Final Exam Diseases Flashcards
(92 cards)
1
Q
Syphilis
A
T. pallidum
2
Q
Whooping cough
A
B. petussis
3
Q
Lyme disease
A
B. burgdorferi
4
Q
Plague
A
Y. pestis
5
Q
Diptheria
A
C. diptheriae
6
Q
Legionnaires’ disease / Pontiac fever
A
Legionella spp.
7
Q
Tuberculosis (TB)
A
M. tuberculosis
8
Q
CDI
A
C. difficile
9
Q
Cholera
A
V. cholerae
10
Q
The Lonely Sheppard
A
Poem of a story of a Shepherd named Syphilis
Syphilis defies Apollo by refusing to set up a shrine to the god. As punishment, Apollo inflicts him with painful, burning boils
11
Q
why it is difficult to study T. pallidums physiology
A
Does not survive outside mammalian host
Infectious capability is lost w/in hours
Animal model for propagation: Rabbit (testicles)
Doubling time is 30-33 hr in vivo
In vitro survival is prolonged by low O2 concentrations
Heat lability
Genetic manipulation may not be possible due to the fragility of its outer membrane
12
Q
What is a chancre
A
A painless genital ulcer most commonly formed during the primary stage of syphilis.
13
Q
Primary syphilis
A
The first stage of syphilis happens two to 12 weeks after exposure to someone with syphilis. During this stage, a smooth, hard sore called a chancre develops on your genitals or mouth
14
Q
Secondary syphilis
A
Characterized by a generalized and usually symmetrical rash, which is often widespread and may also involve the scalp, palms and soles. Can also cause wart-like lesions called condylomata lata
15
Q
Tertiary syphilis
A
The three main manifestations of late syphilis are neurosyphilis, cardiovascular syphilis, and gummatous syphilis.
16
Q
Describe and discuss up to six reasons why syphilis is an ongoing public health concern in Alberta (and elsewhere)
A
Social stigma
Long incubation period
Long period of infectivity
Easy to ignore symptoms
May be asymptomatic
Propagates rapidly with multiple partners
Fatal complications of untreated disease
Congenital transmission
Most physicians have never seen syphilis
17
Q
Describe the transmission cycle of B. pertussis and the source of outbreaks
A
The sole reservoir for infection is people
You get cycles of this organism being transmitted to people that dont have immunity like infants or children that have not had the vaccine or you get adults that have waning immunity because they haven’t had their booster
Susceptible adults serve as a reservoir and then it is transmitted to vulnerable population
Outbreaks are tied to lower vaccine immunity
18
Q
Describe three of the the major virulence factors produced by B. pertussis and how they result in immune evasion and tissue damage
A
Fimbriae- Type I pili (chaperone usher pathway) – filamentous adhesins required for persistence during infection
Tracheal cytotoxin (TCT) - Stimulates host cell IL-1 production and nitric oxide (NO) synthase. Destroys cilia and disrupts mucociliary clearance
Pertussis toxin (PT) - AB5 bacterial toxin Secreted by type IV secretion system. ADP-ribosyltransferase (A-subunit). Binds to sialoglycoprotein (receptor). Transfers ADP-ribose moiety of NAD+ to a family of G proteins, inhibiting their ability to inhibit cyclic AMP (cAMP) production. Suppresses inflammatory cytokine production and inhibits immune cell recruitment. PT is trafficked through the Golgi to the endoplasmic reticulum (ER). A subunit binds ATP in ER, then dissociates from B-subunits. A subunit is trafficked in exosome to the cell membrane.
19
Q
Describe the features of two-component signal transduction systems
A
Consist of a sensor histidine kinase (HK) that senses a specific environmental signal and response regulator (RR) that mediates cellular response
May relay via histidine phosphotransfer (Hpt) proteins
Uses ATP
RR is a transcription factor controlling a target gene regulon
20
Q
Describe regulation of virulence factors by the BvgAS two-component system
A
BvgAS is a master regulator of virulence
Bordetella spp. exhibit different phenotypic phases:
Bvg- (avirulent), BvgI (intermediate) and Bvg+ (virulent)
These states are controlled by a two-component system - BvgAS.
BvgS = histidine kinase; BvgA = response regulator.
BvgA also represses a transcriptional repressor, BvgR.
