Antibiotics

Front 1

beta-lactam action

Back 1

target PG syntehsis , have a structure very similar to D-alanyl-alanine so it binds to the active site of the transpeptidase.

Front 2

Structure of Peptidoglycan

Back 2

Carb backbone of alternating N-acetylmuramic acid and N-acetylgycosamine connected with L-ALA, D-Gly-NH2 L-Lys (in gram - mDAP) , D-Ala . IN E. coli then the two side chains are directly connected and in S.Aureus L-Lys and D-Alanine are connected via 5 Gly

Front 3

How do bacteria become resistant to beta-lactams

Back 3

The enzyme beta lactamase cleaves the beta lactam ring.

Front 4

How do we over come beta-lactamase

Back 4

Chemically modified side-chain to give steric hinderance - fluctoxacilin (only effective vs gram + though)

Combine with clavulonic acid (amoxicilin) or sulbactam (ampicilin)

Front 5

What are problems of benzyl- penicillin? What antibiotics overcome them?

Back 5

It is not effective vs Gram negatives, poor absorption from the Gi . (amoxicillin- broad spectrum, well absorbed) it can lead to hypersensitivity reaction (cephalosporins, broad spectrum)

Front 6

Is penicillin bacteriocidic or bacteriostaitc

Back 6

Bacteriocidic to fast proliferating, bacteriocidic otherwise. It kills by osmotic shock

Front 7

What's another way to destroy bacterial cell walls? HOw is it activated?

Back 7

Isoniazid . It targets long chain Mycolic acids so is used against TB. It needs to be activated by bacterial catalase peroxidase

Front 8

What ribosomes do bacteria have?

Back 8

they have 70s with a 50s and 30s subunit

Front 9

What ribosomes do humans have

Back 9

80s with 60s and 40s

Front 10

How do aminoglycosides work

Back 10

bind to 30s subunit binding both on a ribosomal protein and rRNA, lead to inhibition of the initiation comple of translation and mRNA misreading. Membrane damage in the bacteria occurs and it leads to death.

Front 11

Examples of aminoglycosides and what are they used against

Back 11

Gentamicin vs gram negative rods and streptomycin (now mostly a reseve) vs tuberculosis and plague. It has major side effects - can give you vertigo, tinitus, fever, rashes

Front 12

How does tetracycline work

Back 12

Blocks tRna from entering the receptor site, can block both human and bacterial chromosomes, specificity based on significantly greater uptake in bacteria

Front 13

Is tetracycline bacteriostatic or bacteriocidic

Back 13

It is bacteriostatic

Front 14

Side effects of tetracycline

Back 14

It is incorporated into calcifying tissues so it leads to brown staining of teeth in children ; also supresses normal flora of the gut

Front 15

Uses of tetracycline

Back 15

Against acne and rosacea most often because there is wide spread resistance for it

Front 16

How do macrolides work?

Back 16

They act on the 50S subunit of the ribosome and prevent the peptidyl transferase from adding the growing polypeptide chain to the peptide brought in by the tRNA.

Front 17

What antibiotic works like macrolides

Back 17

Chloramphenicol - it is broad spectrum and no longer first-line treatment in the first world but as is cheap to manufacture still a good choice for the developing world. Broad range,

Front 18

When is chloramphenicol bacteriostatic and bacteriocid

Back 18

Bacteriostatic vs S.typhi but due to resistance not really used anymore and bactericidal against meningitis causing organisms. Excellent BBB passage

Front 19

What are side effects of chloramphenicol

Back 19

It acts also on mitochondria as they also have 70s and as such it is partially toxic to them. SO it is a bone marrow depressant

Front 20

Examples of macrolides

Back 20

erythromycin - bacteriostatic wide spectrum ,
azythromycin- similar spectrum, slightly better vs gram negatives- can be used to treat acute otitis media, pneumonia

Front 21

A vital component of guanine, thymine and adenine

Back 21

Tetrahydrofolic acid. We acquire its precursor dihydrofolic acid from diet,

Front 22

How do bacteria synthesise dihydrofolic acid

Back 22

From dihydropteroate. It has no use in human cells. To make dihydropteroate PABA and dihydropteroate phosphate joined by dihydropteroate synthase

Front 23

What are sulfonamides and how can bacteria overcome them?

Back 23

PABA analogues , bacteriostatic action. As it is a competitive inhibitor of dihydropteroate synthesis , excess PABA or obtainining dihydrofolate from diet. Used for UTIs but are now rarely used due to bacterial resistance for them

Front 24

Example of sulfonamide

Back 24

Sulfamethoxazole

Front 25

What can be given together with a sulfonamide

Back 25

Trimethoprim which acts on a subsequent step, inhibiting dihydrofolate reductase and doesn't allow bacteria to make tetrahydrofolate

Front 26

What do quinolones do?

Back 26

Inhibit DNA gyrase which is an enzyme needed to cut the DNA during replication to relieve the stress of the loop

Front 27

Name one quinolone

Back 27

ciprofloxacin- against a broad range of bacteria but can damage growing bone

Front 28

HOw do rifamycins work ?

Back 28

Block synthesis of mRNA selectively in bacteria. They do this by inhibiting the RNA polymerase and are bactericidal.

Front 29

An example of rifamycin and what are they used for

Back 29

Rifampicin, to treat TB and inactive meningitis with other antibiotics, as well as methicillin resistant Staph aureus in combo with fusidic acid.

Front 30

Adverse effects of rifamycins

Back 30

Hepatotoxic, induce the upregulation of cytochrome P450 in liver, increasing the rate of metabolism of hormones and drugs which can also reduce the efficiency of hormonal contraception. Turns urine, tears and saliva orange

Front 31

what is a lipopeptide antibiotic? What is it used for?

Back 31

Daptomycin for treatment of life threatening gram positive / systemic infecitons. It can attack multi-resistant bacteria