Chapter 12 - Duncan Rossduncanross.net/MIC2010/Chapter 12 - Duncan.pdf · antibiotics kill the good bacteria leaving Candida free to grow How Candida causes an infection: The infections

Chapter 12

The Eukaryotes

Kingdom Fungi

Multicellularity All, except yeasts

Cellular Arrangement Unicellular, filamentous, fleshy

Food Acquisition Method Absorptive

Characteristic Features Sexual and asexual spores

Mycology: the study of fungi

Fungi

Table 12.1 Selected Features of Fungi and Bacteria Compared.

Some Things We Like About Good Fungi

• Have been used to produce antibiotics • Essential role in the decomposition of matter • Can be used in food such as mushrooms and truffles • Used to leaven bread • Starter cultures of bread were taken from each batch of

leaved dough and added to the next • 1500 strains of Yeast have been identified

YEASTS

Yeasts are unicellular May become multicellular through connections known as pseudohyphae Yeast measure 3-4 uM in diameter Reproduce asexually by mitosis, but also through budding Saccharomyces cerevisiae converts carbohydrates to carbon dioxide and alcohols via fermentation . The same type of yeast (different strains) are used in Bread and Beer.

FUNGI PLANTS Cell Wall of Chitin Cell Wall of Cellulose Eukaryotic Eukaryotic Often Symbiotic

Lichens

• Mutualistic combination of an alga (or cyanobacterium) and fungus

• Alga produces and secretes carbohydrates; fungus provides holdfast

Figure 12.11b Lichens.

Lichen thallus

Fungus Alga

Cortex

Algal layer

Fungal hyphae

Cortex

Rhizine

Medulla

Economic Effects of Lichens

• Dyes • Antimicrobial (Usnea) • Litmus – litmus paper

Medically Important Phyla of Fungi

• Zygomycota • Microsporidia • Ascomycota

– Anamorphs

• Basidiomycota

Microsporidia

• No hyphae • No mitochondria • Intracellular parasites

– Encephalitozoon intestinalis

Figure 12.8 The life cycle of Encephalitozoon, a microsporidian.

Asexual reproduction

Cytoplasm breaks up around nuclei to form spores.

Cytoplasm grows, and nuclei reproduce.

New spores are released.

Spores are ingested or inhaled.

Vacuole Mature spores

Cytoplasm and nucleus enter.

Host cell

Spore injects tube into host cell.

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Ascomycota

• Sac fungi • Septate – septa to divide cells • Teleomorphic fungi

– Produce sexual and asexual spores • Ascospores and frequently conidiospores

– Aspergillus (opportunistic, systemic mycosis) – Blastomyces dermatitidis, Histoplasma

capsulatum (systemic mycoses) – Microsporum, Trichophyton (cutaneous mycoses)

Figure 12.9 The life cycle of Talaromyces, an ascomycete.

Vegetative mycelium grows.

Sexual reproduction Asexual

reproduction

Conidium germinates to produce hyphae.

Ascospore germinates to produce hyphae.

Conidia are released from conidiophore.

Hypha produces conidiophore.

Conidia

Conidiophore

Ascus opens to release ascospores.

Meiosis then mitosis.

Karyogamy.

Plasmogamy.

Ascospore

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Figure 12.3a Aerial and vegetative hyphae.

Aerial hyphae

Aspergillus niger

ASPERGILLUS FUMIGATUS

• Causes black mold on fruits and vegetables • Ubiquitous in soil • Spores can be inhaled causing a serious lung disease, aspergillosis • Has been found in mummies, could have contributed to the curse of King Tut • The toxicity of Aspergillus is due to Ochratoxin A • Gliotoxin excreted by the mold can cause immunosuppression and immunotoxicity in

animals, possibly linked to depletion of macrophages • Serious pathogen in immunocompromised individuals • Voriconazole - treatment

Anamorphs

• Produce asexual spores only – rRNA sequencing places most in Ascomycota; a

few are Basidiomycota – Penicillium – Sporothrix (subcutaneous mycosis) – Stachybotrys, Coccidioides, Pneumocystis

