NTA Level 5 • Semester 1 • PST05103

Subcutaneous and Systemic Mycoses

Pharmaceutical Microbiology • Source Session/Topic 32

Full source-text version: all educational wording from the extracted learning source is retained; only presenter/tutor metadata and web-layout noise are removed, while formatting is improved for readability.

Session 32: Subcutaneous and Systemic Mycoses

Total Session Time: 120 minutes

Pre-requisites

• Human anatomy and physiology

Students Learning Tasks

By the end of this session students are expected to be able to:

• Classify and describe common mycoses (causative agents, transmission,

signs and symptoms)

• Describe treatment, prevention and control of common fungal diseases

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board and chalk/whiteboard markers

SESSION OVERVIEW

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing

STEP 2: Subcutaneous Mycoses (50 minutes)

• The fungi that cause subcutaneous mycoses normally reside in soil or

on vegetation. They enter the skin or subcutaneous tissue by traumatic

inoculation with contaminated material.

• Subcutaneous mycoses are less common than superficial fungal

infections and are characterized by a heterogeneous group of

infections that often result from direct penetration of the fungus

into the dermis and subcutaneous tissue through traumatic injury

• The fungus spreads by local deep tissue invasion from the inoculation

site

• The disease usually remains localized and then slowly spreads to

adjacent tissue and eventually to the lymphatics

• The common subcutaneous mycoses are sporotrichosis,

chromoblastomycosis, phaeohyphomycosis, eumycotic mycetoma, and

hyalohyphomycosis

• Sporotrichosis

o It is a chronic granulomatous infection caused by Sporothrix

schenckii

o The fungus is introduced into the skin by trauma

o Present with facial lesions which becomes granulomatous

o Draining lymphatics become thickened and cord-like

o Multiple subcutaneous nodules and abscesses occur along the

lymphatics

o Treatment

▪ Oral Potassium iodide for weeks

▪ Oral antifungals e.g. itraconazole

• Chromoblastomycosis

o Chromoblastomycosis (chromomycosis) is a subcutaneous mycotic

infection that is usually caused by traumatic inoculation of any

of the recognized fungal agents, which reside in soil and

vegetation

o Caused by dematiaceous fungi (with melanized cell walls)

Phialophora verrucosa, Fonsecaea pedrosoi, Fonsecaea compacta,

Rhinocladiella aquaspersa, and Cladophialophora carrionii

o The infection is chronic and characterized by the slow development

of progressive granulomatous lesions that in time induce

hyperplasia of the epidermal tissue

o The fungi are introduced into the skin by trauma, often of the

exposed legs or feet

o Treatment involves

▪ Surgical excision with wide margins is the therapy of choice

for small lesions.

▪ Antifungal agents e.g. flucytosine, itraconazole

• Phaeohyphomycosis

o Phaeohyphomycosis is a term applied to infections characterized by

the presence of darkly pigmented septate hyphae in tissue

o Signs and symptoms

▪ Cyst-Lump produced by over-secreting gland

▪ Skin lesions

▪ Skin infections

▪ Skin discoloration

▪ Pigmented lesions

o Treatment

▪ Itraconazole

▪ Amphotericin B

▪ Oral phenytoin

▪ Voriconazole

• Mycetoma

o Mycetoma is a chronic subcutaneous infection induced by traumatic

inoculation with any of several saprophytic species of fungi or

actinomycetous bacteria that are normally found in soil

o A “mycetoma” is a chronic granulomatous progressive inflammatory

disease that involves the subcutaneous tissue after a traumatic

inoculation of the causative organism

o Mycetoma may be caused by fungi (Eumycetes) or by higher bacteria

(actinomycetes) and therefore mycetoma are grouped into eumycetoma

and actinomycetoma.

