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Bacteria > Antimicrobial Chemotherapy > Flashcards

Antimicrobial Chemotherapy Flashcards

1
Q

Benzyl penicillin’s

A

Inhibit cell wall synthesis
Beta lactam
Bactericidal
Mainly effective against gram positive bacteria
Gram negatives are widely resistant

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2
Q

Cephalosporins

A

Inhibit cell wall synthesis
Bactericidal
Second large group of beta lactams

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3
Q

What is the mechanism of beta lactams?

A

They inhibit peptidoglycan synthesis by inhibiting the enzymes (penicillin binding proteins) that cross link the carbohydrate chains of the peptidoglycan cell wall.

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4
Q

Glycopeptides

A

Group of antibiotics that inhibit cell wall synthesis
Bactericidal
Only act on gram positive organisms
Act on cell wall synthesis a stage prior to beta lactams
Inhibit assembly of a peptidoglycan precursor
Only given parenterally

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5
Q

Vancomycin

A

Glycopeptide
Toxicity is common
I.V. infused and carefully monitored

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6
Q

Teicoplanin

A

Glycopeptide
Less toxic than vancomycin

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7
Q

Aminoglycosides

A

Inhibit protein synthesis
Concentration dependant bactericidal antibiotics
Useful in treating serious gram-negative infection

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8
Q

Mechanism of aminoglycosides

A

Inhibit protein synthesis
Acts only on bacterial protein synthesis due to differences in bacterial and mammalian ribosomes.
Binding impairs the proofreading of translation leading to mistranslation of the RNA message and inaccuracy of the translated protein product.

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9
Q

Gentamicin

A

Aminoglycoside
Toxic and requires a careful dosing regime and close monitoring.

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10
Q

Macrolides

A

Inhibit protein synthesis
Bactericidal or bacteriostatic
Useful in treating gram positive infections when patient has a penicillin allergy

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11
Q

Macrolide mechanism

A

Inhibit protein synthesis
Prevent peptidyltransferase from adding the growing peptide attached to tRNA to the next amino acid
Also inhibits ribosomal translation

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12
Q

Erythromycin

A

Example of a macrolide

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13
Q

Tetracyclines

A

Inhibit protein synthesis
Batceriostatic antibiotics
Treats gram positive infections
A significant percentage of staph. and strep. strains are resistant

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14
Q

Mechanism of tetracyclines

A

Tetracyclines prevent the introduction of new amino acids to the nascent peptide chain

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15
Q

Oxazolidinones

A

Inhibit protein synthesis
Bacteriostatic or bactericidal dependant on the bacteria being treated
Usually treat gram positive infections

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16
Q

Linezolid

A

Oxadolidinone
Only antibiotic in this class in common use
Generally reserved for serious infections

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17
Q

Cyclic lipopeptides

A

Inhibit protein synthesis
Strong bactericidal agents
Treat gram positive infections

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18
Q

Daptomycin

A

Cyclic lipopeptide
Acts against gram positives and MRSA in particular
Alters the curvature of the membrane, causing holes that leak ions, deplarization and bacterial cell death

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19
Q

Purine synthesis inhibitors

A

Inhibit nucleic acid synthesis
Bacteriostatic and bactericidal when combined
Inhibit DNA synthesis directly or by interrupting precursors for DNA synthesis

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20
Q

Trimethoprin and sulphamethoxazole

A

Often used in combination as co-trimoxazole
Does not predispose C.difficle

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21
Q

Fluroquinolones

A

Bactericidal
Inhibit nucleic acid synthesis
Particularly effective against gram negative organisms
Inhibit DNA synthesis more directly

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22
Q

Ciprofloxacin and levofloxacin

A

Fluroquinolones

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23
Q

What are the two types on antibiotic resistance

A

Inherent and acquired

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24
Q

Inherent resistance

A

When all strains of a given species are resistant to an antibiotic
Streptococci are always resistant to aminoglycosides
Gram negative organisms are always resistant to vancomycin

25
Q

Acquired resistance

A

May be present in certain strains but not others
Laboratory sensitivity testing is required to establish the sensitivity of the patients bacterial isolate

26
Q

What is antibiotic resistance a good example of?

