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Microbiology > Antibiotics > Flashcards

Antibiotics Flashcards

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1
Q

General cell wall composition of bacteria
What enzyme catalyzes the formation?

Importance?

A

Peptidoglycan: Repeating disacharides with 4 a.a. that covalently link to other disacharides through their a.a.

Enzyme = transpeptidase/PCN bindiing protein

Important bc PCN inhibits transpeptidase -> cell wall cannot be regenerated/formed -> cell death/can’t make new cells

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2
Q

PCN
MOA
Must do what to be effective?
Resistance mechanisms?

A

MOA: competitively inhibit cytosolic transpeptidase

Effective

1) penetrate cell layers (in G - must go through porin)
2) keep beta lactam ring intact
3) Bind transpeptidase

Resistance

1) Porin’s (GNB)
2) beta lactamase/penicillinase
- Staph secretes it, GNB keep it in cytoplasm
3) Alter transpeptidase molecular structure
4) efflux pump

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3
Q

PCN G vs PCN V

A

PCN G is primarily IV/IM

PCN V is acid resistant, can be taken PO

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4
Q

Aminopenicillins

General Use

A

More effective in gram negatives, have amino group… still sensitive to beta-lactamase’s

Ampicillin (IV, oral is meh)
Amoxicillin (good oral)

Amox: Listeria! Triple therapy H. Pylori!

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5
Q

Penicillinase-Resistant PCN’s
General use
IV/ORAL?

A

Good at Gram +, not Gram -, too bulky
Use staph A serious infections that aren’t resistant (cellulitis, endocarditis, sepsis)

IV: Methicillin (d/c), nafcillin, oxacillin. “Met Nasty Ox”

Oral: cloxacillin, dicloxacillin

CLOX!!!

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6
Q

Antipseudomonal PCN’s

A

Car, Tic, Pipe

Carbenicillin, ticarcillin, piperacillin

Tx; Pseudomonas and anaerobic coverage

** These are sensitive to penicillinase so don’t really work against Staph ect. unless combined with an inhibitor

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7
Q

Beta-lactamase inhibitors

A

As the name implies

Clavulanitc acid, sulbactam, tazobactam

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8
Q

Cephalosporins
MOA
General Generational considerations
Who has innate resistance?

A

Also contain beta-lactam ring, but add a chemical group that makes them much more resistant to penicillinases

Generations:
1st Strong G positive action, poor G negative, Alt. to PCN
**Have ph in name (must first get PHD), don’t let cefazolin FAZE you (also 1st gen and only IV first gen)

2nd Medium on G+- and streptococci
** impossible to remember, good at anaerobic coverage and unknown com-acq-pneumonia

3rd Poor G positive action, strong gram negative

        * * All have t for tri in the name (note that cefotetan is second gen, not third.)
       * *use in-hospital for Comm-acq-pneumoina, meningitis, pyelo

ONLY ONE OF EACH BELOW
4th Strong Gram positive and negative coverage! Cefepime
5th Works against MRSA (Ceftaroline)

**Enterococci are resistant to cephalosporin, as is MRSA, except Ceftatoline

Allergies: 10% ppl with allergy to PCN will be allergic to cephalosporins. IgE mediated

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9
Q

Enterococci resistances

A

Innate to PCN G and cephalosporins, used to use ampicillin but they are becoming resistant. They are also becoming resistant to vancomycin, which we used after resistance to ampicillin began.

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10
Q 
Vancomycin 
MOA
Use
Side effect and prevention
Resistance profile
Allergies
A

Complexes with D-alanine D-alanine to prevent transpeptidation

Use in all Gram Positives, not absorbed orally (good for C. Diff), synergistic with aminoglycosides

Side effects: Red man syndrome: release of histamine -> red rash of torso/pruritis, can prevent with slow infusion or antihistamine premedication

Resistance Profile: Most notable is resistance by Enterococcus and Staphylococcus. Resistance occurs by altering D-alanine-D-alanine to D-alanine-D-lactate

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11
Q

MRSA resistance

What’s the only beta-lactam that will work?

A

S. Aureus resistance to ALL PCN’s, including the cephalosporins EXCEPT 5th gen ceftaroline

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12
Q

What’s special about Cefazolin?

