13 Infectious Diseases Part 2 : Viruses and Fungi Flashcards
- Describe viral structure and basic life cycle
- Attachment: Capsid proteins bind specific receptors of host cell
- Entry: Receptor-mediated endocytosis; Membrane fusion -> Capsid comes apart (uncoating) degradation by host cytoplasm
- Replication and gene expression
- Assembly: Capside formation and genome packing
- Release
Associate the route of infection with the type of viral transmission
* Droplet/Airborne
* GI, Fecal-oral
* Contact
* Sexual
* Blood-borne
* Arthropod Vector
-
Droplet/Airborne:
1. RNA viruses: Influenza, SARS-CoV-2, Measles, mumps, rubella
2. DNA viruses: Parvovirus, smallpox, varicella zoster virus (VZV), Adenovirus -
GI, Fecal-oral
1. RNA viruses: Hep A (HAV), Norovirus, Enteroviruses (polio), Rotavirus
2. DNA Viruses: Enteric adenoviruses -
Contact
1. DNA Vir: Herpes simplex virus (HSV), varicella zoster virus (VZV), Smallpox, Orf virus, Human papillomavirus (HPV) -
Sexual
1. RNA: HIV, HSV
2. DNA: HPV, Adenovirus (certain types) -
Blood-borne
1. RNA: HIV, HCV
2. DNA: HBV, CMV, EBV -
Arthropod Vector
-RNA: - Dengue
- Yellow fever
- WNV
- Zika
Lytic cycle vs Lysogenic Cycle?
Lytic cycle = ends in cell death to release newly assembled virus
Lysogenic Cycle = Viral DNA combines with bacterial chromosome and replicates with Cell division
Lytic Cycle
1. Attachment
2. Entry
3. DNA replication and protein synthesis
4. Assembly
5. Lysis
Lysogenic Cycle
1. Attachment
2. Entry
3. Integration
4. Cell division
DNA Viruses:
- Examples
- Adenovirus
- Hepatitis B Virus
- Herpes viruses
- Human Papillomavirus (HPV)
- Smallpox
Examples of RNA viruses
- Influenza, SARS-CoV-2
- Measles, mumps, rubella
- Respiratory syncytial virus (RSV)
- Hepatits A virus (HAV), Hep C virus (HCV)
- West nile virus, Dengue, yelow fever
- Rhinovirus, poliovirus
- Norovirus, rotavirus
- Ebola
Differentiate between the three main groups of fungi:
* yeasts,
* moulds (filamentous),
* dimorphic fungi
- yeasts: Single cell fungal forms; Asexual (budding)
- moulds (filamentous): Multiple cells that, together, form a filament; usually asexual; rare sexual reprod
- dimorphic fungi: Mould at room temperature and yeast at 37C
MOULDS
- Morphology
- Divide by?
- Human disease?
- 4 examples
- Filamentous fungi
- Multicellular, filamentous, branching growth
- Hyphae (mycelium = group of hyphae) growth at hyphal tip
—–Reproduce primarily by conidia: Asexual spores that give moulds their range of colour; easily airborne; transmission, allergy, infection - In human infection, source is environmental
- *aspergillus
- Mucor
- Scedosporium
- Penicillium*
YEAST:
- Morphology
- Divide by?
- Human disease?
- 3 examples
- Unicellular, round or ovoid cells
- Larger than bacteria (>5um)
- Divide by budding (asexual)
Daughter cell forms as ougrowth of mother cell - In human disease, yeast infections are typically from our endogenous flora (eg GI tract)
- Examples:
1. candida
2. Cryptococcus
3. Malassezia
Describe mycoses
- Superficial infections
1. Dermatophytes: - group of closely related fungi which parasitize skin, hair and nails
- Grow only in keratinized tissue of stratum corneum
- Anthrophilic, zoophilic, and geophilic species
Most common fungal infection worldwide:
1. Dermatophytosis
2. Cutaneous mycosis
3. Tinea/ringworm
Classify Mycoses (3):
-
Subcutaneous infections
- Deep, ulcerated skin lesions; rarely invade deeper tissues; sporotrichosis (sporothrix) -
Opportunistic infections
- Not “true pathogens” low virulence potential;
- require immune compromised state;
- eg aspergillus, candida, mucor, cryptococcus -
Invasive infections
- Endemic/dimorphic fungi;
- True pathogens - cause severe disease in healthy people;
- restricted geographically;
- usually involve lungs, but can disseminate to other deep organs ;
- eg histoplasma, blastomyces, coccidioides
List cellular targets of the following antifungal agents:
* Amphotericin B
* Azoles (fluconazole, voriconazole)
* Echinocandins (Caspofungin, micafungin)
* Topical agents
- Amphotericin B: Cell membrane function; Ergosterol pore formation
- Azoles (fluconazole, voriconazole): Cell membrane funcion; inhibit ergosterol synthesis
- Echinocandins (Caspofungin, micafungin): Cell wall function
- Topical agents: Terbinafine, miconazole; inhibit ergosterol synthesis
- Identify common viral and fungal pathogens causing human disease
pending
How are viruses classified?
- Genome Type and Organization
- Blank structure
- Blank or Blank
- Genome Type and Organization
- DNA vs RNA
- Linear, circular, segmented
- Double-stranded vs Single-stranded
- Sense or anti-sense (if single stranded) - Capsid Structure
- Capsid made of capsomeres
- Icosahedral, helical, or complex - Enveloped or non enveloped (naked)
Describe Viral Disease manifestation:
- Latency:
- Viruses may co-exist with human cells without causing disease or injury
- Viral replication coincides with host cell division - Active Infection:
- Cell damage and disease
- Acute cell necrosis (VZV, ebola)
- Increased cell proliferation (HPV, HBV, HCV, EBV)
Some viruses cycle between latency and active infection (Herpes simplex virus HSV)
Targets of antiviral agents?
- DNA and/or RNA synthesis
- Prevention of virus assembly
- Activation of host responses (eg interferon)
