When a critical # of the population is immune to a particular disease..either through NATURAL immunity or by VACCINATION
IE: US with TB, or Polio
2. How do vaccines work?
Uses a killed or weakened form of the pathogen and introduces this to a host, which develops an immune response to the pathogen, so that when the actual disease presents itself to the host, the host will have an “immunologic memory” to this pathogen and be able to produce antibodies much more quickly to fight off the disease.
3. Different types of vaccines (Look @ chart to compare)
LIVE attenuated: LONG Term protection. SINGLE dose. Slight Risk of mutation of virus. GOOD cellular immune response
IE: BCG – against TB
Inactivated Vaccine: contains the KILLED microbe or virus. SHORT term protection. Usually need MULTIPLE doses. NO Risk of mutation of virus. POOR cellular immune response
IE: Polio vaccine, Influenze vac.
4. Current progress in immunization
Working on RECOMBINANT DNA vaccines (genetically engineered microorgs)
These are safe and highly reproducible
6. List 4 types of vaccines in current clinical use, give an example of a disease prevented by each type.
1. BCG: live attenuated virus to prevent tuberculosis
2. Influenza vaccine: can be live attenuated (nasal spray form) or inactivated vaccine to prevent the flu
3. DPT: toxoid vaccine against diphtheria, tetanus and Pertussis.
4. Polio Vaccine: inactivated vaccine against Polio
7. Match common vaccines with the vaccine type:
hepatitis B: Protein Subunit vaccine
measles: LIVE attenuated virus
mumps: LIVE attenuated virus
rubella(German measles): LIVE attenuated virus
oral polio(Salk): INACTIVATED vaccine
injected polio: LIVE attenuated vaccine
influenza: Live attenuated (nasal spray form) or Inactivated vaccine
tetanus: Toxoid Vaccine
diphtheria: Toxoid Vaccine
8. Monoclonal and polyclonal antibodies
MONOCLONAL: antibodies against ONE EPITOPE (difficult to develop). Use only in research or if commercially useful. IE: Pregnancy test, herpes simplex, flu, hepatitis diagnosis
POLYCLONAL: a mix of Various Ab’s against various EPITOPES presented by the whole cell or virus.
9. Different way of detecting and quantifying antigen-antibody reactions
IMMUNOASSAYS: to ID unknown bac or antigens & detect SPECIFIC Antibodies
Microtitter Plate: Use to estimate the amount of antibodies presnt in blood by doing serial dilutions to observe a precipate formation from antigen-antibody binding that is of optimal proportions.
Immunodiffusion: use an agar plate with antibodies at center, and different ANTIGENS at ends. The antigen-antibody binding will create precipitate in the plate, leaving a line b/w the antibody and antigen in the plate.
Agglutination Reaction: blood typing uses this, so uses anti-A for example to look for A antigens, and confirm type A blood type.
Fluorescent or Enzyme labeled antibodies (labeled with dye and once bound to antigen, the fluorescent dye is shown)
10. What does pregnancy test detect? What other example you could give where you use antigen-antibody reaction as a diagnostic test?
Detects hCG (Human chorionic gonadotropin hormone). (Direct ELISA) – testing for specific antigen presence – use Monoclonal antibodies to see if pregnant - recognizes subunit of hCG
Can test to see if you have the antibodies against tuberculosis (Indirect ELISA).
11. How the penicillin and streptomycin producing microbes different?
Penicillin: MOLD mold producing a bacterial substance that was effective AGAINST a wide arrange of microbes (wonder drug during WWII – helped treat wounded soldiers). Kills gram + bac by INHIBITING cell wall synthesis!!
If you change a group or two in the lab – semisynthetic antibiotic (penicillin is natural)
Secreted from soil
Streptomycin: PRODUCED BY BAC. Act to inhibit PROTEIN Synthesis??
12. How are antibiotics not toxic to human cells? (selective toxicity?)
Selective Toxicity: Antibiotics that generally interfere w/biological structures or biochem processes common to bacteria, NOT humans
Drug can target synthesis only going on in prokaryotes and not in Eukaryotes. IE: different ribosome’s we use in pro vs. euk, and cell wall in pro vs. no cell wall in euk.
Inhibit metabolic pathway: Human cells lack specific enzyme in Folic acid pathway that prokaryotic cells have
Facts of Antibiotics:
Bacteriostatic – inhibits growth & relies on human host to kill
BacterioCIDAL – kill the bacteria
Inhibition of cell wall synthesis: bacteria cell wall is unique, as it contains peptidoglycan membrane (not in eukaryotes).
Narrow spectrum = ie: penicillin: only effective towards Gram +
Broad spectrum = ie: amoxycilin – can kill multiple types of bac
Tissue distribution: if distributed locally, can be more toxic than if given orally, for example.
