medical mycology for nurses in kenya

Medical

MycologyIntroduction

to

Basics

for nurses

WALTER WASWA,

BSC.MLS

5/18/2017 WALTER WASWA 1

Reference books

• Brooks, Geo. F. etal, (2007):Medical microbiology, 24ed. The McGraw-Hill Companies, Inc. New York.-----an e book in the library.

• Other books on microbiology in the library.


Introduction• Mycology is the study of fungi

• The study of fungi is known as mycology and scientist who study fungi is known is a mycologist.

• Fungal infections are termed as mycoses

• Fungi are differ from bacteria and other prokaryotes.

1. Cell walls containing chitin (rigidity & support), mannan & other polysaccharides

2. Cytoplasmic membrane contains ergosterols

3. Possess true nuclei with nuclear membrane & paired chromosomes.


Characteristics of Fungus

• Diverse group of chemo heterotrophs– > 90,000 known species

• Saprophytes– Digest dead organic matter

• Parasites– Obtain nutrients from tissues of organisms

• Molds & mushrooms are multicellular

• Yeasts are unicellular


CHARACTERISTICS OF FUNGI (Continued)

Dimorphic Fungi

Can exist as both multicellular fungi (molds) and yeasts.

Many pathogenic species.

– Mold form produces aerial and vegetative hyphae.

– Yeast form reproduces by budding.

Dimorphism in pathogenic fungi typically depends on

temperature:

– At 37oC: Yeast form.

– At 25oC: Mold form.

Dimorphism in nonpathogenic fungi may depend on other

factors: Carbon dioxide concentration.


Understanding the Structure of Fungi

• Yeasts and molds have different structural and reproductive characteristics– Yeast are unicellular, nucleated rounded fungi while

molds are multicellular, filamentous fungi

– Yeast reproduce by a process called budding while molds produce spores to reproduce

– Some yeast are opportunistic pathogens in that they cause disease in immuno-compromised individuals

– Yeast are used in the preparation in the variety of foods


Predisposing factors to fungal infection

1.Use of Antibiotics,

2.Use of steroids,

3.Immunosuppressive

conditions


Fungal Diseases• Mycosis- fungal infection

–< 100 cause human disease–Not highly contagious–Humans acquire from nature

• Groups based on degree on tissue involvement and mode of entry

• Cutaneous mycoses-dermatophytes– Epidermis, hair & nails–Contagious-direct or indirect contact– Secrete keratinase that degrades keratin


CLASSIFICATION

• Depending on cell morphology

1. Yeasts

2. Yeast like fungi

3. Molds

4. Dimorphic fungi


1.Yeasts• Unicellular fungi

which reproduce by budding

• On culture -produce smooth, creamy colonies

e. g Cryptococcus neoformans (capsulated yeast)


2.Yeast like fungi

• Grow partly as yeasts and partly as elongated cells resembling hyphae which are called pseudo hyphae. e.g. Candida albicans


3.Molds/ Filamentous

fungi• Form true mycelia &

reproduce by formation of different types of spores.

• Vegetative/ aerial hyphae

e.g. Rhizopus, Mucor


4. Dimorphic fungi• Occur in 2 forms

Molds (Filaments) – 25C (soil)Yeasts – 37C (in host tissue)

Most fungi causing systemic infections are dimorphic: – Histoplasma capsulatum– Blastomyces dermatidis– Paracoccidioides brasiliensis– Coccidioides immitis– Penicillium marneffei– Sporothrix schenkii


Reproduction in fungi • Sexual - formation of Zygospore, ascospores

or basidiospores

• Asexual reproduction – budding or

fission

• Asexual spores are formed on or in specialized structures.

• Vary in size, shape & colour but these characteristics are constant for a particular species.


conidia-asexual reproductive

structure –can be inhaled• Micro conidia

- Small, single celled

• Macro conidia – Large, single or many celled

• Seeds


Structure• The main body of most fungi is made up of fine,

branching, usually colourless threads called hyphae

• Several of these these hyphae, all intertwining to make up a tangled web called the mycelium

• Most fungi are multinucleate and multicellular organisms with cross wall called septa or aseptate(coenocytic)

• Yeasts are unicellular

• One major difference is that most fungi have cell walls that contain chitin, unlike the cell walls of plants, which contain cellulose

Single Hyphae

Reproduction

• Life cycle involves the fusion of hyphae from two individuals (Male & Feamle

• Each parent hyphae has haploid nuclei• The fusion of hyphae is called plasmogamy.• The fused hyphae containing haploid nuclei from

two individuals is heterokaryotic.• In some cases, plasmogamy results in cells with

one nucleus from each individual. This condition is called dikaryotic.

