Fungi, Protozoa, and Helminthes

Fungi

Kingdom Fungi

Divided into 2 groups: macroscopic fungi

(mushrooms, puffballs, gill fungi)

microscopic fungi (molds, yeasts)

Majority are unicellular or colonial

Fungal OrganizationMold

Hyphae Mycelium

Yeast Soft, uniform texture and

appearance Thermal dimorphism

grow as molds at 30°C and as yeasts at 37°C

Fungal Organization - Mold

Fungal Cell Structure Cell wallsCell walls contain chitin Energy reserve is glycogen Nonmotile

Produce wind-blown sporesGrow toward food source

Conidia / spores

Fungal Organization

Yeasts Unicellular (bicellular) False hyphae Beta-glycan cell wall

structure

Fungal Nutrition

All are heterotrophicMajority harmless saprobes Some are parasites

Live on the tissues of other organisms, but none are obligate

Fungal Reproduction

Primarily through spores formed on reproductive hyphae

Asexual reproduction spores are formed through: Budding or mitosis Sporangiospores Conidia

Arthrospore Chlamydospore Blastospore Phialospore Microconidium or macroconidium porospore

Reproductive strategies

Sexual reproduction Spores are formed following fusion of male and

female strains and formation of sexual structure Sexual spores and spore-forming structures

are one basis for classification Zygospores Ascospores Basidiospores

Zygospores

Ascospores

Basidiospores

Yeast

Budding “cloning” Sometimes form

pseudohypha

Fungal Classification

Yeast verse Mold Asexual verse Sexual (reproductive strategies) Terrestrial or water

Fungal Classification

Subkingdom Amastigomycota Terrestrial inhabitants including those of medical

importance:

1. Zygomycota – zygospores; sporangiospores and some conidia

2. Ascomycota – ascospores; conidia

3. Basidiomycota – basidiospores; conidia

4. Deuteromycota*** – majority are yeasts and molds; no sexual spores known; conidia

Fungal Classification

Subkingdom Mastigomycota

Diagnosis and identification require: macroscopic and microscopic observation of:

asexual spore-forming structures and spores hyphal type colony texture and pigmentation physiological characteristics genetic makeup culturing in selective and enriched media

Reverse important!!!!

Roles of Fungi Adverse impact

mycoses, allergies, toxin production

destruction of crops and food storages

Beneficial impact decomposers of dead

plants and animals sources of antibiotics,

alcohol, organic acids, vitamins

used in making foods and in genetic studies

Characterization of Fungal Infections

Systemic Subcutaneous Cutaneous Superficial Opportunistic

Systemic fungal infections by true

pathogens

Histoplasma capsulatum Histoplasmosis typically dimorphic distributed worldwide

most prevalent in eastern & central regions of US grow in moist soil high in nitrogen content inhaled conidia produce primary pulmonary infection

may progress to systemic involvement of a variety of organs & chronic lung disease amphotericin B, ketoconazole

Coccidioides immitis Coccidioidomycosis distinctive morphology

blocklike arthroconidia in the free-living stage

arthrospores inhaled from dust Creates spherules and

nodules in the lungs lives in alkaline soils in

semiarid, hot climates endemic to southwestern US amphotericin B treatment

Blastomyces dermatitidis Blastomycosis dimorphic free-living species distributed

in soil midwestern and southeastern

US inhaled 10-100 conidia

convert to yeasts & multiply in lungs

symptoms include cough, chest pains and fever

chronic cutaneous, bone, & nervous system complications

amphotericin B

Blastomyces dermatitidis

Paracoccidioides brasiliensis

Paracoccidioidomycosis distributed in Central & South

America lung infection occurs through

inhalation or inoculation of spores

systemic disease not common ketoconazole, amphotericin B,

sulfa drugs

Subcutaneous Mycoses

Sporothrix schenckii Sporotrichosis (rose-gardener’s disease) dimorphic very common saprobic fungus that decomposes

plant matter in soil infects appendages and lungs Lymphocutaneous variety

occurs when contaminated plant matter penetrates the skin pathogen forms a nodule spreads to nearby lymph nodes

