Download Ch. 10 Part 3 Antibiotics vs. Vaccines

Ch. 10 Part 3
Antibiotics vs. Vaccines
•Antibiotics
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What happens when your body can’t fight off infection?
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Must call for extra help…Medicine/drugs called
ANTIBIOTICS
Drugs used to treat or kill bacterial or fungal
infections
Selective toxicity kill or disable pathogen with no
effects to host cells
Derived from living organisms or man-made
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Penicillin-1st antibiotic
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1928
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Used to be effective against many bacterial infections
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Today, it is the least effective antibiotic against many of
the infections it fought
Penicillin Produced by fungus Penicillium
•How Antibiotics Work
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Interfere with growth or metabolism of
target organism
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Synthesis of bacterial wall
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Protein synthesis
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DNA synthesis
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Cell surface membrane protein function
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Enzyme action
Main sites of action of antibiotics
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Cell Walls
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Viruses do NOT have these sites/targets
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Antivirals used on certain viral sites of
action
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Not many
Different diseases treated with different
antibiotics
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Main Sites of Action of
Antibiotics
Cell Wall synthesis inhibitor
Transcription inhibitor
Protein synthesis inhibitor
Ribosome, DNA, MRNA, RNA
polymerase
Metabolic action
interference
Membrane inhibitor
•Understand Bacteria to Understand Antibiotics
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Bacterial cell wall 
peptidoglycan
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Long chains of carbohydrates
and peptides (chains of
amino acids)
Peptidoglycans are held
together by Cross-Links made
by enzyme called
Glycopeptidases
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Glycopeptidases used to
form cross-links between
peptidoglycan molecules in
cell walls of bacteria; makes
cell wall rigid so cell do not
burst when taking up water
Penicillin prevents the
formation of these cross-links
•Broad vs. Narrow Spectrum Antibiotics
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Broad Spectrum
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Effective against a wide range of
antibiotics
Ex. Penicillin
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Prevents synthesis of Glycopeptidases
enzyme that forms the cross-links
between the peptidoglycan
polymers in cell walls
Narrow Spectrum
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Effective only against a narrow range
of bacteria
Prevents bacterial resistance from
occuring
Antibiotic
Resistance
• Penicillin
• Treats wide range of bacteria
• Stops cell wall formation  prevents bacterial
cell reproduction
• Kills all bacteria sensitive to penicillin
• Inhibitor of enzymes called glycopeptidases
• Hopefully the ENTIRE population
• What happens when entire population is
NOT killed by antibiotic?
• Due to one or more individual bacteria carrying
an allele that makes them resistant to penicillin
• NOT GOOD
• Exposure to antibiotics exerts STRONG
selective pressure on bacterial population
• Resistant bacteria have selective
advantage…more likely to survive and reproduce
• Bacterial DNA
• Single loop of DNA
• Only ONE copy of each gene
• Mutant alleles have IMMEDIATE effect on
phenotype
Antibiotic Resistance
• Arises when an existing gene with
the bacterial genome changes
(mutates) spontaneously to give
rise to a nucleotide sequence that
codes for a slightly different
protein that is NOT affected by
antibiotic
• DNA MUTATION!!!!
• A change in the nucleotide sequence
of DNA
• Incorrect dosage or stopping a
cycle of antibiotic treatment
increase chances of antibiotic
resistant bacteria
• Two Ways for Bacteria to become
resistant
1. Vertical transmission
2. Horizontal transmission
Antibiotic Resistance
• Vertical Transmission
• Binary fission bacterial reproduction fast
• Method of spreading antibiotic resistance in a
population of bacteria
• Occurs rapidly in ideal conditions when a bacteria with
a mutant gene survives after antibiotic treatment
• Horizontal Transmission
• Genes for Antibiotic Resistance occur on plasmids
• Plasmids: small loops of double stranded DNA
• Frequently transferred from one bacteria to another during
CONJUGATION
• PLASMIDS TRANSFEERRED FROM DONOR BACTERIA TO
RECIPIENT BACTERIA
• Enables resistance to arise in one type of bacteria and be
passed onto another species of bacteria
• Bacteria can pass off genes to other bacteria
increase proliferation of resistant bacteria
Penicillin Resistant Bacteria
• Produces enzymes that make
penicillin ineffective against them
• B lactamase (penicillinase)
• Group of Enzymes that breaks apart the
penicillin molecule
• Enzyme that inactivates penicillin
• Staphylococcus
• Cause Staph Infection
• may cause disease due to direct infection
or due to the production of toxins by the
bacteria
• Methicillin-resistant Staphylococcus
aureus
• MRSA type of Staphylococcus
aureus that is resistant to the antibiotic
methicillin and other drugs in this class
(penicillin)
Human Use of Antibiotics
• Antibiotic use  change in environmental
factors of bacteria
• Exert selection pressures on bacteria
• Enable more antibiotic bacteria to proliferate
• Constantly trying to find new antibiotics that
bacteria are NOT resistant to
• More humans use antibiotics = greater
selection pressures exerted on bacteria to
evolve resistance to antibiotics
• BAD!
