DDT 16 - Antibiotics

Question 1

New antibiotic

Answer 1

An antibiotic not used clinically before, but belonging to an existing class of antibiotics

Question 2

novel antibiotics

Answer 2

An antibiotic with a mechanism of action that has never been used against bacteria before - less likeliness of resistance

Question 3

name the 4 enzymes S. aureus normally produces

Answer 3

Penicillin Binding Proteins 1-4

Question 4

how can antibiotics react to PBPs

Answer 4

PBP can be modified by B-lactam antibiotics and leads to inhibition and bacterial death

Question 5

How does MRSA react to PBP inhibition from beta-lactam antibiotics

Answer 5

MRSA produces an altered PBP (PBP2a), which is not inhibited by b-lactam antibiotics and can perform the functions of the 4 PBPs of S. aureus.

Question 6

last resort drug for MRSA

Answer 6

Vancomycin - resistance soon began

Question 7

treatment of MRSA

Answer 7

linezolid
synercid
daptomycin

Question 8

what class does linezolid belong in

Answer 8

oxazolidinone class
novel antibiotics

Question 9

linezolid is effective against disease

Answer 9

MRSA and VRE infections

Question 10

Mechanism in which linezolid is used to stop infection

Answer 10

inhibition of protein synthesis

Question 11

synercid has what 2 variations

Answer 11

quinupristin

dalfopristin

Question 12

what illness does synercid treat

Answer 12

intravenous treatment of VRE caused infections and skin infections of staphylococcus aureus and streptococcus pyogenes

Question 13

how does synercid treat infection

Answer 13

inhibit protein synthesis by binding to 70S ribosome both agents bind at same place in ribosome

Question 14

synercid bacteriostatic or bactericidal

Answer 14

Bacteriostatic when administrated individually, but act synergistically in combination (bactericidal).

Question 15

daptomycin is used for what kind of infections

Answer 15

gram positive infections particularly in the skin

Question 16

how does daptomycin treat infection

Answer 16

Binds to cell membranes and causes their depolarisation

interrupts protein, DNA and RNA synthesis

Question 17

why does daptomycin have slow emergence of resistance

Answer 17

is novel antibiotic

Question 18

enterococci

Answer 18

Antibiotic resistant opportunistic pathogens commonly found in patients hospitalized for prolonged periods and receiving multiple courses of antibiotics.

Question 19

what enterococci are most difficult to treat

Answer 19

Enterococcus faecium

Question 20

2 enterococci

Answer 20

Enterococcus faecalis and Enterococcus faecium

Question 21

how many years were for emergence resistance against vancomycin to occur

Answer 21

32 years it took 5 genes

Question 22

how many years were for emergence resistance against penicillin to occur

Answer 22

2-3 years 1 gene

Question 23

what kind of antibiotic is vancomycin

Answer 23

glycopeptide antibiotic

Question 24

how does vancomycin treat infection

Answer 24

inhibit cell wall biosynthesis
blocks substrate
must interact with peptide chain with 5 hydrogen bonds

Question 25

how does bacteria for vancomycin occur?

Answer 25

Loss of a single hydrogen bond when vancomycin binds to substrate = 1,000-fold drop in drug-binding affinity: enough for the bacteria to become resistant

Question 26

clostridium difficile Associated Disease

Answer 26

Clostridium difficile is a Gram-positive, spore-forming, obligate anaerobic bacterium.

Question 27

what does clostridium difficile mainly cause

Answer 27

nosocomial diarrhoea | toxins A and B can cause extensive damage to colonic mucosa

Question 28

when does clostridium difficile Associated Disease occur

Answer 28

90 of CDAD occur after or during antibiotic treatment

Question 29

treatment of CDAD

Answer 29

1. medical therapy - discontinuation of the inciting antibiotics 2. specific antibiotic treatment metronidazole = first line antibiotic agent - vancomycin as alternate agent for second line therapy spores can still stay in colon of patient

Question 30

metronidazole is what kind of compound

Answer 30

prodrug | Nitroaryl compound

Question 31

how is metronidazole activated

Answer 31

Prodrug activated by anaerobic organisms by reduction of the nitro group to hydroxylamine group During reduction, reactive derivative/species produced that can damage bacterial cell components such as DNA, proteins, membranes

Question 32

advantages of metronidazole as first line agent

Answer 32

Prevent selection of vancomycin-resistant enterococci | Reserve vancomycin use for the treatment of MRSA infections

Question 33

when is vancomycin prescribed instead of metronidazole

Answer 33

Failure to respond to metronidazole after 3-5 days of treatment Pregnancy & lactation Intolerance to metronidazole Metronidazole-resistant infecting organism Critically ill patients

Question 34

what percentage of gram negative bacteria are responsible for HAI

Answer 34

30%

Question 35

main HAIs caused by gram negative bacteria

Answer 35

pneumonia bloodstream infection urinary tract infection

Question 36

how does bloodstream infection occur

Answer 36

Most commonly caused by central vascular catheter. | Can be associated with an initial infection of the lung, genitourinary tract, or abdomen.

Question 37

how is UTI caused

Answer 37

Associated almost exclusively with urethral catheterization. | Risk of infection increases by 5 to 10% per day.

Question 38

bacterial resistant against penicillin

Answer 38

beta-lactamases

Question 39

reisstance against cephalosporins

Answer 39

Extended Spectrum | b-Lactamases (ESBLs)

Question 40

resistance against Carbapenems

Answer 40

Carbapenemases

Question 41

what does carbapenemases inactivate and what is it inhibited by?

Answer 41

Carbapenemases can inactivate all types of b-lactam antibiotics and are not inhibited by inhibitors of b-lactamases (clavulanic acid). Represent one of the main clinical challenges.

Question 42

antibiotic treatment of HAI in response to resistance

Answer 42

Gram-negative pathogen expressing ESBLs: Carbapenems (eg. meropenem Gram-negative pathogen expressing carbapenemases: - Colistin or tigeclycine.

Question 43

what kind of antibiotic is meropenem

Answer 43

Carbapenem, b-lactam antibiotic

Question 44

describe how strcuture of meropenem is similar to penicillin

Answer 44

Structure similar to penicillins: | bicyclic structure, with 1 b-lactam ring and a 5-membered ring

Question 45

how does meropenem different to pencillin

Answer 45

however, sulfur atom not in the 5-membered ring, but attached on that ring as part of a functional side-chain 1 carbon-carbon double bond in the 5-membered ring

Question 46

what type of antibiotic is colistin

Answer 46

Polymyxin antibiotic. | Peptide antibiotic

Question 47

describe structure of colistin and from what process is it produced?

Answer 47

Mixture of 2 cyclic peptides (colistins A and B) produced by fermentation of Bacillus polymyxa.

Question 48

colistin is used as a last resort for what infection and why

Answer 48

'last resort’ antibiotic against MDR Gram-negative bacteria. last resort because of nephrotoxicity

Question 49

how does colistin attack bacteria

Answer 49

Binds to phosphate groups in lipids on the cell cytoplasmic membrane. Disrupts its integrity

Question 50

describe type of tigecycline

Answer 50

Novel tetracycline class: glycylcyclines | Broad spectrum antibiotic.

Question 51

how is tigecycline characterised

Answer 51

Characterised by additional glycylamido substituent.

Question 52

how does tigecycline treat infection

Answer 52

Inhibitor of bacterial protein synthesis by binding to the 30S ribosomal subunit  blocks entry of amino-acyl tRNAs into the ribosome.