Potassium iodide orally Amphotericin B in unresponsive cases

Lymphocutaneous Sporotrichosis

Mycetoma

when soil microbes are accidentally implanted into the skin

progressive, tumorlike disease of the hand or foot due to chronic fungal infection may lead to loss of body

part caused by

Pseudallescheria or Madurella

Cutaneous Mycoses

Cutaneous Mycoses

Dermatophytoses infections strictly confined

to keratinized epidermis (skin, hair, nails)

ringworm & tinea 39 species in the genera

Trichophyton, Microsporum, Epidermophyton

communicable among humans, animals, & soil

infection facilitated by moist, chafed skin

Examples of dermatophytespores. (a) Regular, numerous microconidia of Trichophyton.

(b) Macroconidia of Microsporumcanis, a cause of ringworm in cats,

dogs, and humans. (c) Smooth-surfaced macroconidia in clusterscharacteristic of Epidermophyton.

Dermatophytoses Ringworm of scalp

tinea capitis affects scalp & hair-bearing regions of head hair may be lost

Ringworm of body tinea corporis occurs as inflamed, red ring lesions anywhere on smooth skin

Ringworm of groin tinea cruris “jock itch” affects groin & scrotal regions

Ringworm or foot & hand tinea pedis & tinea manuum spread by exposure to public surfaces; occurs between digits & on soles

Ringworm of nails tinea unguium persistent colonization of the nails of the hands & feet that distorts the nail

bed

Ringworm Treatment

Topicals: ointments containing tolnaftate, miconazole or

menthol & camphor lamisil or griscofulvin 1-2 years

Superficial Mycoses

Superficial Mycoses

Tinea versicolor causes mild scaling, mottling of skin Malassezia furfur

White piedra is whitish or colored masses on the long hairs of the body Trichosporan beigelli

Black piedra causes dark, hard concretions on scalp hairs Piedraia hortae

Hortaea werneckii

Tinea nigra Dematiaceous yeast-like

hyphomycete found in tropical and subtropical areas

Extremely halophilic environments

Slow growing

Opportunistic Pathogens

Candida albicans

Candidiasis widespread yeast infections can be short-lived, superficial skin

irritations to overwhelming, fatal systemic diseases

budding cells of varying size may form both elongate pseudohyphae & true hyphae

forms off-white, pasty colony with a yeasty odor

Candida albicans Normal flora of oral

cavity, genitalia, large intestine or skin 20% of humans

Account for 80% of nosocomial fungal infections

Account for 30% of deaths from nosocomial infections

Candida albicans

Thrush occurs as a thick, white, adherent growth mucous membranes of mouth & throat

Vulvovaginal yeast infection painful inflammatory condition of the female

genital region causes ulceration & whitish discharge

Cutaneous candidiasis occurs in chronically moist areas of skin and burn

patients

Cryptococcus neoformans

Crypotcoccosis widespread encapsulated

yeast inhabits soils around

pigeon roosts common infection of

AIDS, cancer or diabetes patients

Cryptococcus neoformans

infection of lungs leads to cough, fever, and lung nodules

dissemination to meninges and brain causes severe

neurological disturbance death

Pneumocystis (carinii) jiroveci

causes pneumonia (PCP) most prominent opportunistic

infection in AIDS patients forms secretions in the lungs

that block breathing can be rapidly fatal if not

controlled with medication

small, unicellular fungus

Aspergillus

Aspergillosis very common airborne soil fungus 600 species

8 involved in human disease inhalation of spores causes fungus balls in

lungs and invasive disease in the eyes, heart, & brain

amphotericin B & nystatin

Zygomycosis

Zygomycota are extremely abundant saprobic fungi

found in soil, water, organic debris, & food Genera most often involved are Rhizopus, Absidia,

& Mucor usually harmless air contaminants invade the membranes of the nose, eyes, heart, &

brain of people with diabetes, malnutrition with severe consequences

Mycotoxicoses

Fungal toxins lead to mycotoxicoses usually caused by eating poisonous or

hallucinogenic mushrooms aflatoxin toxic and carcinogenic

grains, corn peanuts lethal to poultry and livestock

Stachybotrys chartarum sick building syndrome severe hematologic and neurological damage

Parasites

Parasitology

Study of eucaryotic parasites, protozoa and helminths

Cause 20% of all infectious diseases

Less prevalent in industrialized countries

Increasingly common in AIDS patients

Kingdom Protista

Algae Protozoa

Protozoa

100,000 species @ 25 are important pathogens

Vary in shape, lack a cell wall Most are unicellular Colonies are rare Most are harmless, free-living in a moist habitat Some are animal parasites

Spread by insect vectors

All are heterotrophic Feed by engulfing other microbes and organic matter

Protozoa

Most have locomotor structures flagella, cilia, or pseudopods.