Virulence factors controlled by this system: FHA (fhaB), fimbriae
(fim), PT (ptx-ptl), pertactin, ACT (cyaABCDE), bsc (a T3SS), other virulence repressed genes (vrg loci)
In the laboratory, the switch to Bvg+ state is controlled by Mg2+restriction or a shift from 25 °C to 37 °C.
21
Q
What is the natural resevoir for B. burgdorferi
A
The natural reservoir is small mammals
22
Q
The transmission cycle is
A
Small mammal <-> Tick -> Human
23
Q
Describe the pathogenesis of Lyme borreliosis
A
Bacteria multiply, alter gene expression, disseminate in tick
Bacteria are inoculated into skin
Bacteria spread in skin
Continued multiplication, penetration through vasculature, entry into tissue matrix, tissue colonization
Persistent infection of multiple tissues, including joints, CNS, PNS, skin
24
Q
Describe the molecular interactions between B. burgdorferi and host vasculature that allow it to disseminate in the body (Bbk32, P66, host receptors)
A
BBK32 is a multi-functional B. burgdorferi outer surface protein with roles in adhesion to fibronectin (Fn) and glycosaminoglycans (GAGs) conferred by distinct domains of the protein (thethering and dragging)
P66 – A porin and αvβ3 integrin binding protein (extravasation)
25
Describe intravital microscopy
The direct observation of biological processes in a living organism
26
Advantages of intravital microscopy
Advantages
1) Direct, real-time, high-resolution observation of a pathogen at work in a specific location in a living host.
2) Quantification is possible.
3) Mechanistic studies are possible by coupling the method with genetics, injection of peptides, antibodies and small or macromolecules.
4) Multichannel fluorescence experiments and 3D imaging is possible.
27
Disadvantages of intravital microscopy
Disadvantages
1) The method is labor intensive.
2) It relies on the study of sites that can be effectively imaged (skin, joint, lung, liver, heart, spleen, brain, cremaster).
3) Requires fluorescent spirochetes.
4) Not always valid as a model for natural infections, so questions to be answered must be carefully chosen.
5) Definitely not high throughput
28
What was the origin of the plague
The plague is thought to have originated in Asia over 2,000 years ago
29
What are the three major plague events?
Justinian plague
Black Death
Mordern/Third Pandemic
30
What is the current prevelance of the plague?
About 1 to 17 people are diagnosed with the plague each year in the USA, with worldwide rates reported at 1,000 to 3,000 cases a year (in the US cases are clustered in south west)
31
What is bubonic plague
Infection enters through skin and travels through lymphatic system
32
What is septicemic plague
A form of sepsis – endotoxins cause disseminated intravascular coagulation (DIC)
Disseminated Intravascular Coagulation (DIC) - clots in small blood vessels that cause localized ischemic necrosis
33
What is peneumonic plague
Respiratory infection by:
1. Inhalation of plague bacteria
2. Dissemination of septicemic plague to lungs
34
The ecological cycle and transmission route of Yersinia pestis
Ecological cycle of Y. pestis has 3 phases that includes an environmental reservoir:
1. Enzootic – endemic reservoir in wild rodents
2. Epizootic – a rapid increase or change in the number of infected animals
3. Zoonotic – indirect transmission of disease from animals to humans by fleas *Note that in zoonotic phase plague can be transmitted from person-to-person by inhalation
The plague bacterium is transmitted by fleas and cycles naturally through small mammals
Humans and animals that are bitten by fleas from dead animals are at risk of contracting the plague
35
Why is biofilm formation crucial for Y. pestis to colonize fleas
Survival in fleas requires biofilm formation
Blocks the GI tract of the flea and starves them infected fleas bite more frequently
Genetically linked to the hmsHFRS operon of Y. pestis – thought to synthesize an extracellular polysaccharide
Expressed at low temperature
36
Describe a few Yops and how they function as virulence factors allow Y. pestis to suppress and evade the immune response
YopT YopO YopE disrupt actin cytoskeleton rearrangements to suppress phagocytosis by targeting targeting RhoA GTPases.
YopJ also mediates apoptosis of naïve macrophges.
37
What is a Yop and what is its function
Yersinia outer protein (Yop)
Subvert host cell signaling and trigger apoptosis, inhibit phagocytosis and block cytokine production.
