Dermatophytes

Summary

This presentation from Andy Alpa of Duke University's School of Medicine delves into dermatophyte fungi, the most common cause of superficial skin infections. These keratinophilic fungi infect keratinized tissues like skin, hair, nails, and feathers. The talk covers clinical manifestations, transmission through fomites, and the unique ecological niche of anthrophilic, zoophilic, and geophilic dermatophytes. It also discusses diagnosis through skin scrapings and microscopy, and treatment options ranging from topical antifungal agents to systemic therapy for conditions like tinea capitis and onychomycosis. The presentation highlights the importance of addressing these infections to prevent more serious complications.

Takeaways

• 🦠 Dermatophytes are a group of fungi that cause superficial skin infections, commonly known as ringworm, and are among the most widespread infectious agents globally.
• 🔬 Dermatophytes are classified into three ecological groups based on their preferred host: anthrophilic (human tissue), zoophilic (animal tissue), and geophilic (environment).
• 📚 The presentation's objectives are to review clinical manifestations of dermatophyte infections, discuss how they are acquired, and consider diagnosis and treatment methods.
• 👨‍⚕️ A typical patient case described involves a 70-year-old man with scaling, itching, and nail changes, indicative of athlete's foot and a fungal nail infection.
• 🌱 Dermatophytes are keratinophilic, meaning they primarily grow on keratinized tissue such as skin, hair, nails, and feathers, which is a remarkable adaptation.
• 🧬 In the lab, dermatophytes grow slowly on artificial media, and specific species can be identified by observing their growth and development.
• 🚫 Dermatophyte infections typically do not invade deep dermal structures, as they grow only in the most superficial skin layers, causing symptoms through their metabolic products.
• 🤝 Dermatophytes are transmitted by direct contact or indirectly through fomites, such as hotel carpets, locker rooms, swimming pools, and shared personal items.
• 🔍 Dermatophyte infections are diagnosed by their clinical appearance, skin scrapings under a microscope, and sometimes fungal culture or biopsy.
• 💊 Treatment for dermatophyte infections often involves topical antifungal agents for hands, feet, or body, with systemic therapy required for conditions like tinea capitis.
• 🛑 Onicomicosis, or nail infections, is particularly challenging to treat due to the deep location of fungi in nail structures, requiring prolonged treatment with potentially higher cure rates but also more side effects.

Q & A

What is the main topic of the presentation by Andy Alpa from Duke University?

The presentation explores a group of fungi known as dermatophytes, which are the cause of superficial skin infections and are arguably the most common infectious agents in the world.

What are the learning objectives for the module on dermatophyte infections?

The learning objectives are to review the clinical manifestations of infections due to these fungi, discuss how one might acquire dermatophyte infections, and consider how to diagnose and treat these common infections.

What is the typical presentation of a patient with dermatophyte infection affecting the feet?

A typical patient may present with scaling, itching, thickening, and discoloration of the skin and nails on their feet, with no systemic symptoms, and the condition may have progressed over several months.

What does 'dermatophyte' mean in terms of the fungi's ecological niche?

Dermatophytes are keratinophilic fungi, meaning they primarily grow on keratinized human and animal tissue such as skin, hair, nails, and feathers.

How are dermatophyte species categorized based on their preferred host?

Dermatophyte species are categorized as anthrophilic (growing on human tissue), zoophilic (growing on certain animal species), and geophilic (growing in the environment).

What is the typical growth pattern of dermatophytes in a microbiology lab?

Dermatophytes tend to grow very slowly on artificial growth medium, and specific species can be identified using the structures observed during various times of their growth and development.

How do dermatophyte infections usually present symptomatically, and what causes these symptoms?

Symptoms of dermatophyte infections are typically due to the host's response to fungal metabolic products rather than fungal invasion, as these organisms typically only grow in the most superficial layers of the skin.

What are some common transmission sources for dermatophyte infections?

Transmission sources include hotel carpets, locker rooms, swimming pools, shared hats and brushes, poorly washed bedding, and theater or airplane seats.