•Choosing Effective Antibiotics
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Lab testing of effectiveness (isolated
bacteria/fungal strains)
Antibiotic Sensitivity Tests
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Collect bacteria and culture
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Treat with different antibiotics on discs
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Measure diameter of inhibition zone
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Use standardized chart to determine
resistance or sensitivity
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Largest diameter = largest area of
inhibition = more effective antibiotic =
bacteria is SENSITIVE to antibiotic
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Smaller diameter/same size as disc =
Bacteria are RESISTANT to that
antibiotic
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We want bacteria to be SENSITIVE to
antibiotic to use if effectively
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Discs are treated with
ANTIBIOTICS
Bacteria is grown on nutrient
agar on petri dish
•How to Prevent bacterial Resistance to
Antibiotics
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Only use antibiotics when appropriate and
necessary
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Reduce # of countries in which antibiotics are
sold without prescription
Avoid use of broad/wide spectrum antibiotics
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Do not take for viral infections
Use narrow spectrum instead
Complete entire course of antibiotics
Do not use un-used antibiotics for selfmedication in the future (do NOT re-use later)
Change the type of antibiotic used for certain
disease so that same antibiotic is not always
prescribed for the same disease
Avoid using antibiotics in farming to prevent
rather that cure infections
•Examples of Antibiotics
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Isoniazid man-made; treatment of tuberculosis
Rifampicin (rifampin) inhibits enzyme required for
RNA synthesis in bacteria
Tetracycline binds to bacterial ribosomes and
inhibits protein synthesis
•MSRA
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Methicillin-resistant Staphylococcus aureus
Bacteria resistant to many
antibiotics
Due to wide spread and
inappropriate use of
antibiotics
Resistant to last resort
antibiotic (VANCOMYCIN)
•Antitoxins
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Class of antibodies
Block the toxins released by
pathogens
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Ex. Those that block the toxins released
by bacteria that cause tetanus
•Vaccines
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Weakened OR deactivated forms of
pathogen that are introduced into
your body to cause YOUR immune
system to produce antibodies that
fight off the pathogen
Many different vaccines have been made to
protect people from viruses and bacteria
1)
2)
•4 Ways Vaccines Work
Weaken the Virus
Click Here! How Vaccines
Work VIDEO
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viruses are weakened so that they reproduce themselves very poorly once inside the body
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Body is able to make “memory B cells” to protect patient against the virus for life
+ only one or two doses need for life long immunity
- may cause a mild version of disease and people with weakened immune systems (cancer or
AIDS) cannot get them
Inactivate the Virus
Viruses are completely inactivated (or killed) with a chemical
the virus is still "seen" by the body and cells of the immune system that protect against disease
are generated
+ anybody can get this vaccine
- Many doses are required
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3)
Use Part of the Virus
just one part of the virus is removed and used as a vaccine (proteins on the surface of the
virus)
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can be used when an immune response to one part of the virus (or bacteria) is responsible
for protection against disease
+ a few doses= long lived immunity
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4)
Use Part of the Bacteria
Make vaccine by inactivating toxin with a chemical (the toxin, once inactivated, is called a
toxoid).
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Toxoid no longer causes harm and body create immune cells against this specific
toxin
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Make vaccine using the sugar coat of specific bacteria
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Body build immunity against bacteria with that specific sugar coat
- requires many doses to build immunity
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