Lecture 13: Saliva & Oral Yeast Flashcards
1
Q
What are the 2 basic structural forms of fungi?
A
Yeast & Mould
2
Q
Which basic structural form of fungi is unicellular with spherical or ovoid bodies?
A
Yeast
3
Q
Which basic structural form of fungi is multicellular with specialized structures to perform specific functions (different shapes, colors, sizes, etc btwn different genera)?
A
Moulds
4
Q
__________ is the structural unit of mold; multicellular with each cell separated by a septa that has pores
A
Hyphae
5
Q
________ is a mass of hyphae that form the mould colony
A
Mycelium
6
Q
Which opportunistic fungi of the oral cavity is dimorphic?
A
C. albicans
7
Q
Which opportunistic fungi of the oral cavity is Not dimorphic and is yeast?
A
Cryptococcus neoformans
8
Q
Which opportunistic fungi of the oral cavity is Not dimorphic and is a mycelium
A
Aspergilus umigatus
9
Q
What is the study of fungi called?
A
Mycology
10
Q
What does yeast look like on a colony plate?
A
A smooth colony
11
Q
What does branching hyphae look like on a colony plate?
A
fuzzy mold colony
12
Q
How can you tell bacteria and fungi apart under a microscope?
A
fungi is bigger than bacteria (only need 40x undermicroscope)
13
Q
How do fungi reproduce?
A
Asexually and Sexually (asexual mode is more clinically relevant)
14
Q
What are the 3 classifications of Fungi?
A
Yeast
Filamentous fungi
Dimorphic fungi
15
Q
How are Moulds identified?
A
based on color, texture, colony and microscope morphology, especially their specialized asexual structures
16
Q
How are Yeasts identified?
A
Biochemical reactions based on fermentation of and assimilation of carbohydrates and utilization of enzyme substrates and other metabolic activities
17
Q
What is the oxygen requirement of fungi?
A
majority are aerobic
18
Q
Which Fungi species can grow in anaerobic conditions?
A
Candida
19
Q
What are the growth mediums for fungi?
A
Sabouraud Dextrose Agar (SBD)
Potato Dextrose Agar (PDA)
Yeast Peptone Dextrose (YPD)
20
Q
If using Peptone Dextrose in medium what kind of medium is it?
A
Complex medium b/c peptone extract is an undefined component
21
Q
What are some special features of fungal growth medium?
A
high carbohydrate content
acidic pH
antibiotics
22
Q
If there is a lot of candida present in the saliva what is there a higher risk for and why?
A
Higher risk for caries b/c of acidic pH
23
Q
What species of fungi is most present in the oral cavity?
A
Candida
24
Q
What genus could be the second most abundant fungi in the oral cavity?
A
Malassezia
25
What is Candidiasis?
infection (local or disseminated) in which Candida species are the primary infectious agents
26
Which species of candida is very similar to C. albicans?
C. dubliniensis
27
What is the primary candida species in candidiasis?
C. albicans
28
What are Localized candidiasis infection?
mucous (oropharyngeal candidiasis, OPC) burning or pain, alterted tased sensation, and difficulty swallowing liquids and solids (dysphagia); mucosal (skin, vaginal, and uro-genital) infection
29
What are Systemic Candidiasis infections?
(deep organ infection) in the bloodstream, 36-56% mortality, invasion of GI mucosa-passage across the bowel wall-bloodstream (candidaemia, sepsis)
30
What are the 2 most important localized infections and how do they differ?
Pseudomembranous (white patches, high microbial load)
| Erythematous (red) Deture Stomatitis: more inflammation of tissue and less microbial load
31
_______________ is a polymorphic fungus that normally colonizes at mucosal surfaces as harmless commensals
C. albicans
32
How are Candidal Infections Triggered?
triggered by the attenuation of normal host immunity or disturbance of normal microbial flora
33
What is an exogenous infection?
introduction of pathogen is external
| example is food poisoning
34
What is an endogenous infection?
introduction of pathogen is internal- you already hat it so when immune system when down, there is an increase in that pathogen
35
Are candidal infections usually endogenous or exogenous?
Endogenous
36
How does C. albicans go from harmless to a pathogen?
- Rapid adaptation of C. albicans to the host environment mediated by cell-signalling
- virulence genes are co-regulated with cell morphogenesis (yeast-hyphae transition)
- Escape from surveillance of immune system
37
What are the immune deficiency factors that increase susceptibility to candida infections?