• Two nuclei that originated from different individuals fuse to form a diploid zygote.

• Meiosis then produces either four haploid nuclei or four haploid cells.

YEASTS AND MOLDS

•Molds - multicellular

•Yeasts - unicellular

•The simplest form of growth is budding.

•Buds are called blastoconidia.

•Seen in yeasts.

..Reproduction in yeast

• Reproduce by budding.

Microbiology: A Clinical Approach © Garland Science

YEASTS

© CDC/ Dr. Edwin P. Ewing, Jr.

.

The life cycle of Rhizopus stolonifera ( bread

mold).

Fungal Infections/ Mycoses

• superficial

• CUTANEOUS MYCOSES

• SUBCUTANEOUS MYCOSES

• SYSTEMIC

• OPPORTUNISTIC

• FUNGAL TOXINS AND ALLERGIES


SUPERFICIAL MYCOSES

Fungal infections that do not involve a tissue

response:

…SUPERFICIAL MYCOSES

•Pityriasis Versicolor. chronic mild superficial

infection of the stratum corneum caused by

Malassezia globosa,

•M restricta,

•M furfur complex.

• Invasion of the cornified skin and the host

responses are both minimal.

SUPERFICIAL MYCOSES

• Tinea Nigra- is a superficial chronic and asymptomatic infection of the stratum corneum caused by the dematiaceous fungus Hortaea (Exophiala) werneckii

• This condition is more prevalent in warm coastal regions and among young women.


SUPERFICIAL MYCOSES

• Piedra

• Black piedra is a nodular infection of the hair shaft caused by Piedraia hortai.

• White piedra, due to infection with Trichosporon species, presents as larger, softer, yellowish nodules on the hairs.


CUTANEOUS

•caused by fungi that infect only the

superficial keratinized tissue (skin, hair, and

nails)/cannot grow at 37degrees

•Dermatophytes eg

microsporon/trichophyton/epidermophyton

•Sometimes reffered as Ringworm – skin lesions

characterized by red margins, scales and itching

•Image?

…CUTANEOUS MYCOSES

•Classified based on location of infectiona) Tinea pedis – on the feet or between the toesb) Tinea corporis – between the fingers, in wrinkles

on the palms c) Tinea cruses – lesions on the hairy skin around

the genitaliad) Tinea capitis – scalp and eyebrows

e) Onychomycosis – chronic infection of the nail bed

•Commonly seen in toes•Hyperkeratosis – extended scaly areas on the hands and feet


..CUTANEOUS

www.doctorfungus.org

http://www.doctorfungus.org/

Mucocutaneous …

•MUCOCUTANEOUS MYCOSES colonization of

the mucous membranes

•Caused by the yeast Candida albicans

•Often associated with a loss of

immunocompetence

•Thrush – fungal growth in the oral cavity

•An indicator of immunodeficiency.

•Vulvovaginitis – fungal growth in the vaginal

canal

•Can be associated with a hormonal

imbalance

SUBCUTANEOUS MYCOSES

•Agent –from the soil /vegetable

•Entry-through trauma

•localized primary infections of

subcutaneous tissue:

•Can cause the development of cysts and

granulomas.

•Provoke an innate immune response -

eosinophilia.

SUBCUTANEOUS MYCOSES

There are several types:•Sporotrichosis – traumatic implantation of fungal

organisms

•Paranasal conidiobolae mycoses– infection of the

paranasal sinuses

•Causes the formation of granulomas.

•Zygomatic rhinitis– fungus invades tissue through

arteries

•Causes thrombosis.

•Can involve the CNS.