Exist as trophozoite motile feeding stage

cyst Dormant resting stage when

conditions are unfavorable for growth and feeding

All reproduce asexually, mitosis or multiple fission

Many also reproduce sexually

Protozoan Classification

Difficult because of diversity Simple grouping is based on method of

motility, reproduction, and life cycle

Protozoan Classification

Mastigophora primarily flagellar

motility sexual reproduction cyst and trophozoite

Protozoan Classification

Sarcodina primarily ameba asexual by fission most are free-living

Protozoan Classification

Ciliophora Cilia trophozoites and

cysts most are free-living,

harmless

Protozoan Classification

Apicomplexa motility is absent

except male gametes sexual and asexual

reproduction complex life cycle – all

parasitic

Protozoan Classification Phyla grouping based on method of

motility, reproduction, and life cycle:

Hemoflagellates: Vector-Borne Blood Parasites

Obligate parasites that live in blood and tissues of human host Spread in specific tropical regions by blood-sucking insects that serve

as intermediate hosts Categorized according to cellular and infective stages

Protozoal Diseases

An Intestinal Ciliate: Balantidium coli

An occupant of the intestines of domestic animals such as pigs and cattle

Acquired by ingesting cyst-containing food or water

Trophozoite erodes intestine and elicits intestinal symptoms

Healthy humans resistant Rarely penetrates intestine or enters blood Treatment – tetracycline, iodoquinol,

nitrimidazine or metronidazole

Leishmania species Leishmaniasis Endemic to equatorial

regions Promastigotes are

injected with sand fly bite convert to amastigote

and multiply if macrophage is fixed

the infection is localized systemic if macrophage

migrates L. major

Entamoeba histolytica

Amebiasis Alternates between a large trophozoite Motile by means of pseudopods and a smaller

nonmotile cyst Humans are the primary hosts Ingested Carried by 10% of world population

Entamoeba histolytica

Cysts swallowed and travel to small intestine alkaline pH and digestive juices stimulate cysts to release 4

trophozoites

Trophozoites attach, multiply, actively move about and feed

Asymptomatic in 90% of patients Ameba may secrete enzymes that dissolve tissues

and penetrate deeper layers of the mucosa Causing dysentery, abdominal pain, fever, diarrhea

and weight loss

Entamoeba histolytica

Life-threatening manifestations are Hemorrhage Perforation Appendicitis Amebomas

Tumor-like growths May invade liver and lung Severe forms of disease

result in 10% fatality rate Effective drugs are

iodoquinol, metronidazole, and chloroquine

Giardia lamblia

Giardiasis Pathogenic flagellate Cysts are small, compact,

and multinucleate Reservoirs include beavers,

cattle, coyotes, cats, and humans

Cysts can survive for two months in environment

Usually ingested with water and food

10 to 100 cysts

Giardia lamblia Cysts enter duodenum, germinate,

travel to jejunum to feed and multiply

Diagnosis difficult because organism is shed in feces intermittently

Treatment: quinacrine or metronidazole

Agent is killed by boiling and iodine

Trichomonads: Trichomonas species

Small, pear-shaped 4 anterior flagella and an undulating membrane Exist only in trophozoite form 3 infect humans:

T. vaginalis T. tenax T. hominis

Trichomonas vaginalis

Causes an STD called trichomoniasis Reservoir is human urogenital tract Strict parasite 3 million cases yearly Female symptoms

foul-smelling, green-to-yellow discharge; vulvitis; cervicitis; urinary frequency and pain

Male symptoms urethritis, thin, milky discharge, occasionally prostate

infection Metronidazole

Ping-pong effect!

