Antio

Question 1

What are most antibiotics derived from?

Answer 1

→natural products by fermentation

Question 2

Why are antibiotics chemically modified?

Answer 2

→pharmacological properties ie can they survive in the stomach
→antimicrobial effect

Question 3

What is an example of totally synthetic antibiotics?

Answer 3

→sulphonamides

Question 4

What are natural products of fungi and bacteria derived from?

Answer 4

→- soil dwellers natural antagonism and selective advantage

→kill or inhibit the growth of other microorganisms

Question 5

Why is there selective toxicity?

Answer 5

→Due to the differences in structure and metabolic pathways between host and pathogen

Question 6

Why is selective toxicity difficult in viruses?

Answer 6

→intracellular

Question 7

What are the principles of selective toxicity?

Answer 7

→Due to the differences in structure and metabolic pathways between host and pathogen
→Harm microorganisms, not the host
→Target in microbe, not host (if possible)
→Difficult for viruses (intracellular), fungi and parasites
→Variation between microbes
→effect on commensals

Question 8

What is therapeutic margin?

Answer 8

→active dose (MIC) versus toxic effect

Question 9

What types of drugs have narrow therapeutic margins?

Answer 9

→toxic drugs

Question 10

Why is microbial antagonism important?

Answer 10

→Maintains flora

→Limits growth of competitors and pathogens

Question 11

What happens with loss of flora?

Answer 11

→bacterial or pathogen overgrowth

Question 12

Example of a disease cause by loss of flora

Answer 12

→Antibiotic Associated Colitis

Question 13

Which bacteria can cause pseudomembranous colitis?

Answer 13

Clostridioides difficile

Question 14

Which antibiotics most commonly cause colitis?

Answer 14

→Fluoroquinolones
→clindamycin,
→broad-spectrum lactams

Question 15

What conditions cause immunosuppression?

Answer 15

→cancer chemotherapy,
→transplantations,
→myeloma,
→leukaemias,

→HIV with low CD4

→Neutropenics,
→asplenics,
→renal disease,
diabetes

Question 16

How are antibiotics classified?

Answer 16

→Type of activity

→Structure

→ Target site for activity

Question 17

What are bactericidal antibiotics?

Answer 17

→Kill bacteria

→Used when the host defense mechanisms are impaired

→Required in endocarditis, kidney infection

Question 18

Describe bacteriostatic antibiotics

Answer 18

→Inhibit bacteria eg tetracyclin

→Used when the host defense mechanisms are intact

→Used in many infectious diseases

Question 19

What might a bacteriostatic antibiotic become if dose is increased?

Answer 19

→bactericidal if dose is increased

Question 20

Examples of broad spectrum antibiotics

Answer 20

→Cefotaxime

→

Question 21

Example of narrow spectrum antibiotics

Answer 21

→Penicillin G

Question 22

What are cephalosporins now most effective against?

Answer 22

→gram negatives

Question 23

What are basic penicillin active against?

Answer 23

→streptococci,
→pneumococci,
→meningococci,
→treopnemes

Question 24

Which bacteria are resistant against basic penicilin?

Answer 24

→Staphylococcus aureus

Question 25

What type of natural substance does penicilin have?

Answer 25

→Beta-lactams

Question 26

What are anti-staphylococcal penicillin?

Answer 26

→narrow spectrum, →G+ves, →beta-lactamase resistant

Question 27

Compare Pen G and Pen V?

Answer 27

Pen G →not acid stable →i/v or i/m →good for some G-ves as well as G+ves Pen V →oral (more acid stable than penG) →less active v G-ves, → same activity with G+ves as PenG

Question 28

What are broader spectrum penicillins?

Answer 28

→Spectrum of activity is similar to basic penicillins but also includes some Gram-negative organsims and also enterococci

Question 29

What are anti-pseudomonal penicillin?

Answer 29

→extended spectrum beta-lactam antibiotic →also G+ve, G-ve, anaerobes

Question 30

Example of anti-pseudomonal penicillin

Answer 30

→piperacillin

Question 31

What are beta-lactam/lactamase inhibitors?

Answer 31

→Spectrum like amoxicillin plus activity against some Gram-negatives and Staph aureus

Question 32

What are pseudomonal?

Answer 32

→a major cause of lung infections in people with cystic fibrosis. →thrive in moist environments and equipment

Question 33

What are the molecular structure classifications of antibiotics?