38
What is Bulls neck?
Bull neck is a big, thick neck that results from profound swelling of cervical lymph nodes and mucosa.
Caused by C. diptheriae
39
How to identify toxigenic Corynebacterium diphtheria (Elek’stest)
Distinguishes toxin vs. non-toxin producing strains
Immunodiffusion technique that relies on antigen-antibody interactions to drive formation of visible DTX precipitates
40
AB toxins
Binary (two part) toxins: A = Active domain + B = Binding domain
Key determinants of virulence expressed by many pathogens
Vary with respect to:
Quaternary architecture
Enzymatic function
Target
Intracellular trafficking in host cells
41
How can diphtheria be prevented and treated
Immunization
Antibiotic therapy
Antitoxin
42
Jim the horse
The first modern medical disaster
A former milk wagon horse named Jim showed signs that he had contracted tetanus and was euthanized. He was used to produce serum containing diphtheria antitoxin (antibodies against diphtheria toxin).
After the death of a girl was traced back to Jim's contaminated serum, it was discovered that the serum contained tetanus in its incubation phase.
These failures in oversight led to the distribution of antitoxin that caused the death of 12 more children
43
Legionnaire’s disease
Lower respiratory tract infection (pneumonia)
Immunocompromised individuals; 2-10 d incubation.
High mortality rate (15-25%)
Caused by legionella spp.
44
Pontiac Fever
Upper respiratory tract infection; self-limiting
Healthy individuals; 1-2 d incubation
Flu-like symptoms (fever, malaise, headache, nausea,
diarrhea, etc.)
Very low mortality rate (nearly 0%)
Caused by legionella spp.
45
Describe the ecological cycle of L. pneumophila in the environment
Found in soil and aquatic environments. Well known as contaminants of water distribution systems.
Thought to replicate within amoeba but may also exist as biofilms in the environment.
Relative to in vitro grown cells, bacteria grown in protozoa are different:
More infectious and invasive
More stress resistant (antimicrobial resistance)
Altered fatty acid profiles and surface proteins
Motile
Legionella is thought to have multiple forms, including:
MIF = Mature infectious form, RF = Replicative phase form
Certain conditions that may be present in buildings and homes promote the
growth of the bacteria. These include stagnant water, warm water
temperatures (especially between 20°C and 50°C) and the presence of biofilm, scale and sediment. These conditions may be found in: *cooling towers, such as those used with the air conditioning systems of large buildings; *whirlpool bathtubs, hot tubs and public spas; *plumbing systems (including water heaters, faucets and showers) either in
the home or in larger buildings; and
*humidifiers.
When water contaminated with larger quantities of Legionellais released into air in the form of droplets or mist, people may be exposed to the bacteria by
breathing in the contaminated air.
46
Describe the ecological cycle of L. pneumophila in the environment and in the host
This bacterium gets into the cell via the endocytic pathway
Alters the way in which endocytic compartments come together
Uses T4SS to deliver effectors into host cell
Ligonella hijacks the cell machinery and constructs its own compartment for the replication of itself (can have ER and ribosomes)
47
What is the Legionella containing vacuole (LCV)
A compartment dedicated to the replicated of Legionella
A sophisticated organelle that Ligionella constructs from the parts of the eukaryotic cell by hijacking the cell machinery and makes its own niche to replicate in
48
Describe the Icm/Dot T4SS and explain its function in virulence
A type IV secretion system that delivers proteins to a target cell.
The Icm/Dot apparatus has >25 proteins:
Denoted: Icm = Intracellular multiplication or Dot = Defective organelle trafficking
Introduces a large number of effector molecules (>330) into the host cell:
Sids = Substrate of Icm/Dot transporter
The functions of most effectors are unknown, but some identified functions include subversion or manipulation of: apoptosis, the endocytic pathway, the ubiquitin/proteasome pathway, NF-κB signaling, and host cytoskeletal arrangements.
The system has an OM embedded ring (OMER) (comprised of DotC, DotD, and DotH),
connected by a periplasmic complex (collar) that sits in the IM.
Export is powered by DotO and DotB ATPase complexes. DotB binding is thought to
induce a conformational change that leads to export of substrates.
49
What does the stringent response do?
In Legionella, the stringent response controls gene expression for motility, virulence, and stress resistance.