(systemic mycoses) – Candida albicans (cutaneous mycoses)

Candida Albicans

• Diploid fungus

Candida Albicans

Natalie Tijerina Sandra Albarracin

General Information Classification: Dimorphic

fungus- can exist in yeast and fungal form (virulence factor)

Genus: Candida Species: albicans Shape: spores and

hyphae(branching tubes that make up the body of a multicellular fungus)

Size: 10-12 µm in diameter

Gram + Growth: reproduces by

budding pH: Needs a slightly

alkaline environment to thrive , a pH about 7.4

Temperature: 37°C, warm and damp environments

Oxygen: Facultative anaerobes

Spores / Hyphae

Diagnosis • Complete medical evaluation and history, with physical exam

that focuses on the area of the body with symptoms • Diagnosis is made based on signs and symptoms, and

clusters of budding yeast • Generally, a doctor takes a sample of the vaginal discharge

or swabs an area of oral or skin lesions, urine, feces, and nail clippings

• Fungal blood and stool cultures for detection of Candida should be taken for patients suspected of having deep organ candidiasis

• Tissue biopsy may be needed for invasive systemic disease.

Route of Transmission/Portal of Entry

• C. Albicans is normally present on the skin and in mucous membranes such as the vagina, mouth, rectum, and digestive tract

• The fungus also can travel through the blood stream in immunocompromised individuals

• Candida can enter newborn infants during or shortly after birth

• This organism is OPPORTUNISTIC- for example, antibiotics kill the good bacteria leaving Candida free to grow

How Candida causes an infection: The infections caused by all species of Candida are

called Candidiasis-most commonly Candida albicans Candida is known to impair immune functioning by

directly and negatively impacting the helper-suppresser ratio of T lymphocytes

Organism causes disease by invading human tissue by means of pseudohyphae (long filaments) which can penetrate intracellular cracks

The overgrowth of Candida is complex and a difficult condition to overcome once it enters the body. It is one of the most highly adaptive organisms, and has the ability to mutate and develop stronger forms of itself

Toxins

Produces toxins -Gliotoxin: inactivates important enzymes, and is

cytotoxic -Acetaldehyde: normal by-product of metabolism,

however excess production of this by Candida can cause impaired neuro-transmission in the brain

Candida Albicans and its toxins can infiltrate and effect any organ or system in the body and can be responsible for a large variety of physical and mental health conditions that we see so commonly in people today

Toxic waste can also be absorbed into the blood stream

Demographics:

Candidiasis is an extremely common infection. Thrush occurs in approximately 2–5 percent of healthy newborns and occurs in a slightly higher percentage of infants during their first year of life.

Over 1 million adult women and adolescent girls in the United States develop vaginal yeast infections each year. It is not life-threatening, but the condition can be uncomfortable and frustrating.

Common factors that can cause infection:

A common cause of Candida albicans fungus is the overuse of antibiotics or oral contraceptives

Steroid hormone medication, ex. Cortisone, or corticosteroids often prescribed for skin conditions such as rashes, eczema

Suppressed immune systems, ex. Patients with diabetes, HIV/AIDS, and that receive radiation or chemotherapy

High sugar and starch diet (yeasts live on sugar, and starches are converted into sugar very quickly during our digestion process)

Areas affected: Candida species can infect tissues in essentially every

body system, producing a wide range of clinical manifestations

is called thrush when it grows in the mouth, especially in infants

shows up on skin as a red, inflamed, and sometimes scaly rash, ex: diaper rash

causes vaginitis, commonly known as a yeast infection causes candidal onchomycosis in the nails can affect the esophagus and the digestive tract Candidal infection of the penis may result from sexual

intercourse with an infected partner

c. Albicans in aids patients

In immunocompromised patients, when body resistance is low as in leukemia or HIV/AIDS, Candida albicans can enter the bloodstream and causes systemic infection

The more debilitated the host the more invasive the disease

Candida albicans is one of several mycoses (fungal disease) that account for most deaths associated with AIDS

So common in HIV+ individuals that their mycoses are part of what defines end-stage AIDS

Treatment: Antifungal medications -- these include oral rinses and tablets,

vaginal tablets and suppositories, and creams. For vaginal yeast infections, medications that are available over the counter include creams and suppositories such as Monistat, Vagistat, and Gyne-Lotrimin. Your doctor may prescribe a pill, Diflucan

Creams combined with low-strength corticosteroids -- reduce inflammation and itching.

