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Questions and Answers
What is false regarding the Major Histocompatibility Complex?
What is false regarding the Major Histocompatibility Complex?
- MHC I presents peptide antigens from endocytosed extracellular protein (correct)
- MHC II is exclusively found in antigen presenting cells
- Mutations in MHC can lead to autoimmunity
- Also called Human Leukocyte Antigen
Which of the following is TRUE about helper T cells?
Which of the following is TRUE about helper T cells?
- TH1 cells combat extracellular fungal pathogens by activating macrophages
- TH2 cells secrete IL-2 to activate eosinophils to fight helminthic infections
- Treg cells are activated by IL-10 to suppress immune responses
- TH17 cells, when dysregulated, can lead to autoimmunity (correct)
Which of the following best describes 'Where the adult parasites live'?
Which of the following best describes 'Where the adult parasites live'?
- Definitive Host (correct)
- Intermediate Host
- Paratenic Host
- None of the Above
Identify the type of vector: Cockroaches carrying Ascaris and Trichuris eggs
Identify the type of vector: Cockroaches carrying Ascaris and Trichuris eggs
Match the following parasitic infections with their clinical consequences:
Match the following parasitic infections with their clinical consequences:
Which of the following is NOT CORRECT concerning Strongyloides stercoralis?
Which of the following is NOT CORRECT concerning Strongyloides stercoralis?
What is the name of the vector with straight white markings on the thorax?
What is the name of the vector with straight white markings on the thorax?
What are the municipalities in Palawan declared to be free from active transmission of malaria?
What are the municipalities in Palawan declared to be free from active transmission of malaria?
The larvae of this mosquito lie parallel on the surface water or water table when at rest. The larvae of _____ lie parallel to the surface water when at rest.
The larvae of this mosquito lie parallel on the surface water or water table when at rest. The larvae of _____ lie parallel to the surface water when at rest.
The natural cycle of Japanese encephalitis virus involves rice-field-breeding mosquitoes and domestic pigs. The pigs serve as _____ of the virus.
The natural cycle of Japanese encephalitis virus involves rice-field-breeding mosquitoes and domestic pigs. The pigs serve as _____ of the virus.
The first line of defense of the immune system is:
The first line of defense of the immune system is:
The basis for vaccination is the immune system’s capability for memory and specificity, which is the function of the:
The basis for vaccination is the immune system’s capability for memory and specificity, which is the function of the:
The substance that is recognized by the immune system and induces the production of antibodies is called the:
The substance that is recognized by the immune system and induces the production of antibodies is called the:
Statement A: Innate immunity responds quickly because it has diverse pattern recognition receptors. Statement B: Adaptive immunity takes a longer time to act but it recognizes highly specific antigens.
Statement A: Innate immunity responds quickly because it has diverse pattern recognition receptors. Statement B: Adaptive immunity takes a longer time to act but it recognizes highly specific antigens.
Statement A: Lysozyme in tears is bactericidal as it cleaves glycosidic bonds in bacterial cell walls. Statement B: Chief cells produce hydrochloric acid contributing to the antibacterial environment of the stomach.
Statement A: Lysozyme in tears is bactericidal as it cleaves glycosidic bonds in bacterial cell walls. Statement B: Chief cells produce hydrochloric acid contributing to the antibacterial environment of the stomach.
Which antibody triggers mast cell degranulation?
Which antibody triggers mast cell degranulation?
Match the following antibody with its function:
Match the following antibody with its function:
What is the primary component of the fungal cell membrane?
What is the primary component of the fungal cell membrane?
Which of the following contents of fungal culture media controls the growth of saprobic fungi?
Which of the following contents of fungal culture media controls the growth of saprobic fungi?
What would you expect on microscopy in cutaneous mycosis?
What would you expect on microscopy in cutaneous mycosis?
Which of the following is TRUE of coenocytic hyphae?
Which of the following is TRUE of coenocytic hyphae?
Which best describes yeast cells?
Which best describes yeast cells?
In nature, dimorphic fungi exist as:
In nature, dimorphic fungi exist as:
Which of the following is classified as an endemic fungus?
Which of the following is classified as an endemic fungus?
Which of the following is false about viruses?
Which of the following is false about viruses?
Which of the following is NOT a part of the viral structure?
Which of the following is NOT a part of the viral structure?
Surface glycoproteins of virions usually function in:
Surface glycoproteins of virions usually function in:
Which of the following is not a bacteria?