50
Descrribe the mechanism of the stringent response
In response to particular stresses, SpoT and RelA catalyse pyrophosphoryl transfer from
ATP to GTP or GDP to synthesize the signalling nucleotides guanosine pentaphosphate and guanosine tetraphosphate, respectively; these nucleotides are collectively referred to as ppGpp.
Together with DnaK suppressor (DksA), ppGpp directs transcription initiation at particular gene promoters through direct interaction with RNA polymerase. In part, ppGpp and DksAact by promoting the interaction of RNA polymerase with alternative σ-factors (σ*), such as σE.
When metabolic precursors are plentiful, SpoT instead degrades ppGpp, and the vegetative σ-factor, σ70, directs RNA polymerase to genes that are crucial for bacterial replication. PPi, pyrophosphate.
51
The global prevelance of TB
About 1/4 of the world population is infected with TB.
52
Risk factors of TB
There are socio-economic factors that dictate this prevalence such as: undernutrition, diabetes, HIV infection, alcohol use disorders and smoking.
53
How TB is spread and how this integrates with disease pathogenesis
The principal risk behavior for getting TB is BREATHING.
Inhalation of bacteria
Bacteria reach lungs enter Mφ
Bacteria divide in Mφ
Granulomas form
Lesion liquification
Bacteria coughed up in sputum
54
What is a tubercle
AF ibrous lesion caused by Mycobacterium tuberculosis that can be seen on x-rays because immune cells form thick fibrin coats around necrotic lesions. The lesion eventually calcifies. These tubercles are also known as granulomas
55
What is caseous necrosis
A form of cell death and the process that drives granuloma formation. They are characterized by a cheese-like consistency that has calcified around the fibrous lesions, layers of phagocytes, B-cells and T-cells that are built up. Infected macrophages fuse to form “giant cells.” Bacteria may survive and may persist for decades before escaping
56
The primary mechanisms that M. tuberculosis uses to escape and suppress the immune system
Type VII secretion (The EXS-1 system) – Export folded proteins that are essential for virulence and is involved in maintenance of cell wall structure and integrity.
PGL and PDIM redirect Mφ phagocytosis (Fatty Acids)
Phthiocerol dimycocerosate (PDIM) is a cell wall component.
PDIM dampens TLR activation by PAMPs allows bacteria to escape phagocyotosis by microbicidal macrophages in upper airways (MyD88 pathway).
Phenolic glycolipid (PGL) induces recruitment of permissive macrophages in lower airways (CCL2-CCR2 pathway).
Phagosome maturation suppression
Internalized bacteria are trafficked into a series of increasingly acidified structures via interaction with subcompartments of the endocytic pathway.
The small GTPase Rab5 and ↑ phosphitidyl-inositol 3-phosphate (PI3P) are crucial for early endosomes to mature
PIM and LAM impair Rab5 effectors (EEA1 and hVPS34) that ↑[Ca2+] associated with phagosome maturation
SapM is a phosphatase that cleaves (PI3P)
PIM, LAM, SapM suppress transition to late phagosome and phagolysosome stages allows intracellular growth of M. tuberculosis
All of these factors work to suppress phagosomal maturation
57
Why are directly observed therapy – short-course (DOTS) programs are necessary to treat TB
It is important for controlling the spread of TB across the world
Examples include: standardized treatment, diagnosis by microscopy, continuous evaluation of patients etc.
58
What is the microbiome
the collective genomes harbored by the microbiota.
59
What is the microbiota
the microorganisms living on and in the body.
60
What is the core microbiome
A set of shared genomes harbored by microbiota that is found in a given habitat (e.g. gut, mouth, skin) in all humans
61
Describe an “ecological landscape” and provide an example as it pertains to the human microbiome
In ecology, a landscape is a mosaic of interacting ecosystems or habitats (at any scale), in which areas are spatially heterogeneous in at least one key factor.
The GI tract is a good example of an ecological landscape because there is a major difference in pH in the stomach and in the large intestine. The pH in the stomach is very low so bacteria have to be acid tolerant in order to survive there (prevotella) whereas the pH towards the colon is near neutral therefore we can have a much different microbiota composition (Staphylococcus).
