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Microbiology ` microbiology—aNtimicrobials Microbiology ` microbiology—aNtimicrobials SEcTioN ii 195

Fluoroquinolones Ciprofloxacin, enoxacin, norfloxacin, ofloxacin; respiratory fluoroquinolones—gemifloxacin,
levofloxacin, moxifloxacin.

mecHaNism Inhibit prokaryotic enzymes topoisomerase
II (DNA gyrase) and topoisomerase IV.
Bactericidal. Must not be taken with antacids.
cliNical Use Gram ⊝ rods of urinary and GI tracts (including
Pseudomonas), some gram ⊕ organisms, otitis
externa.

aDVerse eFFects GI upset, superinfections, skin rashes, Fluoroquinolones hurt attachments to your
headache, dizziness. Less commonly, can bones.
cause leg cramps and myalgias.
Contraindicated in pregnant women, nursing
mothers, and children < 18 years old due
to possible damage to cartilage. Some may
prolong QT interval.
May cause tendonitis or tendon rupture in
people > 60 years old and in patients taking
prednisone. Ciprofloxacin inhibits cytochrome
P-450.
mecHaNism oF resistaNce Chromosome-encoded mutation in DNA
gyrase, plasmid-mediated resistance, efflux
pumps.

Daptomycin
mecHaNism Lipopeptide that disrupts cell membranes of
gram ⊕ cocci by creating transmembrane
channels.
cliNical Use S aureus skin infections (especially MRSA), Not used for pneumonia (avidly binds to and is
bacteremia, endocarditis, VRE. inactivated by surfactant). “Daptomyskin” is
used for skin infections.

aDVerse eFFects Myopathy, rhabdomyolysis.

Metronidazole

mecHaNism Forms toxic free radical metabolites in the
bacterial cell that damage DNA. Bactericidal,
antiprotozoal.

cliNical Use Treats Giardia, Entamoeba, Trichomonas, GET GAP on the Metro with metronidazole!
Gardnerella vaginalis, Anaerobes (Bacteroides, Treats anaerobic infection below the diaphragm
C difficile). Can be used in place of amoxicillin vs clindamycin (anaerobic infections above
in H pylori “triple therapy” in case of penicillin diaphragm).
allergy.
aDVerse eFFects Disulfiram-like reaction (severe flushing,
tachycardia, hypotension) with alcohol;
headache, metallic taste.

FAS1_2019_03-Microbiology.indd 195 11/14/19 12:22 PM