a selective agar you want to use that kind of uh an enriched um agar. So you also use two percent malt agar and that will allow you to just grow anything that's going on. Usually we'd set up, certainly in our lab, you get your sample in, you do the microscopy, you look for fungal hyphae, you set up your culture plate.

And you set up a Sabaro with chloramphenicle and then you also set up a malt acar um is what you would routinely do for this sort of sample. I think the SMI says read at seven to twenty-one days. Yeah. And then the identification is also important, I understand, from like an epidemiological aspect for scalp infection if you've got an anthropophilic species. then you should probably look at classmates and family of affected children, because they might be passing it between each other.

Definitely. Okay, so we've got our nail sample or skin sample in and we've seen hyphae, 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 therapy. So for things like your athlete's foot, your tiniocorporus or your tiniocororus. yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw'n yw

And then for some of the other sites, topical therapies are are very rarely effective. So for teenia capitus. And for onicomycosis 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 you're going to need an an oral agent. Yeah, turbinophene is our first line. You've got it here eighty percent cure after six weeks for fingernails and twelve weeks for toenails.

But it's a a very commonly prescribed drug, but it does have quite significant side effects, I think, of seeing 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 turbinofin, you might be looking at something like systemic itchonazole. And all these sort of azole drugs that we talk about, as we talk about in an episode on that specifically.

There's pretty significant side effects and risks from 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 podiatrist.

some of these drugs might be conjugated in the patients, particularly the your elderly, polypharmacy, other health problems. I guess if you're gonna say what's a 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 something? Yeah, so in the table it's just really to summarise the different species that cause Dematophytosis, so grouping them by trying to do that. trichophyton, microsporum, and epidermophyton, and then describing if they're predominantly anthropophilic, zoophilic, or geophilic.

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 about, the citricophyt and mentagrophytes. and trichophyton and endotiniae 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 you need to be worried about and there are these emerging pathogens that you've you've mentioned which is I think useful thing to to be keeping tabs on because it will affect

empirical treatments but yeah okay that's dramatophytes. This mycology episode was produced with support The BSMM brings together clinicians For more information on the benefits of the Yeah.