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CHHD > Antimicrobial Agents > Flashcards

Antimicrobial Agents Flashcards

1
Q

What are some of the ideal characteristics of an Antimicrobial Agent

A
  • Selective toxicity against microbial target
  • Minimal toxicity to host
  • Kills micro-organisms
  • Long plasma half-life
  • Good tissue distribution
  • Low binding to plasma proteins
  • Oral and parental preparations
  • No adverse interactions with other drugs
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2
Q

Name some mechanisms that antibiotics use to kill microbes

A
  • Inhibition of cell wall synthesis
  • Inhibition of protein synthesis
  • Inhibition of nucleic acid synthesis
  • Inhibition of folate synthesis
  • Disruption of the cytoplasmic membrane
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3
Q

What can microbes do to develop and show a resistance to antimicrobial agents

A
  • Production of enzymes
  • Alteration in the outer membrane permeability
  • Alteration of target sites
  • Efflux pumps
  • Alteration of metabolic pathways
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4
Q

Name some types of enzymes that can be produced to show resistance to antimicrobial agents

A
  • Beta-lactamases
  • Aminoglycoside - modifying enzymes
  • Chloramphenicol acetyl transferase
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5
Q

What problems arise from human use of antibacterials

A
  • Adverse side effects
  • Drug interactions
  • Rising rate of resistance
  • Few organisms have become virtually untreatable
  • Superinfection - candida albicans and C.Diff
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6
Q

What are the main features of the chemical structure of the penicillin family of drugs

A
  • Acyl side chain
  • Beta lactam ring
  • Thiazolidine ring
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7
Q

What are the 6 groups drugs in penicillin family

A
  • Benzylpenicillin
  • Orally absorbed penicillin
  • Anti-staphylococcal penicillin
  • Extended spectrum penicillin
  • Antipseudomonal penicillin
  • B-lactamase resistant penicillins
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8
Q

Give an example of an orally absorbed penicillin

A

Penicillin V

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9
Q

Give an example of an anti-staphylococcal penicillin

A

Flucloxacillin

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10
Q

Give an example of an extended spectrum penicillin

A

Amoxicillin

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11
Q

Give an example of an anti-pseudomonal penicillin

A

Ticracillin

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12
Q

What is the mechanism of penicillins

A

Inhibiting cell wall synthesis by binding to penicillin binding proteins and inhibiting transpeptidation of peptidoglycan

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13
Q

How do microbes show resistance to penicillins

A

Resistance by beta-lactamases, failure to penetrate the outer membrane of gram negative bacteria, efflux and low affinity binding of antibacterial to target PBP

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14
Q

What are the potential side effects of drugs in the penicillin family

A
  • Allergic reaction like anaphylactic reaction or delayed hypersensitivity
  • GI problems like diarrhoea and enterocolitis
  • Renal - interstitial nephritis or haemorrhagic cystitis
  • CNS - encephalopathy or seizures - rare and occurs with renal failure or high prolonged doses
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15
Q

Name a beta lactamase inhibitor that can be administered with penicillins

A

Clavulanic acid

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16
Q

Describe the structure of cephalosporins

A

Beta lactam ring

Six membered Dihydrothiazine ring but modified at certain positions to produce different compounds

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17
Q

When are cephalosporins used in place of penicillins

A

When the patient is allergic to penicillins there is a low chance that they are also allergic to cephalosporins

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18
Q

Give examples of macrolides

A

Erythromycin, Clarithromycin and Azithromycin

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19
Q

What does bacteriostatic mean

A

Prevents the growth of bacteria

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20
Q

How do microbes show resistance to macrolides

A
  • They decrease their outer membrane permeability
  • efflux
  • alteration in rRNA
  • enzymatic inactivation by phosphotransferases
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21
Q

Are macrolides bacteriocidal or bacteriostatic

A

Bacteriostatic

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22
Q

What is the general mechanism of macrolides

A

They inhibit RNA dependent protein synthesis (50S ribosomes)

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23
Q

What are the potential side effects of Macrolides

A
  • GIT symptoms
  • Skin rash
  • fever
  • eosinophilia
  • cholestatic jaundice
  • transient hearing loss
  • potential for increase effect of warfarin because it inhibits its metabolism and clearance
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24
Q

What is the spectrum of activity for macrolides

A
  • Gram positive bacteria
  • Mycoplasma
  • Legionella
  • Chlamydia
25
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

Macrolides can be used as an alternative to penicillin in penicillin-allergic patients

26
Q

Give an example of Lincosamide

A

Clindamycin

27
Q

Describe the general mechanism of Lincosamides

A

Inhibits RNA-dependent protein synthesis (50S)

28
Q

How do microbes show resistance to Lincosamides

A
  • Decrease outer membrane permeability
  • Alteration in rRNA
  • Alteration in 50S ribosomal proteins of the receptor sites
  • Enzymatic inactivation by transferase
29
Q

