Chapter 8 - Infectious Diseases Flashcards
Is Epstein-Barr virus (EBV) found in circulating T lymphocytes?
No. EBV infects B lymphocytes, in which it resides in a latent state for the remainder of the patient’s life.
How is response to therapy assessed in AIDS patients?
RT-PCR amplification of HIV-1 RNA
What are 3 mechanisms by which pathogens may establish symptomatic gastrointestinal disease?
- Toxin production - without necessarily establishing infection in host (eg. Staph aureus)
- Bacterial colonisation and toxin production (e.g V. choleraie and enterotoxigenic E. coi)
- Adhesion and mucosal invasion (Shigella, Salmonella, Camylobacter jejuni, Entamoeba histolytica)
the predilection for viruses to infect certain cells and not others
tropism
the persistence of viral genomes in cells that do not produce infectious virus
Latency
Cells latently infected by CMV
Monocytes
Bacteria that expresses surface receptors for fibrinogen, fibronectin and vitronectin and uses these molecules to bind to host endothelial cells
S. aureus
Expresses surface protein A which binds the Fc portion of immunoglobulins, allowing the organism to escape antibody-mediated killing
S. aureus
Causes polyclonal T cell proliferation by binding to conserved portions of MHC molecules and to relatively conserved portions of T cell receptor beta chains
May stimulate up to 20% of T lymphocytes leading to large cytokine release
Can trigger SIRS response
Bacterial superantigens
Bacteria that can cause Ritter disease
Staph aureus can cause Staphylococcal scaled-skin syndrome (Ritter disease)
Most important virulence factor of S. pneumoniae
Antiphagocytic capsule
Bacteria that is a major source of dental caries
Streptococcus mutans
Slender gram positive rod with clubbed ends. Spreads from person to person in respiratory droplets or skin exudate.
Causes pharyngeal or less often nasal/laryngeal infection
Damage to heart, nerves and other organs may be present
Corynebacterium diphtheriae
Bacteria that catalyses the covalent transfer of ADP-ribose to elongation factor 2 (EF-2), inhibiting E2 function which is required for the translation of mRNA into protein
C. diphtheriae
Gram positive bacillus (intracellular pathogen) that causes gastroenteritis in most individuals who ingest it in sufficient quantity, and severe food borne infections in vulnerable hosts
Listeria monocytogenes
Bacterial infection characterised by necrotising inflammatory lesions in the skin or GI tract or systemically
Large spore-forming gram positive rod-shaped bacteria found in environmental sources
Anthrax (Bacillus anthracis)
Bacteria that has 2 A subunits (Edema Factor and Lethal Factor) and 1 B subunit (Protective Antigen, serves to deliver the EF and LF into cells)
B. anthracis
Aerobic gram positive bacteria found in soil that cause opportunistic infections.
Grows in distinctive branched chains
Nocardia spp.
Bacteria that causes whooping cough
Bordetella pertussis
acute, ulcerative STI caused by Haemophilus ducreyi
Chancroid (soft chancre)
chronic inflammatory STI caused by Klebsiella granulomatis
Granuloma inguinale (or donovanosis)
Receptors used by M. tuberculosis to enter macrophages
Mannose-binding lectin and type 3 complement receptor (CR3)
are expressed on the phagocyte
Cytokines that promote differentiation of Th1 cells about 3 weeks after infection with M. tuberculosis
IL-12 and IL-18
Cytokine that is a critical mediator of Th1-mediated macrophage activation and killing of bacteria in TB infection
IFN-gamma
when vertebrae are affected by TB
Pott disease
most frequent presentation of extrapulmonary tuberculosis
Lymphadenitis
Spirochete that causes syphillis
Treponema pallidum
protein on outer membrane of T. pallidum which accumulates structural diversity during the course of infection through gene conversion (recombination)
TprK
spirochetes that cause Lyme disease
Borrelia
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Clostridium species that can cause spontaneous gas gangrene and highly associated with underlying malignancy
Clostridium septicum
Bacteria that causes tetanus
Clostridium tetani
Cause of botulism
C. botulinum
Produced in yeast which contributes to virulence by the following functions:
1) antioxidant properties
2) reduces antibody-mediated phagocytosis
3) counteracts the effects of antifungal agents
4) binds iron
5) provides cell wall integrity
Melanin
this yeast form has a highly characteristic thick gelatinous capsule containing a polysaccharide that stains intense red with periodic acid-Schiff and mucicarmine in tissues
Cryptococcus
can cause ‘soap-bubble lesions’ in the perivascular Virchow-Robin spaces within the gray matter
Cryptococcus
Toxin produced by Aspergillus that grow on the surface of some crops. Causes acute and chronic hepatotoxicity and is associated with increased risk of liver cancer
Aflatoxin
caused by the intracellular parasite Plasmodium
Malaria
In malaria infection, the first stage of the parasite in the red cell defined by the presence of a single chromatic mass is known as
Trophozoite
In malarial infection, the stage of the parasite in the RBC with multiple chromatin masses is known as
Schizont
In malaria infection, form of parasite that is released from lysis of hepatocytes and RBCs
Merozoites
Form of Plasmodium with the greatest pathogenicity
P. falciparum
Diagnostic test for a malarial infection?