Which of the following is not a bacteria?
In SARS-CoV-2, the protein usually used in vaccine development is the spike protein. Antibodies developed against the spike protein inhibit which step of the virus life cycle?
In SARS-CoV-2, the protein usually used in vaccine development is the spike protein. Antibodies developed against the spike protein inhibit which step of the virus life cycle?
The presence of a lipid structure that coats a virion is used as a basis for classifying viruses. This structure is called a/an?
The presence of a lipid structure that coats a virion is used as a basis for classifying viruses. This structure is called a/an?
Prion diseases affect:
Prion diseases affect:
The protein that prions are made of is found throughout the body, even in healthy people and animals, and is encoded by the host’s DNA.
The protein that prions are made of is found throughout the body, even in healthy people and animals, and is encoded by the host’s DNA.
Which of the following is not found in prokaryotic cells?
Which of the following is not found in prokaryotic cells?
What structure differentiates gram-positive from gram-negative cells?
What structure differentiates gram-positive from gram-negative cells?
If a fungus grows as a single cell, it is called a
If a fungus grows as a single cell, it is called a
A 30-year-old man had a fungal infection in his toenails. He most likely has:
A 30-year-old man had a fungal infection in his toenails. He most likely has:
A 30-year-old man had a fungal infection on his left arm. He most likely has:
A 30-year-old man had a fungal infection on his left arm. He most likely has:
Which part of the bacterial cell is also known as the 'bag of enzymes'?
Which part of the bacterial cell is also known as the 'bag of enzymes'?
An unknown organism with thick peptidoglycan, no capsule, and no flagella has which of the following characteristics:
An unknown organism with thick peptidoglycan, no capsule, and no flagella has which of the following characteristics:
A pathogenic organism has lipid A. What would be the most likely presentation in a severely ill patient?
A pathogenic organism has lipid A. What would be the most likely presentation in a severely ill patient?
Under the electron microscope, an unknown bacteria showed movement through the axial filament. What is the most probable organism involved?
Under the electron microscope, an unknown bacteria showed movement through the axial filament. What is the most probable organism involved?
What structure allows the passage of solutes across the cell membrane?
What structure allows the passage of solutes across the cell membrane?
Which bacterial structure found in Gram-positive bacteria mediates passage of cations and provides antigenic specificity?
Which bacterial structure found in Gram-positive bacteria mediates passage of cations and provides antigenic specificity?
Which enzyme allows a bacterium to grow near the surface of a solid media compared to within or near the bottom?
Which enzyme allows a bacterium to grow near the surface of a solid media compared to within or near the bottom?
Which process involves a bacterium transferring DNA to another bacterium through a bacteriophage?
Which process involves a bacterium transferring DNA to another bacterium through a bacteriophage?
What characteristic of the endospore allows it to tolerate adverse conditions?
What characteristic of the endospore allows it to tolerate adverse conditions?
In what part of the growth curve do you expect to find smaller cells with different complement of enzymes and fewer ribosomes?
In what part of the growth curve do you expect to find smaller cells with different complement of enzymes and fewer ribosomes?
What are Gram-positive bacteria characterized by the presence of?
What are Gram-positive bacteria characterized by the presence of?
What is correct about bacterial capsules?
What is correct about bacterial capsules?
What are the essential components of the cross linkages of the cell wall that assists in the strength and shape of the bacteria?
What are the essential components of the cross linkages of the cell wall that assists in the strength and shape of the bacteria?
Fungi are traditionally named based on their _______ state.
Fungi are traditionally named based on their _______ state.
COVID-19-associated mucormycosis, popularly known as 'black fungus infection,' are caused by fungi with which characteristic?
COVID-19-associated mucormycosis, popularly known as 'black fungus infection,' are caused by fungi with which characteristic?
Which of the following are spherical spores formed from the thickening of a hyphal cell at the cross walls?
Which of the following are spherical spores formed from the thickening of a hyphal cell at the cross walls?
What describes a zygospore?
What describes a zygospore?
Which phylum of fungi has the most number of medically-relevant species?
Which phylum of fungi has the most number of medically-relevant species?
If a cutaneous mycosis is suspected, what do you expect to see under the microscope after a KOH smear?
If a cutaneous mycosis is suspected, what do you expect to see under the microscope after a KOH smear?