What are some common terms used to describe dermatophyte infections?

Common terms include 'ringworm' for body infections, 'onychomycosis' for nail infections, 'tinea pedis' for foot infections, 'tinea manum' for hand infections, 'tinea cruris' for groin infections, 'tinea corporis' for body infections, and 'tinea capitis' for scalp infections.

How is the diagnosis of dermatophyte infections typically made, and what methods can be used for confirmation?

Diagnosis is usually made by characteristic clinical appearance. Confirmation can be done by skin scrapings onto a microscope slide with potassium hydroxide to dissolve human skin and observe fungal forms, or by sending scrapings for fungal culture.

What are the general treatment approaches for dermatophyte infections involving different body parts?

Most cases involving hands, feet, or body can be treated with topical antifungal agents. Tinea capitis often requires systemic therapy, and onychomycosis may require prolonged treatment with either topical or oral antifungal agents.

Why are dermatophyte infections considered important despite not invading deeper structures?

Dermatophyte infections are important because they are common, can cause cosmetic changes and discomfort, and disrupt the protective skin barrier, increasing the risk for more serious infections.

Outlines

00:00

🦠 Dermatophytes: Causes and Characteristics

This paragraph introduces dermatophytes, a group of fungi responsible for skin infections, and discusses their ecological niche and adaptation to keratinized tissues. Andy Alpa from Duke University's School of Medicine presents a case study of a 70-year-old man with symptoms of athlete's foot and fungal nail infection. Dermatophytes are keratinophilic, meaning they grow on human and animal tissues like skin, hair, nails, and feathers. They are categorized into anthrophilic, zoophilic, and geophilic based on their preferred host. The paragraph also explains how dermatophyte infections are typically transmitted through fomites and the symptoms they cause, which are a result of the body's reaction to fungal metabolic products rather than invasion by the fungi themselves.

05:00

🌟 Clinical Terms and Treatment of Dermatophyte Infections

The second paragraph delves into the clinical terms used to describe dermatophyte infections and the methods for diagnosing and treating them. It explains the use of terms like 'ringworm' and 'onychomycosis' for nail infections, and how the site of infection influences the terminology (e.g., 'tinea pedis' for foot infections, 'tinea capitis' for scalp infections). The paragraph outlines the standard diagnostic process, which includes clinical appearance and skin scrapings analyzed under a microscope with potassium hydroxide. It also discusses various treatment options, emphasizing that while most infections can be treated topically with antifungal agents, some conditions like tinea capitis may require systemic therapy. The challenges of treating onychomycosis due to the deep penetration of fungi in the nail structures are highlighted, along with the considerations for using topical versus oral antifungal treatments.

10:02

🛡️ Importance and Prevention of Dermatophyte Infections

The final paragraph underscores the significance of dermatophyte infections due to their prevalence and potential to cause cosmetic issues and local irritation. It also points out that these infections can disrupt the skin's protective barrier, increasing the risk of more severe infections like cellulitis and diabetic foot infections. The paragraph concludes by emphasizing the importance of careful attention to dermatophyte infections to ensure a lasting cure and prevent long-term adverse outcomes, thus highlighting the need for proper diagnosis and treatment to maintain skin health and prevent secondary infections.

Keywords

💡Dermatophytes

Dermatophytes are a group of fungi that cause skin infections. They are the main focus of the video, as they are responsible for a wide range of conditions collectively known as dermatophytosis. The term is used to describe the fungi that primarily grow on keratinized human and animal tissue, such as skin, hair, nails, and feathers. In the script, dermatophytes are mentioned as the cause of the patient's symptoms, including scaling, itching, and nail changes, which are indicative of athlete's foot and a fungal nail infection.

💡Keratinophilic

Keratinophilic refers to the characteristic of certain fungi, like dermatophytes, to primarily grow on keratinized tissue. Keratin is a protein found in the outer layer of the skin, hair, and nails. This term is important in the video as it explains the ecological niche of dermatophytes and their adaptation to grow on specific structures of the human body, which is central to understanding the types of infections they cause.

