Introduction to Parasitology and Mycology

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Questions and Answers

What is the primary mechanism of parasite entry into the host?

Disruption of host defenses

Direct penetration through the skin

Cell and tissue damage

Oral ingestion or direct penetration through the skin or other surfaces (correct)

What is the primary characteristic of a parasite?

It is an organism that never causes harm to its host

It is an organism that spends a significant portion of its life in or on a host organism (correct)

It is an organism that only lives on dead tissue

It is an organism that immediately kills its host

What determines the organs or tissues of the host in which a parasite can survive?

Nutritional requirements

Species and tissue tropisms (correct)

Reproductive potential

Infective doses and replication

What is the term for the complex interactions between a parasite, its host, and the environment?

Parasitology Signup and view all the answers

What is the result of parasite invasion of host tissues?

Cell and tissue damage Signup and view all the answers

Which of the following is NOT a characteristic of protozoa?

They have a cell wall Signup and view all the answers

What is the primary mechanism of parasite attachment to the host?

Parasite adhesins and host glycoprotein or glycolipid receptors Signup and view all the answers

Where do most protozoan parasites replicate?

Intracellularly and extracellularly Signup and view all the answers

What is the function of the ectoplasm in protozoa?

It is responsible for locomotion and ingestion of food Signup and view all the answers

What is the final outcome of parasite infection in the host?

Immunologically mediated inflammatory response Signup and view all the answers

What is the classification of tapeworms and flukes?

Platyhelminthes Signup and view all the answers

Which of the following is an example of a protozoan parasite?

Ameba Signup and view all the answers

What is the role of clamp connections in septate hyphae?

To connect hyphal elements and allow movement of elements Signup and view all the answers

What is the term for the ability of a fungus to exhibit either the yeast form or the hyphal form?

Dimorphism Signup and view all the answers

What is the primary function of fungal spores?

To serve as the primary means for dispersal and survival Signup and view all the answers

Which of the following is an example of a dimorphic fungus associated with human infection?

Histoplasma capsulatum Signup and view all the answers

What is the term for the thread-like filaments that make up the hyphal stage of fungal growth?

Hyphae Signup and view all the answers

What is the factor that influences spore production in fungi?

Light, oxygen levels, temperature, and nutrient availability Signup and view all the answers

What enables mold spores to survive for months or even years?

Their ability to withstand adverse conditions Signup and view all the answers

What is necessary for spore germination?

Both nutrient availability and moisture Signup and view all the answers

Why do fungi rarely cause systemic infections?

Because they are widely distributed in nature Signup and view all the answers

What is a characteristic of pathogenic fungi?

Their ability to generate disease Signup and view all the answers

What indicates a deficiency of host defenses?

The dissemination of fungi in the body Signup and view all the answers

What is the basis of resistance to fungi in healthy individuals?

Their cutaneous and mucosal physical barriers Signup and view all the answers

What is the mode of introduction of causative organisms of mycoses?

Through trauma to the feet or legs Signup and view all the answers

What is the characteristic of opportunistic mycoses?

Infections due to fungi with low inherent virulence Signup and view all the answers

What is the purpose of using India Ink in the diagnosis of mycoses?

To detect encapsulated organisms Signup and view all the answers

What is the type of stain used to reveal fungi in tissue sections?

Gomori methenamine silver (GMS) stain Signup and view all the answers

What is the medium used to grow pathogenic fungi?

Sabouraud dextrose agar Signup and view all the answers

What is the purpose of a biopsy in the diagnosis of mycoses?

To determine the source of the tissue-invading fungi Signup and view all the answers

Study Notes

What is Parasitology?

Study of the complex interactions between parasites, their hosts, and the environment
Not just limited to the study of parasites, but also the interactions between parasites and their hosts

Classification of Parasites

Protozoa (single-celled organisms)
Metazoa (multicellular organisms)
- Helminths (worms)
- Sarcomastigophora (Ameba, flagellate)
- Platyhelminthes (flatworms)
  - Class Cestoda (tapeworms)
  - Class Trematoda (flukes)
- Ciliophora (ciliates)
- Nemathelminthes (roundworms)
- Apicomplexa (sporozoa, coccidia)
- Microspora (microsporidia)

Characteristics of Protozoa

Single "cell-like unit" that is morphologically and functionally complete
Can perform all functions of life
Ectoplasm (outer layer) functions in protection, locomotion, ingestion of food, excretion, and respiration
Endoplasm (inner layer) houses the nucleus, mitochondria, and various food and contractile vacuoles
Lacks cell walls

Parasite-Induced Injury

Results from parasite invasion of host tissues
Penetration of anatomic barriers
Cell and tissue damage
Reproductive potential
Nutritional requirements

Pathogenesis of Parasitic Disease

Niche selection contributing to attachment
Disruption, evasion, and inactivation of host defenses
Evolves into immunologically mediated inflammatory response

Fungi

Dimorphic: can exhibit either yeast or hyphal form, depending on growth conditions
Spores can remain dormant for months or years
Spore germination requires specific environmental and biological factors

Pathogenesis of Fungal Disease

Fungi accidentally penetrate host barriers
Immunologic defects or debilitating conditions exist
Disease results when fungi multiply within the host

Aspects of Fungal Disease

Pathogenic fungi develop virulence mechanisms and morphologic forms
Dissemination of fungi in the body indicates a deficiency of host defenses

Fungal Morphology and Growth

Hyphal growth: thread-like filaments release enzymes for degradation and absorption of substrates
Spore formation: dependent on environmental variables
Spores serve as primary means for dispersal and survival

Diagnosis of Fungal Infections

Skin scrapings or pus from a lesion can be mounted in KOH and examined under a microscope
India Ink can detect encapsulated organisms
Serology can detect IgG antibodies
Molecular direct fluorescence microscopy can identify fungi
Biopsy and histopathology can identify tissue-invading fungi

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Description

Learn about the basics of parasitology and mycology, including the definition of parasites and their relationship with host organisms. Understand how parasitism affects the host and the characteristics of infectious agents. Test your knowledge with this quiz!