62
Provide biologically relevant numbers for the human microbiota and microbiome
100 Trillion symbiotic microbes live in and on every person and make up the human microbiota
Genes in microbiome outnumber the genes in our genome by about 150:1 (about 3.3 million unique genes in human gut)
63
List some of the functions of the microbiome in human physiology
Digestion of otherwise inaccessible nutrients
Vitamin synthesis
Protection from pathogens
Regulation of innate and adaptive immunity
Metabolic rate
Metabolism of xenobiotics (i.e. drugs)
Odour
Behaviour
Cardiac size (Gnotobiotic animals tend to have smaller hearts)
64
What is competitive exclusion
Competition for localized colonization sites.
Competition for essential nutrients and metabolites.
Conversion of nutrients or host metabolites to compounds inhibitory to C. difficile or C. difficile spore germination.
65
Describe how antibiotic use leads to loss of competitive exclusion and can lead to C. difficile infection (CDI)
Antibiotics reduce the number and complexity of the normal microbiota thereby eliminating or reducing competitive exclusion.
Antibiotics can deplete competing commensal bacteria, which leads to an abundance of sialic acid and succinate, a short-chain fatty acid that is produced during fermentation. C. difficile has genes for both sialic acid catabolism and succinate transporters, which enables it to use the excess sialic acid and succinate for growth.
66
Describe the pathogenesis of CDI
Sporulation drives CDI transmission
Endospores are highly resilient and allow C. difficile to withstand oxygen and disinfectants.
Flagella faciulitate movement
Capsule discourages phagocytosis
Gut mucosa facilitates adherence to the colonic epithelium
67
Explain the molecular mode-of-action for the toxins TcdA, TcdB and CDT
Disease results from the production of toxins.
TcdA (308 Kda) and TcdB (260 Kda) are both single chain toxins which possess five functional domains.
TcdA is essential for virulence in animal models.
C. difficile transferase (CDT)
Also known as binary toxin.
Binds to the LSR receptor and is internalized.
CdtB creates a pore in the endosome that facilitates release of CdtA.
CdtA inhibits actin polymerization via ribosylation of actin.
This action causes fibronectin protrusion, increasing attachment sites for C. difficile.
68
Define fecal microbiota transplantation (FMT) and explain how it works to treat CDI
Fecal microbiome transplantation (FMT)
FMT involves instilling NF from a healthy donor into the colon of a patient suffering from rCDI.
FMT restores competitive exclusion and has been shown to be highly effective in treating rCDI.
69
Describe the geographic distribution of pandemic Vibrio cholerae strains.
The "classical" strain of V. cholerae was responsible for the first six pandemics of cholera, which occurred between 1817 and 1923. The geographic distribution of the classical biotype was mainly limited to the Indian subcontinent, Southeast Asia, and the Middle East. However, it eventually spread to other parts of the world, including Africa, Europe, and South America, through trade routes and international travel.
The "El Tor" (7th pandemic clone) biotype of V. cholerae was first identified in the 1960s and is responsible for the seventh pandemic, which began in Indonesia in 1961 and has since spread globally. Unlike the classical biotype, the El Tor biotype is much more widespread and has a more diverse geographic distribution, including Asia, Africa, Europe, and the Americas. It is also the predominant strain responsible for current cholera outbreaks.
The 0139 strain originated in India is still present today
70
Provide details for two historical epidemics in England (1850s) and Haiti (2010s).
England (1850s)
Broad Street cholera outbreak
Happened in Soho district of Westminster, in London, England
Killed 616 people
By talking to local residents, Snow identified the source of the outbreak as the public water pump on Broad Street (now Broadwick Street) at Cambridge Street which was contaminated with the cholera-causing bacterium Vibrio cholerae
John Snow later used a dot map to illustrate how cases of cholera occurred around this pump.Snow's efforts to connect the incidence of cholera with potential geographic sources was based on creating what is now known as a Voronoi diagram. He mapped the locations of individual water pumps and generated cells which represented all the points on his map which were closest to each pump.
Haiti (2010s)
In January 2010, a magnitude 7.0 earthquake hit Port-auPrince and killed nearly 300,000 people while leaving 1.5M homeless with no infrastructure.
In October 2010, cholera broke out in Haiti 10 months after the earthquake.
Approximately 600,000 cases and 7,000 deaths in Haiti and over 20,000 cases in The Dominican Republic.
Where did cholera come from?
Environmental Source
Latin American strain?