A

Only first gen cephalosporin that is fiven IV, also the only one without a PH in the name.

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13
Q

What is special about ceftaroline?

A

Ceftaroline is the only 5th generation cephalosporin with action against MRSA.

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14
Q

What is special about Cefepime?

A

Only 4th generation cephalosporin. Good at gram positives and gram negatives. Useful against pseudomonas.

Ceftazidime (3rd gen) is also effective against pseudomonas

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15
Q

What generation of cephalosporin is ceftriaxone?

Activity against what?

A

3rd gen

best at gram negatives, nt bad against streptococci, poor Gram positive

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16
Q

Ceftriaxone and cefotaxime uniqueness

A

Both have excellent CSF penetration -> tx meningitis (usually due to gram negatives).

Ceftriaxone is used in adults
Cefotaxime in children (bc ceftriaxone interferes with bilirubin metabolism)

17
Q 
Carbapenems
MOA
USE
Resistance
Side effects
Notes
A

Similar action as PCN, inhibit transpeptidase. They are super small and have GREAT coverage of gram positive and negative organisms.

BROADEST spectrum we have.

Resistant to beta-lactamase and ESBL but cabapenemases are emerging. MRSA is also resistant. Works on SOME pseudomonas.

SE: 10% cross reactivity, lowers seizure threshold (don’t use for meningitis/strokes)

Notes: Imipenem needs cilastatin which inhibits an enzyme in kidney that breaks it down. The other carbapenems are resistant to breakdown.

18
Q

Aztreonam
MOA
Use
SE

A

Has beta lactam ring, but ONLY used against gram negatives. Including pseudomonas

Not useful with anaerobic or gram positive bacteria

SE PCN allergy is not a concern

19
Q

MRSA mechanism of resistance

A

Altered binding site of PCN on transpeptidase

20
Q

anti-ribosomal antibiotics
Name the 7 important antibiotics using the mnemonic (including which ribosome subunit they inhibit)

Which 2 are IV only (the rest are orally available)

A

CLEan TAG

CLEan is 50s
Chloramphenicol
Clindamycin
Linezolid
Erythromycin (clarithromycin, azythromycin, telithromycin)

TAG is 30s
Tetracycline
Tigecycline
Aminoglycosides

** Aminoglycosides and Tigecycline are solely IV/IM

21
Q 
Chloramphenicol
MOA
USE
Side/adverse effects
Notes
A

Bacteriostatic. inhibit 50s subunit bacteria

USE
#Wide spectrum of activity (G+, G-, anaerobes)
#CNS penetration = use for meningitis
#Use when severe allergies to PCN's
SE
#may cause reversible anemia
#May cause irreversible aplastic anemia -> death
# Gray Baby Syndrome: shock, abdominal distention, cyanosis in neonates that cannot fully conjugate it
22
Q 
Clindamycin
MOA
USE
Side/adverse effects
Notes
A

Bacteriostatic. Inhibit 50s subunit

USE
#NOT useful with gram negatives. Strong with gram positive and anaerobes
#Use in toxic shock syndrome combined with another drug (it will limit the toxic shock protein production -> increase survivability)
#Use in anaerobic infections ABOVE diaphragm (aspiration pneumonia/lung abscess/oral infection)
Adverse effect
#Prototypical cause of pseudomembranous colitis, though many PCN's and other drugs do this as well... tx with metranidazole or vanco.
23
Q 
Linezolid
MOA
USE
Side/adverse effects
Notes
A 
Inhibit 50s subunit +- bactericidal/static
USE
#Gram + bugs
#Active against VRE and MRSA
Adverse
#occasional bone marrow suppression
#Can cause serotonin syndrome (don't use in pts on antidepressants)

NOTES:
EXPENSIVE!!!!

