C3.2 (2) Defense Against Infectious Diseases Flashcards
How can HIV pass to another?
- Unprotected sex
- Sharing of hypodermic needles
- Transfusion of infected blood
- Childbirth
- Breastfeeding
Human Immunodeficiency Virus (HIV)
- Causes acquired immunodeficiency syndrome (AIDS).
- Virus can’t survive long outside body.
- Infection occurs if blood or bodily fluids pass from infected to uninfected.
What does HIV do to the body?
- Invades and destroys helper T-cells, leading to progressive loss of capacity to produce antibodies.
- Retrovirus (genes made of RNA).
- Creates DNA copies of its genes after entering host cell using reverse transcriptase.
Outline process of HIV infection.
- In early stages, immune system makes antibodies against HIV.
- If these detected, patient is HIV-positive.
- Assuming no treatment, antibody production becomes so ineffective—making patient susceptible to opportunistic infections (caused by pathogens which would be fought easily by a healthy immune system).
- Antiretroviral drugs inhibit reverse transcriptase; Other drugs target enzyme used by HIV to insert DNA to host cell’s chromosomes.
- Treatment with group of antiretroviral drugs greatly slows down or prevents damage to immune system.
Syndrome
A collection of several diseases or conditions existing together.
When conditions in patient caused by HIV are combined, they have AIDS.
Antibiotics
A chemical that inhibits the growth of microorganisms.
What do antibiotics do to bacteria?
- Most antibacterial.
- Block processes that occur in prokaryotes (not eukaryotes) → Hence, used to kill bacteria inside body, without harming human cells.
- Target processes of bacterial: DNA replication, transcription, translation, ribosome function and cell wall formation.
- Control bacterial infections.
- Not effective against viruses.
- Should not be prescribed to treat viral infections → Overuse of antibiotics increases antibiotic resistance of bacteria.
Outline the discovery of Penicillin.
- In 1929, Alexander Flemming observed older bacterial plates.
- Discovered fungal colony, which killed bacteria.
- Identified as Penicillin notatum, and grew it in broth.
- Mould produced substance that was bactericidal.
- Published his findings in scientific journal.
- Development of Penicillin into treatment for disease done by Harold Florey and Ernst Chain.
- Widespread use in World War II.
How do viruses reproduce?
- Viruses are non-living; Reproduce when inside living cells.
- Use chemical processes of living host (don’t have their own metabolism).
- Rely on host cell’s enzymes for ATP synthesis and other metabolic pathways (don’t have their own means of transcription or protein synthesis).
- Said processes can’t be targeted by drugs → host cells could be damaged.
What are key points regarding overuse of antibiotics?
- ↑ use of antibiotics, ↑ resistance of bacteria (develop new ways to fight antibiotics).
- Resistance has ↑, and few new antibiotics marketed.
- Antibiotic resistance is major public health threat.
- Without antibiotics, return to “pre-antibiotic era”; Medical procedures no longer possible, spread of bacterial diseases (can no longer be treated) causing death.
- Loss of effective drugs to treat bacterial infections.
- Strains of bacteria with resistance discovered soon after introduction of antibiotics.
- Not huge risk, unless strain develops multiple resistances (which is now widespread).
- Evolution of multiple antibiotic resistance made easier as genes can be passed from one species of bacteria to another. Also, evidence suggests antibiotic-resistance genes not lost from genomes of pathogenic bacteria rapidly when antibiotic no longer used.
For example: Methicillin-resistant Staphylococcus aureus (MRSA) can infect the blood or surgical wounds of hospital patients and resists all commonly used antibiotics.
What are measures used to avoid multiple antibiotic resistance?
- Prescribe antibiotics only for serious bacterial infections, for minimum period.
- Maintain high standard of hygiene in hospitals to prevent cross-infection.
- Farmers avoid use of antibiotics in animal feed (as growth stimulants).
- Have pharmaceutical companies develop new classes of antibiotics → No new types introduced since 1980s.
Zoonosis
A disease that can be transmitted to humans from other animals in natural circumstances.
What factors contribute to zoonotic diseases?
- Humans living in close contact with livestock
- Displacement of wild animals when habitant disrupted by spread of human population.
COVID-19 thought to have originated from bats (likely other animal species). Classed as a zoonotic disease even though, since the initial transfer from animal-to-human, the spread of the disease has been human-to-human.
Immunization
Involves use of a vaccine to trigger immunity.
Vaccines
Administered either by injected, nasal spray, or mouth.
What active ingredients are often found in vaccines?
- Dead or attenuated (weakened) bacteria or virus
- Purified polysaccharides from bacterial walls
- Inactivated virus
- Inactivated toxins
- Recombinant DNA produced by genetic enginnering.
- mRNA
mRNA used to make COVID-19 vaccine.
How do vaccines works?
- Contain antigens (allow pathogen to be recognized by immune system) or nucleic acids (make antigens).
- Said antigens trigger a primary immune response, by activation of T-cells → B-cells → Production of plasma cells → Specific antibodies.
- If memory cells also produced, long-lasting immunity develops.
- If vaccine successfully triggers such immunity, pathogenic microorganism will be destroyed by a secondary immune response if it ever enters the body.
Herd Immunity
Achieved when a significant portion of a population have already contracted a disease or have been vaccinated.
- Spread of a virus or pathogen is impeded, as it repeatedly encounters people who are already immune.
- Any new outbreak of disease will decline and disappear.
- Not everyone has to be immune, hence “herd protection”.
- Vulnerable individuals who have compromised immune systems and cannot be vaccinated are unlikely to contract the disease.
Herd Immunity Formula
(1-1/R) x 100%
R is the average number of people that an infected person infects.
Percentage Formula
percentage = (first # / second #) x 100%
Used to express one number as a percentage of another number.
Percentage Change Formula
percentage change = ((first # - initial #) / initial #) x 100%
Percentage Difference Formula
percentage difference = ((number A - number B) / number A) x 100%
Can use percentage A or B as divisor (answers will be different, however).