Newly emerged
Human Source
Caribbean region
Relief workers
Security forces
Isolates from Haiti and Nepal nearly identical
South Asian “variants” *
Illumina sequencing used to construct whole genome phylogenies
Nepal group 4 strains from 2010 have only 1 or 2 SNPs relative to Haitian 2010 strains
71
What are some V. cholerae virulence factors
Toxin co-regulated pilus (TCP)
Cholera toxin (CT)
Type III secretion system (T3SS)
Type VI secretion system (T6S)
72
Describe the role of phage CTXΦ in acquisition of cholera toxin (CT)
CTXΦ is a filamentous phage particle
Contains the genes ctxAB that encode the cholera toxin (CT)
TCP is the receptor for phage CTXΦ
Only cells that have TCP will end up being infected by this phage which leads to the production of the cholera toxin
73
Explain the molecular function of CT and how it causes watery diarrhea in the host.
CT binds to the ganglioside receptor on the host epithelial cells, triggers endocytosis
of the holotoxin.
The internalized CT moves from the endosomes to the Golgi complex and endoplasmic reticulum (ER).
The catalytic CT-A1 polypeptide transfers from the ER to the cytosol by retrotranslocation through the action of the ER-linked degradation pathway to activate the Gsα subunit of guanine nucleotide-binding regulatory (Gαs) protein.
Activation of Gαs-protein leads to increased adenylate cyclase (AC) activity, which cleaves ATP to cyclic adenosine monophosphate (cAMP) and subsequently activates protein kinase-A (PKA).
Activation of PKA inhibits NaCl absorption through Na+/H+ exchanger (NHE transporters) and phosphorylate the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel proteins, which leads to ATP-mediated efflux of chloride ions and induce secretion of HCO-3, Na+, K+ and H2O.
Loss of chloride ions induces massive fluid secretion in the small intestine, deposing
the resorptive ability of the large intestine, which results in severe watery diarrhea.
(Loss of ion homeostasis compromises H2O resorption → Watery diarrhea)
74
Provide molecular details about the type VI secretion system and its delivery of toxic effectors to prokaryotic cells
T6S can target both Eukaryotic host cells (cytoskeleton, membrane and DNA) and other prokaryotic cells (cell wall, membrane and DNA).
However, its primary function is thought to be interbacterial antagonism (i.e., to eliminate bacterial competitors).
The Type VI secretion (T6S) system is Comprised of proteins that are structural homologs of bacteriophage tail-like proteins
Crystalized Hcp forms hexameric rings that stack in tubes with 40 A°channels.
VgrG homologous to phage T4 tail spike “sharpened arrowhead”
VipA-VipB tubules are phage sheath homologs (Very similar to contracted T4 phage sheath)
Delivery of toxins occurs by physical puncture of a cell
75
How microbiota play a role in the maturation of tolerogenic T cells (Tregs) and that there is evidence that this occurs during a critical window in early life
In utero the gut is lined with naive T cell lymphocytes. When delivered the baby is colonized with microbes that essentially educate immune tolerant mechanisms and many of the T cells become T regs that produce anti-inflammatory cytokines important for ensuring tolerant response to antigens in gut.
Immune diseases are defined by a break in immune tolerance when inflammation remains unchecked
76
That microbiota changes associated with the Western lifestyle (i.e. diet, sanitation, antibiotics, C-sections, etc) have implications for health
Association with western sanitation, antibiotics, C-sections and formula, diet and increase in autoimmune disease and allergies
Over 2-3 generations (too fast for genetics to account for this) so it is thought the microbiome plays a role
First 100 days of human life represent an early ‘critical window’ in which microbial dysbiosis enhances the risk of asthma and allergic disease
77
That gut microbiota are linked to asthma
FLVR are reduced!
78
The epidemiological evidence for microbial exposure in children and asthma
Farm children less likely
C-section and use of antibiotics increase risk
Breastfeeding decrease risk (modulate effect of antibiotics)
79
linkages between bacteria (ex. “FLVR”) and fungi in the early life microbiome and their association with asthma later in life
Faecalibacterium, lachnospira, veillonella, rothia (these are good because adding them was seen to reduce inflammation)
Fungi that was associated with asthma= Malassezia (they increase eosinophils- important immune cell for allergy as well as migratory dendritic cell)
80
How germ free mice can be used in experiments designed to interrogate the function of the microbiome
Germ free mice grow in isolators so they are devoid of microbes
Nice model to test hypotheses because you can lavage certain microbes and test specific questions. Simplifies the complex reality of the gut microbiome
81
Why is study of the vaginal microbiome important? What makes it interesting?
