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Infectious Disease Exam 1 > Antimicrobials I > Flashcards

Antimicrobials I Flashcards

1
Q

One good principle to keep in mind, when prescribing antibiotics, is that bacteriostatic drugs are only effective in ______________ patients.

A

immunocompetent

Think about it: if someone is neutropenic or otherwise immunologically impaired, then the static population of bacteria would still be able to live and produce toxins.

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2
Q

What is PAE?

A

Post-antibiotic effect: a period in which the drug is below its MIC yet the bacteria do not grow

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3
Q

Interestingly, all of the broad-spectrum antibiotics –chloramphenicol, sulfonamides, tetracycline, and trimethoprim –are ________________.

A

bacteriostatic

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4
Q

What two properties make cell-wall synthesizers have high selective toxicity?

A

(1) Only bacteria have cell walls, so the proteins targeted by cell-wall synthesis inhibitors do not inhibit human proteins.
(2) Cell-wall synthesis occurs outside the cell, so cell-wall synthesis inhibitors don’t need to penetrate cell membranes.

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5
Q

What is the incidence of type I hypersensitivity reactions to penicillin?

A

1 : 10,000 (of which about 10% will die)

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6
Q

Which penicillin can be given orally?

A

Penicillin V (think of how penicillin G is associated with the IVy around Princess Ellen’s neck –the vine that is grabbing her from behind)

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7
Q

Which beta-lactam has a neutralizing amino group?

A

The amino-group beta-lactams have “am-“ in their names: amoxicillin and ampicillin. This allows them to pass through the outer cell membrane.

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8
Q

Although the second-generation cephalosporins are not commonly used, what bacteria can they kill that the first-generation cephalosporins cannot?

A

HeNS: Haemophilus influenzae, Neisseria, and Serratia

Remember General Fox’s teapot with hens on it.

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9
Q

Quickly recap the ribosomal spots targeted by different antibiotics.

A

30S: aminoglycosides, tetracyclines
50S: clindamycin, chloramphenicol
50S – 23S subunit: macrolides

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10
Q

Which of the ribosome-targeting antibiotics is bacteriocidal? And why?

A

Aminoglycosides are bacteriocidal because they cause misreading of mRNA and subsequent accumulation of garbled protein.

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11
Q

Aminoglycosides are only effective against _____________.

A

aerobic, Gram-negative bacteria

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12
Q

Use of which antibiotic can cause fungal superinfections?

A

Tetracyclines

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13
Q

You might use tetracyclines to treat _________________.

A

Chlamydia, Mycoplasma, Rickettsia, Brucella, Borrelia burgdorferi, and spirochetes

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14
Q

Again, what is Dr. French’s mnemonic for the hepatically metabolized antibiotics?

A 
DQ CRIMES: 
Doxycycline
fluoroQuinolones
Clindamycin, Chloramphenicol 
Rifampin
Isoniazide 
Metronidazole
Erythromycin 
Sulfonamides
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15
Q

Why is sulfamethoxazole-trimethoprim not toxic to human cells?

A

Because bacteria need to make their own folate, while humans take it in from the environment

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16
Q

What is unique about the metabolism of sulfonamides?

A

It is metabolized to a less-soluble form. This can aggravate renal crystalluria.

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17
Q

Which enzyme is inhibited by the antibiotic that can form crystals in the renal tubule?

A

Dihydropteroate synthase (being sulfonamides)

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18
Q

Trimethoprim inhibits ______________.

A

dihydrofolate reductase

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19
Q

What is the teratogenic mechanism of sulfamethoxazole-trimethoprim?

A

It displaces bilirubin from albumin and can cause kernicterus.

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20
Q

Fluoroquinolones inhibit ______________.

A

DNA gyrase and topoisomerase IV –both involved in the uncoiling of DNA

21
Q

True or false: fluoroquinolones are highly toxic because they inhibit human DNA gyrase.

A

False. Humans don’t have gyrase.

22
Q

What can decrease the absorption of fluoroquinolones?

A

Metal cations (e.g., antacids, iron, milk)

23
Q

What two drug interactions are common in use of fluoroquinolones?

A

(1) Concomitant use of NSAIDs increases risk of seizure

(2) Fluoroquinolones inhibit metabolism of theophylline

24
Q

Metronidazole causes a shift to _______________.

A

lactate metabolism

25
Q

The mechanism of _______________ is similar to that of metronidazole.

A

nitrofurantoin

26
Q

Use of nitrofurantoin for UTIs is increasing due to increasing resistance to _____________.

A

sulfamethoxazole-trimethoprim

27
Q

What adverse effect can fluoroquinolones cause in children younger than 12?

A

Impaired cartilage development

28
Q

What is the most common use of polymyxin?

A

Pseudomonal meningitis

29
Q

How can you enhance the excretion of Bactrim?

A

By raising the pH of the urine

30
Q

How are penicillins excreted?

A

Renally (hence the interstitial nephritis that can result from penicillin use)

31
Q

True or false: penicillins are competitive inhibitors of transpeptidases.

A

False. They covalently bind and thus irreversibly inhibit PBPs.

32
Q

Which antibiotic concentrates in the lungs?

A

Macrolides

33
Q

Which antibiotic can cause cholestatic hepatitis?

A

Macrolides

34
Q

How does nitrofurantoin work?

A

It is a DNA-damaging agent.

35
Q

Nitrofurantoin is mainly used for ________________.

A

Gram-negative UTIs

36
Q

Sulfamethoxazole inhibits a reaction that has what starting reactants?

A

Para-amino benzoic acid (PABA) and pteridine

37
Q

By what ways do bacteria become resistant to sulfonamides?

A
  • Increased production of PABA
  • Modified dihydropteroate synthase
  • Decreased permeability to sulfonamides
  • Obtaining folate and other end products from pus
38
Q

Which antibiotic is metabolized by acetylation?

A

Bactrim

39
Q

Sulfasalazine is converted to _________________ in the gut, accounting for its benefit in those with ulcerative colitis.

A

5-ASA

40
Q

Topical Bactrim is frequently used to prevent what infection in burn patients?

A

Pseudomonas aeruginosa

41
Q

Fluoroquinolones are most effective against ___________ bacteria, though they can also kill _____________.

A

Gram-negative; Gram-positive

42
Q

Bacteria resistant to ___________________ are usually still susceptible to fluoroquinolones.

A

aminoglycosides and beta-lactams

43
Q

How do bacteria typically become resistant to fluoroquinolones?

A

Efflux pumps

44
Q

There is one fluoroquinolone that is not renally cleared and will thus not treat UTIs: _____________.

A

moxifloxacin

45
Q

The most common use of fluoroquinolones is ________________.

A

UTIs in the elderly

46
Q

Which antibiotics affect tRNA binding?

A

Tetracycline

47
Q

Bactrim can cause agranulocytosis, aplastic anemia, crystalluria, and _____________.

A

photosensitivity

48
Q

Which antibiotic can treat prostatitis?

A

Fluoroquinolones

49
Q

Metronidazole resistance can occur when bacteria _______________.

A

shift from acetate to lactate

Infectious Disease Exam 1 (17 decks)

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