Vaccines and Antimicrobial Drugs Flashcards
vaccination
- inoculation of a living host with inactive or attenuated (weakened) pathogens, or pathogen products, to stimulate protective active immunity
- active immunity means that your body is making the antibodies
- passive immunity involves obtaining antibodies from a different organism
vaccine
- the substance given to a host (usually by injection) that induces artificial active immunity
- acts as an antigen, but does not cause disease
- stimulates the production of antibodies
herd immunity
- resistance in a population to a pathogen (disease) as a result of the immunity of a large portion of the population
- breaks the chain of pathogen transmission from one susceptible host to another
- the more highly infectious a pathogen, the greater the proportion of immune individuals needed to prevent disease spread
How do vaccines stimulate active immunity?
- the initial exposure to the antigen from the vaccine causes the primary immune response
- the primary immune response causes a rise in antibody concentration that decreases over time
- when exposed to the antigen a second time, the secondary immune response occurs
- the secondary immune response causes a rise in antibody concentration that is higher and faster
What are the different types of SARS-CoV-2 vaccines being used or in development?
- mRNA vaccines (Pfizer and Moderna): mRNA that codes for spike protein is purified and injected, body produces spike protein
- adenovirus vector vaccine (Johnson and Johnson): spike protein gene is purified and put inside an adenoviral vector, body produces spike protein
- protein based: spike protein is purified and injected
- all cause the immune system to produce the antibody against the spike protein antigen
antimicrobial drugs
- compounds used to treat disease by destroying or inhibiting the growth of pathogenic microbes within a host (in vivo)
- synthetics, antibiotics, semi-synthetics
What are synthetics?
chemicals
antibiotics
- naturally produced antimicrobial agents (microbial products)
- produced by bacteria and fungi
semi-synthetics
chemically modified antibiotics
How are antimicrobials classified?
- molecular structure
- mechanism of action
- spectrum of antimicrobial activity
selective toxicity
- ability of a drug to kill or inhibit the pathogen while damaging the host as little as possible
- ex: penicillin goes after peptidoglycan
therapeutic (effective) dose
drug level required for clinical treatment
toxic dose
drug level at which drug becomes too toxic for the patient (produces side effects)
therapeutic index
- ratio of toxic dose to therapeutic dose
- the larger the therapeutic index, the better
narrow spectrum drugs
attack only a few different pathogens
broad spectrum drugs
attack many different pathogens
cidal agent
kills microbes
static agent
inhibits growth of microbes
side effects
undesirable effects of drugs on host cells
growth factor analogs
- structurally similar to an essential growth factor
- disrupt cell metabolism
- ex: isoniazid (narrow spectrum, cidal if actively growing, static if dormant)
quinolones
- interfere with bacterial DNA gyrase
- prevent DNA packaging
- ex: ciprofloxacin (narrow spectrum, cidal)
macrolides
- target the 50S ribosomal subunit
- ex: erythromycin (broad spectrum, static)
- ex: azithromycin (Z-pack) (semisynthetic)
tetracyclines
- target the 30S ribosomal subunit
- ex: tetracycline (broad spectrum, static)
lipid biosynthesis disruptors
- target fatty acid biosynthesis
- ex: platensimycin (broad spectrum, static, effective againt MRSA and VRE)
beta-lactam antibiotics (from fungi)
- include penicillins and cephalosporins
- target cell wall synthesis
- effective primarily against gram-positive bacteria
- cidal against actively growing cells
isoniazid
- type: synthetic
- mode of action: lipid synthesis (especially mycolic acid)
- effect: cidal if actively growing, static if dormant
- spectrum of activity: narrow
ciproflaxin
- type: synthetic
- mode of action: bacterial DNA gyrase (prevents DNA packing)
- effect: cidal
- spectrum of activity: narrow
penicillin
- type: antibiotic
- mode of action: cell wall synthesis
- effect: cidal (if actively growing)
- spectrum of activity: narrow
erythromycin
- type: antibiotic
- mode of action: 50S ribosomal subunit
- effect: static
- spectrum of activity: broad
tetracycline
- type: antibiotic
- mode of action: 30S ribosomal subunit
- effect: static
- spectrum of activity: broad
platensimycin
- type: antibiotic
- mode of action: fatty acid biosynthesis (MRSA and VRE)
- effect: static
- spectrum of activity: broad
Why is antimicrobial resistance a threat to public health?
- once resistance originates in a bacterial population, it can be transmitted to other bacteria
- resistance mechanisms are not confined to a single class of drugs
- erroneous practices select for the growth of resistant bacteria
What are the mechanisms of bacterial resistance?
- target modification
- preventing entrance
- inactivation
- efflux pumps
- alternate pathway
- impermeability
What is the origin of resistance?
- natural immunity genes
- spontaneous mutations
- resistance genes are located in chromosome, plasmids (R factors), or mobile genetic elements such as transposons
How is resistance transmitted?
horizontal gene transfer (transformation, conjugation, and transduction)
How do drug resistant bacteria emerge?
- Prescription of antibiotics
- Antibiotic selective pressure
- Genetic factors
- Spread of antimicrobial-resistant bacteria in the community
How can drug resistance be prevented?
- give drug in high concentrations to destroy susceptible
- use antimicrobials only when necessary
- take full course of antimicrobial
- use narrow spectrum antimicrobials
- give a combination of unrelated drugs
- possible future solutions: continued development of new antimicrobials and use of bacteriophages to treat bacterial disease
How did MRSA become VRSA?
- vancomycin was used to treat MRSA
- increased selective pressure
- VRSA strains have high resistance to vancomycin
