Flashcards in Epidemiology and Control of Infectious Disease Deck (18):
Whole-genome analysis in epidemiology ??
- detecting a hospital outbreak of MRSA via antibiotic sensitivity profile, DNA based techniques
-this is possible because of new rapid cheap sequencing methods
-helps identify source of MRSA outbreak on infant ward
Special Care Baby unit and genome sequencing analysis case study?
- connecting a strain in 11 babies...staff were screened and a carrier was identified
What are the general principles of infection control?
- remove reservoir or source of infection
-interrupt transmission of infection
- increase host resistance to infection
How do we remove reservoir or source of infection.
-case finding and treatment : Tuberculosis
- contact tracing: STDs , meningitis "kissing contacts"
- Culling of infected Animals: Tuberculosis
- Sanitation: clean water
-Human to human, Animals and environment?
-avoid overcrowding,handwashing, changes in behaviour (safe sex), isolation of infectious cases (from school or work)
- food hygiene, vector control , animal vaccination and treatment , poop-scooping
How do we increase host resistance to infection?
- improved diet
- chemoprophylaxis(prevents infection)
L> Meningitis and TB
What are the four types of immunization?
1. Life attenuated : grown in animal cells at a temp that isn't good for it causing it to mutate and can no longer cause disease (Polio -sabin and measles, mumps rubella)
2. Killed/inactivated : provide antigens (Polio- Stalk)
3. Toxoid: inactive of the toxin (Anthrax)
4. Recombinant DNA vaccine: produce protein of outer coat of virus which assembles into virus like particle and elicit an immune response (HPV)
What is the difference between live attenuated and killed vaccines?
A. multiplies inside human host to provide strong antigenic stimulation. Provides prolonged immunity (years to life) often with a single dose. Vaccine often provides cell mediated immunity. Unsafe in immunocompromised or pregnancy. Can't revert to virulent form
B. Does not multiple in human host. Immune response depends on antigen content. Multiple doses of vaccine required with booster doses. Provides little cell mediated immunity. No possibility of a vaccine associated infection
What is herd immunity?
- resistance of a population as a result of immunity of a large proportion of the population.
-vaccination of an entire population but some people are resistant or some people cannot be given it to. Protects entire population een those it did not work on bc of high percentage it did.
* Polio: 70%, Measles and influenza: 90%
- selective toxicity
- kill or inhibits growth of microbe
- doesnt damage host
- targets a metabolic pathway in a micro organism which is absent or radically diff in mammalian cells
- targets are easier to identify in bacteria
L> Fungi and eukaryotes share many cell processes with mammals
- Viruses are intracellular parasites.
Explain B-lactam antibiotics
- penicillin ex
- transpeptidases (Penicillin Binding Proteins)
- form peptide cross links between adjacent glycan chains
- final step in peptidoglycan synthesis
- essential for structure of peptidoglycan
Anti-bacterial agent: B Lactams
L> damage to bacteria how?
- bind to transpaptidase- permanently inactivate it
- weakened cell wall with fewer cross links
- antibiotic - transpeptidase complex stimulates autolysins
- osmotic lysis
- Selectivity: peptidoglycan and transpeptidases are unique to abcteria
How does resistance to B-lactam antibiotics occur?
-b-lactamase enzymes hydrolyse the B-lactam ring, inactivate the b-lactam antibiotic
Describe anti fungal agents.
- polyenes: amphotericin B
- Target: binds erogsterol in fungal membranes, disrupts the membrane f(x), membrane permeability and cell death occurs.
- selectivity: euks have cholesterol in cell membrane
L> still very toxic to humans
*can treat some protist infections since they have erogsterol in membranes
Typical fungal cell structure>
- typical eukaryote cell except ergosterol instead of cholesterol in PM (some protists as well), very rarely flagellated and has a cell wall
L> Azidothymidine (AZT)
- Targets reverse transcriptase. Effective against retroviruses (HIV), structural analogue of thymidine, incorporated into DNA but acts as a chain terminator
- Usually given as part of a multidrug therapy (reduces risk of resistance developing)
Retroviruses and anti viral agents.
- ssRNA genome
-Reverse transcriptase (RNA dependent DNA poly)
- selective toxicity: AZT has 100 to 300 fold greater affinity for the HIV reverse transcriptase than mammalian DNA poly.