Antibiotics Flashcards
Which ABx is active against MRSA?
Ceftaroline
With increasing cephalosporin generations, how is the coverage changing?
Increasing G- coverage and less G+ coverage (until 4 and 5 which are broad spectrum)
1st generation cephalosporin?
Cefazolin
2nd generation cephalosporin?
Cefoxatin
3rd generation cephalosporin?
Ceftriaxone
4th generation cephalosporin?
Cefepime
5th generation cephalosporin?
Ceftaroline
First generation cephalosporin is active against?
MSSA and strep infections
Mechanism of action of Beta-Lactam inhibitors?
Interruption of the D-Ala-D-Ala by binding to the PBPs which inhibits the cross-linking of the cell wall
Penicillin V and G are active against?
G+ bacilli and cocci, most anaerobes
What causes resistance to penicillins?
B-lactamases which render the ABx ineffective because the B-lactam ring is broken
Nafcillin is active against?
MSSA and strep
How is nafcillin different from penicillin?
Bulkier R group which helps with inactivation by B-lactamases
Amoxicllin is part of which group of ABx?
Aminopenicillins
What enables amoxicillin to be more active than penicillin?
the amino group as an R group which helps get the ABx through the G- outer membrane
Piperacillin is active against which major group of infections?
Pseudomonas
What are the B-lactamases inhibitors?
-tazobactam and -clavulanate
Adverse effects of piperacillin?
NVD, neurologic reactions from high dose IV who have poor renal function, allergic reactions; SJS
Ceftriaxone is inactive against?
G- strains that express ESBLS
Aztreonam is part of which group of ABx
Monobactams
What is axtreonam’s spectrum of action?
Aerobic Gram Negative
Imipenum is paired with what to protect against kidney degradation?
Cilistatin
What is causing resistance to imipenum-cilistatin?
Class A KPC and Class B NDM-1 metalo-beta-lactamases
Aztreonam is a good alternative drug for patients with…?
Penicillin allergy or can’t handle a aminoglycoside
What is the mechanism of action of vancomysin?
Binding to D-Ala to prevent the addition of NAM-NAG
What group of ABx does vancomycin belong to?
glycopeptides
What is vancomysin’s spectrum of action?
Gram + aerobes and anaerobes
What causes the resistance to vancomycin?
The changing of the D-Ala-D-Ala
What are the side effects of vancomycin?
Ototoxicity and nephrotoxicity
What is the MOA of fosfomycin?
Inhibition of enolpyruvate so NAM can’t be synthesized anymore
What is fosfomycin used for?
Broad spectrum UTIs
What group does gentamicin belong to?
Aminoglycosides
What is the spectrum for gentamicin?
Gram negative aerobes
What is the mechanism of action for gentamicin?
Binding to the 30S subunit blocking the initiation complex and causing misreading of the mRNA
Describe the resistance that has developed against aminoglycosides.
Bacterial kinase and acetyltransferase inactivation of the antibiotics
What symptoms does the ototoxicity cause due to the aminoglycosides?
Tinnitus, ataxia, dizziness due to cochlear and vestibular damage
When shouldn’t aminoglycosides be used?
Pregnancy and Myasthenia gravis
How does the structure of aminoglycosides affect its distribution?
No CNS, lungs, or eye penetration; low oral availability since it’s a large hydrophilic molecule
How do tetracyclines affect protein synthesis?
Bind to the 30S subunit and inhibit translation by binding to the A site of mRNA causing bacteriostatic effects
Tetracyclines can be used to treat…
atypical bacteria, tick borne illnesses, and protozoans
What can cause decreased absorption of tetracyclines?
Taking with a divalent cation
Why shouldn’t doxycycline be used in children?
Binds to Ca and deposits there causing discoloration of teeth and accumulates in bones
What other side effects does doxycycline have?
Photosensitivity reactions
How has resistance developed against tetracyclines?
Increased efflux out of the bacterial cell and alteration of the ribosomes
What ABx is a macrolide?
Azithromycin
Azithromycin binds to which ribosomal subunit?
50S
What is the spectrum of azithromycin?
G+/G- aerobes and anaerobes; atypical bacteria
What contributes to the resistance against azithromycin?
Increased efflux transporters
How can the azithromycin resistance be overcome?
Increase the dose
Which CYP450 is inhibited by azithromycin?
CYP3A4
What are the adverse effects of azithromycin?
GI irritation, hepatotoxicity, prolonged QT interval
What ABx binds to the 50S subunit and blocks peptide bond formation?
Clindamycin
What enzyme is blocked by clindamycin?
Peptidyl transferase
What is the spectrum of clindamycin?
G+ anaerobes
What is the major side affect of clindamycin?
C. diff infection
What antibiotic belongs to the oxazolidiones group?
Linezoid
What is the mechanism of action of linzoid?
Binds to the 23S rRNA of the 50S subunit
What is the spectrum of linezoid?
G + aerobes
In addition to MRSA, what other resistant variant can linezoid go after?
VRSA
What drug interaction do you need to be aware of when using linezoid?
MAOIs; could result in serotonin syndrome
What neuropathies could result with linezoid use?
Optic and peripheral neuropathy
Ciprofloxacin belongs to which group of ABx?
Fluoroquinolones
What does ciprofloxacin bind to and what is the the result?
Binds to DNA-topoisomerase complexes; inhibition of DNA synthesis (bactericidal)
What is the unique adverse effect of fluoroquinolones?
Tendon rupture
What can reduce the absorption of ciprofloxacin?
divalent cations
Ciprofloxacin binds to what in gram + bacteria?
Topoisomerase IV
Ciprofloxacin binds to what in gram - bacteria?
DNA gyrase
What is the spectrum of metronidazole?
Obligate anaerobes, microaerophilic bacteria; anaerobic protozoa
the MOA of action of metronidazole causes what action to the bacteria DNA via what?
Loss of helical structure due to free radicals
What drug causes dark red urine?
metronidazole
What do you need to educate patients on on when using metronidazole?
avoidance of alcohol due to disulfiram-like reaction
Sulfamethoxazole is an analog of what?
PABA
How does SMX work to stop growth of the bacteria?
competitive inhibition of dihydropteroic acid
When shouldn’t you use SMX?
patients with G6PD deficiency
How does the bacteria synthesize its folic acid?
Pleridine, PABA, and glutamate
What is TMP inhibiting? and what is the effect of this?
DHFR; blocks reduction of dihydrofolate to tetrahydrofolate
What happens if you use TMP in a patient that is folate-deficient?
bone marrow suppression
Co-trimoxazole is a combo of which two drugs?
SMX and TMP
What is the spectrum of co-trimoxazole?
Aerobic G+ and G- and opportunistic fungal pathogens
Daptomycin belongs to which group of ABx?
cyclic lipoproteins
MOA of daptomycin?
insertion of the lipophilic tail into the plasma membrane to form an efflux channel
Spectrum of daptomycin?
Gram +
Adverse effects of daptomycin?
myopathy and eosinophilic pneumonia
Colistin binds to what on the outer membrane of what kind of bacteria?
(-) charged LPS and phospholipids of outer membrane of Gram - bacteria
What are the adverse effects of colistin?
Nephrotoxicity and neurotoxicity