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1. MICROBIOLOGY Reenam Khan - 2nd year medic
Nasif Mahmood - 2nd year medic
2. Whats a virus? 20-240nm
Obligate intracellular parasites
Nucleic acid + protein
3. The steps in viruses causing disease Binding
Virus proteins bind receptors
Penetration
enveloped ? fusion at cell surface
non-enveloped ? genome/core passes through
Eclipse phase
Virus proteins expressed
Nucleic acids replicated
Assembly
Release (cell lysis or budding)
4. Virus Replication- the one-step growth curve
5. An example- influenza Helical nucleocapsid
13.6kb
RNA Ss ve
8 segments
enveloped
6. An example- influenza
7. Why do new endemics occur?
Antigenic Shift - radical change of surface proteins
Antigenic Drift - point mutations? small changes in surface proteins
8. HIV (retrovirus, subgroup lentivirus) 120nm, enveloped
10kb Ss RNA genome +ve
Reverse transcription?dsDNA? integration into host DNA.
Expression controlled by differential splicing.
Regulatory proteins e.g. tat and rev.
9. HIV structure
10. HIV (retrovirus, subgroup lentivirus) Transmission- blood products, sexual, mother?baby
Gp120 binds CD4 + co-receptor (CCR5 or CXCR4) ? homozygotes for CCR5 mutation are resistant
AIDS: T-cell levels drop, unrestricted virus replication, immunodeficiency
11. HIV drugs Chain terminators e.g. retrovir
Protease inhibitors e.g. ritonavir
transription, translation, post-translational modification? protein
Drug combinations (HAART) (resistance to single drugs develops)
12. How do chain terminators work?
13. Preventing viral disease: Passive ? Ig
? maternal antibodies
Live (a) Attenuated form of virulent organism
(b) Immunologically related organism
(c) Virulent organism
Dead ? Antigen preparation has infectivity and toxicity inactivated
Genetically engineered subunit vaccines/ live organisms ? identify and express genes encoding antigens from protein/virus
14. Gram Staining: Stain bacteria with violet dye and iodine
Rinse in alcohol
Stain with red dye
16. Fungi Eukaryotes
E.g. live on bread,
release enzymes
? stuff digested
outside
? products reabsorbed
by diffusion
? spores released
for reproduction
17. Targeting bacteria
18. Types of fungal infection Allergies (to fungal products)
Mycoses (ingestion of fungi and their products)
Mycoses (superficial, subcutaenous, systemic)
19. Fungal cell wall Main distinction between mammalian & fungal cells
Main target of antifungal therapy
20. Antifungal drugs: Must target structures not in humans so not to damage host!
Fungi have:
ergosterol instead of cholesterol:
- synthesis inhibited by azoles e.g. Triazoles (fluconazole)
- interaction with ergosterol by polyenes e.g. amphotericin B
(b) cell wall made of chitin echinocandins
(C) DNA synthesis. Ability to selectively activate some compounds e.g flucytosine
21. Pathogens: An infecting agent capable of causing disease
Whats the difference between a true pathogen and an opportunistic pathogen?
22. Bacterial Structures:
23. Antibacterial Drugs Antibiotic = metabolic product of fungi, actinomycetes or bacteria that kills or inhibits the growth of other micro-organisms
Antimicrobial = Derived from natural substances which have been chemically modified to improve their activity
24. Mechanisms of Antibiotic Action
25. Antibiotic Concepts Whats the difference between a broad spectrum and narrow spectrum antibiotic?
Antibiotics can synergise or antagonise each others effects when used together. What does this mean?
Whats the difference between a bacteriostatic and bacteriocidal antibiotic?
26. Antibacterial Resistance When micro-organisms:
Produce enzymes that attach to a key bond ?inactivate the antibiotic
Change permeability to the antibiotic:
alter cell wall or
pumping the antibiotic out of the cell
Altered structural target
Altered metabolic pathway
27. How does resistance occur? Innate:
lack suitable target or impermeable to the agent.
Acquired:
Mutations? altered target
May be acquired by jumping genes (transposons) which can be integrated into either the chromosome or plasmid.
a) Cell to cell contact Conjugation
b) Transfer by bacteriapharges Transduction
c) Transfer of free DNA Transformation
*** Therefore use should be limited e.g. not used in animal husbandry ***
28. Horizontal gene transfer
29. Pathogenicity islands Result from horizontal gene transfer
Differentiate pathogens from their relatives
Characteristics e.g. different G/C content from genome average
30. Techniques for getting past our immune defences
31. Vaccination
32. Virulence This refers to the degree of damage and depends on:
Tropism
Replicate (through nutrient acquisition)
Immune invasion
Inflict damage e.g using toxins
Disseminate
33. Cholera toxin Toxin co-regulated pilus
A1 subunit of toxin ribosylates g-proteins? more GTP? adenyl cyclase stimulation
Ion channels stay open
Na+, Cl- and H2O loss? profuse, watery diarrhoea
34. Clostridial Disease Two types of toxins- botulinium and tetani
They block exocytosis of neurotransmitter
In botulinium: block excitatory transmission? floppy paralysis
In tetani: block inhibitory transmission? flaccid paralysis
35. How does the clostridium toxin exert its effect?
36. Malaria Cycle
37. Malaria cycle: terminology Female Anopheles mosquito
Liver (Ex-erythrocytic)
Sporozoites
Schizont
Merozoites
Hypnozoite Blood (Erythrocytic)
Ring
Trophozoite
Schizont
Merozoites
Gametocytes
Gametes
Macro (female)
Micro (male)
38. Quiz time! TRUE or FALSE MCQs
Confidence marking:
correct incorrect
3 +6 -3
2 +2 -1
1 +1 0
39. True or False?
Eukaryotes have mitochondria
59.
Thank You!
60. Reminders Membership
Next tutorial -
send any feedback for the tutorial to nj104@ic.ac.uk or bh04@ic.ac.uk
The lecture slides will go online, check the website: http://www.union.ic.ac.uk/medic/muslim/
Any help from us?
Please email rk206@ic.ac.uk or mnm04@ic.ac.uk