Microbiology 205

Georgetta Seidel

Definitions

• Mycologists--scientists who study fungi

• Mycology--scientific discipline dealing with fungi

• Mycoses--diseases caused in animals by fungi

The five kingdom system• Eukarya (includes all organism with a

nucleus & membrane bound organelles) • Plants and Animals are fairly obvious• Fungi, are very distinct from the other

kingdoms• Kingdom Protista is a “dumping

ground” for organisms that don’t fit into the other eukaryotic kingdoms

Exoenzymes are found in fungi and some bacteria. They are digestive enzymes that are secreted into the environment, where they digest the

food into small molecules that can be absorbed and used by the fungus.

• FUNGI• 100,000 species• 100 human pathogens, fungi associated

diseases are rising, due to nosocomial infections and in immunocompromised patients (ie. HIV, diabetes, lupus, transplant folks)

• Aspergillosis, Blastomycosis—pulmonary infections and dissemination may be involved

• 5,000 plant pathogens=$1 billion/yr

IMPORTANCE OF FUNGI• Fermentation industry• Remember fermentation is an anaerobic process

- Wine (yeast) - Beer- Bread - Cheese (bacteria)- Soy sauce (filamentous fungi (Aspergillus oryzae

provides a low protein diet with amino acids, yeast & bacteria) soy beans & flour are held in a container for mold to grow—moldy beans are incubated for several months

- Sauerkraut- Vinegar (yeast and bacteria)- Yoghurt (Bacteria)

IMPORTANCE OF FUNGI• Drug manufacturing (usually their

waste products are to our benefit)– Citric acid–Ethanol (yeast)–Antibiotic griseofulvin, penicillin– Cortisone (Rhizopus)– immunosuppressive agents (cyclosporine)

IMPORTANCE OF FUNGI (cont.)

• SAPROPHYTE • Degrade complex organic

materials into simple ones, which become available for other organisms

Importance of Fungi (cont.)• MYCORRHIZAE• Fungi associated with plants

Symbiosis• Fungi help plant roots absorb

minerals and water in the soil-serve as root extensions

• Fungi benefit by absorbing nutrients exuded by plant roots

• They are often called “ancient plants”

• 4 broad classes exist• Algal fungi• Sac fungi• Imperfect fungi• Club (basidium) fungi

Algal fungi• All are microscopic and grow in

water and damp soil• Many species in this group are

responsible for blights (like Irish Potato Famine)

• Some species, such as Rhizopus however, are used as a source of cortisone and other "drugs"

• yeasts and the blue and green molds often seen on decaying citrus fruits, in jellies and on leather

• Some species, like Penicillium are economically useful, but others such as Ergot (Clavicep s purpurea) which infects rye crops, can cause mass destruction

• In controlled doses, however, Ergot becomes an important alkaloid used to control hemmorrage (during the birthing process) as well as in the treatment of migraine

• Candida albicans is another species of sac fungi that is parasitic in human beings and aids in the normal functioning of the digestive tract

Sac fungi

Imperfect fungi• molds that mildew walls and

spot clothes, as well as those that cause plant diseases, athlete's foot, and ringworm.

• Some of these fungi are useful like Aspergillus, used in the production of miso (fermented soy paste)

Club (basidium) fungi• largest group of fungi which

includes rusts and smuts that attack specific plants, such as corn, beans, apples, wheat, asparagus, coffee, roses and barberry

• many of the mushrooms in this division are edible and delicious, a large number of them, such as the Amanita's are deadly poisonous

FUNGAL STRUCTURE• Thallus-”body”

–Molds & fleshy fungi have these structures•Long filaments of cells (hyphae)•Septate-Cross Wall (Most Fungi)

•Coenocytic-No cross wall, continuous mass with many nuclei

MYCELIUM

• Intertwined filamentous mass formed by hyphae, visible to the unaided eye

• Forms when environmental conditions are right

YEASTFacultative Anaerobes• Fermentation=ethanol and CO2

• Non-filamentous unicellular fungi–Spherical or oval

• Reproduction–Two types exist –a)Fission or b) budding

Yeast Reproduction• FISSION• “even” reproduction, nucleus divides

forming two identical cells, like bacteria

• BUDDING• “uneven” reproduction, parent cell’s

nucleus divides and migrates to form a bud and then breaks away

DIMORPHIC FUNGI• Growth as a mold or as a yeast• Most pathogenic fungi are

dimorphic fungi• At 37o C yeast-like• At 25o C mold-like• Can also occur with changes in