The “Candida diet”- detox, probiotics, improve what you eat Most treatments last from 2 - 3 days to 2 weeks. Be sure to

take all medicine exactly as prescribed. If you do not, the same infection could come back, or you could become infected with a new strain of candida.

For severe candidiasis that could be life threatening to someone with a comprised immune system, your doctor may prescribe an IV medication, amphotericin B.

Basidiomycota

• Club fungi • Septate • Produce basidiospores and sometimes

conidiospores – Cryptococcus neoformans (systemic mycosis)

Figure 12.10 A generalized life cycle of a basidiomycete.

Sexual reproduction

Asexual reproduction

Basidiospore germinates to produce hyphae.

Plasmogamy.

Vegetative Mycelium grows.

Fruiting structure (“mushroom”) develops.

Basidiospores are formed by meiosis.

Basidiospores mature.

Basidiospores are discharged.

Fragment grows to produce new mycelium.

Hyphal fragment breaks off vegetative mycelium.

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Economic Effects of Fungi

• Saccharomyces cerevisiae: bread, wine, HBV vaccine

• Trichoderma: cellulase • Taxomyces: taxol • Entomophaga: biocontrol • Coniothyrium minitans: kills fungi • Paecilomyces: kills termites

Fungal Diseases (Mycoses)

• Systemic mycoses: deep within body • Subcutaneous mycoses: beneath the skin • Cutaneous mycoses: affect hair, skin, and nails • Superficial mycoses: localized, e.g., hair shafts • Opportunistic mycoses: caused by normal

microbiota or environmental fungi

Kingdom Various

Nutritional Type Chemoheterotroph

Multicellularity None

Cellular Arrangement Unicellular

Food Acquisition Method Absorptive; ingestive

Characteristic Features Motility; some form cysts

Protozoa

Characteristics of Protozoa

• Vegetative form is a trophozoite • Asexual reproduction is by fission, budding, or

schizogony • Sexual reproduction by conjugation • Some produce cysts

Medically Important Phyla of Protozoa

• Diplomonads • Parabasalids • Euglenozoa • Amebae • Apicomplexa • Dinoflagellates • Ciliates

Diplomonads • No mitochondria • Multiple flagella • Giardia lamblia

Figure 12.18 Members of the super kingdom Excavata.

Giardia trophozoites. Giardia cyst.

Cyst

Parabasalids

• No mitochondria • Multiple flagella • No cyst • Trichomonas vaginalis

Figure 12.18d Members of the super kingdom Excavata.

Trichomonas vaginalis.

Axostyle Undulating membrane

Flagella

Euglenozoa

• Move by flagella • Euglenoids

– Photoautotrophs

• Hemoflagellates – Trypanosoma spp.

• Sleeping sickness • Chagas’ disease

Figure 12.18e Members of the super kingdom Excavata.

Euglena.

Chloroplasts

Eye spot

Flagella

Figure 23.23 Trypanosoma cruzi, the cause of Chagas’ disease (American trypanosomiasis).

Amebae

• Move by pseudopods • Entamoeba • Acanthamoeba

Figure 12.19 Amebae.

Pseudopods

Nucleus

Food vacuole

Amoeba proteus

Entamoeba histolytica

Nucleus

Red blood cells

Apicomplexa

• Nonmotile • Intracellular parasites • Complex life cycles • Plasmodium • Babesia • Cryptosporidium • Cyclospora

Figure 12.20 The life cycle of Plasmodium vivax, the apicomplexan that causes malaria. Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human.

Sporozoites undergo schizogony in liver cell; merozoites are produced.

