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Medical Pharmacology Exam 4 > Cell Wall Agents 2 > Flashcards

Cell Wall Agents 2 Flashcards

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USMLE® Step 1 flashcards
1
Q

Generally speaking regarding cell wall synthesis inhibitors, are they more likely to inhibit gram positive or negative organisms? What 2 of the following describe their spectrum: narrow, broad and extended?

A

Gram positive

Narrow and extended

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2
Q

Generally speaking regarding cell wall synthesis inhibitors, are they bacteriocidal or bacteriostatic? How are they cleared from circulation?

A

Bacteriocidal

Renal clearance

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3
Q

What is the unique component of bacteria cell walls that is targeted by cell wall agents?

A

Peptidoglycan

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4
Q

What are the 5 examples of peptidoglycan synthesis inhibitors provided?

A 
Vancomycin 
Fosfomycin 
Beta-lactams 
Bacitracin 
Cycloserine
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5
Q

What is the mechanism of action of fosfomycin? What Kreb cycle component is it analagous to? How is it excreted? How is its spectrum characterized?

A

Blocks 1-PDG synthesis by mimicking phosphoenol pyruvate (Kreb cycle)
Excreted unchanged in urine
Considered broad spectrum

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6
Q

While fosfomycin doesn’t have a lot of associated toxicities, what are 2 known toxicities? What is it used to treat, and how?

A

Diarrhea and vaginitis

Single dose treatment of uncomplicated UTI

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7
Q

D-cycloserine work by blocking _. It is an analogue to _. It is considered _ spectrum. It is used for the treatment of _

A

2 steps of PDG synthesis
D-alanine
Broad spectrum
Tuberculosis (2nd line treatment)

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8
Q

D-cycloserine is administered via _, It is excreted in _ in its [active/inactive] form. It [does / does not] enter the CNS and its major toxicity is _

A 
Orally 
Urine 
Active form 
Does enter CNS 
CNS side effects (serious)
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9
Q

What is the mechanism of action of bacitracin? How is it administered? How is its spectrum characterized? What is the major associated toxicity?

A

Depletes lipid carrier necessary for PDG synthesis
Topically
Narrow spectrum
Major nephrotoxicity

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10
Q

What a 2 uses of bacitracin? What is it usually mixed with? What are 2 bugs it is effective against?

A

Skin and Eye infections
Mixed with polymyxin B
Neisseria and T. Pallidum

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11
Q

What is the mechanism of action of vancomycin? It is rapidly bacteriocidal in _. What is the exception where vancomycin is bacteriostatic?

A

Binds d-ALA, prevents cross linking of PDG
Dividing bacterial cultures
Bacteriostatic in enterococci cultures

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12
Q

Vancomycin is administered _. Why is it not administered intramuscularly? Orally? How is it excreted? Under what conditions does it get through the CNS?

A 
IV 
Causes muscle tissue necrosis 
Poor absorption orally 
Excreted renally 
If meminges are inflamed
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13
Q

How is the spectrum of vancomycin characterized? What types of bugs is it active against?

A

Narrow

Mainly gram +, mainly MRSA

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14
Q

What are 2 mechanisms by which bugs can develop resistance to vancomycin?

A

vanco resistant enterococci - express vanA, vanB and vanC genes coding for different subunits with reduced binding to vanco
vanco resistant staph aureus - overexpress D-ala which bindings up drug

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15
Q

What are the 3 toxicities associated with vancomycin?

A

Red man syndrome
Ototoxicity
Nephrotoxicity

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16
Q

What are 2 types of bugs that vancomycin is used to treat? What drug class is it synergistic with?

A

MRSA, penicillin resistant staph aureus

Aminoglycosides

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17
Q

What are the 4 examples of beta lactam antibiotics provided?

A

Penicillin
Cephalosporin
Carbapenems
Monobactams

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18
Q

In general, beta lactams act by inhibiting what enzymes? They are structural analogues to what cell wall protein? What is their net effect on PDGs?

A

Transpeptidases (PBP)
D-alanine
The prevent their crosslinking by binding penicilin binding proteins (PBP)

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19
Q

Beta lactams are bacteriocidal. However, what condition must be met for them to have this property?

