Micro Exam 4 Final Material PDF

Early final 12/9 8am aclc 002 Wk 12: Antimicrobial therapy/ antibiotics Chemicals that either synthesize by themselves or another organism. They inhibit growth of other microorganisms. Up to 1970s, the golden age of antibiotic discovery Running out of useful antibiotics now It...

Early final 12/9 8am aclc 002 Wk 12: Antimicrobial therapy/ antibiotics Chemicals that either synthesize by themselves or another organism. They inhibit growth of other microorganisms. Up to 1970s, the golden age of antibiotic discovery Running out of useful antibiotics now It takes 2-3 to found exact code that is infecting a person Antibiotic resistance is now one of the major health problems Antibiotics Can be overprescribed, misused, used in animal feed 60-70% nosocomial staph infections of MRSA Drug resistance is a problem that will only get worse S. pneumoniae is known for horizontal gene transfer (griffins postulate) Golden age of antibiotic discovery Compounds produced by one microbe that affect other microbes Moldy bread to put on wounds in ancient egypt Ernest duchesne proposed that bac and molds engaged in battle for survival, they do not like each other 1928, alexander fleming rediscovered penicillin, mold P. notatum Penicillin purified by howard florey and ernst chain Mary hunt discovered penicillium chrysogenum produced 200x more than penicillium notatum Penicillin g Gerhard domagk: sulfa drugs ○ Prontosil dye ○ Antimicrobial (synthetic)  ○ Inactive until converted by body to active agents ○ Analogs of PABA, precursor needed vitamin for DNA synthesis Selman waksman ○ Streptomycin ○ Antibiotic produced by actinomycete bacteria found in soil, streptomyces griseus ○ Better than penicillin , most effective Antimicrobial therapy fundamentals 1. Antibiotic must affect target organism a. Drug should affect microbial physiology b. Does Not exist or is greatly modified in humans i. Peptidoglycan ii. Differences in ribosomes structure iii. Biochemical pathway missing in humans 2. But it not affect humans/host a. Many have side effects at high concentration i. Chloramphenicol interferes with RBC dev ii. Some may cause allergic responses. Spectrum of activity Broad- effective against g+ and g-, kills all Narrow- isoniazid only works in mycobacterium tuberculosis (lipid layer), kills some Bactericidal- antibiotics kill target organisms Bacteriostatic- antibiotics prevent growth of organisms ○ Cannot kill organism ○ Immune sys remove invading microbe Drug susceptibility MIC Minimal amount of drug that can inhibit visible bacterial growth Done by serial dilutions ○ Increasing antibiotics from A-J ○ Clear= no bac, cloudy= bac present Then take sample of MIC and plate to see if organisms are dead ○ MBC/MLC= minimum bactericidal concentration. Varies by dif bac species Tests by diluting antibiotics mic= TUBE GROWTH, not growth in agar mbc/mlc= PLATE CONCENTRATION Kirby-bauer disk susceptibility test Test strain sensitivity to multiple antibiotics 1. Inoculate agar 2. Add antibiotic disc 3. Measure IZ Large iz= bac is susceptible and antibiotic is effective Small iz= bac is not susceptible and antibiotic is not as effective against that bac Take iz measurement and look at susceptible value to see if the diameter is >x (on table) YOU CANNOT COMPARE ANTIBIOTICS SIMPLY BASED OFF OF THEIR DIAMETER MEASUREMENTS Quantity in disk measurements has an effect on the resistant, intermediate, and susceptibility #’s. ○ CANNOT COMPARE BASED OFF OF QUANTITY IN DISK Mechanisms of action How do antibiotics work? 1. Cell wall antibiotics- peptidoglycan synthesis is complex a. Precursors are made in cytoplasm i. UDP-NAG and UDP-NAM peptides b. Precursors are polymerized to the existing cell wall structure by transglycosylases c. Peptide chains are cross-linked by transpeptidases All amino acids/sugars made in cytoplasm Outside of wall in G+ Sugar will connect to amino acids, one by one. ○ NAM + 5 amino acids NAG will be added to it= NAM + NAG (sugars) Aided movement by proteins, bacterial prenol. flipped form inside to outside. Now it is outside. Then added to the growing chain outside of the cell wall. 2 layers form eventually till the wall is formed all around the cell. (CELL WALL SYNTHESIS) We want to stop bac from building cell wall Peptide linkage: penicillin and vancomycin. They prevent 2 enzymes (PBPs) from building the wall. Beta-lactam antibiotics: mimicry d. square e. Penicillins and cephalosporins f. B-lactam and d-alanine-d-alanine  g. D-alanine is needed for the wall, but the beta lactam mimics d-alanine and thus stops the cell wall formation because it cannot tell the difference but is functionally different. Remember G + has two cell walls. Vancomycin Large size Blocks the peptide interbridge in G+ bacteria.a Binds to left and right d-alanines. Gives access to cell wall Does not cross the LPS outer membrane of G-. LPS is the giraffe that builds the outer membrane. Penicillin resistance Active site of penicillin= ring Replacing side chains can actually make it more useful. Making it acid resistant, helps it further work in the GI tract. 