CO2

• Fungi grow differently in tissue vs nature/culture; often dictated by temp

Within Agar=mold, Agar Surface=yeast

Changes in CO2

Types of REPRODUCTION• Asexually-fragmentation of hyphae• Asexually and Sexually-spores

–Spores: Used for IdentificationFour groups of true fungi–Zygomycetes (common bread mold—Rhizopus)–Basidiomycetes (puffballs & common mushrooms)–Ascomycetes (Dutch elm disease/rye smut)–Deuteromycetes (fungi imperfecti)

Classification of these groups

• First three groups is based on their method of sexual reproduction

• 4th group, the Deuteromycetes, have NO sexual reproduction

REPRODUCTION (cont.)• Asexual Reproduction• Progeny will be identical to parent

–Spores (Conidiospores, Blastospores,Chlamydospores, Sporangiospores)

–Hyphae fragmentation (Arthrospores)

IDENTIFICATION OF FUNGI• Examination of asexual spores• **Fungal spores are different than the

endospores of bacteria• Endospores are not for reproduction,

but an environmentally resistant life stage

• Fungal spores are for reproduction, do not ensure resistance to environmental conditions

Asexual spores

• Conidiospores• Chlamydospores• Sporangiospores• Blastospores

ASEXUAL SPORESConidiospore

–Multiple (chains) or single spores formed at the end of an aerial hypha

–Not enclosed within a sac

–Aspergillus spp.–Penicillium spp.

Conidial fungus

• reproduces by means of asexual spores called conidia

• Conidia vary greatly in shape, size and color

• Most of the common household molds & mildews are conidial fungi

ASEXUAL SPORES (cont.)• Another type of Conidiophore:• Blastospores

–A bud coming off the parent cell– Candida

albicans

Blastospore

Blastospores

ASEXUAL SPORES (cont.)• Chlamydospore

–Formed within hypha–Thick-walled spore

•Candida albicans

Chlamydospores

• The chlamydospore is a method of producing a substantial resting spore very quickly

• Nutrient is shunted from adjacent cells into a preferred cell and it swells up, converts nutrient materials to oil droplets for efficient storage, then rounds off with a thick, often roughened outer wall for protection

Chlamydospores

ASEXUAL SPORES

• Sporangiospores–Hundreds formed within a sac (sporangium) at the end of an aerial hypha

–Rhizopus spp.

Rhizopus spp

Chlamydospores

Arthrospores

Sporangiospores

Conidiospores

Blastospores

1

3

1A

1B

2

NUTRITIONAL ADAPTATIONS

• Acidic pH (5.0)• Most molds are aerobic• Yeasts are facultative

anaerobes

NUTRITIONAL ADAPTATIONS (cont.)

• High osmotic pressure• Low moisture• Less N2 than bacteria• Complex carbohydrates

–Lignin(component of wood) *Saprophytes

MEDICALLY IMPORTANT FUNGI

part II

(Some characters used in identification of deuteromycetes)

ALL FUNGI:• are eukaryotes • develop from spores • display neither flagella, cilia, nor chloroplasts • have cell walls (though not necessarily ones

composed of cellulose as are plant cell walls, but instead of chitin and other polysaccharides)

• Though displaying great variety and complexity, the fungi are routinely divided into two major groups:

• the macroscopic (fleshy) fungi • the microscopic fungi (molds and yeasts)

Fungal growth requirements

• In contrast to bacteria, fungi tend grow in places that are:

– more acidic – have higher osmotic pressures – are lower in moisture – are low in nitrogen – contain complex

carbohydrates

Fungal structuresHyphae are one dimensional

arrangements of cells. • septa are the cross walls which

separate individual cells in hyphae.

• Mycelium are a tangled mass of hyphae.

• Mycelium can extensively permeate the substrate within which the fungi grows whether it be soil, water, or even living tissue.

Molds vs Yeast• Molds • Molds are aerobic, filamentous fungi including

– mildews – rusts – smuts

• Molds tend to grow on surfaces rather than throughout substrates.