Giemsa-stained peripheral blood smear, which permits the asexual stages of the parasite to be identified within infected red cells
Once released from the liver, Plasmodium merozoites use a lectin-like molecule to bind to sialic acid residues on these molecules on the surface of RBCs to invade by active membrane penetration
Glycophorin
Sporozoites (the infectious stage of Plasmodium) are released into the humans blood and use this receptor to attach and invade liver cells
Thrombospondin
Life cycle of this parasite involves 2 forms: the promastigote, which develops and lives extracellularly in the sandfly vector, and the amastigote, which multiplies intracellularly in host macrophages
Leishmania
Kinetoplastid parasites (containing a large mass of DNA called a kinetoplast) that proliferate as extracellular forms in the blood and cause sustained or intermittent fevers, lymphadenopathy, splenomegaly, progressive brain dysfunction (sleeping sickness), cachexia and death
African Trypanosomiasis
Kinetoplastid, intracellular protozoan parasite that causes American trypanaosomiasis (Chagas disease)
Trypanosoma cruzi
Organ primarily affected by Chagas disease
Heart. In endemic areas it is a major cause of sudden death due to cardiac arrhythmias
Most common opportunistic pathogen of the CNS in AIDS patients
Toxoplasma
What features are unique to gram negative bacteria compared to gram +ve?
- Outer membrane: site of endotoxin/LPS
- Periplasm (space between the cytoplasmic membrane and outer membrane). Contains many hydrolytic enzymes including B-lactamases
- Porin
In this virus, lymphoid organs and lungs typically have multinucleated giant cells (known as Warthin-Finkeldey cells) which have eisinophilic nuclear and cytoplasmic inclusion bodies
Measles
3 cell surface receptor proteins that have been identified for measles haemagglutinin protein
- CD46 (first cell-surface receptor identified for measles but found to be used only by the culture-adapted virus, including vaccine strain, and not wild-type)
- SLAMF1 (expressed on activated lymphocytes, dendritic cells, monocytes. Serves as the initial receptor for viral infection)
- Nectin-4 (found on basal surface of epithelial cells and thought to be important for replication in the respiratory tract)
Measles and mumps are part of this virus family
Paramyxoviridae
Site of replication of mumps virus?
Lymph nodes and salivary glands
Poliovirus infects human cells by binding to which receptor
CD155
In what proportion of patients with poliovirus does that virus affect the CNS (spinar poliomyelitis or brainstem poliomyelitis)
1/100
Where does West Nile Virus replicate/spread?
After inoculation by a mosquito, WNV replicates in skin dendritic cells,
then migrates to LNs and replicates further,
enters the bloodstream
In some cases crosses the blood brain barrier and infects neurons in the CNS
Antibody-dependent enhancement, in which the cross-reactive antibodies enhance uptake of virus into macrophages via Fc receptors, is thought to increase the infectivity of this virus and contribute to severe forms
Dengue
Site of replication of HSV infections?
HSV-1 and HSV-2 both replicate in the skin and the mucous membranes at the site of entry of the virus (usually oropharynx or genitals)
Spread to sensory neurons that innervate these primary sites of replication and release
How does HSV evade the immune system?
Can evade antiviral CTLs by inhibiting the class I MHC recognition pathway and eludes humoral immune defences by producing "decoy" receptors that bind Fc domain of immunoglobulin and inhibitors of complement
Which glycoproteins are used by HIV to infect immune cells?
gp120 and gp41
What does EBV bind to on B cells and integrins?
EBV envelope glycoprotein (gp120) binds to CD21 (CR2) on B cells and integrins
Infectious stage of malaria. Uses thrombospondin receptor to attach to and invade liver cells after mosquito takes a blood meal
Sporozoite
What immune deficiency can lead to reduced defence against N. meningitides and N. gonorrhoea?
Inherited defects in complement proteins (C5 to C9)
With what 2 extracellular devices does N. gonorrhoea adhere to host cells?
- long pili
- OPA proteins
What strategy does Neisseria use to escape the immune system
Antigenic variation
What organism causes chancroid?
Haemophilus ducreyi
What are the 2 types of leprosy?
Tuberculoid
Lepromatous
Which type of leprosy is paucibacillary?
Tuberculoid
What are the 3 main manifestations of tertiary syphillis?
- Cardiovascular (aortitis)
- Neurosyphilis
- Benign tertiary syphillis (gummas)
What is the most important toxin of C perfringens?
Alpha toxin
Which neurotransmitter release is inhibited by C. tetani?
γ-aminobutyric acid
Protein F is expressed on this bacteria. Binds to surface of host cells via fibronectin
Strep pyogenes
Bacteria that escapes the phagolysosome using a pore-forming protein, listeriolysis O and two phospholipases
Listeria monocytogenes
This bacterium blocks phagolysosome formation by recruiting a host protein called coronin
M. tuberculosis
