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Pharm Y2S1 > Bacterial Infections > Flashcards

Bacterial Infections Flashcards

1
Q

What is the main bacterial cause of syphilis?

A

Spirochaete bacterium- Treponema pallidum

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2
Q

What did Paul Ehrlich receive a nobel prize for?

A

Investigated cure for sleeping sickness, but product he developed caused blindness. One of the compounds he synthesised actually cured syphilis and later derived neosalvarsan.

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3
Q

What is salvarsan?

A

Prodrug that metabolises to give oxophenarsine, used clinically against syphilis in 1930s. Reacts with protein thiol groups causing denaturation.

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4
Q

Describe the mechanism of action of beta lactams.

A

Inhibit cell wall synthesis in bacteria causing lysis. Enzymes responsible for forming crosslinks form covalent bonds with beta-lactam ring.

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5
Q

What are the three amino acids that penicillin is based on?

A

Phenylalanine
Cysteine
Valine

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6
Q

What does beta-lactam activity depend on?

A

Ability to penetrate cell wall
Resistance to beta-lactamases
Affinity of transpeptidases
Resistance to stomach acid

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7
Q

What are semi synthetic penicillins derived from?

A

6-aminopenicillanic acid

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8
Q

Why is penicillin G difficult to synthesise?

A

Requires 90 degree bond angles in the lactam ring

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9
Q

Describe the disadvantages of penicillin G.

A

Sensitive to beta-lactamases
Acid labile
Not given orally

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10
Q

Which beta-lactam is resistant to class I beta-lactamases?

A

Amoxicillin

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11
Q

Which beta-lactams are resistant to all beta-lactamases?

A

Flucloxacillin

Methicillin

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12
Q

What are celphasporins?

A

Beta lactams
2nd generation used in gram -ve infections
3rd generation used in serious gram -ve infections

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13
Q

What are carbapenems?

A

Broad spectrum beta-lactams with high incidence of resistance.

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14
Q

What is vancomycin?

A

Aminoglycoside, monobactam class. Used in serious gram +ve infections, not taken orally.

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15
Q

Describe the three types of ribosomal imaging that won the 2009 nobel prize.

A

Ramikrishnan- 30s subunit from Thermus thermophilis
Steitz- 50s subunit of Halocura marismortui
Yonath- drug ribosome structures in Deinococcus radiodurans

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16
Q

What are the features of tetracyclines?

A

Biosynthesised from acetate by Streptomyces.
Broad spectrum antibiotic with resistance being mostly membrane associated.
Work via inhibition of EFTu binding

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17
Q

Why are tetracyclines contraindicated in children?

A

Stain growing tooth enamel.

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18
Q

How do aminoglycosides work?

A

Cause misfunctioning of ribosomes by binding of aminoacyl-tRNA to the ribosomal A site. Especially active against gram -ve bacteria.

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19
Q

What is a disadvantage of aminoglycosides?

A

Often cause nephrotoxicity. Due to their chiral centres, they are hard to alter.

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20
Q

What is linezolid?

A

An oxazolidinone, works by inhibiting ribosome function. Active in MRSA and hospital acquired gram +ve infections. Toxic to 70s ribosomes.

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21
Q

What features of the structure of linezolid are advantageous?

A

Electron donating nitrogen improves its safety profile.

N-aryl group is required for activity.

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22
Q

Describe the original structure of erythromycin.

A

Derived from Saccharopolyspora erythema, originally existed of a mixture of closely related compounds, A and B. Around 90% of the mixture was the active erythromycin A.

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23
Q

What is erythromycin?

A

A macrolide, blocks the ribosomal exit tunnel in bacteria.

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24
Q

What are the disadvantages of erythromycin?

A

Foul tasting and extremely difficult to taste mask.

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25
Q

What makes telithromycin more active than erythromycin?

A

As a second generation ketolidem it is able to over come RNA ribosomal modification and is more hydrophobic and stable.

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26
Q

What is the complication of using chloramphenicol internally?

A

Aplastic anaemia

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27
Q

Describe the structural features of chloramphenicol.