• Yeasts – unicellular/nonfilamentous:

• Yeasts are fungi which are: • typically spherical or oval • facultatively anaerobic • They are often observed as powdery

coatings on plant material.

Dimorphic fungi

• Dimorphic fungi are fungi that behave like molds (multicellular---consist of hyphae) under some conditions, and like yeasts (unicellular---lack hyphae) under others.

Review

Fungal reproduction

• fungi replicate by mitosis rather than the binary fission employed by bacteria.

• Types of fungal reproduction, : – budding – fission – hyphae fragmentation – sporulation

Sexual and asexual:Fungal spores come in two varieties: asexual spores and sexual spores – Spores are used extensively to identify fungi.

• Asexual spores – asexual spores are formed by a single parental

fungi and therefore genetically identical to the parental fungi.

– Asexual spores come in a variety of types formed by a variety of mechanisms including:

• Arthrospores (sliced bread pieces)• Blastospores (buds on a twig)• Chlamydospores (giant cell with oil)• Conidiospores (fingers)• Sporangiospores (sac)

Ascomycetes• Asexual phase- Conidiospores

(Penicillium and Aspergillus & budding yeast

• Sexual phase (morels lichens)

Zygomycetes• Asexual phase—Sporangium—bread

mold (Rhizopus stolonifer)• Sexual phase--- sporgangium ---

shotgun fungus (lives on dung) it shoots its sporgangium explosively towards light or fly pathogen (Entomophthora muscae—--these types of fungi have been used as agents for biological control of insects)

Basidiomycetes• Basidiospore• Examples: boletes,

puffballs,smuts, stinkhorns and tooth fungi

DEUTEROMYCETES (cont.)

–Aspergillus - Microsporum

(dematophytes)–Blastomyces - Penicillium–Candida - Trichophyton–Histoplasma - Pneumocystis ?

Zygomycetes• “saprophytic” molds• common bread mold

(Rhizopus)• coenocytic hyphae• Asexual spores:

Sporangiospores

Approximately 600 species including bread molds (such as Rhizopus) exist

Ascomycetes• “sac” fungi• Septate hyphae and yeasts• Asexual spore:

–Conidiospores

Approximately 30,000 species including yeasts (Saccharomyces cerevisiae), some of the molds (Aspergillus), morels, and truffles. Ascomycetes have typical reproductive structures called asci.

Basidiomycetes• “club”fungi• Mushrooms

Approximately 25,000 species including many macroscopic fungi (mushrooms, puffballs, shelf fungi) as well as a number of plant pathogens (rusts, smuts).

FUNGAL DISEASES

• Mycosis: Fungal infection• Usually chronic• Four groups of mycoses based on degree of tissue involvement and mode of entry

TYPES OF MYCOSES• Systemic• Subcutaneous• Cutaneous• Opportunistic

Because fungi are slow growing, mycoses are generally long-lasting

SYSTEMIC MYCOSES• Deep within the body

–effects a number of different tissues and organs

• Usually soil fungi• Spore inhalation=Route of

transmission-starts in the lungs and spreads to other body tissues

• Not contagious

SYSTEMIC MYCOSES (cont.)

• Histoplasmosis• Coccidiomycosis• Coccidioides immitis got renamed for the

AZ Valley fever Coccidioides posadasii

SUBCUTANEOUS MYCOSES

• Infections beneath the skin

• Soil and plant fungi• Hyphae or spores in

wounds

CUTANEOUS MYCOSES• Called “Dermatophytes”• Epidermis• Hair • Nails• Secrete keratinase-degrades keratin

(protein found in hair, skin and nails)• Contagious-direct contact with

infected hairs and epidermal cells

CUTANEOUS MYCOSES

• Skin high osmotic pressure

• Low moisture

OPPORTUNISTIC MYCOSES• Broad-spectrum antibiotics• Transplant patients• AIDS patients• Cancer patients

–Ex: Stachybotrys (mold), Mucormycosis and Aspergillosis

DERMATOPHYTES• Grow on keratin

–Hair–Nails

• Tinea or ringworm

TINEA

• Capitis (scalp)-can lead to bald patches

• Cruris (groin)• Pedis (athlete’s foot)

FUNGI IN CUTANEOUS MYCOSES

• Three genera involved in cutaneous mycoses:

• Trichophyton• Microsporum• Epidermophyton

TRICHOPHYTON

• Hair• Skin• Nails (Tinea ungulum)

MICROSPORUM

• Hair• Skin

EPIDERMOPHYTON

• Skin• Nails

Fungi in Cutaneous Mycoses

Trichophyton Microsporum Epidermophyton

Hair Hair Skin

Skin Skin -

Nails - Nails

Tinea capitis

Tinea capitis Tinea barbae

Tinea cruris

Tinea unguium

Tinea pedis

SUBCUTANEOUS MYCOSES

• More serious than cutaneous mycoses

• Sporothrix schenkii–Soil organism

• Gardeners=ulcers on hands

Subcutaneous mycosis (mycetoma)

Mycetoma• Mycetoma is a chronic infection of the skin,

subcutaneous tissue and sometimes bone• It is generally found on the foot where it is given the

name watering can foot

• Mycetoma may be due to several fungi or actinomycetes (actinomycetoma).

• Actinomycetes are bacteria producing filaments like fungi. Both the fungi and the actinomycetes are found in soil and plant material in tropical regions.

• The organism is inoculated into the skin by a minor injury, for example, a cut with a thorn when barefoot.

Mycetoma—a deep fungal infection

Clinical features• Mycetoma is more common in men than women,

particularly those aged 20 to 50. It generally presents as a single lesion on an exposed site and may persist for years.

• It starts as a small hard painless lump under the skin. • It grows slowly but eventually involves underlying muscles

and bones.

• The middle of the lesion caves in, ulcerates and discharges pus, which contains grains.

• Eventually, sinus tracts (holes) develop which also discharge pus and grains.

• The surface skin is scarred and pale. • Considerable deformity often makes it difficult to walk. • Mycetoma may cause no discomfort but it often itches or

burns. • Secondary bacterial infection is common. • Treatment is slow

CANDIDIASIS

• Mucosal normal microbiota suppresses the growth of Candida albicans

CANDIDIASIS (cont.)• Vaginitis and thrush are initiated

by:–Antibiotics eliminate normal microbiota

–pH changes• Infants that may not have their

normal microbiota established=thrush

Candidiasis

Thrush

Vaginal

CANDIDIASIS (cont.)

• Hematogenous dissemination•Kidney•Spleen•Lung•Liver

Invasive candidiasis

MYCOSES OF THE RESPIRATORY SYSTEM• Histoplasmosis-resembles

TB, starts in the lungs, most cases are minor–Histoplasma capsulatum

• Coccidioidomycosis–Coccidioides immitis in CA–Coccidioides posadasii in AZ

MYCOSES OF THE RESPIRATORY SYSTEM

(cont.)• Blastomycosis

–Blastomyces dermatidis• Pneumocystis pneumonia

–Pneumocystis carinii

HISTOPLASMOSIS

• Resembles tuberculosis• May affect all organs• Vague symptoms• Yeast lives within

macrophages and multiplies

HISTOPLASMOSIS (cont.)

• Histoplasma capsulatum• Dimorphic fungi• Mississippi river and Ohio

river states

HISTOPLASMOSIS (cont.)• Very low mortality

–50/year/USA• Transmission

–Airborne conidia–Bats: Carry fungus in feces –Birds: Feces

HISTOPLASMOSIS (cont.)

• Diagnostic–Blood test—AB titer

• Treatment–Amphotericin B–Itraconazole

Histoplasmosis• second most significant fungus disease• It is infectious but not contagious• The "summer flu" that Midwesterners use to get

often is now thought to have been histosplasmosis

• Histoplasmosis basically is a pulmonary or respiratory disease, but may extend to the liver, lymph nodes, and spleen; it may disseminate to the blood and bone marrow and be fatal

• The victim frequently has chills and fever to 105 degrees, night sweats, chest pains, and fatigued. A non-productive cough is fairly common.

Histoplasmosis

COCCIDIOIDOMYCOSIS

• Valley fever–Coccidioides immitis–Coccidioides posadasii

–Dimorphic fungi

COCCIDIOIDOMYCOSIS (cont.)

• Southwest deserts–Arthrospores in dry alkaline soils

–San Joaquin Valley (CA)–Tucson area

RANGE OF CASES OF

VALLEY FEVER:

inapparent -- 60% mild - moderate --30% complications -- 5-10% fatal--<1%

COCCIDIOIDOMYCOSIS (cont.)