2. Drugs that target cell membrane Highly toxic If we can damage bac cell membrane, we could possibly damage our own cell membrane Typically a last resort kind of thing. Gramicidin Polymyxin ○ Similarly, acts on outer membrane ○ G + are NOT affected bc they lack an outer membrane ○ Topically 3. Drugs that affect DNA synthesis and Integrity  Quinolones ○ Blocks DNA gyrase, toperisomer II , blocking DNA rep in bac ○ Bactericidal ○ Does Not affect human DNA replication bc gyrase is unique to bacteria Sulfa drugs= sulfonamide ○ Inactive until converted by the body to active agents ○ Using diethylene glycol as solvent, very toxic ○ Elixir sulfanilamide ○ They block folic acid synthesis. They help with DNA synthesis. ○ Sulfanilamide is similar to PABA and it will replace the P-PABA-G. Then there will be no folic acid made. ○ It does not affect folic acid synthesis in human cells. Bc we dont make our own folic acid, we consume it. Vitamin B9. 4. RNA synthesis inhibitors (DNA transcription) Trans important to make proteins Bac rna poly is diff from human rna poly. One of the best targets for antibiotics. Work by blocking the DNA (actinomycin) or physically stopping the RNA polymerase (rifamycin) Rifamycin b Actinomyicn b However if it stops the bac dna, it will bind to our own dna and can be very toxic. Not normally use as an antibiotic, instead as anticancer chemotherapy. 5. Protein synthesis inhibitors Targeting ribosome bc bac + humans don't share the same ribosomes, except mitochondria. Our mitochon has similar ribosomes to bac. Antibiotics that target bac ribosomes can possibly damage humans ribosomal rna. Drugs targeted 30s subunit Aminoglycosides (streptomycin +gentamicin)= causes translational misreading mrna. ○ Bactericidal  ○ Binds to 30s, causing code on mrna to be read incorrectly ○ Then trna binds and determines which amino acids will be produced, but this wil be misread. ○ Codons will change and trna that's supposed to bind will bind to a new codon. ○ May have a premature STOP codon tetracyclines(doxycycline)= block binding of charged trnas to the a-site (acceptor site) of ribosome ○ Only antibiotic out of all we’ve talked abt is Bacteriostatic ○ Interferes to attachment of trna to mrna-ribosome complex ○ At the border b/w mrna and trna Drugs that target 50s subunit Macrolides (erythromycin) ○ Inhibits translocation, movement of ribosomes for next trna to bind Chloramphenicol ○ Inhibits peptidyl transferase activity ○ Binds to 50s portion and inhibits formation of peptide bond Clindamycin + metronidazole ○ Bind at same ribosomal site as chloramphenicol ○ Active in anaerobic environments ○ Metronidazole exclusively targets obligate anaerobes bac and some protozoa Antiviral agents Rhinovirus does not have an antibiotic designed for bac can touch it Selective toxicity is much harder for viruses than it is for bac ○ Viruses are hidden within cell ○ Seize host cell functions to make copies of themselves  Influenza ○ Amantadine Prevents entry of virus into host cell Developed resistance Neuraminidase inhibitors ○ Prevents release of mature viruses ○ Tamiflu Antiviral: dna synthesis inhibitors These drugs resemble normal dna nucleotides, but lack a 3’ oh, and so causes chain termination Zidovudine is an analog of thymine Inhibits dna rep bc dna needs Thymine Does Not affect human DNA replication bc our dna poly can proofread and replace things if needed. Usually targets hiv Assignment: study antifungal agentsby urself. Bonus question is abt antifungals Challenges of drug resistance and discovery Types of resistant 1. Prevent entry or expel antibiotics a. Destroy antibiotic before entering cell i. B- lactamase destroys b-lactam antibiotics b. Decrease membrane permeability across outer membrane i. G- bac generally have inherent resis to some antibiotics due to presence of outer mem ii. Penicillin and B. multidrug resistant efflux pump- particularly dangerous bc they can expel kinds of antibiotics with little regard to structure. (b-lactqms0, tetracyclines, fluoroquinolones). Cancer cells use similar strategies fighting chemotherapy. Requires E to move antiibotics out of cell (pump before bind) 2. Prevent binding to target a. Modify target so it no longer binds to antibiotics i. Penicillin-binding proteins and ribosomal proteins resistance to methicillin and streptomycin b. Add modifying group that inactivate the antibiotic i. 3 classes of enzymes are used to modify and inactivate the aminoglycosides antibiotics ii. Enzymes modify antibiotics by adding