SUBCUTANEOUS MYCOSES• At ambient environmental temp-mould

• At 35-37degrees grow as budding yeast

• Sporothrix schenckii -Sporotrichosis

• Phialophora verrucosa, Fonsecaea pedrosoi, others - Chromoblastomycosis

• Pseudallescheria boydii, Madurellamycetomatis, others - Mycetoma

• Exophiala, Bipolaris, Exserohilum, and others -Phaeohyphomycosis


DEEP/systemic MYCOSES

Deep mycoses Usually seen in immunosuppressedpatients with:

•AIDS•Cancer•Diabetes

•Can be acquired by:•Inhalation of fungi or fungal spores•Use of contaminated medical equipment

•Deep mycoses can cause a systemic infection –disseminated mycoses

•Can spread to the skin

Common examples

• Coccidioides immitis, C posadasii -Coccidioidomycosis

• Histoplasma capsulatum- HistoplasmosisBlastomyces dermatitidis -Blastomycosis

• Paracoccidioides brasiliensis -Paracoccidioidomycosis



..DEEP MYCOSES

www.doctorfungus.org

http://www.doctorfungus.org/

..DEEP MYCOSES

Coccidiomycoses – caused by genus Coccidioides

•Primary respiratory infection

•Leads to fever, erythremia, and bronchial

pneumonia

•Usually resolves spontaneously due to immune

defense

•Some cases are fatal

…DEEP MYCOSES

Histoplasmosis – caused by Histoplasma

capsulatum

•Often associated with immunodeficiency

•Causes the formation of granulomas

•Can necrotize and become calcified

•If disseminated, histoplasmosis can be fatal.


..DEEP MYCOSES

© CDC/Susan Lindsley, VD

…DEEP MYCOSES

Aspergillosis – caused by several species of

Aspergillus

•Associated with immunodeficiency

•Can be invasive and disseminate to the blood

and lungs

•Causes acute pneumonia

•Mortality is very high.

•Death can occur in a matter of weeks.

opportunistic mycoses eg.1. Candida albicans and other Candida species -

Systemic candidiasis

2. Cryptococcus neoformans- Cryptococcosis

3. Aspergillus fumigatus and other Aspergillusspecies -Aspergillosis

4. Species of Rhizopus, Absidia, Mucor, and other zygomycetes - Mucormycosis (zygomycosis)

5. Penicillium marneffei- Penicilliosis

Candidiasis

Cause: Candida albicans

–Dimorphic fungus of the class Deuteromycetes

–Grows as yeast or pseudohyphae

– Spread by contact; often part of normal flora

–Opportunistic infections common

–Vulvovaginitis

–Oral candidiasis (thrush)

– Intestinal candidiasis

Candidiasis

Cutaneous

Thrush

Vaginal candidiasis is the most common clinical infection. Local factors such as pH and glucose concentration (under hormonal control) are of prime importance in the occurrence of vaginal candidiasis. In mouth: normal saliva reduces adhesion (lactoferrin is also protective).

Chronic mucocutaneouscandidiasis

Chronic mucocutaneous

candidiasis (CMC) is the label

given to a group of overlapping

syndromes that have in common

a clinical pattern of persistent,

severe, and diffuse cutaneous

candidal infections. These

infections affect the skin, nails

and mucous membranes.

Immunologic studies of patients with

CMC often reveal defects related to

cell-mediated immunity, but the

defects themselves vary widely.

http://www.dermnetnz.org/img/tinea/compl.jpg','Complete nail destruction

http://www.dermnetnz.org/img/tinea/compl.jpg','Complete nail destruction

Mucutaneous candidiasis: response to fluconazole

Transfusion of a Candida-specific transfer factor has

been reported to be very successful (remission for > 10

years) when combined with antifungal therapy. The

availability of effective oral agents, especially the azole

antimicotics, has dramatically changed the life of

patients living with CMC.

Cryptococcosis

Respiratory Fungal Infection

–Cryptococcus neoformans

–A yeast of class Basidiomycetes

– Soil; esp. contaminated with bird droppings

–Airborne to humans

–Gelatinous capsules resist phagocytosis

–Respiratory tract infections

–Occasional systemic infections involving brain & meninges

Opportunistic Mycoses

•Opportunistic mycoses are fungal infections that do not

normally cause disease in healthy people, but do cause

disease in people with weakened immune defenses.

•The most common infections are:

•Candidiasis

•Aspergillosis

•Cryptococcosis

•Zygomycosis

•Pneumocystis carinii

Cryptococcus neoformans

• Primary infection in lungs

• Cryptococcal meningitis is most common disseminated manifestation

• Can spread to skin, bone and prostate

Organism is ubiquitous and infections

occur worldwide

C. neoformans recovered in large

amounts in pigeon poop

Does not cause disease in birds

Diagnosis

• Lumbar puncture and microscopic examination of cerebrospinal fluid is diagnostic.

• (India ink staining)

Cyrptococcal antigens in CSF and serum.

