Antibiotics Questions And Answers – Flashcards

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question

Sulfonamides

- SMX

-Sulfisoxazole

-Sulfadiazine

answer

- Bactericidal

- Available in combination with TMP

 

- Spectrum of activity:

Gram (+) ; not Enterococci

Gram (-) ; limited to respiratory pathogens

Poor against atypicals or anaerobes



E.coli, Chlamydia, Nocardia, PCP, MRSA, Simple UTIs 

 

Toxicity: cross allergenicity, hyperkalemia, bone marrow suppression, Warfarin binding competition

 

question
Which antibiotics are folate synthesis inhibitors?
answer

Sulfonamides

Trimethoprim

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Trimethoprim
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- Bacteriostatic

- Often used in combination with sulfonamides as TMP-SMX

 

Spectrum of activity:

Only Staphylococcus and E.coli

 

Recurrent UTIs, Shigella, Salmonella, PCP, Ocular infections

 

Toxicity: Bone marrow suppression resulting in megaloblastic anemia, leukopenia, granulocytopenia

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Which antibiotics inhibit protein synthesis?
answer

Clindamycin

Chloramphenicol

Linezolid

Aminoglycosides

Macrolides

Tetracyclines

Tigecycline

 

(CCLAMTT)

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Mechanism of resistance:

Chloramphenicol

answer
Plasmid-encoded acetyltransferase that inactivates the drug
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Chloramphenicol
answer

- Bacteriostatic

- Binds to 50s ribosomal subunit

- Excellent CNS penetration

 

Spectrum of activity:

Gram (+) ; MRSA and some VRE

Gram (-) ; common respiratory pathogens

Most anaerobes and atypicals


Meningitis (SHiN), Resistant Gram (+)


Toxicity: SEVERE, anemia, Grey Baby syndrome, aplastic anemia

 

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What is unique about chloramphenicol?
answer
It has excellent CNS penetration; thus, it can be used to treat meningitis
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Mechanism of resistance:

Aminoglycosides

answer
Acetylation, phosphorylation, or adenylation of key amino and -OH groups via bacterial enzymes
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Aminoglycosides

- Gentamicin

- Streptomycin

- Neomycin

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- Bactericidal

- Bind to the 30s ribosomal subunit, misreading of genetic code

- Require OXYGEN for uptake

 

Spectrum of activity:

Gram (-)

Limited Gram (+) but synergistic when combined with β-lactam

Part of TB therapy

NO ANAEROBIC/ATYPICAL activity

 

 

 

 

GRAM (-) infections

Used in combination to treat Gram (+)

 

Toxicity: Nephrotoxicity, Ototoxicity, Teratogen (NOT)

 

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Mechanism of resistance:

Tetracyclines

answer

Production of efflux proteins(increased efflux)

Production of ribosomal protection proteins (decreased uptake)

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Tetracyclines

- Tetracycline

- Doxycycline

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- Bacteriostatic

- Doxycycline can be used in patients with renal failure

- DO NOT take with dairy produces, antacids, vitamins/mineral supplements because they prevent absorption in the gut 

 

Spectrum of activity:

Gram (+) ; some MRSA

Gram (-) ; common respiratory pathogens

Oral anaerobes and atypicals

 

Rickettsia, Chlamydia, Syphilis, Borrelia, H.pylori, M.pneumoniae, B.anthracis

 

Toxicity: Photosensitivity, do not take with chelating agents, GI distress, inhibition of bone growth in children

question
Tigecycline
answer

- Ribosomal 30s subunit inhibition

- Similar to tetracyclines

 

Spectrum of activity:

Gram (+)

Gram (-)

Anaerobes

 

SSTIs, Intra-abdominal infections

 

Toxicity: hyperemesis

question

Mechanism of resistance:

Clindamycin

answer
Alteration of the 50s subunit
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Clindamycin
answer

- Bacteriostatic

- Binds to 50s ribosomal subunit

 

Spectrum of activity:

Anaerobes

Gram (+); some MRSA and enterococci

 

Anaerobes = Bacteroides fragilis, Clostridium perfringens

abscesses, acne, PID

 

Toxicity: can cause C.diff overgrowth

question
Linezolid
answer

- Bacteriostatic against Staph, Entero

- Bactericidal against Strep

- Prevents tRNA binding to A site of ribosome

 