Neonates
Elderly
AIDS
Tumors
38
What are the mechanical factors that increase susceptibility to candida infections?
Burns
Oral prosthesis
Catheters
Hemodialysis
39
What are the pharmacology factors that increase susceptibility to candida infections?
Antibiotics
Corticosteroids (asthma-inhalers)
Antineoplastic
Psycho-active drugs
40
What is Pseudohyphae?
the yeast form that keep multiplying by haven't separated yet
41
What conditions are optimal for C. albicans in yeast form?
growth below 30C or pH 4
42
What are the optimal conditions for C. albicans to transition from yeast to Pseudohyphae?
pH 6, 35C
Nitrogen limited growth on solid medium (SLAD)
High Phoshpate
43
What are the environmental conditions that signal morpholigcal switching of C. albicans into Hyphae form?
Serum, greater than 34C
Lee's medium 37C
pH 7, 37C
44
The higher the temp goes the more ________ form in morpholigical switching in response to environmental signaling.
hyphae
45
What test is used to distinguish C. albicans from other species?
Germ Tube Test
46
What are the different mechanisms for the invasion of Candida at Host mucosal surfaces?
1st adherence has to happen before invasion mechs
-Germination
Persorption
Induced Phagocytosis
47
What is Persorption?
invasion mechanism by which yeast can go through random leaks in membrane
48
What are some enzymes that can damage the host tissue that help with invasion of candida at host mucosa surfaces?
Saps, Plb1p
49
What are the stages of C. albicans epithelial colonization?
1. Adherence
2. Evasion of Host Defenses
3. Invasion and Destruction of the Host tissue
50
What are some of C. albicans virulence factors for its adhesion step in epithelial colonization?
- Relative cell surface hydrophobicity: Non-specific adherence process
- Expression of cell surface adhesion molecules: facilitates specific adhesion mechs
51
What are C. albicans virulence factors for its Evasion of host defenses step in epithelial colonization?
- High frequency phenotypic switching
- Hyphal development
- Secretes aspartyl proteinase production: secretory IgA destruction
- Binding of complement molecules: antigenic masking
52
What are C. albicans virulence factors for its Invasion & Destruction of host tissue stage in epithelial colonization?
- Hyphal development-promotes invasion of oral epithelium
- Secreted aspartyl proteinase production: host cell & extracellular matrix damage
- Phospholipase production= damage to host cell
53
What are responsible for phagocytic clearance of candida in the innate immunity against C. albicans?
Neutrophils (PMN) and Macrophages (monocytes)
| -first line of defense in oral cavity
54
The interaction of Dectin receptors in fungal cell wall components like B-glucans stimulates what?
macrophage initiation
55
What is the Innate Response to Oral Candidaisis?
- Phagocytic clearance of Candida by PMN (neutrophils) and monocytes (macrophages)
- Stimulation of machrophages initiated by interaction of Dectin receptors on these with fungal cell wall components like B-glucan
- Cationic antimicrobial peptides: antifungal peptides like histatins
56
What components of the fungal cell wall interact with receptors on epithelial cells?
Beta-glucans and Mannans
57
What receptors are responsible for recognizing fungal pathogens?
TLR2/4 (toll-like receptors)
58
The interaction of fungal cell wall components (B-glucan & mannons) with TLR2/4 lead to what?
Leads to the activation of intracellular pathways leading to cytokine production, activation of the innate immune response, and release of AMPs
59
What is innate immunity?
front-line defense, rapidly induced, relatively non-specific
60
What innate peptides are secreted from the oral mucosa?
Keratinocytes and Calprotectin and B-defensins
61
What is the function of the innate peptide Keratinocytes?
physical barrier
62
What innate peptides are secreted by saliva and are fungicidal proteins?
Histatins, lysozymes, and lactoferrins
63
What kills Candida by sequestering metals (copper & zinc)?
Calprotectin
64
What 2 saliva components can bind candida and physically remove it?
mucins and IgA
65
What antifungal protein secreted from the saliva can kill/prevent C. albican growth?
Hst 5
66
How does mucins promote C. albicans growth?
When bound with PRPs, statherins and Tgase it binds candida and helps its adherence to the oral cavity
67
What are Cationic peptides properties?
12-50 amino acids with a net positive charge (+2 to +7)
- >50% of amino acids are hydrophobic
- these properties plus the anionic microbial cell membrane and large transmembrane electrical potential makes the peptide more accessible to pathogens
68
What are the Cationic Peptide Classifications?