Protozoal Diseases of the Blood and Nervous System

The Plasmodium Parasite Infects the Blood Malaria affects 300-500 million people

Four species of Plasmodium cause malaria P. vivax P. ovale P. malariae P. falciparum

Plasmodium:

Malaria Dominant protozoan

disease Obligate intracellular

sporozoan Female Anopheles

mosquito is the primary vector blood transfusions, mother

to fetus 2 million deaths each year

Plasmodium

Africans with sickle-cell anemia gene Resistant!!!

Trypanosoma species and Trypanosomiasis

Distinguished by their infective stage trypomastigote

elongate, spindle-shaped cell with tapered ends, eel-like motility

2 types of trypanosomiasis: T. brucei

African sleeping sickness T. cruzi

Chagas disease

Trypanosoma brucei

African Sleeping Sickness Spread by tsetse flies

Biting of fly inoculates skin with trypomastigotes Multiplies in blood and damages spleen, lymph

nodes and brain Harbored by reservoir mammals Two variants of disease caused by 2

subspecies: T.b.gambiense – Gambian strain; West Africa T.b. rhodesiense – Rhodesian strain; East Africa

Trypanosoma brucei Chronic disease symptoms

are sleep disturbances, tremors, paralysis and coma.

Blood, spinal fluid or lymph nodes

Treatment before neurological involvement with melarsoprol, eflornithine

Control involves eliminating tsetse fly

Trypanosoma cruzi

Chagas disease Endemic to Central and South America Reduviid bug (kissing bug) is the vector

Bug feces is inoculated into a cutaneous portal

Local lesion, fever, and swelling of lymph nodes, spleen, and liver

Heart muscle and large intestine harbor masses of amastigotes

Chronic inflammation occurs in the organs (especially heart and brain)

Treatment nifurtimox and benzonidazole

Toxoplasma gondii

Toxoplasmosis Intracelllular apicomplexan

parasite with extensive distribution Lives naturally in cats

harbor oocysts in the GI tract Acquired by ingesting raw meats

or substances contaminated by cat feces

Most cases go unnoticed Except in fetus and AIDS patients Can suffer brain and heart damage

Treatment: pyrimethamine and sulfadiazine

Parasitic Helminths

Parasitic Helminths

Multicellular animals Parasitize host tissues Organs for reproduction, digestion, movement,

protection Mouthparts

Attachment Digestion of host tissues

Well-developed sex organs that produce eggs and sperm Fertilized eggs go through larval period in or out of host body

Helminths

Flatworms (Phylum Platyhelminthes) do not have respiratory or circulatory

structures, or a digestive tractCestodes (tapeworms)Trematodes or flukes

Roundworms (Phylum Nematoda)

Flatworms Cestodes have a head

region called a scolex Fertilized eggs are

produced in proglottids which break off and spread eggs

Tapeworms generally live in host’s intestine, absorbing nutrients

They have limited host range, but usually at least 2 hosts

Flatworms

Trematodes have complex life cycles and often 2 hosts• Eggs develop into

larvae (miracidia) in water, which invade snails

• Trematodes evade the immune system by having a surface similar to host cells

Roundworms (Phylum Nematoda) Damage to the host often occurs by large worms

burdens in vessels or intestines

Tapeworms Beef and pork tapeworm disease are caused by

Taenia saginata and T. solium, respectively acquired by eating poorly cooked beef or pork scolex attached to the intestine, causing obstruction and

mild diarrhea

Humans Host to at Least 50 Roundworm Diseases

Pinworm disease is caused by Enterobius vermicularis Infection of the intestines

leads to diarrhea and anal itching

Reinfection can occur if contaminated hands contact food or the mouth

Worms die in a few weeks, even without treatment

Trichinellosis caused by Trichinella spiralis

T. spiralis lives in pig intestines and can encyst in skeletal muscles

Transmission to humans occurs by eating raw or poorly cooked pork

Symptoms include: pain vomiting nausea constipation

Larvae can migrate to the tongue, eyes, and ribs

Hookworms

have a set of hooks or suckers to attach to the upper intestine Hookworms suck blood

from intestinal capillaries This cause blood loss and

anemia

Humans are the only host Larvae in soil penetrate the

skin of bare feet and enter the bloodstream