Spectrum of activity:

Gram (+)

Some Gram (-)

 

Gram (+) and VRE infections

 

Toxicity: hypertension, serotonin syndrome

 

question

Mechanism of resistance:

Macrolides

answer
Alteration of macolide ribosome binding site (23s) via methylation
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Macrolides

- Clarithromycin

-Azithromycin

- Erythromycin

answer

- Bacteriostatic

- Binds to 50s ribosomal subunit

 

Spectrum of activity:

(SHAM)

Strep, Staph, Enterococci

H. pylori

Atypicals and anaerobes

Mycobacteria

 

Atypical pneumonias (Chlamydia, Legionella, Mycoplasma),

Gram (+) bacteria, Neisseria

 

Toxicity: GI upset, potency, hepatic clearance, CYP inhibitors, can prolong QTc interval

 

question

Ketolides

- Telithromycin

answer

- 2nd generation macrolide

- Able to bind at more sites than macrolides

- Active against resistant strains

 

Spectrum of activity:

Respiratory tract infections

Atypical bacteria

 

Atypical bacteria, Macrolide resistant strains

 

Toxicity: highly toxic, same as macrolides

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Beta-Lactam Antibiotics
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Penicillins

 

Cephalosporins

 

Carbapenems

 

Monobactams

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General considerations:

Penicillins

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- Bactericidal

- No Atypical Activity

- Inactivation of degrading enzymes (Penicillin-resistant)

- Alterations in PBP enzyme targets (MRSA)

- Well-tolerated

- May need dose reductions due to renal elimination

(exc. Nafcillin, Oxacillin)

question

Natural Penicillins

- Penicillin V

- Penicillin G

- Procaine

- Benzathine

answer

- Beta-lactam

- Method of resistance is the production of Beta-Lactamases

 

Spectrum of activity:

Gram (+) aerobes ; Strep and Entero

Treponema pallidium

 

Strep and Syphilis, Meningitis, Endocarditis

 

 

question

Aminopenicillins

- Ampicillin

-Amoxicillin

- Unasyn

- Augmentin

answer

- Combined with Beta-Lactamase inhibitors, they become more effective

 

Spectrum of activity:

Gram (+) ; Strep, Enterococci

Limited Gram (-)

Combined: Improved Gram (+), more Gram (-) and some anaerobic activity

 

SSTIs, Otitis, Lyme disease (2nd line tx)

 

 

question

Anti-Staphylococcal Penicillins

- Nafcillin, Oxacillin

- Cloxacillin, Dicloxacillin

answer

Spectrum of Activity:

Limited to only Staph and Streptococci

 

Osteomyelitis, SSTIs


Toxicity: Some hepatic elimination, mild elevations in liver function enzymes

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Anti-Pseudomonal Penicillins

- Piperacillin

- Piperacillin/Tazobactam

answer

- Less Gram (+) activity

 

Spectrum of activity:

Gram (-)

Anaerobes

Addition of the beta-lactamase inhibitor improves activity

 

Broad-spectrum empiris or targeted therapy of nosocomial infections

 

 

question

Clinical considerations:

Cephalosporins

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ALL cephalosporins have NO activity against enterococci

 

MOST cephalosporins have NO activity against anaerobes

 

MOST need to have doses reduced due to renal metabolism

 

Beta-lactam rash considerations

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1st Generation Cephalosporins

- Cefazolin

- Cephalexin

answer

Spectrum of activity:

Gram (+) ; no enterococci or MRSA

 

SSTIs, Tonsilitis, UTIs

 

 

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2nd Generation Cephalosporins

- Cefuroxime

- Cefotetan

- Cefoxitin

answer

Spectrum of activity:

Gram (+)

Some beta-lactamase Gram (-)

 

UTIs, sinusitis, Lyme Disease (2nd line tx)

 

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3rd Generation Cephalosporins

- Ceftazidime

- Ceftriaxone

 

answer

Spectrum of activity:

Gram (-) ; except Pseudomonas

Ceftazidime has Pseudomonal activity

less Gram (+) activity

 

All of the activity of other cephalosporins

+

Meningitis, UTIs, chronic Lyme disease

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