Ch. 10 Part 3 Antibiotics vs. Vaccines

Antibiotics 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 Penicillin-1 st antibiotic 1928 Used to be effective against many bacterial infections Today, it is the least effective antibiotic against many of the infections it fought Penicillin Produced by fungus Penicillium What happens when your body can’t fight off infection?

Interfere with growth or metabolism of target organism Synthesis of bacterial wall Protein synthesis DNA synthesis Cell surface membrane protein function Enzyme action Main sites of action of antibiotics Cell Walls Viruses do NOT have these sites/targets Antivirals used on certain viral sites of action Not many Different diseases treated with different antibiotics How Antibiotics Work 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 Bacterial cell wall  peptidoglycan Long chains of carbohydrates and peptides (chains of amino acids) Peptidoglycans are held together by Cross-Links made by enzyme called Glycopeptidases 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 Broad Spectrum Effective against a wide range of antibiotics Ex. Penicillin Prevents synthesis of Glycopeptidases enzyme that forms the cross-links between the peptidoglycan polymers in cell walls Narrow Spectrum 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) MRSAdrugs

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!

Lab testing of effectiveness (isolated bacteria/fungal strains) Antibiotic Sensitivity Tests Collect bacteria and culture Treat with different antibiotics on discs Measure diameter of inhibition zone Use standardized chart to determine resistance or sensitivity Largest diameter = largest area of inhibition = more effective antibiotic = bacteria is SENSITIVE to antibiotic Smaller diameter/same size as disc = Bacteria are RESISTANT to that antibiotic We want bacteria to be SENSITIVE to antibiotic to use if effectively Choosing Effective Antibiotics Discs are treated with ANTIBIOTICS Bacteria is grown on nutrient agar on petri dish

How to Prevent bacterial Resistance to Antibiotics Only use antibiotics when appropriate and necessary Do not take for viral infections Reduce # of countries in which antibiotics are sold without prescription Avoid use of broad/wide spectrum antibiotics Use narrow spectrum instead Complete entire course of antibiotics Do not use un-used antibiotics for self- medication 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 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

Bacteria resistant to many antibiotics Due to wide spread and inappropriate use of antibiotics Resistant to last resort antibiotic (VANCOMYCIN) Methicillin-resistant Staphylococcus aureus MSRA

Class of antibodies Block the toxins released by pathogens Ex. Those that block the toxins released by bacteria that cause tetanus Antitoxins

Many different vaccines have been made to protect people from viruses and bacteria 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 Vaccines

1)Weaken the Virus viruses are weakened so that they reproduce themselves very poorly once inside the body 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 2)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 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) 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 4)Use Part of the Bacteria Make vaccine by inactivating toxin with a chemical (the toxin, once inactivated, is called a toxoid). Toxoid no longer causes harm and body create immune cells against this specific toxin Make vaccine using the sugar coat of specific bacteria Body build immunity against bacteria with that specific sugar coat - requires many doses to build immunity 4 Ways Vaccines Work Click Here! How Vaccines Work VIDEO