If Aspergillus sp. is the causative agent, what is the typical description of fungal structures in tissue on histopathology?
If Aspergillus sp. is the causative agent, what is the typical description of fungal structures in tissue on histopathology?
What are the advantages of histopathology as a lab work-up for deep fungal infections?
What are the advantages of histopathology as a lab work-up for deep fungal infections?
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Study Notes
Introduction to Microbiology
- Candida albicans is a fungus, not a bacterium.
- In SARS-CoV-2, the spike protein is used in vaccine development and is involved in the binding and entry step of the virus life cycle.
- The presence of a lipid structure called an envelope is used to classify viruses.
- Prion diseases can affect both humans and animals and are sometimes spread to humans by infected meat products.
- The protein that prions are made of is found throughout the body and is encoded by the host's DNA.
- Prokaryotic cells do not have a nuclear membrane.
- Gram-positive cells have a thick layer of peptidoglycan, while gram-negative cells have a thin layer of peptidoglycan sandwiched between the surface and plasma membrane.
- If a fungus grows as a single cell, it is called a yeast.
- Tinea infections are common dermatologic fungal infections that affect different parts of the body, such as the scalp, arms, legs, and trunk.
Fundamentals of Bacteriology
- The periplasmic space is a "bag of enzymes" that can degrade macromolecules, protect against toxic intruders, and gather essential nutrients.
- An unknown organism with a thick peptidoglycan, no capsule, and no flagella would have a Gram stain that is purple.
- Lipid A is a component of the lipopolysaccharide of the outer membrane of Gram-negative bacteria and can trigger a host immune response, leading to septic shock.
- Spirochetes move by flexing and spinning movements using the axial filament.
- Integral proteins allow the passage of solutes across the cell membrane.
- Plasmids are small, circular, double-stranded DNA molecules that can be transferred through conjugation, transformation, or transduction.
- Peroxidase is an enzyme that allows bacteria to grow near the surface of a solid media by breaking down reactive oxygen species (ROS).
- Transduction is the process of transferring DNA to another bacterium through a bacteriophage.
Microbiology and Parasitology
- Endospores can survive extreme heat, lack of water, and exposure to many toxic chemicals and radiation due to their low water content and large amount of calcium dipicolinate.
- In the stationary phase, microbial cells are smaller, have different enzymes, and fewer ribosomes.
- Gram-positive bacteria are characterized by the presence of teichoic acids.
- Bacterial capsules are composed of polysaccharides/polypeptides and play a role in bacterial virulence, but do not contribute to growth and multiplication.
- The components of cross-linkages in the cell wall are D-glutamic acid, D-alanine, and meso-diaminopimelic acid (DAP).
Fundamentals of Mycology
-
Fungi are traditionally named based on their teleomorph state.
-
The black fungi associated with COVID-19 belong to the phylum Mucoromycotina, which produces sexual spores known as zygospores.### Fungi
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Asexual spores are produced at the top of sporangiophore and are released when the sporangium is ruptured.
-
Zygospores are formed inside a sac-like structure and are diploid spores.
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Chlamydospores are spherical spores formed from the thickening of a hyphal cell at the cross walls.
Medically Relevant Fungi
- Ascomycota is the phylum of fungi with the most number of medically-relevant species.
- Examples of medically-relevant fungi in Ascomycota include Pneumocystis, Candida, Aspergillus, Penicillium, and Sporothrix.
Cutaneous Mycosis
- Cutaneous mycosis is suspected if annular plaques with central clearing are present.
- On microscopy, narrow hyphae with parallel walls are expected.
Fungal Structures
- Aspergillus sp. produces acute angle branching hyphae in tissue on histopathology.
- Histopathology is more sensitive than KOH smear for deep fungal infections.
Fungal Cell Membrane
- Ergosterol is the main component of the fungal cell membrane.
Fungal Culture Media
- Cycloheximide is used to control the growth of saprobic fungi in fungal culture media.
Coenocytic Hyphae
- Coenocytic fungi are aseptate and have imperforate, sparse to none septa in hyphae.
- This allows for the isolation of cytoplasmic material.
Yeast Cells
- Yeast cells reproduce by budding and produce round, pasty or mucoid colonies.
Dimorphic Fungi
- Dimorphic fungi exist as molds in the environment and yeast in the host.
Endemic Fungi
- Blastomyces dermatitidis is an example of an endemic fungus.
