30 Questions
What is the primary mechanism of parasite entry into the host?
Oral ingestion or direct penetration through the skin or other surfaces
What is the primary characteristic of a parasite?
It is an organism that spends a significant portion of its life in or on a host organism
What determines the organs or tissues of the host in which a parasite can survive?
Species and tissue tropisms
What is the term for the complex interactions between a parasite, its host, and the environment?
Parasitology
What is the result of parasite invasion of host tissues?
Cell and tissue damage
Which of the following is NOT a characteristic of protozoa?
They have a cell wall
What is the primary mechanism of parasite attachment to the host?
Parasite adhesins and host glycoprotein or glycolipid receptors
Where do most protozoan parasites replicate?
Intracellularly and extracellularly
What is the function of the ectoplasm in protozoa?
It is responsible for locomotion and ingestion of food
What is the final outcome of parasite infection in the host?
Immunologically mediated inflammatory response
What is the classification of tapeworms and flukes?
Platyhelminthes
Which of the following is an example of a protozoan parasite?
Ameba
What is the role of clamp connections in septate hyphae?
To connect hyphal elements and allow movement of elements
What is the term for the ability of a fungus to exhibit either the yeast form or the hyphal form?
Dimorphism
What is the primary function of fungal spores?
To serve as the primary means for dispersal and survival
Which of the following is an example of a dimorphic fungus associated with human infection?
Histoplasma capsulatum
What is the term for the thread-like filaments that make up the hyphal stage of fungal growth?
Hyphae
What is the factor that influences spore production in fungi?
Light, oxygen levels, temperature, and nutrient availability
What enables mold spores to survive for months or even years?
Their ability to withstand adverse conditions
What is necessary for spore germination?
Both nutrient availability and moisture
Why do fungi rarely cause systemic infections?
Because they are widely distributed in nature
What is a characteristic of pathogenic fungi?
Their ability to generate disease
What indicates a deficiency of host defenses?
The dissemination of fungi in the body
What is the basis of resistance to fungi in healthy individuals?
Their cutaneous and mucosal physical barriers
What is the mode of introduction of causative organisms of mycoses?
Through trauma to the feet or legs
What is the characteristic of opportunistic mycoses?
Infections due to fungi with low inherent virulence
What is the purpose of using India Ink in the diagnosis of mycoses?
To detect encapsulated organisms
What is the type of stain used to reveal fungi in tissue sections?
Gomori methenamine silver (GMS) stain
What is the medium used to grow pathogenic fungi?
Sabouraud dextrose agar
What is the purpose of a biopsy in the diagnosis of mycoses?
To determine the source of the tissue-invading fungi
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
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!
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