What is the spectrum of activity for Lincosamides

A

Gram positive and anaerobic bacteria

30
Q

What are some side effects

A
  • C. Diff colitis
  • Allergic reaction
  • Transient hepatitis
  • Neutopenia
  • Thrombocytopenia
31
Q

Give some examples of Tetracyclines

A
  • Tetracycline
  • Chlortetracycline
  • Oxytetracycline
  • Doxycycline
  • Tigecycline
32
Q

What is the mode of action of Tetracyclines

A
  • Inhibits bacterial protein synthesis (30S)
33
Q

Are tetracyclines bacteriocidal or bacteriostatic

A

bacteriostatic

34
Q

What is the spectrum of activity for tetracyclines

A
  • Broad spectrum for gram positive
  • Gram negative
  • Intracellular organisms
35
Q

How can microbes show resistance to tetracyclines

A
  • Efflux
  • Ribosomal protection protein
  • Enzymatic inactivation
36
Q

What are the potential side effects of Tetracyclines

A
  • GIT symptoms
  • Photosensitivity
  • Pigmentation (skin, nail and sclera)
  • Deposition in growing bone and teeth
  • Hepatotoxicity
  • Exacerbate renal impairment
  • Superinfection
  • Allergy
37
Q

What is the general mechanism of Nitroimidazoles (metronidazole)

A

DNA synthesis inhibitor that interacts with nucleic acids and proteins causing breakage, destabilisation and cell death

38
Q

What is the spectrum of activity for nitroimidazoles (metronidazole)

A
  • Anaerobic
  • Facultative anaerobic bacteria
  • Protozoa
39
Q

What are the potential side effects of Nitroimidazoles (metronidazole)

A
  • Metallic taste
  • GIT symptoms
  • Peripheral neuropathy
  • Disulfiram-like reaction with alcohol
  • Allergic reaction
  • Genitourinary
  • Increase effect of warfarin
40
Q

What are the effects of a disulfiram like reaction

A 
Nausea
Vomiting
Flushing 
Tachycardia 
Hypotension
Confusion
Psychosis
Sudden death
41
Q

What are polyenes

A

Antifungal ting

42
Q

Name some examples of polyenes

A

Amphotericin (IV)

Nystatin (PO)

43
Q

What do polyenes interact with and what effect does this have on fungal cells

A
  • Interacts with ergosterol and forms a transmembrane ion channel
  • Increases membrane permeability, leakage of cell contents and cell death
44
Q

How are polyenes able to show a selective action on the fungi

A

As the main sterol in the human cells is cholesterol and not ergosterol

45
Q

How is Nystatin (polyene) administered and why

A

Only used topically on the skin and mucous membrane, does not get absorbed from the GI tract

46
Q

What are some potential side effects of amphotericin

A 
Anaphylaxis
Nephrotoxicity
GIT upset
Muscle and joint pain
Anaemia
Cardiovascular toxicity
47
Q

How can resistance be shown to polyenes

A

Intrinsic resistance like in dermatophytes, acquired resistance is rare

48
Q

What are the 2 categories of Azole

A

Imidazoles

Tiazoles

49
Q

What are some types of Imidazoles

A
  • Ketoconazole
  • Miconazole*
  • Clotimazole
50
Q

What are some types of tiazoles

A
  • Itraconazole
  • Fluconazole
  • Voriconazole
  • Posaconazole
  • Ravuconazole
51
Q

What is the general mechanism of azoles

A

They inhibit the synthesis of ergosterol

52
Q

When should imidazoles not be used

A

In patients with hepatic impairment, pregnancy or breast feeding

ketoconazole is associated with fatal hepatotoxicity

53
Q

What side affects and adjustments need to be made when administering Fluconazole

A
  • Fluconazole can cause abnormal Liver Function Test (LFT)

- Fluconazole dose needs to be reduced in renal impairment

54
Q

What azole is candida krusei resistant to

A

Fluconazole

55
Q

What targets in viruses are there for antiviral agents to attack

A
  • Attachment
  • Viral entry
  • Viral uncoating
  • Nucleic acid synthesis
  • Assemble and release of viral particle (protease and neuraminidase inhibitors)
56
Q

What viruses is Aciclovir effective against

A
  • Herpes Simplex Virus (HSV)

- Vesicular Stomatitis Virus (VSV)

57
Q

What are the side effects of Aciclovir

A
  • Skin irritation when used topically
  • High dose IV can cause nephrotoxicity
  • GIT disturbance
  • Confusion and hallucinations
58
Q

Describe the mechanism of Aciclovir

A
  • Aciclovir = analogue of guanosine
  • Phosphorylated by the thymidine kinase enzyme of HSV and VZV
  • Becomes trapped in the infected cell
  • Two further phosphate groups are added so becomes triphosphate by cellular kinase
  • Triphosphate compound is a potent and selective inhibitor of HSV DNA polymerase
  • DNA chain termination

CHHD (27 decks)

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