The study of the vaginal microbiome is important to understand:
Sexual Health – Sexually Transmitted Infections (HIV)
Cervical Cancer
Reproductive Health – Pregnancy (Preterm Birth)
What makes this field so interesting is because our scientific understanding of the basic biology is lagging…
Female leadership is driving a woman-centered, anti-racist agenda
82
Introduction to the structure and dynamics of the human vaginal microbiome – what makes it unique?
Diverse tissue architecture
Most often dominated by one of four Lactobacillus spp., possibly due to availability of host glycogen
But frequently dysbiotic (Bacterial vaginosis) – highly diverse, variable, and dynamic, particularly in response to hormones/menses
83
How does the vaginal microbiome change throughout a woman’s life and impact her sexual health?
Vaginal microbiome can change from a range of factors such as stress, antibiotics and sexual activity
L. crispatus vs. L. iners is key differential in risk of BV/STI
Only L. crispatus is associated with pullulanase activity in vivo
Pullulanase activity may be important for maintaining a maximally protective (low pH environment)
84
How might we therapeutically support or alter the vaginal microbiome to improve women’s health?
Simple removal/replacement strategies are not working
Need to figure out how to support change…
Selectively support L. crispatus? Ensure probiotic strains cannot loose pulA?
Block BVABs?ht we therapeutically support or alter the vaginal microbiome to improve women’s health?
85
how does E. coli Nissle functions as a probiotic
Host cell signaling
Increase in biofilm formation, mucin production, tight junction sealing
Increase in immunomodulation
Increase in anti-inflammatory effects
Increase in inhibition of invasion gut epithelial cells by Salmonella, EIEC, AIEC, Shigella, Yersinia, Listeria, Candida
Direct antagonistic activity
Inhibition of growth / killing of pathogenic bacteria and yeasts
Augmentation of intestinal colonization resistance
EcN - new insights into probiotic mode of action
During S. enterica gastrointestinal infection, S. enterica uses salmochelin to gain a competitive advantage over commensals but is outcompeted for siderophores by the probiotic E. coli strain Nissle, which reduces S. enterica colonization
86
What is the LEE
The genes responsible for A/E lesion phenotype are encoded on a 35.6 Kb pathogenicity island known as locus of enterocyte effacement (LEE). which comprises the structural components of type III secretion system (TTSS), regulators, chaperones, and effectors secreted by the TTSS.
LEE comprises the genes responsible for causing attaching and effacing lesions, a characteristic lesion that involves intimate adherence of bacteria to enterocytes, a signaling cascade leading to brush border and microvilli destruction, and loss of ions, causing severe diarrhea. Ex. EspB, Tir, EspF, EspG, EspH, EspZ and Map
87
Define and describe autotransduction
Relies on the use of phages
Virus particles that can pack up some DNA that is found in Staphylococcus chromosomes and can move it between strains
S. aureus
88
What is Bacteremia
Presence of bacteria in the bloodstream. This can result from an infection (or even tooth brushing). Bacteria are most often removed by the body on its own, but can sometimes cause an infection.
89
What is sepsis
An inflammatory immune response triggered by bacteremia or other severe infection that causes life-threatening injury to tissues and organs (30% mortality).
90
What is septic shock
Low blood pressure due to sepsis that does not improve with fluid replacement (80% mortality).
91
What is TSST-1
It is a pyrogenic toxin superantigen (PTSAg).
All superantigens cause non-specific activation of Tcells driving polyclonal T cell activation and massive cytokine release.
A normal antigen activates 0.001% (or less) of the body’s T-cells; however, a PTSAg can activate up to 20%.
The T-cells release a proinflammatory cytokine called IFN-γ, which stimulates macrophages to release additional inflammatory cytokines (IL-1, IL-6, TNF-α)
92
How does TSST-1 work?
TSST-1 activates T-cells by cross-linking the variable β-chain of the TCR to the α-chain of the MHCII molecule of an antigen presenting cell.
