Abx

Question 1

Penicillin

Answer 1

G - IV, IM (“given at hosp”)
V - oral

MAO: D-ala-D-ala analog that binds PBPs (transpeptidases) to block transpeptidase crosslinking of peptidoglycan in cell wall

Resistance: Penicllinase (beta lactamase) cleaves beta-lactam ring

Question 2

Amoxicillin, Ampicillin, Aminopenicillin

Answer 2

“amped up penicillins”

Same MAO and resistance by penicillinases

Wider spectrum than penicillin (HHEELPSS - H flu, H pylori, E coli, enterococci, Listeria, Proteus, Shigella, Salmonella)

amOx - Oral

Question 3

Nafcillin, Dicloxacillin, Oxacillin

Answer 3

Same MAO as PCN but NOT resistant to penicillinases b/c bulky R group blocks access to beta lactam ring

Use naf for staph aureus (not MRSA)

Question 4

Piperacillin, ticarcillin

Answer 4

Same MAO and resistance as PCN but extended spectrum to cover Pseudomonas and gram neg rods

Combine w/ beta-lactamase inhibitor

Question 5

Beta Lactamase Inhibitors

Answer 5

CAST

Clavulanic acid

Avibactum

Sulbactam

Tazobactam

Question 6

Cephalosporins (generations 1-4)

Answer 6

Same MAO as PCN but less susceptible to penicillinases

Organisms not covered by generations 1-4: LAME

Listeria
Atypicals
MRSA
Enterococci

1: cefazolin, cephalexin (skin and soft tissue)
2: cefaclor, cefoxitin, cefuroxime (cover HENS - H flu, E coli, Neisseria, Serratia)
3: Ceftriaxone (good CNS), Ceftazidime (Pseudo)
4: Cefepime (Pseudo)

Resistance: structural change in PBPs

Question 7

5th Generation Cephalosporins

Answer 7

Ceftaroline

Broad gram pos and neg

Now covers Listeria, MRSA, enterococcus BUT no Pseudo or atypicals

Question 8

Carbapenems

Answer 8

Same MAO as PCN

Cover anaerobes but sig side effects (skin rash, GI, sz)

Imipenem (give w/ colistin), meropenem, ertapenem, doripenem

Question 9

Monobactams

Answer 9

Aztreonam

Same MAO as PCN but less susceptible to beta-lactamases

Specifically binds PBP 3

synergistic w/ aminoglycosides

Gram neg only; good for allergy

Question 10

Vancomycin

Answer 10

MAO: binds D-ala-D-ala portion of wall precursors to prevent synthesis of peptidoglycan

Resistance: not sensitive to beta lactamases but AA modification of D-ala-D-ala to D-ala-D-lac

Nephrotoxic, Ototoxic, Thrombophlebitis (NOT)
Red Man’s Syndrome

MRSA, C diff, some enterococcus

Question 11

Aminoglycosides

Answer 11

Gentamicin, tobramycin, neomycin, amikacin, streptomycin

Bacteriacidal

MAO: bind 30S subunit to irrev inhibit formatino of initiation complex - misread mRNA and blocks translocation

Need oxygen for uptake so does not work on anaerobes

Nephro and ototoxic

Resistance: acetylation, phosphorylation, adenylation by bacterial transferase enzymes

Question 12

Tetracyclines

Answer 12

Tetracycline, Doxycycline

MAO: bind 30S subunit to prevent aminoacyl-tRNA attachment (bacteriostatic)

Do not take w/ divalent cations

Resistance: dec uptake or efflux pumps

Good for borrelia, m pneumonia, rickettsia, chlamydia

Question 13

Tigecycline

Answer 13

Tetracycline derivative; also binds 30S; bacteriostatic

MRSA, VRE (aggressive like tiger)

Question 14

Chloramphenicol

Answer 14

MAO: blocks peptidyltransferase at 50S subunit (bacteriostatic)

Meningitis and Rocky Mt Spotted Fever

Resistance: plasmid encoded acetyltransferase blocks drug

Question 15

Clindamycin

Answer 15

MAO: blocks peptide translocation at 50S subunit (bacteriostatic)

Anaerobic infections above diaphragm (aspiration or oral)

Bad for C diff

Question 16

Linezolid

Answer 16

MAO: inhibit protein synthesis by binding 50S subunit and prevent formation of initiation complex

Gram POS only - MRSA and VRE

Resistance: pt mutation of rRNA

Question 17

Macrolides

Answer 17

Azithromycin, clarithromycin, erythromycin

MAO: inhibit protein synthesis by preventing translocation (macro-SLIDE) bind 23S rRNA of 50S subunit

Side effects = MACRO (motility, arrhythmia, cholestatic hepatitis, rash, eOsinophilia)

Atypicals

Resistance: methylation of 23S rRNA binding site

Question 18

Sulfonamides

Answer 18

SMX, sulfisoxazole, sulfadiazine

MAO: inhibit dihydropteroate synthesis thus no folate synthesis; bacteriostatic

UTI, Nocardia

Resistance: altered dihydrop synthase enzyme, dec uptake, inc PABA precursor synthesis to overcome

Question 19

Dapsone

Answer 19

MAO similar to SMX but diff structure

Uses: PJP prophylaxis and leprosy

Question 20

Trimethoprim

Answer 20

MAO: inhibits bacterial dihydrofolate reductase (bacteriostatic)

PJP, toxo prophylaxis, in combo w/ SMX for UTI

Bad for marrow

Question 21

Fluoroquinolones

Answer 21

Ciprofloxacin, levo, oflo, moxi, gemifloxacin, enoxacin

MAO: inhibit prok topoisomerase II (DNA gyrase) and topo IV (bacteriacidal)

NO ANTACIDS

Tendon rupture

Resistance: chromosome encoded mutation in DNA gyrase, plasmid-mediated resistance, efflux pumps

Question 22

Daptomycin

Answer 22

MAO: lipopeptide that disrupts cell mem of gram pos cocci by creating transmembrane channels

Uses: MRSA skin infections, bacteremia, endocarditis, VRE

Do not use for pneumonia b/c inact by surfactant

Question 23

Metronidazole

Answer 23

MAO: form toxic free radical metabolites in bac cell that damade DNA (bacteriacidal)

Metal taste

Question 24

Rifamycins

Answer 24

Rifampin and rifabutin

MAO: Inhibit DNA-dep RNA polymerase

Inc CYT P450 for rifampin

Orange body fluids (non-hazardous)

Resistance: mutations dec binding to RNA polymerase; RAPID if used alone

Tb

Question 25

Isoniazid

Answer 25

MAO: dec synthesis of mycolic acids (requires catalase-peroxidase encoded by KatG to convert to active metabolites)

CYP450 inhibition, B6 def

Resistance: mutations leadint to KatG underexpression

Tb prophylaxis

Question 26

Pyrazinamide

Answer 26

Unknown MAO

Converted to active pyrazinoic acid

Works best at acidic pH (in phagolysosomes)

Tb

Question 27

Ethambutol

Answer 27

MAO: dec carb polymerization of mycobacterium wall by blocking arabinosyltransferase

Red-green color blindness

Tb

Question 28

Streptomycin

Answer 28

MAO: interferes w/ 30S ribosome

2nd line for Tb