• Symptoms–Chest pain–Fever–Cough–Extreme fatigue

RISK FACTORS FOR DISSEMINATED DISEASE:

Immunosuppressed Patients-- organ transplant lymphoma HIV+/AIDS adrenal corticosteroid therapy diabetes 3rd trimester pregnancy

Gender male

Race African-American Filipino

Valley Fever

COCCIDIOIDOMYCOSIS • In tissues C. immitis forms

spherules –Thick-walled structures filled with spores

–In soil, forms filaments that reproduce by the formation of arthrospores, transmitted by wind, 100,000 infections per year

Spherule form (top half)

multiplies in

the lungs; mycelia

(bottom half)

grow in the soil

Life cycle ofC. immitis

C. immitis spherule in lung tissue

Spherules in brain tissue

Brain lesions caused byC. immitis

COCCIDIOIDOMYCOSIS (cont.)

• Most infections are asymptomatic

• Most recover in a few weeks

COCCIDIOIDOMYCOSIS (cont.)

• Solid immunity follows recovery

• 1/1000 cases a tuberculosis-like condition develops throughout the body

COCCIDIOIDOMYCOSIS (cont.)

• Diagnostic–Resemblence to TB requires Identification of spherules in tissues

–50-100 deaths in the USA•92% San Joaquin Valley

BLASTOMYCOSIS

• Blastomyces dermatitidis or North American Blastomycosis

• Dimorphic fungus• Soil in Mississippi Valley

BLASTOMYCOSIS (cont.)

• Most infections are asymptomatic

• Begins at lungs and spreads

• 30-60 deaths/year

BLASTOMYCOSIS (cont.)

• Cutaneous ulcers• Abscess formation• Tissue destruction

Blastomycosis—Glichrists Disease

• Blastomycosis is a chronic, systemic fungal disease that affects humans

• The disease affects the lungs.• It is caused by Blastomyces dermatitidis. • The main route of infection is by inhalation of

spores• The disease is infectious but is not contagious. • Major symptoms in humans include loss of

weight, fever, cough, and bloody sputum and chest pains.

• The disease may disseminate into the skin, bones, or urogenital tract.

BLASTOMYCOSIS (cont.)

• Diagnostic–Isolation of organism from pus and biopsies

• Treatment–Amphotericin B

PNEUMOCYSTIS PNEUMONIA

• Pneumocystis carinii• Opportunistic pathogen• Leading cause of death in

AIDS patients• Present in healthy lungs• Immunosuppressed individuals

PNEUMOCYSTIS PNEUMONIA (cont.)

• Rare before AIDS epidemic–Less than 100 cases/year

• 1993-Indicator of AIDS• Currently, one of the most

common infectious diseases

OTHER FUNGAL RESPIRATORY DISEASES

• Aspergillus fumigatus• Aspergillus spp.-present

in decaying vegetation• Rhizopus spp.• Mucor spp.

Those darn pigeons!!• Cryptococcosis: Yeast Meningitis

Affects: Humans

The disease is caused by a systemic pathogenic yeast called Cryptococcus Neoformans, which is found worldwide.

• Cryptococcosis in humans usually begins as a primary infection of the lungs.

• There are no visible early symptoms may include cough, chest pain, weight loss, fever or dizziness. The disease may be in the lungs, mucous membranes, bones, and joints, with no organ or tissue of the body exempt.

• It very frequently involves the brain covering as cryptococcal meningitis.

• Pigeon excreta is the most common source of C. Neoformans. The yeast is carried in the intestinal tract of pigeons.

• Pulmonary cryptococcsis has occurred in the workmen who have been exposed to the yeast while demolishing old buildings where pigeons had roosted.

• Most of the cryptococcal infections occur from inhalation of the fungas along with the dust from areas enriched with pigeons manure.

Other diseases associated with pigeons

• Salmonellosis is more than just food poisoning.• Pigeons are important factors in the spread of

salmonellosis, since the bacteria are left wherever the pigeons defecate

• Pigeons trample back and forth through their copious excretions on ledges and air intake vents

• The dust enters through air conditioners and ventilators.