a different func group to structure iii. Causing it not to bind to ribosome 3. Reverse binding a. Not much is known abt this mechanism b. Ribosome protection/rescue c. Bind but suddenly stops binding (erythromycin) Why are bac becoming resistant? Lack of hygiene and poor sanitation Lack of new antibiotic Poor infection control Overuse in livestock farming Not taking it as prescribed ○ Overprescription 6 highly resistant bac species collectively cause abt ⅔ us nosocomial(hospital) infections Wk 14: microbial pathogenesis To cause disease, must have virulence factor And must survive in host Why are some people susceptible to certain infections while others are not? Why some pathogens have broad host specificity while other more narrowly target their host Will be provided virulence factors on test How organisms too small to see with the naked eye can kill humans a million times larger? They exist in very large numbers pathogen= microbial agent of disease ○ ectoparasite= lives on surface ○ endoparasite= lives inside of body infection= parasite/pathogen grows on host Determine by min. Infectious dose Acid-sensitive, they die w acid ○ All effect by ingestion Pathogenicity Ability to cause disease infectivity= how easily it can cause disease virulence= how severe it is primary= disease in healthy host Opportunistic- only in immunocompromised ppl ○ Pneumocystis pneumonia (aids patients) Virulency Measured in infectious dose and lethal dose # of microbes that kills half of test animals= LD50 Less number in ld50= more deadly virus Contact a. Direct b. Indirect c. Vertical d. Arthropod Walter reed confirmed in 1901 that aeded aegypti is the cause of yellow ever Carlos j finally thought aedes aegypti cause yellow fever Immunopathogenesis: virulence factors Friendly fire= immune sys attacking pathogen and causing tissue damage in hose Dengue hemorrhagic fever Virulence factors use genes to accomplish goal Toxins, proteins, capsules Must enter host, unique niche/location, trick immune sys, multiply, transmit  Koch’s postulates ○ Phenotype should be associated w/ pathogenic strains of species ○ Virulence genes should be isolated by m molecular methods ○ Spef inactivation of sus virulence genes should lead to measurable loss in virulence ○ Reversion of mutated gene should restore pathogenicity Pathogenicty island Virulence may be found on islands in chromosomes on plasmid A piece of genome that codes for pathogenesis/virulence factors ○ Gc content ○ Phage plasmid genes ○ Linkage to trna gene 1. Whic virulence factors associated w each pathogen 2. How facts help pathogen Attachment Factor promotes adhesin 1. Attach by pilli a. Type i: adhere to mannose residues i. Produces a static attachment to host cell ii. Grow from outer membrane iii. Uropathogenic e. Coli b. Type iv: twitching i. Continually assemble and disassemble ii. Grow from inner membrane iii. Neisseria meningitidi B. endotoxin (LPS) Made only by G neg bac Present in LPS of outer membrane ○ Lipid A released as bac die ○ Causes massive cytokine release from host cells ○ Can trigger, fever, shock, and death Portions on outer membrane (giraffe) C. secretion systems They use different secretion sys ○ Protein complexes present on cell mem of bac for secretion of substance (effector proteins) aka toxins ○ T2ss like a syringe. Release outside bac. Enzyme find its way to host cell. Pseudomonas aeruginosa and vibrio cholerae. Cells will lose water and minerals ○ Type iii is like syringe and needle. When protein is made, it is injected into the cell. Salmonella, yersinia, shigella, and escherchia species (G-) ○ Type iv, secretes protein and transfers dna, agrobacterium tumefaciens and bordetella pertussis (plant tumor) ○ Deliver dna to create gmo plants D. surviving within host Strep pneumo uses capsule to prevent phagocytosis Bind to antibodies and prevents opsonization Overview of microbial disease Mult kind of diseases ○ By organ sys ○ Skin,resp, gi,sys, CNS protozoa= euk Be able to match disease to type of microbe (bac/virus) ○ w/ characteristics Skin and soft tissue infect Staph aureus Boils Toxic shock syndrome superantignw MRSA ○ Major cause of infect in hospitals Skin infection scalded skyn to exfoliative toxin Antibio resistance Beta-lactamase and penicillinase Strep pyogenes (group a strep) Sore throat, scarlet fever, rheumatic fever ○ Flesh eating diseases ○ Cellulitis ○ Sensitive to antibiotic Prophages Enters bloodstream Resp trac infections Mucociliary escalator is primary defense ○ Bordetella pertussis (whooping cough) ○ Pneumonia Mucus ○ Strep pneumoniae ○ Capsule prevent phagocytosis ○ Bloodstream and brain Mycobacterium tuberculosis ○ Acid fast bacillus ○ Disseminate thru bloodstream ○ High mortality to multidrug resistant and high susceptibility of aids ○ 2ndary or reactivation TB ○ xdr-tb