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Pharmacology > Antimicrobial agents > Flashcards

Antimicrobial agents Flashcards

1
Q

Aminoglycides act by

A

Inhibiting bacterial ribosomes thus inhibiting DNA translation / protein synthesis -> inhibiting bacterial replication.

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2
Q

Aminoglycosides can only work on gram negative AERObic bacteria why?

A
  1. Cannot enter the thick cell wall layer of gram positive bacteria.
  2. Aminoglycosides require O2-dependent cotransporters on the cell membrane - therefore cannot enter anerobic bacteria.
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3
Q

Which Aminoglycoside is used in the treatment of Mycobacterium terberculosis?

A

Streptomycin

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4
Q

What are examples of aminoglycosides?

A

Gentamicin
Steptomycin
Tobramycin - topical for eye infections

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5
Q

What kinds of conditions are treated by Aminoglycosides?

A

Infections in the:
1. Respiratory tract
2. Urinary tract
3. Blood
4. Bone
5. Soft tissue

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6
Q

What is combined with Aminoglycosides to treat Gram positive bacteria?

A

A cell wall synthesis inhibitor (Beta-lactam antibiotic) such as Penicillin or Vancomycin. These antibiotics reduce the structural integrity of the cell wall thus providing entry points for the Aminoglycosides.

*Used to treat enterococci infections such as infective endocarditis.

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7
Q

What is the route of administration for Aminoglycosides?

A

Not absorbed via gut therefore administration via:
* IV
* IM
* Topical (creams, gels, drops).

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8
Q

Red flag Aminoglycosides

A

Unwanted effects of critical importance inlcude:
1. Ototoxic - damage hair cells and cochlea. The risk increases if the pt is taking Loop diuretics (as they are also ototoxic).
2. Nephrotoxic - can lead to kidney failure (monitor kidney function).
3. Contraindicated for Myasthenia Gravis - can cause fatal respitory paralyis at high does.
*As Myasthenia Gravis antibodies bind post synaptic Ach neurons the effect of Aminoglycosides reducing the release of Ach at the presynaptic neuron proivdes a double hit to Ach neurons causing weakness, paralysis in skeletal muscles (ie diaphram)!

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9
Q

Are Aminoglycosides safe in pregnancy?

A

No! They have teratogenic effects (deafness).

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10
Q

Non-specific side effects of Aminoglycosides include:

A
  1. Nausea
  2. Vomitting
  3. Allergic reaction
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11
Q

What is the MOA of Antimetabolites?

A

Antimetabolites, such as sulfonamides and trimethoprim, act by inhibiting bacteria folate synthesis.
Without folate the bacteria cannot produced the building blocks for DNA / RNA > thus reducing bacterial cell functioning and inhibiting cell division.

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12
Q

What are the two main groups of Antimetabolites?

A
  1. Sulfonamides
  2. Trimethoprim
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13
Q

Are Antimetabolites bacteriostatic or bacteriocidal?

A

When used individually these are bacteriostatic, however when used in combination they are bactericidal (synergistic effect) as they inhibit folate synthesis via two pathways (enzyme in step 1 of the bacterial folate synthesis pathway and step 2).

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14
Q

What microbial agents are antimetabolites used to treat.

A

Antimetabolites such as sulphonamides and trimethoprim are broad spectrum and are used to treat both Gram positive and negative bacteria.

They are effective in travellers diarrhea, UTI, Pneumonia, sinus infect MRSA, Pheumocystis Jirovecii (yeast lung infection in immunocompromised pts).

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15
Q

General unwanted effects of Sulfonamides include?

A
  1. Nausea,
  2. Photosensitivity,
  3. Crystalluria,
  4. Nephritis
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16
Q

Red Flags for Sulfonamides

A
  1. Allergies
  2. Cross-reaction (thiazide diuretics, glyburide (DM).
  3. Stevens-Johnson Syndrome (a medical emergency involving skin & mucous membranes symptoms begin flu-like > painful rash > blisters > top layer of skin dies, sheds and begins to heal after several days).
  4. Fulfilment hepatic necrosis.
  5. Haemolytic anemia (in GGPD deficient individuals).
  6. Can cause jaundice and increase plasma biliruben as sulfonamides can bind albumin preventing biliruben from binding.
17
Q

Trimethoprim unwanted effects

A

Bone marrow suppression (megablastic anemia, leukopenia, granulocytopenia : proivde folic acid supplements).

18
Q

Is trimethoprim safe in pregnancy?

A

NO! Teratogenic effects including neural tube defects.

19
Q

What is the impact of sulfonamides inhibiting the effects of cytochrom p450?

A

Cytochrome p450 acts to metabolise drugs such as Warfarin. Inhibition by sulfonamides increases the plasma concentration of Warfarin and other drugs metabolised in this pathway.

20
Q

What is the most common Beta lactam antibiotics?

A

Penicillin

21
Q

Are Beta lactam antibiotics bacteriocidal or bacteriostatic?

A

Bacteriocidal

22
Q

What are examples of narrow spectrum beta lactase antibiotics?

A

Penicillin V & Penicillin G
Used to treat common Gram positive bacteria such as:
* Strepacococus pyrogenies - larengitis
* Nisseria meningitidis - bacterial meningitis.
* Spirrochetes - sphylis; lyme disease.

DO NOT work well anymore with gram negative bacteria such as:
- Staphylococcus aureus, - Streptococcus pneumonia and
- Neisseria gonorrhoea

23
Q

What are examples of broad spectrum beta lactase antibiotics

A

Amoxicillin
Ampicillin

24
Q

What types of bacteria are sensitive to broad spectrum beta lactase antibiotics (Amoxicillin / Ampicillin)?

A

Respiratory:
* Haemophillus influenza
* Moraxella catarrhalis

Gastrointestinal:
* Helicobactorpilori
* Salmonella sp,
* Shigella sp,
* Listeria sp.

25
Q

What antibiotic is the antibiotic of choice in pregnancy?

A

Amoxacillin

26
Q

What class of antibiotics is Doxycycline?

A

Tetracycline - blocker of translation of bacterial proteins.

Inhibits 30s

27
Q

What is the MOA of erythromycin?

A

Inhibition of bacterial ribosomal subunit 50s

28
Q

What class of antimicrobial drugs are erythromycin?

A

Macrolides

29
Q

What is the MOA of tetracycline antibiotic drugs?

A

Inhibition of the bacterial ribosomal 30s subunit.

30
Q
A

Pharmacology (13 decks)

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