💡Anthropophilic

Anthropophilic dermatophytes are those that are adapted to grow exclusively on human tissue. The term is used in the video to categorize one type of dermatophyte, which is significant for understanding the specificity of certain fungal infections to humans. This specificity is important in the epidemiology of fungal infections and their transmission.

💡Zoophilic

Zoophilic dermatophytes are fungi that can grow on certain animal species. The term is used in the script to differentiate between types of dermatophytes based on their host specificity. Understanding zoophilic dermatophytes is important for recognizing infections that can be transmitted from animals to humans.

💡Geophilic

Geophilic refers to a type of dermatophyte that can grow in the environment. This term is used in the video to describe a group of fungi that are not host-specific and can survive independently in the environment. Recognizing geophilic dermatophytes is crucial for understanding the environmental sources of fungal infections.

💡Tinea

Tinea is a general term used to describe infections caused by dermatophytes. In the video, specific types of tinea infections are mentioned, such as tinea pedis (athlete's foot), tinea manum (infection of the hand), and tinea capitis (infection of the scalp). The term helps categorize different dermatophyte infections based on the body part affected.

💡Onychomycosis

Onychomycosis is a term used to describe fungal nail infections. In the video, it is mentioned as a condition characterized by nail thickening and discoloration. The term is significant as it highlights a specific type of dermatophyte infection that can be challenging to treat due to the nail's structure and slow growth rate.

💡Fomites

Fomites are inanimate objects that can transmit infections. In the context of the video, fomites are mentioned as a common mode of transmission for dermatophyte infections, such as through shared hats, brushes, poorly washed bedding, or surfaces in hotel carpets, locker rooms, and swimming pools. Understanding fomites is important for recognizing how fungal infections can spread in everyday environments.

💡Topical antifungal agents

Topical antifungal agents are medications applied directly to the skin to treat fungal infections. The video discusses their use in treating most cases of dermatophyte infections involving the hands, feet, or body. Examples given include topical azoles and naphthoquinones. The term is central to the discussion on treatment options for superficial fungal infections.

💡Systemic therapy

Systemic therapy refers to the treatment of infections through medications that are absorbed into the bloodstream and distributed throughout the body. In the video, systemic therapy is mentioned as a necessary treatment for conditions like tinea capitis, which can be difficult to eradicate and may require oral antifungal agents. The term is important for understanding the treatment of more severe or resistant fungal infections.

💡Pigment changes

Pigment changes refer to alterations in the color of the skin. In the video, the term is used in the context of tinea versicolor, a superficial fungal infection caused by the Malassezia group of fungi. Unlike other dermatophyte infections, tinea versicolor presents with simple pigment changes without significant scaling or inflammation. Understanding pigment changes is important for diagnosing certain types of fungal infections.

Highlights

Introduction to dermatophytes, a group of fungi causing superficial skin infections.

Dermatophytes are the most common infectious agents worldwide.

Location of dermatophytes within the fungal Kingdom and their growth as hyaline molds.

Learning objectives: clinical manifestations, acquisition, diagnosis, and treatment of dermatophyte infections.

Case study of a 70-year-old man presenting with symptoms of athlete's foot and fungal nail infection.

Dermatophytes are keratinophilic, growing on keratinized human and animal tissue.

Ecological niches of dermatophytes: anthrophilic, zoophilic, and geophilic.

Slow growth of dermatophytes on artificial medium and identification through growth structures.

Symptoms of dermatophyte infections are due to local irritation and skin scaling caused by fungal metabolic products.

Transmission of dermatophytes through fomites and environmental sources like hotel carpets and swimming pools.

Common terms for dermatophyte infections: ringworm, onychomycosis, tinea pedis, and tinea capitis.

Diagnosis of dermatophyte infections through clinical appearance and skin scrapings.

Treatment of dermatophyte infections with topical antifungal agents for hands, feet, or body.

Tinea capitis often requires systemic therapy due to its deeper involvement in hair follicles.