A

The bacteria must be dividing

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20
Q

In general, beta lactam are widely distributed. What is the one area where they are not? How are they excreted and through what route?

A

Don’t get to CNS

Unmetabolized, via kidneys

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21
Q

In general, most beta lactams are not metabolized. What are the 2 exceptions?

A

Nafcillin and imipenem

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22
Q

What is the main target of beta lactams? What are 3 other targets of the beta lactams?

A

Major - gram positive anaerobes

Others - gram negative cocci and rods, spirochetes

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23
Q

What is the most common way by which drugs become resistant to beta lactams? How does MRSA become resistant to beta lactams

A

Production of beta-lactamases

Expression of altered PBPs

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24
Q

Beyond the Production of beta-lactamases and Expression of altered PBPs, what are 2 other ways to become reisstant to beta lactams?

A

Alteration of outer mem. proteins (prevent binding to PBP)

Increased expression of efflux pumps

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25
Q

While toxicity associated with beta lactams are minimal, what are 3 acknowledged associated toxicities?

A

Tissue irritation
Phlebitis with IV admin
Superinfections

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26
Q

Allergy is a major concern with the beta lactams. Cross sensitization can also occur with what types of drugs? What is the difference in time line between acute, accelerated and delayed allergic reaction? Which is most serious? Which is most common?

A

Cross sensitization with chemically related drugs
Acute - 30 min of adminstration (most serious, anaphylaxis)
Accelerated - 30 min - 48 hrs
Delayed - 2 or more days (most common)

27
Q

What are the 2 types of penicillin? How do they differ in stability in acid? How do they differ in routes of administration?

A

Pen G - Acid labile - IM and IV

Pen V - Acid stable - Oral admin

28
Q

What are the types of bugs that penicillin is effective against? What are they ineffective against?

A

Effecive - Gram +, Gram - cocci

Ineffective - Gram - rods, and anaerobes

29
Q

What are the major toxicities associated with both types of penicillin?

A

Allergies

Stevens - Johnson syndrome

30
Q

What is the major toxicity associated with pen G and not pen V?

A

Dose dependent neurotoxicity and seizures

31
Q

What types of microbes should penicilin not be used against? What microbe has many penicilin resistant strains?

A 
Don't use against penicillinase producing microbes
Streptococcus pneumoniae (many are resistant)
32
Q

Beyond strept. pneumoniae, what are 4 other microbes against which penicillin can be used?

A

Staphylococcal sp.
Neisseria meningitidis
Clostridium sp.
Treponema pallidum

33
Q

What are the 4 examples of penicillinase resistant penicillins?

A

Oxacillin
Cloxacillin
Nafcillin
Methicillin

34
Q

What 2 microbes are the penicillinase resistant penicillins used to treat clinically?

A

Penicillinase-producing Staphylococci and

Streptococci

35
Q

What is an adverse effect associated with methicillin? What about oxacillin?

A

Methicillin: interstitial nephritis
Oxacillin: hepatitis at high doses

36
Q

What are the 3 classes of extended spectrum penicillins? What enzyme expressed by bacteria is able to destroy these drugs?

A

Aminopenicillins, carboxypenicillins and
ureidopenicillins
- Beta lactamase

37
Q

What are the 2 examples of aminopenicillins provided? Are the stable or labile in acid? How are they administered? Which is not affected by food?

A

Ampicillin and amoxicillin
Acid stable
Oral admin
Amoxicillin not affected by food

38
Q

What microbes are the aminopenicillins effective against? What are 4 examples provided?

A

Non-lactamase gram- bacilli

E. coli, H. influenza, Salmonella, Shigella

39
Q

What type of penicillin can be used as a prophylactic against bacterial endocarditis?

A

Amoxicillin

40
Q

What are the 2 examples of carboxypenicillins provided? How are they administered? What are they used against?

A

Carbenicillin and ticarcillin
Parenteral admin
Anti-pseudomonas

41
Q

What are the 2 examples of piperacillin provided? How are they administered? What are they used against?