Viruses
- Viruses are microscopic, intracellular parasites that are not living outside their host cells.
- Bacteriophages are viruses that infect bacteria, which are prokaryotes.
- Viral structure consists of capsids and envelope, but not ATPase.
Viral Life Cycle
- Steps in the viral life cycle include attachment and entry, transcription of viral genes, translation of viral proteins, virion assembly, and budding.
Testing Viral Viability
- The best way to test viral viability and infectivity is through visualization of cytopathic effect.
Hepatitis B Virus
- Hepatitis B virus is a gap-dsdDNA virus that converts its genome to dsDNA and removes the protein and mRNA.
(+) ssRNA Viruses
- SARS-CoV-2 is a (+) ssRNA virus that synthesizes (-) ssRNA from the dsRNA genome through the viral polymerase.
- (+) ssRNA is copied to (-) ssRNA to make more (+) ssRNA strands.
(-) ssRNA Viruses
- Influenza virus is a (-) ssRNA virus that makes (+) ssRNA from the (-) ssRNA genome.
Immune System
- The first line of defense of the immune system is innate immunity.
- Adaptive immunity is specific for the pathogen and confers protective immunity to reinfection with the same pathogen.
Vaccination
- The basis for vaccination is the immune system's capability for memory and specificity, which is the function of adaptive immunity.
Antigens
- Antigens are any non-self substance that can interact with immune cells or components.
Pattern Recognition Receptors
- Innate immunity responds quickly but has a limited number of germline-encoded pattern-recognition receptors (PRRs).### Statement Analysis
- Statement A: Bactericidal, cleaves glycosidic bonds in bacterial cell walls, true
- Statement B: Chief cells produce hydrochloric acid, false (parietal cells produce hydrochloric acid)
- Statement 1: Alternative complement pathway is activated by recognition of certain PAMPs, true
- Statement 2: C3b and C5b are inflammatory mediators, true (C3b tags pathogen for phagocytosis, C5b interacts with C6-9 to form Membrane Attack Complex)
- Statement A: Eosinophils contain major basic protein against helminthic infections, true
- Statement B: Kupffer cells in the liver and microglial cells in the brain are tissue resident macrophages, true
- Statement A: NK cells recognize injured and infected cells, true (induce apoptosis)
- Statement B: Type 1 IFN inhibits viral protein synthesis, true (increases defenses by inhibiting viral replication)
Complement System
- IgM is the most effective complement activator, activates classical complement pathway
- TGF-Beta induces production and secretion of IgA
- IgE triggers mast cell degranulation
- IgG is the most effective opsonin for phagocytosis by neutrophils
- IgA is involved in the activation of complement by the lectin pathway or alternative pathway
Vaccines
- Rabies is an inactivated vaccine, not a live attenuated vaccine
- Fully immunized child by 12th month: 1 dose BCG, 3 doses pentavalent vaccine, 3 doses OPV, 1 dose measles/MMR vaccine
Plasma Membranes
- Functions as a selectively permeable barrier
- Made of phospholipid bilayer
MHC
- MHC I presents peptide antigens from intracellular proteins
- MHC II presents endocytosed extracellular proteins
- MHC I is for intracellular pathogens or cytosolic proteins
Helper T Cells
- TH1 cells combat intracellular pathogens, not extracellular
- TH2 cells secrete IL-4, IL-5, and IL-13
- TH17 cells, when dysregulated, can lead to autoimmunity
- Treg cells are activated by both IL-10 and TGF-β
Parasitology
- Definitive host: where the adult parasites live
- Intermediate host: where the parasite goes through preliminary development
- Paratenic host: carrier host that carries the parasite around, but no development occurs
- Biological vector: essential in the life cycle, such as mosquitoes for W. bancrofti
- Phoretic vector: carries the parasite but is not essential in the life cycle, such as cockroaches carrying Ascaris and Trichuris eggs
Soil-Transmitted Helminths
- Ascaris lumbricoides causes Loeffler's syndrome, which manifests as allergies during the pulmonary phase
- Hookworms (N. americanus and A. duodenale) cause pulmonary symptoms and Loeffler's syndrome due to pulmonary migration
- Ascaris can lead to intestinal obstruction as a possible complication
- Kato-Katz method is used to diagnose soil-transmitted helminthiasis
- Trichuris trichiura clinical consequences include abdominal pain, diarrhea, dysentery, and rectal prolapse
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