Challenges in treating onychomycosis due to the deep nail structure and slow turnover.

Comparison of topical and oral antifungal agents for treating nail infections, including cure rates and side effects.

Tinea versicolor, a superficial skin infection caused by Malassezia fungi, responds to topical treatments.

Importance of treating dermatophyte infections to prevent more serious conditions and long-term outcomes.

Transcripts

this is Andy Alpa from Duke University

School of Medicine this presentation

we'll explore a fascinating group of

fungi known collectively as the dermatop

phyes the causes of superficial skin

infections and arguably the most common

infectious agents in the world in our

pathogen map the dryes are located

within the fungal Kingdom growing as

hyul

molds our learning objectives for this

module are first to review the clinical

manifestations of infections due to

these fungi second to discuss how one

might acquire dramafied infections and

third to consider how we diagnose and

treat these very common

infections let's begin with a simple and

exceedingly common patient case of a

70-year-old man who is otherwise well

but who comes to see you with scaling

and itching of his feet the symptoms

have progressed over several months and

include thickening and discoloration of

his nails he has absolutely no systemic

symptoms referable to this condition

your examination of the patient confirms

that he is healthy but that he has well

demarcated regions on his feet with

scaling of the skin and little

underlying inflammation the plantar

surfaces are prominently involved as

well as the regions between his toes he

also has nail changes with thickening

and discoloration of the nail plate this

is a classic case of what in common

parlance would be called athletes foot

with a fungal nail infection

all of these symptoms are caused by the

dermatophyte fungi dermatophytes are

keratinophilic fungi meaning that they

primarily grow on keratinized human and

animal tissue such as Skin hair nails

and Feathers this specific ecological

niche represents a remarkable adaptation

for these particular structures by these

fungi this adaptation also results in a

very narrow range of sites where

particular dropy species can be found

for example many of the causes of human

infections can only grow on human tissue

and they are therefore called anthropic

dermatophytes other species are able to

grow un certain animal species and they

are known as

zoophilic lastly a small group of these

agents can grow in the environment and

therefore they are referred to as

geophilic now mycologically these fungi

tend to grow very slowly on artificial

growth medium in the microbiology lab

specific species can be identified ifed

using the identification of structures

observed during various times of their

growth

development here we are demonstrating

various fungal features that distinguish

some of the most common dermatophytes

that cause infections in humans for the

sake of this presentation it is likely

sufficient that you just recognize a few

common

dermatophytic and troyen

once these fungi establish an infection

on human keratinized tissue such as Skin

how do they result in symptoms and

disease most of the symptoms of dery

infections are not due to fungal

Invasion since these organisms typically

only grow in the most superficial layers

of the skin such as the stratum corium

they rarely invade deep dermal

structures the local irritation and skin

scaling occur as a response to fungal

metabolic products produced during

microbial

growth although dermatophytes can be

transmitted by direct physical contact

these agents are typically transmitted

in what are refer to as fomites or the

desolated skin and Fallen hairs of

infected people and we can all come into

contact with these fomites in many areas

of of the environment however some of

the most famous sources for transmission

include Hotel carpets locker rooms and

swimming pools infected hairs are often

found in shared hats and brushes po

poorly washed bedding and either theater

or airplane

seats let's review some of the common

terms that patients and Physicians will

use to talk about dermaide infections

now patients will often refer to dery

Tois of the body as

ringworm now although this infection is

not truly caused by a worm this older

term does describe some of the most

prominent features of these

infections the infection will often

appear as a well demarcated patch with a

minimally inflammatory border containing

a region of Central clearing with skin

scaling thus the Ring of wi ringworm

demonstrated in this

image other terms include

onicomicosis indicating nail infection

due to the

dermatophytes as demonstrated in this

image anacom micosis typically presents

as a chronic and painless thickening of

the nail plate with an accumulation of

scaling debris in the nail bed this

debris often includes a mixture of human

and fungal

elements other terms will Define the

sight of infection using the word Tena