• S. Typhimurium var. Copenhagen is the most common salmonella isolated from pigeons

• Salmonellosis in humans may manifest itself in one or more of four types (1) temporary carriage without infection (2) Gastroenteritis (food poisoning) (3) enteric fever septicemia (blood poisoning) (4) Persistent infection

OTHER FUNGAL RESPIRATORY DISEASES

(cont.)• Compost piles

–Farmers and gardeners• Impaired immunity• Treatment

–Amphotericin B

Antifungal antimicrobials• Amphotericin B, nystatin

(Streptomyces nodosus)• miconazole Monistat 3 (azole)

–Relatively toxic-Kidneys

FUNGAL DISEASES OF THE DIGESTIVE SYSTEM

• Mycotoxins: Fungal Toxins–Ergot poisoning–Aflatoxin poisoning

ERGOT POISONING• Claviceps purpurea• Infects Grain Crops• Ergotism: Disease caused by

ingestion of contaminated grains

• Claviceps-contaminated grains (rye or wheat)

Claviceps purpurea

• as recently as 1951, in Pont-St. Esprit, a small town in France, there was an outbreak of the disease. In Europe it is the custom to buy fresh bread nearly every day.

• In this small town there was only one bakery and everyone bought bread from it. Strange things started happening. People developed a burning sensation in their limbs, began to hallucinate that they could fly, did strange things to their dogs with forks and in general acted weirdly. This outbreak is chronicled in a marvelous (but out of print) book called "The day of St Anthony's Fire" by John Grant Fuller. St. Anthony is the patron saint of lost causes When all of the other saints have failed, St. Anthony is the one you are supposed to pray to. And St. Anthony's fire was rampant in the town that day. Similar outbreaks probably occurred throughout the world wherever the conditions were right for the growth of Claviceps purpurea.

• The chemical responsible for the hallucinations is actually LSD! lysergic acid. There was even an outbreak of ergotism on the television show "Quincy" starring Jack Klugman, who played a coroner. He was aboard a cruise ship and people were acting very strangely. Quincy finally traced the behavior to contamination of the flour tortillas that had been served aboard ship.

The X-Files also had an episode featuring ergot, although it had a surreal twist (of course). In that episode, Scully got a tattoo that caused her to hallucinate (she thought the tattoo was talking to her). Turns out the tattoo artist was an ex-con who learned his art in prison. He collected plants in the prison yard and extracted dyes from them for his tattoos.

• Another ergot derivative may cause spontaneous abortions in animals-- in small doses this same drug is used to aid in childbirth. Another of the ergot derivatives is used to cure migraine headaches.

ERGOT POISONING (cont.)

• Gangrene• Psychotic delusions• Convulsions• Abortion

ERGOT POISONING (cont.)

• Witchcraft in Salem (1690s)

• Similar Behavior caused by Lysergic acid (LSD)

• There have been various attempts to explain those witch trials. None of them are more logical and interesting than the hypothesis of ergot poisoning, caused by Claviceps purpurea. The behavior was not identified as witchcraft until 1691, and this was just the beginning of the problem.

• All of the accused had similar symptoms: manic melancholia, psychosis, delirium, crawling sensations of the skin, vertigo, headaches, vomiting and diarrhea. All of these are symptoms of ergot poisoning, and it is likely that at least the initial hysteria was started by Claviceps purpurea infecting the grains of rye

• compelling, although circumstantial, evidence that the Salem witch trials coincided with a weather period that would have produced large quantities of ergot on rye, which was grown in the lowlands in that area.

Aflatoxin•Aflatoxin is a naturally occurring mycotoxin produced by two types of mold Aspergillus flavus and Aspergillus parasiticus.

•Aspergillus flavus is common & widespread in nature and is most often found when certain grains are grown under stressful conditions such as drought.

•The mold occurs in soil, decaying vegetation and hay

•At least 13 different types of aflatoxin are produced in nature with aflatoxin B1 considered as the most toxic•While the presence of Aspergillus flavus does not always indicate harmful levels of aflatoxin it does mean that the potential for aflatoxin production is present.

Aflatoxin poisening

• Aspergillus flavus• Peanuts and cottonseeds• Acute intoxication

–Liver damage

AFLATOXIN POISONING (cont.)

• Chronic intoxication–Liver cancer–Depending on the levels, the toxins can severely affect the liver and they are a known human carcinogen