Antibiotics

Question 1

5 targets for antibacterials

Answer 1

cell wall, PM, protein synth, nucleic acid synth, enzyme/metab

Question 2

cell wall antibacterials: major categories (Beta lactams) - 5

Answer 2

monobactams, penicillin, cephalosporin, cabepenam

Question 3

cell wall antibacterials - non beta lactams

Answer 3

vancomycin (inhibit peptidoglycan elongation, only useful against gram +)

Question 4

penicillins

Answer 4

narrow spectrum: penicillin (strep pyrogenes), ampicillin (gram -) oxacillin (staph).

broad spectrum: pipercillin, ticarcillin (use against antibiotic resistant bugs)

Question 5

cephalosporins

Answer 5

5 “Cef-somethings”.

Question 6

carbenapems

Answer 6

-“apem”. big gun drugs, hospital use only, but resistant emerging

Question 7

monobactams

Answer 7

clindamycin (risk factor for c diff)

Question 8

beta lactamase inhibitor combos

Answer 8

clavulonic acid (amoxicillin/ticarcillin)
sulbactam (ampicilin
tazobactam (piperacillin)

Question 9

cell membrane antibiotics

Answer 9

daptomycin (grap +) –> rapid loss of membrane potential.

use against staph aureus + enterococcus

Question 10

protein synthesis antibiotics - major classes (4)

Answer 10

tetracyclines, aminoglycosides, macrolides, lincosamides

Question 11

tetracyclines

Answer 11

old, lots of resistance agains them. bacteriostatic.

Question 12

macrolides

Answer 12

erithromycin/clarithromycin/azithromycin. outpatient URTIs.

Question 13

lincosamides

Answer 13

clindamycin. (gram +)

Question 14

aminoglycosides (3)

Answer 14

gentamycin, tobramycin, amikacin. (parenteral, hospital use, gram -).

side effects: renal toxicity, ototoxicity

Question 15

nucleic acid antibiotics

Answer 15

fluoroquinolenes (end in “floxacin”)

prevent DNA supercoiling (inhibit DNA gyrase)

broad spectrum, oral/parenteral. Lots of resistance.

Question 16

metabolism targeting antibiotics

Answer 16

bactrim. Sulfonamide is PABA analog and inhibits DHF formation, trimethaprim is DHF analog and inhibits tetrahydrofolic acid formation. double action = less resistance, and synergistic.

Question 17

2 types of antibiotic resistance

Answer 17

inherent (vancomycin is inherently resistant to gram -)

acquired (through mutation - bacteria have short replication time and lots of mutation… selective pressure to evolve acquired resistance)

Question 18

define resistance and sensitivity

Answer 18

resistance - bug can grow with drug present

sensitivity - bug cannot grow with drug present

Question 19

the 4 types of horizontal spread of resistance

Answer 19

transformation, transduction, transposition, conjugation

Question 20

what is a plasmid

Answer 20

circular dbl stranded bacterial DNA, not required for cell growth

Question 21

transformation

Answer 21

naked DNA is taken up by bacteria and incorporated into genome. Seen in GI.

not efficient

Question 22

transduction

Answer 22

viral vector transmits bacterial DNA between bacteria

not efficient

Question 23

transposition

Answer 23

rapid gene jumping via plasmids (host/plasmid, plasmid/plasmid, plasmid/host)

Question 24

conjugation

Answer 24

bacterial sex, producing a plasmid which can then be transposed.

requires direct contact

Question 25

what maintains antibiotic resistance?

Answer 25

buying cheap antibiotics w/o prescription, pt compliance, antibiotics in animal feed, urine metabolites of antibiotics, bad doctoring (treating viral URTIs with antibiotics)

Question 26

mechanism of action for beta lactams

Answer 26

bind to transpeptidase enzyme complex, prevent peptidoglycan cross linking. Holes in cell wall = lysis (osmotic barrier broken)

Question 27

bactericidal vs bacteriostatic

Answer 27

kill vs depend on immune system to kill (just prevent growth/replication)

Question 28

narrow vs broad spectrum

Answer 28

targeted vs broad. Try to aim for narrow (doesn’t promote as much resistance, not as bad an effect on normal microbiota)

examples: narrow = penicillin, broad = gentamycin

Question 29

mechanisms of antibiotic resistance (3)

Answer 29

alter the target, alter drug access to target, metabolize drug.

Question 30

mechanisms of antibiotic resistance (altering the target)

Answer 30

can either 1) decrease target site affinity for drug (MRSA - altered PBP for beta lactams), or 2) alter target site (confers amino glycoside and quinolone resistance)

Question 31

mechanisms of antibiotic resistance (alter drug access to target)

Answer 31

can either 1) alter permeability to drug, or 2) increased efflux.

example:
GRAM -: alterred porin proteins + efflux pumps
anti-Quinolones: altered cell wall + efflux pumps

Question 32

mechanisms of antibiotic resistance (metabolize drug)

Answer 32

anti-B lactams: 1) b lactamases, 2) ESBLs (extended spectrum b lactamases) - E coli + Klebsiella

Aminoglycoside modifying enzymes - spread by plasmids

Question 33

the story of STAPH AUREUS antibiotic resistance:

Answer 33

1950s - penicillin –> developed b lactamase –> 1980s methicillin –> altered PBP –> MRSA
1990s vancomycin –> borderline resistant now (VISA/VRSA - vancomycin resistant staph aureus).

new strain: COMMUNITY ASSOCIATED MRSA - CA-MRSA

Question 34

epidemiologic defn of CA-MRSA vs microbiology defn

Answer 34

epi: caught it from non-healthcare place

microbio - different methicillin resistance gene + virulence factors

Question 35

story of VRE

Answer 35

VRE = vancomycin resistent enterococci (gram + normal GI flora, e faecium/faecialis)

infects immunocompromised ppl, not virulent.

screening is useless (invasive + endemic)

Question 36

resistance in enterobacteria (gram -)

Answer 36

ESBL (extended specrum beta lactamases) - e coli + klebsiella. Resistant to CEPHALOSPORINS.

AmpC resistance (providencia, serrate, enterobacter). INDUCIBLE RESISTANCE while on treatment, non-transferrable.

CRE (carbapenem resistant enterobacteria) - resistant to CARBAPENEMS, CEPHALOSPORINS + PENICILLINS. New. (e coli, klebsiella, enterobacter)