CHAPTER 14-PARASITIC & FUNGAL

INFECTIONS

WHY IS THIS IMPORTANT?•Parasitic infections affect billions of people in the world.•Fungal infections are usually opportunistic infections and have increased with the number of immunocompromised individuals.Parasites can be divided into two groups:•Protozoans – microscopic, single-celled eukaryotes.•Helminths – macroscopic, multicellular worms.

SIGNIFICANCE OF PARASITIC INFECTIONS

Parasitic infections are a major problem worldwide.•More than 500 million people are infected with malaria.•More than 2 million (mostly children) die each year from malaria.•Entamoeba are intestinal parasites that infect 10% of the world population.•Trypanosoma parasites infect 16 million people in Latin America each year.

SIGNIFICANCE OF PARASITIC INFECTION

FUNGAL INFECTIONS

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

• A fungus is a member of a large group of eukaryotic organisms

• Microorganisms such as yeasts and molds, as well as the more familiar mushrooms

• Over 60,000 species of fungi are known • Fungi are important for the environment.• They are normally harmless to humans• Fungi can be opportunistic pathogens.

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

branching, usually colourless threads called hyphae ( PG 310)

• 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

Microbiology: A Clinical Approach © Garland Science

YEASTS AND MOLDS

© CDC/ Dr. Edwin P. Ewing, Jr.

.

 The life cycle of Rhizopus stolonifera ( bread mold).

 

….Reproductive structures in Breadmold

.

 

 

Classification of Fungi

By Reproductive Structures (PG 312)

Oomycetes • Water Molds

• Motile sexual spores

• Example: Potato blight Phytophthora

…..Classification of Fungi

Zygomycetes • Unenclosed zygospores produced at ends of

hyphae

• Example: Black bread mold Rhizopus

Ascomycetes • Ascospores are enclosed in asci (sac-like

structures) at the ends of hyphae or yeasts

• Examples: Penicillium, Saccharomyces

..Zygomycota• Conjugation Fungi

…..Classification of FungiBasidiomycetes

• Basidiospores are produced on a club-shaped structure called a basidium

• Example: Mushrooms, Cryptococcus

Deuteromycetes • “Imperfect fungi”

• No sexual stage is known for these fungi

• Many parasitic fungi fall into this class

• Examples: Candida, Epidermophyton

CLASSIFICATION OF PATHOGENIC FUNGI

Fungal diseases are classified into 4 groups:

•Superficial mycoses•Mucocutaneous mycoses•Subcutaneous mycoses•Deep mycoses

SUPERFICIAL MYCOSES

Fungal infections that do not involve a tissue response:•Piedra – colonization of the hair shaft causing black or white nodules•Tinea nigra – brown or black superficial skin lesions•Tinea capitis – folliculitis on the scalp and eyebrows

…SUPERFICIAL MYCOSES

•Favus – destruction of the hair follicle.•Pityriasis – dermatitis characterized by redness of the skin and itching:

•Caused by hypersensitivity reactions to fungi normally found on skin•Mostly seen in immunocompromised patients.

CUTANEOUS AND MUCOCUTANEOUS MYCOSES

Associated with:•Skin•Eyes•Sinuses•Oropharynx and external ears•Vagina

…CUTANEOUS AND MUCOCUTANEOUS MYCOSES

Ringworm – skin lesions characterized by red margins, scales and itching:•Classified based on location of infection

•Tinea pedis – on the feet or between the toes•Tinea corporis – between the fingers, in wrinkles on the palms •Tinea cruses – lesions on the hairy skin around the genitalia•Tinea capitis – scalp and eyebrows

•Onychomycosis – chronic infection of the nail bed•Commonly seen in toes

•Hyperkeratosis – extended scaly areas on the hands and feet

Microbiology: A Clinical Approach © Garland Science

..CUTANEOUS AND MUCOCUTANEOUS MYCOSES

www.doctorfungus.org

…CUTANEOUS AND MUCOCUTANEOUS MYCOSES

•Mucocutaneous candidiasis – 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 MYCOSESLocalized 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.

DEEP MYCOSESDeep mycoses Usually seen in immunosuppressed patients 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

Microbiology: A Clinical Approach © Garland Science

..DEEP MYCOSES

www.doctorfungus.org

..DEEP MYCOSESCoccidiomycoses – 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 MYCOSESHistoplasmosis – caused by Histoplasma capsulatum•Often associated with immunodeficiency•Causes the formation of granulomas

•Can necrotize and become calcified•If disseminated, histoplasmosis can be fatal.

Microbiology: A Clinical Approach © Garland Science

..DEEP MYCOSES

© CDC/Susan Lindsley, VD

…DEEP MYCOSESAspergillosis – 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.

Common Fungal Diseases

Additional Information to read:

• Candidiasis

• Dermatomycoses

• Respiratory Fungal Infections

CandidiasisCause: 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

Dermatomycoses• Dermatomycoses are any fungal infection

of the skin or hair.

• Caused by many different species and are generally named after the infected area rather than the species that causes it.

• Dermatomycoses are one of the most frequent sources of lesions on the skin.

…Dermatomycoses

Cause: Several genera of dermatophytic fungi – Trichophyton, an ascomycete

– Microsporum, an ascomycete

– Epidermophyton, a deuteromycete

– Grow on skin, hair, nails

– Transmitted by contact with infected persons or animals

…Dermatomycoses

• Tinea is a fungus that can grow on your skin, hair or nails. • As it grows, it spreads out in a circle, leaving normal-

looking skin in the middle- look like a ring.• At the edge of the ring, the skin is lifted up by the

irritation and looks red and scaly.• To some people, the infection looks like a worm is under

the skin. • Because of the way it looks, tinea infection is often called

"ringworm." no worm under the skin!!• Pictures!!!!

….Dermatomycoses

– Tinea pedis

– Tinea corporis

– Tinea capitis

– Tinea favosa

– Tinea barbae

– Tinea cruris

– Tinea unguium

Tinea infections: Red, scaly or blister-like lesions; often a raised red ring; “ringworm”

Respiratory Fungal Infections

Cryptococcosis– 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

…. 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 InfectionsBlastomycosis

– 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

References• Microbiology, A clinical Approach -Danielle Moszyk-

Strelkauskas-Garland Science 2010• http://en.wikipedia.org/wiki/Scientific_method• https://files.kennesaw.edu/faculty/jhendrix/bio 2261/home.html

• http://www.cdc.gov/cmv/• Lecture PowerPoints Microbiology Principles and Lecture PowerPoints Microbiology Principles and

Exploration 7Exploration 7thth edt. J G Black ; J Wiley Pub. edt. J G Black ; J Wiley Pub.• http://en.wikipedia.org/wiki/Scientific_methodhttp://en.wikipedia.org/wiki/Scientific_method• https://files.kennesaw.edu/faculty/jhendrix/bio 2261/home.htmlhttps://files.kennesaw.edu/faculty/jhendrix/bio 2261/home.html• http://www.cdc.gov/cmv/http://www.cdc.gov/cmv/• http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb2pg21.htm• http://www.hcs.ohio-state.edu/hcs300/fungi.htm

•http://www.microbiologybytes.com/introduction/myc2.html