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Antimicrobial and chemotherapy > General properties of antimicrobial agents > Flashcards

General properties of antimicrobial agents Flashcards

1
Q

Are fungi classified as eukaryotes or prokaryotes and what problems are caused by this

A

Classified as Eukaryotes so there is no specific toxicity

Attacking common targets can cause side effects.

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2
Q

List classes of anti-fungal drugs

A

Polyenes
Azoles
Echinocandins
Amorolfine

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3
Q

List examples of drugs in the azole categories

A 
Imidazole
Triazole
Clotrimazole
Miconazole
Ketoconazole,
fluconazole
Itraconazole
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4
Q

MOA of azoles

A

Inhibit the production of sterols in cell membrane

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5
Q

What are the best Azoles to use and why?

A

Fluconazole and itraconazole
Less toxic than ketoconazole and has good activity again fungi

Safe to use systemically

Used widely for fungal infection and oral/vaginal infcetions

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6
Q

Examples of Echinocandins

A

Caspofungin

Micafungin

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7
Q

MOA of echinocandins

A

Inhibit the enzyme beta-glucan synthase which produced cross link constituent of fungal cell wall

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8
Q

MOA of Amorolfine

A

Affects sterol production: reduced sterols causes accumulation of related compounds

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9
Q

Used of amorolfine

A

Fungal nail infections only- topically

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10
Q

MOA of polyenes

A

Interact with sterols and increase the permeability of fungal membrane.

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11
Q

Where are polyenes produced

A

in the soil

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12
Q

Examples of polyenes and their properties

A

Amphotericin B: High renal toxicity, Liposomal formulation reduces but is more expensive
Nystain: topical only

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13
Q

why is there a lack of development of antiparasitic drugs

A

Infections were rare

There was no money in it.

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14
Q

List some antimalarial drugs

A

Quinines: Chloroquine, mefloquine, Halofantrine

Artemisinin

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15
Q

List some conversional anti-bacterial drugs used as antiparasitic and how they work

A
  • doxycycline: Malaria prophylaxis (“anti-protein” NB up to 15% photosensitisation)
  • metronidazole : amoebae, giardia, trichomonas (reduced, then nucleic-acid disruption)
  • co-trimoxazole: toxoplasma (and PCP) prophylaxis
  • clindamycin: toxoplasma (and PCP) treatment (50s “anti-protein”)
  • pyrimethamine toxoplasma (and PCP) treatment (DHFR, similar to trimethoprim)

*Toxoplasma gondii and Pneumocystis carinii Pneumonia (PCP)

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16
Q

What are helminths

A

Worms or flukes

17
Q

causes of worms (parasitic infections)

A

Increased world travel has also increased helminth infections (or detection at least)
Hygiene / sewage management
Sushi/sashimi and poorly managed meat but water supplies and raw unwashed veg/fruit are the major contributor in many countries

18
Q

List some anti-Helminths against Threadworm/pinworms/Ascaris/Roundworm and how they work

A

-albendazole / mebendazole
Disrupt microtubule formation and glucose uptake which affects the motility and attachment of the worm

-nitazoxanide or ivermectin are alternatives
nitazoxanide disrupts energy transfer processes
ivermectin disrupts the nervous system

19
Q

Anti-Helminths against taenia/Tapeworm

A

-niclosamide: Inhibits ATP production
-praziquantel (broad-spectrum anti-helminthic)
>Increases the Ca permeability of plasma membranes
>Induces muscle spasms, affects retention, motility and exposes antigenic sites to immune system

20
Q

Anti-helminth treatment against Toxocara/ Roundworm

A

Albendazole: For parasitic worms of cats and dogs

21
Q

What is Aciclovir used to treat

A

Effective against both genital, oral and more serious herpes simplex (HSV) infections
Also used with some success in treatment of varicella virus (chickenpox and shingles)
It can be given intravenously or orally or used topically

22
Q

Lists some new variations of Aciclovir

A

valaciclovir,
famciclovir,
penciclovir

23
Q

How does Aciclovir work

A

-Nucleoside analogue produced as a prodrug (acycloguanosine)
>Phosphorylated once in the patient’s cells *IF virally coded thymidine kinase is present
>Affects DNA polymerases encoded by viral genes, so effective “only” in infected cells:
>Blockade and termination of viral DNA replication

24
Q

steps of Aciclovir mechanisms

A

1: Aciclovir + ATP to create aciclovir phosphate using HSV and Thymidine kinase
2: aciclovir phosphate with human enzymes creates Aciclovir triphosphate
3: Aciclovir triphosphate with HSV and DNA polymerase which causes it to be incorporated into viral DNA
4: Viral DNA synthesis inhibited

25
Q

What are the uses of Aciclovir derivatives (different from the)

A

Ganciclovir: treat cytomegalovirus (CMV) infections

  • Used effectively for cytomegalovirus in immunocompromised patients
  • More toxic, particularly to bone marrow (classified teratogen, mutagen, carcinogen)

valganciclovir is more well absorbed prodrug of Ganciclovir

26
Q

Mechanism of Foscarnet and what does it treat

A

acts against DNA replication by inhibiting pyrophosphate binding to DNA polymerases

Treats herpes/CMV when aciclovir/ganciclovir is unsuitable

27
Q

Side effects/ caution of Foscarnet

A

Toxic to kidneys, principally (approx 40% pts)

28
Q

Anti-viral drugs that aren’t ciclovir

A

Oseltamivir

Zanamivir

29
Q

Mechanism of oseltamivir, zanamivir

A

Selective ininhibitor of viral neuraminidase (NA)

30
Q

Use of oseltamivir, zanamivir

A

Used to prevent infection after exposure, or treat

Glycoproteins on the virion surface, important for entry into cells and for the release of recently formed virus particles from cells, allowing spread within the body.

In uncomplicated influenza, slightly shorter duration of symptoms but may be significant in patients at risk of severe complications

31
Q

Mechanism of viruses

A
  • They are obligate intracellular parasites
  • Because they “hijack” many host cellular processes, selective toxicity is more difficult
  • Many viruses difficult to culture - more difficult to test potential antiviral drugs
  • The lack of easy, rapid tests means it is difficult to differentiate between various viral infections
  • Many viruses have multiple strains and also will readily mutate
32
Q

What are the types of HIV antiretrovirals

A

Entry/fusion inhibitors

Nucleoside Reverse Transcriptase Inhibitors (RTIs

Integrase Inhibitors (INIs)

Protease inhibitors (PIs)

33
Q

How do RTIs work

A

This is a viral enzyme, so useful target. HIV nucleic acid is RNA, so must be “translated” into DNA. In slightly different ways, these drugs all inhibit the process

The “base mimics” are included in the DNA chain but can’t be added to (no 3’OH), so formation is stoppedNon-base inhibitors bind directly to the enzyme

34
Q

Which type of antiviral mechanism is rarely longer used and why

A

Entry/ fusion inhibitors

Not used due to resistance

35
Q

How do Integrase inhibitors work

A

Integrase is a viral enzyme that “integrates” the newly transcripted DNA into host DNA.

The current drugs interact with two Mg2+ ions in the enzyme’s active site structure

36
Q

How to protease inhibitors work

A

Protease is a viral enzyme that is involved in building new virus particles from the various parts that the host cell has manufactured.

These drugs tend not to stop the assembly but the resulting virus particles (virions) are defective

Antimicrobial and chemotherapy (4 decks)

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