A

Piperacillin and mezlocillin
Parenteral administration
Anti- pseudomonas

42
Q

Ureidopenicillins are reserved for use against _, (2) and are used in combination with _ to prevent resistance

A

Serious systemic klebsiella or pseudomonas infections

Used in combo with aminoglycosides

43
Q

What are the 3 examples of beta-lactamase inhibitors? What is their mechanism? How are they used?

A

Clavulanic acid
Sulbactam
Tazobactam
They are beta-lactamase suicide inhibitors
Used in combination with extended spectrum penicillins

44
Q

What is the mechanism of action of the cephalosporins? What is they main adverse effect associated with them?

A

Inhibit cell wall synthesis

Allergy

45
Q

What is the clearance route of the cephalosporins? How are they metabolized?

A

Cleared by kidneys

Minimal metabolism

46
Q

What are the mechanisms of bacterial resistance of the cephalosporins? (2)

A

Induce Amp C (Cephalosporinase)

Low affinity penicillin binding proteins

47
Q

They cephalosporins are likely to be cross allergenic with _

A

Penicillins

48
Q

What are the 4 examples of cephalosporins provided? What generations do they belong to?

A

1st - Cefazolin
2nd - Cefuroxime
3rd - Cefotaxime
4th - Cefepime

49
Q

Which of the cephalosporins has the broadest spectrum against gram+ cocci (surgical
prophylaxis); effective against gram- bacilli?

A

Cefazolin

50
Q

Which of the cephalosporins the the only group with significant activity against anaerobes?

A

Cefuroxime

51
Q

Which of the cephalosporins is most widely used treatment in children / infants with
moderate to severe infections?

A

Cefotaxime

52
Q

Which of the cephalosporins is antipseudomonal and has high resistance to beta-lactamases?

A

Cefepime

53
Q

Which of the cephalosporins is antipseudomonal and antipneumococcal and has activity against serious gram - infections such as meningitis, pneumonia, gonorrhea?

A

Cefotaxime

54
Q

What are the 3 examples of carbapenems provided? What major bacterial resistance product are they largely resistant to?

A

Imipenem, meropenem and ertapenem

Beta-lactamase

55
Q

Among the carbepenems, penicillins and cephalosporins, which has the broadest activity? Why shouldn’t the carbapenems be co-administered with penicillins or cephalosporins?

A

Cerbepenems

Induces beta-lactamases that inactivate penillins and cephalosporins, antagonizing their bacteriocidal effects

56
Q

While the carbepenems are resistant to beta lactamase, what is the major mechanism by which resistance occurs?

A

Alteration of penicillin binding proteins

57
Q

Which of the carbepenems is inactivated by the kidneys? How can this be reduced?

A

Imipenem

Co-admin with cilastatin, a dehydropeptidase inhibitor

58
Q

The carbapenems are cross allergenic with _

A

Penicillins

59
Q

What is the clinical use of the carbapenems?

A

2nd line therapy for serious nosocomial infections

60
Q

What is the example of a monobactam provided? What is its mechanism? What is its interaction with beta lactamases? Like the carbepenems, is it cross reactive with penicillin?

A

Aztreonam
Binds the penicillin binding proteins
Resistant to beta lactamases
It is not cross reactive with penicillins

61
Q

How is aztreonam administered? How is it kept out of the CNS? What are its 3 uses?

A

IM or IV
It enters an inflammed CNS
Gram - UTI, lower resp. tract infection, systemic infection

62
Q

What is the spectrum of aztreonam, i.e. what bugs is it effective against?

A

Gram - aerobes and pseudomonas

63
Q

What is the example of the cell membrane agent provided? What is its mechanism? How is it administered and how is it eliminated?

A

Daptomycin
It causes membrane depolarization
Administered IV
Renal excretion

64
Q

The spectrum of daptomycin is very similar to that of what drug? What are 2 types of drug resistant bacteria that daptomycin treats? What is the major associated adverse effect?

A

Vancomycin
VREF and MRSA
Myopathy

Medical Pharmacology Exam 4 (6 decks)

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