Merozoites released into bloodstream from liver may infect new red blood cells.

Merozoite develops into ring stage in red blood cell.

Intermediate host Ring stage grows and

divides, producing merozoites.

Merozoites are released when red blood cell ruptures; some merozoites infect new red blood cells, and some develop into male and female gametocytes.

Another mosquito bites infected human and ingests gametocytes.

In mosquito’s digestive tract, gametocytes unite to form zygote.

Resulting sporozoites migrate to salivary glands of mosquito.

Sexual reproduction

Asexual reproduction

Female gametocyte

Male gametocyte

Zygote

Male

Gametocytes

Female

Sporozoites in salivary gland

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Schizogony

Toxoplasmosis

• Usually contracted from cats • Causes a mild flu like illness in immunocompetent individuals • Can cause AIDS patients or immunocompromised individuals

to become seriously ill • Parasite can cause encephalitis and neurologic disease as well

as schizophrenia

Figure 23.24 The life cycle of Toxoplasma gondii, the cause of toxoplasmosis.

If a pregnant woman accidentally ingests oocysts (contacted when changing a cat litter box), prenatal infection of the fetus may occur.

If humans eat undercooked meat containing tissue cysts, they may become infected.

Definitive host

Tachyzoites Bradyzoites in tissue cyst Sporocysts

Sporozoite

Intermediate hosts

Mature oocyst (10–13 μm x 9–11 μm)

Sporogony

Immature cyst

Immature oocyst is shed in cat feces.

Mature oocysts develop by sporogony and contain two sporocysts, each with four infective sporozoites.

Oocysts can infect many hosts, including mice, domestic animals, and humans, via ingestion.

Sporozoites from ingested oocysts invade animal tissue and develop into bradyzoites within tissue cysts or into tissue-invading tachyzoites.

Cat ingests bradyzoites in tissue cysts of animals, usually mice.

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Kingdom Animalia

Nutritional Type Chemoheterotroph

Multicellularity All

Cellular Arrangement Tissues and organs

Food Acquisition Method Ingestive; absorptive

Characteristic Features Elaborate life cycles

Helminths

Helminths (Parasitic Worms)

• Kingdom: Animalia – Phylum: Platyhelminthes (flatworms)

• Class: trematodes (flukes) • Class: cestodes (tapeworms)

– Phylum: Nematoda (roundworms)

Characteristics of Helminths

• Reduced digestive system • Reduced nervous system • Reduced locomotion • Complex reproduction

Life Cycle of Helminths

• Monoecious (hermaphroditic) – Male and female reproductive systems in one

animal

• Dioecious – Separate male and female

• Egg → larva(e) → adult

• Why are the drugs used to treat parasitic helminths often toxic to the host? 12-14

• Of what value is the complicated life cycle of parasitic helminths? 12-15

• 12-16 List the characteristics of the two classes of parasitic platyhelminths, and give an example of each.

• 12-17 Describe a parasitic infection in which humans serve as a definitive host, as an intermediate host, and as both.

• 12-18 List the characteristics of parasitic nematodes, and give an example of infective eggs and infective larvae.

• 12-19 Compare and contrast platyhelminths and nematodes.

Helminths Learning Objectives

Figure 12.25 Flukes.

Oral sucker

Intestine

Ventral sucker

Testis Ovary

Fluke anatomy Clonorchis sinensis

Oral sucker Ovary Intestine Testes

(b) Life cycle of Schistosoma, cause of schistosomiasis.

Figure 23.28 Schistosomiasis.

Free-swimming cercariae penetrate human skin, losing tail.

Intermediate host

Cercariae are released from the snail.

Cercariae travel through circulatory system to intestinal blood vessels, where they mature into adults.

Adult female flukes lay eggs.

(a) Male and female schistosomes. The female lives in a groove on the ventral (lower) surface of the male schistosome (“split-body”), is continuously fertilized, and continuously lays eggs. The sucker is used by the male to attach to the host.

Eggs reach body of water after being excreted in human feces or urine.