Immune response

Phagocytosis by neutrophils is inhibited by the presence of a capsule.

However, activated neutrophils have an increased capacity to

phagocytize C. neoformans.

Cell mediated immunity primary defense

About 30% of cryptococcus infections occur in patients with lymphoma

(CNS)

Therapy

Amphotericin B & 5FC

Fluconazole also effective

Aspergillosis

• Genus occurs worldwide and contains hundreds of species.

• These species constitute the most commonly found fungi in any environment

Major portal of entry is the

respiratory tract. Dissemination

can occur from the lungs and

involve other areas of the lung,

the brain, GI tract, and kidney.

CNS and nasal-orbital cavities

can also occur without lung

involvement. Risk factors for

invasive disease are

neutropenia and high doses of

Aspergillosis• Aspergillosis is the most common fatal infection seen in patients with chronic

granulomatous disease of childhood.

• Patients with this condition are unable to form toxic oxygen radicals after phagocytosis.

• Progressive and disseminated disease can complicate neoplastic diseases, especially acute leukemia, bone marrow and organ transplantation (not necessarily AIDS).

In immunosuppressed hosts:

invasive pulmonary infection, usually

with fever, cough, and chest pain.

May disseminate to other organs,

including brain, skin and bone. In

immunocompetent hosts: localized

pulmonary infection in persons with

underlying lung disease. Also causes

allergic sinusitis and allergic

bronchopulmonary disease.

Agent: Aspergillus fumigatus, A. flavus.

http://www.doctorfungus.org/mycoses/human/aspergillus/aspergillosis.htm

Environmental species kill neutropenicpatients.

• Zygomycosis. Zygomycosis due to Rhizopus, Rhizomucor, Absidia, Mucor species, or other members of the class of Zygomycetes, also causes invasive sinopulmonary infections. An especially life-threatening form of zygomycosis(also known as mucormycosis), is known as the rhinocerebral syndrome, which occurs in diabetics with ketoacidosis. In addition to diabetic ketoacidosis, neutropenia and corticosteroids are other major risk factors for zygomycosis.

• Phaeohyphomycosis. Phaeohyphomycosis is an infection by brown to black pigmented fungi of the cutaneous, superficial, and deep tissues, especially brain. These infections are uncommon, life-threatening, and occur in various immunocompromised states.

• Hyalohyphomycosis. Hyalohyphomycosis is an opportunistic fungal infection caused by any of a variety of normally saprophytic fungi with hyaline hyphalelements. For example, Fusarium spp. infect neutropenic patients to cause pneumonia, fungemia, and disseminated infection with cutaneous lesions.

…. Respiratory Fungal Infections

Histoplasmosis

–Histoplasma capsulatum, an ascomycete

–Airborne infection

– Transmitted by inhalation of spores in contaminated spores

–Associated with chicken & bat droppings

–Respiratory tract symptoms; fever, headache, cough, chest pains

….Respiratory Fungal Infections

Blastomycosis

–Blastomyces dermatitidis, an ascomycete

–Associated with dusty soil & bird droppings

– Skin transmission: via cuts & abrasions

–Raised, wart-like lesions

–Airborne transmission: via inhalation of spores

–Respiratory tract symptoms

–Occasional internal infections with high fatality rate

Aflatoxin are a small group of mycotoxins

produced by the fungi from the genus

Aspergillus, Aspergillus flavus and

Aspergillus parasiticus , produces a natural

occurring human carcinogen, bis-

furanocumarin that is found in aflatoxin,

. Aflatoxins are known contaminants on

corn, peanuts, tree nuts, cottonseed

and certain meats and hypoallergenic

milks

Useful Properties of Fungi


Source of food e.g. mushrooms

Fermentation - Production of

alcohol, bread, cheese

e.g. Sacchromyces spps

Antibiotic production

e.g. Penicillin from

Penicillium notatum

Useful Properties of Fungi


Ergot from Claviceps

purpurea, used to induce

uterine contractions

Vaccines for Hepatitis B –

Sacchromyces cerevisiae

Diagnosis/Treatment

1. Grown in medium that selects for fungal growth-Grow at 25 C and 37 C

2. KOH preparations of skin biopsies-Dissolves keratin in skin scrapings or biopsies

-Leaves only fungal cells

3. Therapy- amphotericin B or ketoconazole-Toxic to humans


The end


medical mycology for nurses in kenya

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