Lecture 4

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What does antibiotic mean? =Anti - against, biotic - life

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Question 2 of 54

What is the strict definition of an antibiotic? =(2) A substance produced by a microorganism that is effective in killing or inhibiting the growth of other microorganisms

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What do we call synthetic antibiotics?= Antimicrobrial agents

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What are examples of organic antibiotics?= (2) Penicillin, erythromycin

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What are examples of semi synthetic antibiotics?= (3) Amoxicillin, methicillin, oxacillin

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Question 6 of 54

What are examples of antimicrobial agents?= Sulfonamides, quinolones

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Question 7 of 54

What are desirable qualities of antibiotics? =(6) Kill inhibit pathogens, not harmful to host, not allergenic to host, stable for storage, fast acting, long working

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Question 8 of 54

What is an antibiotic's antibacterial spectrum? =The range of variety of bacteria an antibiotic is effective against

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What is bacteriotatic activity?= Arrests growth of bacteria

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What is bacteriocidal activity?= Kills bacteria

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Question 11 of 54

What are reasons for antibiotic combination?= (4) Broaden spectrum, polymicrobial infections, prevents resistance in long treatments, synergistic effect

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Question 12 of 54

What is antibiotic antagonism?= Where antibiotics inhibit each other so the sum is less than when giving each one alone

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Question 13 of 54

What is antibiotic synergism? =Where two antibiotics work together with a sum result that is greater than giving each one alone

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What does an antibiogram show?= How senstitve/susceptible a bacteria is to an antibiotic

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Question 15 of 54

What can be calculated from the diameter of an antibiogram?= Minimum Inhibitory Concentration (MIC)

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Question 16 of 54

How can MBC be determined?= (2) Subculturing bacteria in graded dilutions. The first dilution where nothing grows in vitro is MIC. The inihibited cultures are then grown on agar. The first dilution where there is no growth is the MBC

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Question 17 of 54

What is targeted in bacteria with antibiotics? =(5) Cell walls of bacteria, RNA, DNA, Antimetabolites, Protein synthesis

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Question 18 of 54

What are examples of β lactam antibiotics?= (3) Penicillin, cephalosporins, carbapenems

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Question 19 of 54

What is the enzyme responsible for crosslinking of bacterial peptide chains?= Transpeptidase (penicillin binding protein)

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Question 20 of 54

What happens to bacteria if cell wall structure is weakened? = Osmotic lysis (take up water, swell and lyse)

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Question 21 of 54

Which bacteria are intrinsically resistant to penicillin?= Gram -ve

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How did chemists overcome penecillin resistant bacteria?= Modified penicillin to allow it enter porins on bacteria cell wall

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Which antibiotic is not β lactam but still prevents cell wall crosslinking? =Vancomycin 

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Which bacteria are sensitive to vancomycin?= Gram +ves, MRSA

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How does vancomycin work?= Enters between glycopeptide chains and blocks cross linking

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Question 26 of 54

How do rifumycins work?= Inhibits RNA polymerase in bacteria

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Question 27 of 54

Which antimicrobials target DNA topoisomerases? =(2) Quinolones and fluroquinolones

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How do antimicrobials that target DNA topoisomerases work?= Prevent unwinding of DNA during transcription

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Question 29 of 54

What are the antimetabolites?= (2) Sulfonamides, trimethoprim

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How do antimetabolites work?= Block pathway for synthesis of tetrahydrofolic acid which is required to make nucleic acids

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Question 31 of 54

Which antibiotics target protein synthesis?= Aminoglycosides

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What are some examples of aminoglycosides?= (3) Neomycin, gentamycin, kanamycin

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How do aminoglycosides work? =Freeze 30s initiation complex

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Which antibiotic are aminoglycosides synergistic with?= Penicillins

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What bacteria are aminoglycosides effective against?= (2) Aerobic, gram -ve

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Question 36 of 54

How do tetracyclines work?= Inhibits binding of tRNA on ribosome

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Question 37 of 54

Which antibiotics bind to the 50s subunit of mRNA? =(2) Macrolides (erythromycin), Chloramphenicol

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Question 38 of 54

How are some bacteria intrinsically resistant? =(3) Metabolic inactivity (nothing to target (ribosomes etc,), lack of target structure (eg. cell wall), exclusion (structurally resistance to penetrance)

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How are some bacteria genetically resistant? =(2) Chromosomal resistance change target receptor (eg. RNA polymerase)

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How does chromosomal mutation occur?= Point mutations

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How may a bacteria acquire resistance? =(3) Transformation, conjucation, transduction

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How does conjugation occur?= Resistant gene in DNA is duplicated in plasmid which is transferred to bacteria via pilli

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How does transduction occur? =Viruses infect bacteria, multiply in bacteria incorporating resistant bacterial gene, infect other bacteria with resistant gene

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How does transformation occur?= Random uptake of DNA fragments from dead bacteria

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What are antibiotic resitant mechanisms? =(4) Exclusion of antibiotic from site of action, new or modified target, efflux pump, modification or degradation of antibiotics

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Question 46 of 54

What does a β lactamase do?= Enzyme that destroys β lactam ring in β lactam antibiotics

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Question 47 of 54

What are β lactamase resistant penicillins?= (3) Methicillin, oxacillin, flucloxacillin

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Question 48 of 54

What is an example of a β lactamase inhibitor? =Clavulanic acid

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Question 49 of 54

How is augmentin produced?= (2) Amoxicillin + clavulanic acid

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Question 50 of 54

How is MRSA resistant?= New target - penicillin binding protein (transpeptidase) 

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What are multi-drug resistant strains?= Resistant to more than one class of drug

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What are pan drug-resistant strains?= Resistant to all clinically safe drugs (superbugs)

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Question 53 of 54

What are examples of drug resistant bacteria?= MRSA (methicillin resistant S. aureus), VISA (Vancomycin-intermediate S. Aureus - resistant to usual dosage), VRSA (Vancomycin resistant S. aureus - resitant to all anti staph drugs), VRE (Vancomycin resistant enterococcus), MRTB (multi drug resistant mycobacterium) 

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Question 54 of 54

Which drug is MRSA not resistant to?= Vancomycin

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