A

Natural selection

27
Q

Two ways that resistance is acquired

A

1) Spontaneous mutation
2) Genes that code for resistance can be spread from organism to organism or species to species
Genes can be carried on plasmids or transposons

28
Q

Conjugation

A

DNA transfer between bacterial cells

29
Q

Transformation

A

Naked DNA uptake by bacteria

30
Q

Transduction

A

Bacterial viruses transferred by viruses

31
Q

Beta lactamases

A

Enzymes produced that cleave the beta lactam ring of an antibiotic and thus render it inactive

32
Q

Where are beta lactamases most often seen?

A

In most hospital strains of staph. aureus and also in many gram-negative bacilli

33
Q

Two ways of combatting beta lactamase

A

1) Modify the antibiotic side chain to include a beta lactamase inhibitor
2) Introduce a second compartment to the antibiotic (beta lactamase inhibitor) protecting the antibiotic from enzymatic degradation

34
Q

Co-amoxiclav

A

Amoxicillin plus beta lactamase inhibitor clavulanic acid

35
Q

Flucoxaicillin

A

Modified form of penicillin that resists beta lactamase

36
Q

Extended spectrum beta lactamases

A

Enzymes that mediate resistance to extended spectrum cephalosporins
Antibiotic resistance transferred by conjugation

37
Q

Carbapenemase-producing enterobacteriaceae

A

Bacteria resistant to carbapenem family of antibiotics by producing carbapenemase

38
Q

Carbapenem Resistant Enterobacteriaceae

A

Bacteria resistant to carbapenem family of antibiotics by any mechanism
Serious problem as this sometimes leaves no options for antimicrobial therapy.

39
Q

What mechanism has MRSA developed to become multi-drug resistant?

A

It has developed resistance to beta lactams by changing the shape of its penicillin protein binding sites. The PBP changes shape causing a modified binding site that beta lactams can’t bind to.

40
Q

What can MRSA be treated with?

A

Vancomycin or Linezolid

41
Q

Glycopeptide resistance

A

Before gram positive resistance to glycopeptides was virtually unknown.
Recently vancomycin resistant enterococci have been emerging
The peptidoglycan precursor that vancomycin usually binds to has an altered structure.

42
Q

Agents used only in UTI’s

A

Nalidixic acid and nitrofurantoin

43
Q

What can cause thrush (overgrowth of candida albicans)

A

Therapy with penicillin’s or cephalosporins

44
Q

Polyenes

A

Anti-fungal drug
Binds to ergosterol, present in the fungal cell wall
Active against yeasts and filamentous fungi

45
Q

Amphotericin B

A

Polyene
Only available for IV use and used in serious fungal infections
Extremely toxic

46
Q

Nystatin

A

Polyene
Available for topical use

47
Q

Azoles

A

Anti-fungal drug
Inhibits ergosterol synthesis

48
Q

Fluconazole

A

Azole
Oral and parenteral treatment of yeast infections
No serious toxicity
Some yeasts are resistant

49
Q

Itraconazole

A

Active against yeasts and filamentous fungi

50
Q

Allylamines

A

Suppress ergosterol synthesis
Anti-fungal
Only allylamine used is terbinafine which is active against dermatophyte infections of the skin

51
Q

Echinocandins

A

Anti-fungal
Inhibit the synthesis of glucan polysaccharide in several types of fungi
Only used in serious candida and aspergillus infections

52
Q

Nucleoside analogues

A

Most anti viral drugs
Interfere with nucleic acid synthesis

53
Q

Aciclovir

A

Nucleoside analogue
Anti-herpes virus drugs
Specific for virus infected cells
Active against herpes simplex and varicella zoster

54
Q

Valaciclovir, famciclovir, valganciclovir

A

Anti-herpes virus drugs

55
Q

Herpes viruses

A

Herpes simplex, CMV, varicella-zoster, epstein-barr virus

56
Q

Zidovudine

A

First anti-HIV drug

57
Q

How do we usually treat HIV now?

A

Combination therapy with at least 3 drugs
Drugs active on at least 2 different stages of HIV replication
2 nucleoside analogue reverse transcriptase inhibitors plus a non-nucleoside reverse transcriptase inhibitor or a viral protease inhibitor

58
Q

Interferon-A, ribavirin, adevofir dipivoxil

A

Drugs for chronic hepatitis B and C

59
Q

Drugs for viral respiratory infections

A

Zanamivir, oseltamivir, ribavirin

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