Group 1: linear a-helical peptides w/out cysteines
Group 2: linear peptides with cysteines linked by disulfide bridges
Group 3: linear with high proportion of specific amino acids
69
What are Histatins?
cationic salivary proteins that offer first line of defense against C. albicans
70
What has the most potent fungicidal activity against C. albicans?
Hst 5
71
What is Hst 5 and what does it do?
its a positively charged cationic salivary protein with killing activity against C. albicans
-requires Dur3 (transporter protein) to enter the cell and has multi-targets inside the cell
72
Hst 5's activity is masked when what binds to it?
```
salts
sugars
metals (iron)
host proteins (salivary mucins)
proteins secreted by pathogens (Saps and Msb2)
```
73
What protease secreted by C. albicans reduces Hst 5 activity?
Sap 6
74
How does the concentration of salivary mucin affect Hst 5 activity?
High mucin concentration reduces Hst 5 activity because it can bind to it and trap it
75
How can mucins indirectly reduce Hst 5 activity?
mucins can also bind candida and clump it together so its like a biofilm so it makes it harder for Hst 5 to penetrate the big clumps of candida
76
What are the characteristics of Adaptive immunity to Candida?
slow growing B and T cells require up to 7 days to mature
hallmarks are specificity, inducibility, and discrimination of self vs non-self (dendritic cell-mediatied T cell response)
77
How does Th1 cell respond in the adaptive immunity to candida?
activation of antimicrobial functions, respiratory burst, degranulation, isotype switching of Ab
78
What is Th2 cell response in adaptive immunity to candida?
eosinophilia, hyper-IgE, Hyper-IgG4 production which exacerbate the symptoms
79
Which T-helper cell response exacerbates the symptoms in the adaptive immunity to candida infection ?
Th2 cell response
80
Which T-helper cell response is more protective in the adaptive immunity to candida?
Th1 cell response
81
IL-12 mediates which T-helper cell response?
Th1
82
IL-6 mediates which T-helper cell response?
Th17
83
IL4,5,10 mediate which T-helper cell response?
Th2
84
What is the connection between oral candidiasis and HIV?
T-helper cells because T-cells are affected in HIV
| -see a lot of oral candida in HIV patients
85
What antifungal agent targets fungal cell walls?
Echinocandins
86
What antifungal agent targets fungal cell membranes?
Polyene
87
What antifungal agent targets sterol synthesis?
Azoles
88
What antifungal agent targets DNA and RNA synthesis?
Flucytosine
89
What antifungal agent targets protein synthesis?
Sordarins
90
What antifungal agent targets microtubule assembly?
Griseofulvin
91
What antifungal agents are frequently used in dental practice for oral infections?
Polyene and
| Azoles
92
What are some examples of Polyene drugs?
Amphotericin B and Nystatin (mycostatin)
93
What is the mode of action of Polyene drugs?
binds to fungal ergosterol and leads to membrane disruption by making it porous
94
What are some examples of Azole drugs?
Clotrimazole (mycelex)
Etoconazole (nizoral)
Fluconazole (diflucan)
95
What is the mode of action of Azole drugs
intracellular target to inhibit synthesis of ergosterols
leads to inhibition of sterol in fungal membranes
Fungistatic but not fungicidal, therefore treat underlying condition with this therapy
96
What are the Therapeutics of Candidiasis?
a broad spectrum to susceptible species
- less toxicity to mammalian cells
- combination therapy-effects on 2 or more disparate targets
- Systemic treatment (HAART) (highly active antiretroviral therapy) in HIV patients
97
Why could Hst 5 be a possible future therapeutic for candidiasis?
its broad spectrum
| has multi-targets so could be effective killer
98
How can one analyze host-pathogen interactions in candida infections?
Candida Gene mutants: in vitro assessment-altered growth rate and morphological defect of mutant strain- can see if that protein is the target of killing
Animal Models: in vivo assessment- survival and organ burdens after C. albicans infection
99
What are some animal models?
oro-esophageal candidiasis in transgenic mice expressing HIV-1
- Congenitally immunodeficient mice w/ individual or combined immune defects
- mice immunocompromised with steroid administration (most advantagenous one)
100
What are the advantages of animal model studies in candida infections?
clinical relevance- closely mimic clinical and pathological features of candida infections in humans
-cause-and-effect analysis of host-candida interactiosn
101
What makes Hst 5 activity against candida more efficient?
Hst5-Spd