Answer 33

``` →nalidixic acid →ciprofloxacin →erythromycin →tetracycline →vancomycin →streptomycin(aminoglycosides) ```

Question 34

What are beta lactams?

Answer 34

Structural mimics of natural substrates for enzymes

Question 35

Why are beta-lactams important?

Answer 35

→Without B lactam there will be no antimicrobial property →stop bacterial growth by inhibiting PBPs that are indispensable for the cross-linking process during cell wall biosynthesis

Question 36

Which bacteria have beta lactams?

Answer 36

→penicillin

Question 37

What are carbepenams?

Answer 37

→effective antibiotic agents commonly used for the treatment of severe or resistant bacteria

Question 38

What are the modes of actions of bacteria?

Answer 38

``` →cell wall synthesis →DNA →folic acid →metabolism →cell membrane →protein sythesis- 50S and 30S →DNA and RNA processing- Gyrase, DNA-directed RNA polymerase ```

Question 39

Is tetracycline -cidal or static?

Answer 39

→static

Question 40

How do antibiotics reach membrane of gram negatives?

Answer 40

→porins in outer membrane mediate the passive diffusion of antibiotics

Question 41

What are the sites of action of inhibitors of bacterial cell wall synthesis?

Answer 41

→cytoplasm- synthesis of cell wall precursors →cytoplasmic membrane- synthesis of cell wall subunits →cell wall- new wall unit attachment

Question 42

What are D-alanines?

Answer 42

→incorporated by PBPs into peptidoglycan

Question 43

How does cycloserine inhibit bacteria cell wall synthesis?

Answer 43

→inhibits incorporation of alanine into cell wall precursor

Question 44

How does vancomycin inhibit bacteria cell wall syntesis?

Answer 44

→bind to terminal D-ala D-ala residues to prevent incorporation of subunit into peptidoglycan

Question 45

How does bacitracin inhibit bacteria cell wall synthesis?

Answer 45

→prevents dephosphorylation of phospholipid carrier which prevents regeneration of carrier to continue synthesis

Question 46

How do penicillin and cephalosporins inhibit bacteria cell wall synthesis?

Answer 46

→inhibit enzymes which catalyse cross linking

Question 47

Which bacteria is resistant against penicillin?

Answer 47

→mycoplasma pneumoniae | →have sterol packed cell membrane

Question 48

What type of antibiotic are folic acid synthesis inhibitors?

Answer 48

→bactericidal | →broad spectrum

Question 49

What are the targets of folic acid synthesis inhibitors?

Answer 49

→PABA | →dihydrofolate reductase- human DHFR is less inhibited hence selective toxicity

Question 50

How do aminoglycosides inhibit protein sythesis?

Answer 50

→Binding fmet t-RNA Initiation complex formation | →streptomycin

Question 51

How does gentamycin inhibit protein synthesis?

Answer 51

→Translocation of fmet t-RNA | to P site

Question 52

How does tetracycline inhibit protein synthesis?

Answer 52

→Competition with new Aminoacyl t-RNA at the A site

Question 53

How does chloramphenicol inhibit protein synthesis?

Answer 53

→Blocks formation of peptide bond peptidyl transferase | →Bind to 50S ribosome

Question 54

How do erythromycin and fusidic acid inhibit protein sythesis?

Answer 54

→Block translocation of peptidyl t-RNA

Question 55

What 2 infections can antibiotics be used prophylaxis?

Answer 55

→meningitis | →tuberculosis

Question 56

How is antibiotic given in a meningitis case?

Answer 56

→i/m injection

Question 57

Which conditions are antibiotics given topically?

Answer 57

→conjunctivitis →antiseptic creams →burns

Question 58

What does minimum inhibition concentration depend on?

Answer 58

``` →age →weight →renal and liver function →severity of infection →susceptibility of the organism →properties of the antibiotic ```

Question 59

What are the two pharmacodynamic properties of antibiotics killing activity?

Answer 59

→time-dependence | →concentration-dependence = max or area above MIC

Question 60

Why are antibiotic combinations used?

Answer 60

→life-threatening infections e.g. endocarditis, septicaemia →Polymicrobial infections →Less toxic doses →synergy eg. penicillin and gentamicin →reduce antibiotic resistance e.g. Tuberculosis