Cercaria (0.33 mm)

Cercaria (0.13 mm)

Definitive host

Female (size: 15–20 mm)

Eggs

Male

Adult flukes

Egg (0.15 mm)

Miracidium (0.2 mm)

Male

Mouth Sucker Female Mouth

Eggs hatch into free-swimming larvae (miracidia).

Miracidium reproduces in snail, forming several cercariae.

Miracidium penetrates snail.

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Figure 12.26 The life cycle of the lung fluke, Paragonimus, spp.

Cercaria

Redia

Cercaria (0.5 mm long)

Intermediate host

Cercaria leaves snail and enters crayfish.

Metacercaria (0.25–0.5 mm)

In crayfish, cercaria encysts to produce metacercaria.

Infected crayfish is eaten by human, and metacercaria develops into adult fluke.

Definitive host

Free-swimming miracidium enters snail.

Intermediate host

Miracidium (0.8 mm long)

Miracidium develops in egg and hatches from egg.

Eggs reach water after being excreted in feces.

Adult fluke (7.5–12 mm long)

Eggs

Inside snail, miracidium develops into redia, which reproduces asexually to produce rediae; several cercariae develop within redia.

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1 Hermaphroditic adult fluke releases eggs into human lung.

Sexual reproduction

Asexual reproduction

Hooks

Sucker

Scolex

Sucker

Genital pore

Ovary

Mature proglottid will disintegrate and release eggs

Figure 12.27 General anatomy of an adult tapeworm.

Neck

Humans as Definitive Hosts

Definitive Host Taenia saginata

Cysticerci in beef muscle

Intermediate Host

Echinococcus granulosus

Adult in dog

Scolex

Definitive host eats intermediate host, ingesting cysts.

Figure 12.28 The life cycle of the tapeworm, Echinococcus, spp.

Definitive host

Adult tapeworm

Scoleces from cyst attach to intestine and grow into adults.

Adult tapeworm releases eggs.

Egg (30–38 µm)

Hydatid cyst

Larvae develop into hydatid cysts.

Brood capsule Scolex

Larva

Eggs hatch, and larvae migrate to liver or lungs.

Intermediate host ingests eggs.

Intermediate host

Human intermediate host ingests eggs. Dead end.

Intermediate host

Sexual reproduction

Asexual reproduction

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Adult pinworm

Figure 12.29a The pinworm Enterobius vermicularis.

Figure 12.30 The heartworm Dirofilaria immitis.

Heartworm

Adult pinworm

Figure 12.29 The pinworm Enterobius vermicularis.

Mouth

Intestine

Ovary

Genital pore

Anus

Female (8–13 mm long)

Mouth

Intestine

Genital pore

Anus

Spicules

Male (2–5 mm long)

Larva

Egg (55 μm long)

Pinworm egg

Testis

Figure 25.26 The life cycle of Trichinella spiralis, the causative agent of trichinellosis.

Ingested cysts develop into Trichinella spiralis adults in the pig’s intestinal wall.

Garbage, including undercooked or raw pork

Meanwhile, other animals eat infected meat that has been dumped.

Capsule

Adult worms produce larvae that encyst in the pig’s muscles.

Section of encysted T. spiralis

Human eats undercooked pork containing cysts that are infective to humans or animals that ingest it.

Trichinellosis in humans; ingested cysts develop into T. spiralis adults. Adults produce larvae that encyst in muscles. T. spiralis adult

Figure 25.23 An Ancylostoma hookworm attached to intestinal mucosa.

Hookworm

Intestinal mucosa

Arthropods as Vectors

• May transmit diseases (vectors) • Kingdom: Animalia

– Phylum: Arthropoda (exoskeleton, jointed legs) • Class: Insecta (6 legs)

– Lice, fleas, mosquitoes

• Class: Arachnida (8 legs) – Mites and ticks

Arthropods as Vectors

• Mechanical transmission • Biological transmission

– Microbe multiplies in vector

• Definitive host – Microbe’s sexual reproduction takes place in

vector

Figure 12.31 Mosquito.