o Presents with a painless subcutaneous mass which discharges to the

skin surface

o The lesion presents as a slowly progressive painless swelling at

the site of previous trauma and gradually increase in size

o It may spread to involve the skin and deep structures resulting in

destruction of bone, deformity and loss of function with serious

social and economic implications

o Treatment

▪ Must establish cause (whether bacterial or fungal)

▪ Surgical

▪ Antibiotics for actinomycetoma (Amikacin, co-trimoxazole)

• Drugs are usually combined

▪ Antifungals e.g. amphotericin B, itraconazole, miconazole

and nystatin

STEP 3: Systemic Mycosis (50 minutes)

• These are fungal infections that affect internal organs, primarily

involving the respiratory system normally occur by inhalation of

spores which develop in the lungs.

• The fungi are dimorphic

• Majority are self-limiting and asymptomatic, while the rest are

symptomatic and disseminate by haematogenous route

• Systemic mycose are:

o Blastomycosis

▪ Caused by inhalation of conidial spores of Blastomyces

dematitidis

▪ Results in a chronic granulomatous infection

▪ Primary infection is pulmonary blastomycosis

▪ Secondary infection is caused by spreading to other organs

including skin (cutaneous mycosis)

▪ Osteoarticular blastomycosis involves the spine, pelvis,

cranial bones, ribs and long bones

▪ Treatment: Amphotericin B

o Coccidioidomycosis

▪ Caused by inhalation of arthrospors of Coccidioides immitis

▪ Primary infection is in the lungs and secondary infection

involves

• Other organs of the body (skin, bone, joints and

meninges)

▪ Treatment: Amphotericin B

o Histoplasmosis

▪ This is fungal infection caused by inhalation of spore of

Histoplasma capsulatum

▪ The disease affects the reticulo-endothelial system (RES),

commonly in AIDS patients

▪ Treated by Amphotericin B

o Paracoccidioidomycosis

▪ Caused by inhalation of spores of Paracoccidioides

brasiliensis

▪ Primarily infects the lungs and sometimes gastrointestinal

mucosa

▪ Starting from the primary sites, the fungi spread through

blood or lymph into the skin, mucosa or lymphoid organs

▪ Treatment involves;

• Areazole derivatives e.g. itraconazole

• Amphotericin B

• Sulphonamides

STEP 4: Key Points (10 minutes)

• Subcutaneous mycoses may be caused by dozens of environmental molds

associated with vegetation and soil

• These infections are usually acquired when minor cuts or scratches

introduce soil or plant debris (e.g. splinters, thorns) containing the

pathogenic fungus.

• The ensuing infections are frequently chronic but rarely spread to

deeper tissues.

• S. schenckii, the cause of sporotrichosis, is a dimorphic fungus that

converts from hyphal growth to yeast cells within the host

• Systemic mycoses are caused by dimorphic fungi and spread by spores

which are inhaled into the lungs, germinate and spread via blood or

lymph to other parts of the body

• Systemic mycoses are lethal if not treated

STEP 5: Evaluation (5 minutes)

• What are systemic mycoses?

• Mention the systemic mycoses

• Name the subcutaneous mycoses

• What is a mycetoma?

References

Hugo and Russell (2011), Pharmaceutical Microbiology 8th Edition, Willey-

Blackwel publications

Karen C. Carroll et al (2013); Jawetz, Melnick and Adelberg’s Medical

Microbiology 26th Ed. McGraw Hill Co. Inc.

Greenwood et al (2012); Medical Microbiology, 18th edition Churchill

Livingstone

← Previous Topic Next Topic →View all Pharmaceutical Microbiology topics Open Complete Full Notes

PDF / OFFLINE NOTES

Unataka kutumiwa notes hizi kupitia WhatsApp?Kwa notes zilizopangiliwa vizuri kwa kusoma offline au PDF, bonyeza kitufe hapa chini. Ujumbe wenye Level, Semester, Module na Topic utaandaliwa moja kwa moja.TUMIWA NOTES WHATSAPP

WhatsApp: 255620339260