13. Mechanism of action of antibiotics, antiviral drugs.
Act on actively DIVIDING cells (when cell wall synthesis or DNA synth occurring, for example)
Inhibit cell wall synthesis: involves peptidoglycan crosslinking. Drugs include *B-lactam drugs, Vancomycin & Bacitracin. IF you have a penicillin allergy, can use B-lactam
Vancomycin- effective to treat MERSA
Inhibition of Protein Synthesis: prokaryotic RIBOSOME (different from Eukaryotes) acts as target and are prevented from working. Drugs include *Aminoglycosides, Tetracyclins, Macrolids, Chloramphenicol, Lincosamides, Oxazolidinones, Streptogramins.
Inhibition of Nucleic Acid Synthesis (DNA or RNA): Drugs include *Rifamycins & Fluoroquinolones. Effective against Gram + and -.
Inhibition of METABOLIC pathway: act to INHIBIT production of FOLIC acid, or GLYCOLYSIS for example. Drugs include Sulfonamides, Trimethoprim. Human cells lack specific enzyme that prokaryotic cells have
Interferenece w/cell membrane integrity: binds to membrane of Gram – bac, alters permeability, causes leakage & cell death. Drugs include Polymyxin B
Interference with essential processes of Mycobacterium tuberculosis: This is a bacteria that is VERY difficult to treat…cause Tuberculosis and Lepracy. Have different type of cell wall & SLOW growth, so can’t use inhibitory cell wall or protein synthesis. First line defense drugs include: Isoniazid, Ethambutol & Pyrazinamide. Some strains resistant to 1st line, so have 2nd line, and some resistant to ALL antibiotics
ANTIVIRAL Drug mechanisms
14. Adverse effect of antimicrobial drugs
Allergic reactions: ie: allergic to penicillin
Toxic effects: ie: aplastic anemia-body can’t make RBCs or WBCs
Suppression of normal flora: ie: broad spectrum antibiotics don’t usually differentiate b/w normal flora and bad bacteria. Ie: antibiotic associated colitis: toxic organisms given the ability to survive
*Antimicrobial resistance: ie: microorgs have innate or adaptive resistance to antibiotics)
15. Antibiotic resistance, acquisition examples, global impact
Bacteria undergo mutations in their chromosomal or plasmid DNA and are selected by ‘natural selection’ (survival of the fittest). Bacteria are resistant to the infection…Not Human host cells resistant.
Resistance through mutation of bacteria – can now grow & divide in presence of Antibiotics, and now can pass down its mutation to the bac offspring.
Mechanisms of resistance??Drug inactivating enzymes, alteration of target molecule, decreased uptake of drug, increased elimination, spontaneous mutation
S. aureus: MRSA – most susceptible to Vancomycin.
PICKING up Plasmid:
Acquisition of new genes through GENE TRANSFER: Conjugation – transfer of R plasmid, which has several resistant genes
If resistance is developed in one country, CAN Transport globally
Many are administered with a non-prescription basis.
Use of antimicrobial drugs added to animal feed – although it produces more $$ productive animals, they are also in the process of selecting for antimicrobial resistance.
16. Will antibiotic be effective against a viral disease? Explain.
Antibiotics NOT effective against VIRUSES.
If you have an ear infection, most likely viral…but if child has it, prescribe antibiotics to treat POSSIBLE secondary infections, which would most likely be bacterial.
Antiviral drugs specific for a viral disease (but don’t eliminate LATENT virus).
Types of antiviral drugs: *KNOW selective toxicity measures to rid viral diseases
Work on Uncoating of protein capsid and prevents cleaving of proteins (protease inhibitors)
Inhibit Viral Nucleic Acid Synthesis. Ie: HIV- RNA virus, needs to be reverse transcribed to DNA (so need a drug to prevent reverse transcription..prevent reverse transcriptase ENZYME) + Drugs that inhibit protease inhibitors, target VIRUSES (not host cells)
Ie: viral uncoating,
17. Antibiotic sensitivity assay (lab)
Disc diffusion method: strain spread on media on plate, then discs w/specific conc of antibiotic placed on plate. Clearing (zone of inhibition) reflects the SUSCEPTIBILITY. Size of clearing can determine if susceptible or RESISTANT to antibiotic
E-test – modification of disc diffusion but w/strips of concentration gradient of Abs
MIC = Minimum Inhibitory Concentration
Quantitative test to determine LOWEST concentration of specific antimicrobial drug needed to prevent growth of specific organism (but still needs to not be too toxic for host!)
18. Define therapeutic index and explain it importance
Toxicity towards host cells should be @ minimum but at same time highly effective against bacteria – finding a BALANCE of both.
The Toxicity of the drug is the THERAPEUTIC Index. Higher therapeutic index, less toxic
Lowest dose TOXIC to humans is divided by the dose typically used for treatment
IE: MIC test
Adjuvants: Vaccine additive which boosts the vaccine’s ability to provide an immune response.
WHICH is more sensitive to antibiotics, E. coli or S. aureus?
E. coli NOT as sensitive (as it is Gram -, so it is more difficult…need to act on nucleic acid synthesis, as cell wall synthesis inhibition doesn’t work too much since it doesn’t have a large peptidoglycan layer to crosslink and inhibit).