plus the Latin name of the involved body

part therefore ten angam refers to dropy

infection of the nail or

onicomicosis tenia pedus refers to

involvement of the feet or athletes foot

as demonstrated in the initial patient

case tenam manum indicates infection of

the skin of the hand a patient with dery

infection involving the inguinal region

and the inner aspect of the thigh has

tenia curus or joet a condition that is

almost exclusively observed in men dery

infection of the thorax or abdomen is

tenia corporis or

ringworm a particularly Troublesome type

of dermatophytosis is tenia capitis or

involvement of the head and scalp this

condition occurs most commonly in

children

it can be somewhat difficult to

completely eradicate and it can also

result in some degree of hair loss as

demonstrated in the top image on this

slide when the infection results in

tissue inflammation the lesion is called

a

Carion because of the deeper involvement

of the hair follicles in tiny capitus

this condition often requires systemic

therapy as opposed to simple topical

antifungal

agents the diagnosis of dropy infections

is usually made by its characteristic

clinical appearance however other

conditions can result in inflammatory

patches such as contact dermatitis and

reactions to various medicines one can

make a more definitive diagnosis by

scraping the involved skin onto a

microscope slide adding potassium

hydroxide to dissolve the human skin and

observing the fungal forms by direct

light

microscopy the skin scrapings can also

be sent for fungal culture if the

diagnosis is in doubt rarely biopsy and

histopath Analysis are needed to

diagnose this

condition on this slide I've attempted

to summarize some of the treatment

issues for D dery infections now most

cases involving the hands feet or body

can be treated with topical antifungal

agents such as the topical azol turbine

or napen treatment often requires at

least two weeks of therapy and should

extend for about one week after the

symptoms clear to ensure that all of the

fungi even those hiding in the dead

layers of the skin are well treated it's

important to note that topical NY Statin

a good agent for superficial candid

infections is not effective against

dermatophytes also patients will often

use topical steroids for many

non-specific skin eruptions but these

agents should be avoided if you are

treating dermaide

infections as I mentioned previously

tinia capitus often requires systemic

therapy to result in a cure historically

the oral antifungal agent Grizzy fulin

was used for this condition mostly due

to its acceptable safety profile in

children however Grizzy fulin must often

be used for 2 to 3 months in contrast

oral azol and oral turban likely require

much shorter courses of therapy however

cost and potential drug drug

interactions can be important issues

with these newer antifungal

agents one of the most difficult and

vexing issu of treatment is what to do

about onicomicosis or nail infections

since these fungi reside deep in the

nail structures and these structures

take many months to turn over one must

often treat onicomicosis for several

months to have any hope for

cure topical agents such as azil creams

topical turbin and various antifungal

nail lacers have a low cure rate for

this infection often less than 50% in

many clinical trials however there are

often few side effects effects from this

type of topical

therapy in contrast oral antifungal

agents have a higher cure rate but

prolonged or pulse do systemic

antifungal therapy can be very very

expensive and some serious side effects

have been noted including liver and

myocardial

toxicity one last superficial infection

of the skin that I want to mention is

not caused by a derhy fungus in contrast

to the intense scale observed with

matify infections tenia Versa color

often presents as simple pigment changes

in the skin without a significant amount

of scale or underlying inflammation it

is caused by the malisia group of fungi

organisms that require exogenous lipids

to grow such as those present on the

surface of your

body this condition is often

comparatively simple to treat responding

to topical azoles or anti dandruff

shampoos containing selenium sulfide

in conclusion we have discussed

superficial infections due to various

groups of fungi although these rarely

invade deeper

structures Derma ofy infections are

important for several reasons first they

are exceedingly common among your future

patients resulting in concerning

cosmetic changes in the skin potentially

hair loss dramatic nail changes and

local irritation also once these

infections cause A disruption of the

normally protective beer barrier of

intact skun your infected patients will

be at a higher risk for more serious

infections such as cellulitis diabetic

foot infections and bacterial infections

of the regions around the nails

therefore careful attention to these

infections can result in lasting cure

and prevention of long-term adverse

outcomes