24
Q 
Macrolides/Ketolide
MOA
USE
Side/adverse effects
Notes
A

Bacteriostatic. Inhlblt 50s subunit, specifically translocation
(Erythromycin was first, now largely replaced by azithromycin) + Clarithromycin
Ketolide: Telithromycin

USE: Well tolerated
#Gram positives, some gram negative
#Atypical pneumonia: Legionella, chlamydia pneumoniae, Mycoplasma pneumonia + Chlamydia STI
#Some syphillis though resistance increasing
#pneumococcus is fairly resistant except to telithromycin, use as alternate to PCN
Adverse: MACRO pneumonic
General:
#motility issues (abdominal discomfort)
#arrhythmia (prolonged QT
#cholestatic hepatitis (microsomal enzyme inhibitor)
#Rash
#eOsinophilia

NOTES Telithromycin can cause acute respiratory failure in myasthenia gravis patients!!!!

Resistance: methylation of 23s rRNA binding site

25
Q

Unique about telithromycin?

A

It is a ketolide (similar to macrolides)
Effective against G +, some G-, atypicals
UNIQUE: More effective against resistant pneumococcus
DON’t give to MG patients! develop respiratory failure.

A MG pt with droopy eyes can’t “TELL IF you THROw a ball at him” his fear of being hurt “takes his breath away.”

26
Q 
Tetracycline, Doxycycline, Tigecycline
MOA
USE
Side/adverse effects
Resistance
Notes
A

Bacteriostatic, inhibits 30s subunit. Prevents binding of tRNA to ribosome. Doxycycline is fecally eliminated and can be used in pts. with renal failure. Poor CNS penetration.

USE
#Venereal Chlamydia Trachomatis
#Walking pneumoina by mycoplasma pneumonia
#Rickettsia, Brucella
#Acne

Adverse effects: GI distress, discolored teeth/inhibit bone growth children (chelation Ca++), photosensitivity. CONTRAINDICATED in pregnancy

Resistance: Decrease uptake or increased efflux

Notes: Doxy > Tetracycline, but they chelate with milk/milk products, aluminum hydroxide, ca++, and Mg++
** Tigexyxline is a newer “glycycline” with similar broad spectrum

27
Q

Antibiotics contraindicated in pregnancy

A 
SAFe Children Take Really Good Care
Sulfonamides -> kernicterus
Aminoglycosides -> Ototoxicity
Flouroquinolones -> Cartilage damage
Clarithromycin -> Embryotoxic
Tetracycline -> Discolored teeth/inhibit bone growth
Ribavirin (antiviral) -> Teratogenic
Griseofulvin (antifungal) -> Teratogenic
Chloramphenicol -> Gray Baby
28
Q 
Aminoglycosides
MOA
USE
Side/adverse effects
Resistance
Notes (what drugs?)
A

Bactericidial. 30s subunit. IV only. Require O2 for uptake –> useless for anaerobes

USE: Severe infections of Gram negative rods. Synergistic with B-lactam antibiotics bc they break down wall for aminoglycosides to diffuse across easier.

Adverse Effects: NNOT: Nephtrotoxicity, neuromuscular blockade, ototoxicity, Teratogenic

Resistance: Transferase enzymes can inactivate drug.

Notes: mnemonic

Mean GNNATS caNNOT kill anaerobes
aMINoglycoside
Gentamicin, Neomycin, netilmicin, Amikacin, Tobramycin, Streptomycin

29
Q

Trimethoprim and Sulfamethoxazole
TMP-Sulfa

MOA
USE
Side/adverse effects
Resistance
Notes (what drugs?)
A

Bacteriostatic
MOA
Sulfa drugs: Look like PABA (para amino benzoic acid), which is a precursor to dihydrofolate (TH2). TH2 synthase is competitively inhibited by Sulfa’s.

Trimethoprim: Prevents by competitive inhibition reduction of TH2 –>TH4 (similar structure to TH2 reductase)

USE: Broad specturm. gram +, Gram -, Nocardia, Chlamydia. UTI’s, respiratory tree, GI. NO anaerobic.
Prevent PCP in AIDS pts -> pneumocystitis carinii pneumonia

HAS ORAL ABSORPTION and RENAL EXCRETION…eat and egg and smell the sulfer come out

Adverse effects: 1/2 aids pts dvlp bone marrow suppression and rash.
Prolongs coumadin half life -> bleeding!!!

Resistance: Altered enzymes

Microbiology (5 decks)

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