A

Two chiral centres but only has one active isomer out of four. Combats growth of both gram +ve and -ve bacteria.

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28
Q

What are lincosamides?

A

Same action as macrolide, blocking the ribosomal exit tunnel. Used in anaerobic and protozoan infections such as TSS.

29
Q

What is the method of action of fusidic acid?

A

Binds to EFG in GTP form, binding to the ribosome as normal, GTP is then hydrolysed preventing the removal of EFG from the ribosome.

30
Q

Describe the action of quinolones.

A

Block a subunit of DNA gyrate, preventing the supercoiling of bacterial DNA. Broad spectrum and are active against penicillin resistant gram -ve infections.

31
Q

What is Nalidixic acid used in?

A

Quinolone with minimal serum levels used in uncomplicated urinary tract infections.

32
Q

What is ciprofloxacin used for?

A

Due to it being a fluoroquinolone, the increased electronegativity gives higher gram +ve and systemic activity. Used in respiratory tract infections and gonorrhoea, prophylaxis of M. meningitis and anthrax.

33
Q

What are the contraindications of ciprofloxacin?

A

Not used in children due to damaging tissues such as tendons.
Severe CNS effects when used with NSAIDs.

34
Q

What is levofloxacin?

A

Quinolone used in Streptococci infections

35
Q

What is levofloxacin derived from?

A

First generation quinolone, ofloxacin, with double the potency.

36
Q

When are nitrofurans used?

A

Broad spectrum urinary tract infections

37
Q

What environment do nitrofurans require?

A

Anaerobic- radical anions extract H from DNA causing cleavage of sugar-phosphate backbone.

38
Q

What is metronidazole used for? How?

A

Treatment of C. difficile infections using radical anions to extract H from DNA causing cleavage of sugar-phosphate backbone. Also treats helicobacter and protozoal infections.

39
Q

What is the main side effect of metronidazole?

A

Alcohol intolerance.

40
Q

How is C. difficile infection acquired?

A

Administration of broad spectrum antibiotics eliminates commensal microflora, thus allowing its proliferation.

41
Q

How was sulphanilamide first discovered?

A

Prontosil was tested as a treatment for Staphylococcal septicaemia by Domagk. Trefouel proved that this was a prodrug for sulphanilamide.

42
Q

How was the foul taste of sulphanilamide first masked?

A

With diethylene glycol solvent which was found to be extremely toxic.

43
Q

How does sulphanilamide work?

A

Mimics para-aminobenzoic acid in the metabolism of folate by inhibiting dihydroperoate synthetase. Not active against serious disease.

44
Q

What is sulphadiazine used for?

A

Treatment of bacterial infection, malaria, cancer and rheumatoid arthritis. 100x more active that sulphanilamide, it is 75% ionized at pH 7.4.

45
Q

What is the mechanism of action of trimethoprim?

A

Inhibits dihydrofolate reductase in folate metabolism. Doesn’t affect mammalian folate as its affinity for the bacterial enzyme is 5000x more than for the mammalian enzyme.

46
Q

What are substituted sulphanilamide used for?

A

Active against Gram-positive bacteria, including pneumococci and meningococci. Largely superseded by penicillins.

47
Q

Describe the required structure for sulphanilamides.

A

Sulfonamide group is required and optimum acidic pKa of the sulfonamide group for antibacterial activity is 6-7
Sulfonamide nitrogen must be SECONDARY
Aromatic ring is required and must be para-substituted with a para-amino group

48
Q

What are trimethoprim combinations used for?

A

Urinary tract infections, typhoid fever, chronic bronchitis, gonorrhoea in penicillin resistant patients

49
Q

Describe the structural uses of pyrimethamine.

A

Chlorophenyl ring makes it more hydrophobic than trimethoprim.
Gets taken up into cells, but is too hydrophobic and gets stuck in bacterial cell walls

50
Q

What is pyrimethamine used for?

A

It is a dihydrofolate reductase inhibitor used in protozoa and as an antimalarial.

51
Q

Describe the structural uses of methotrexate.

A

Pteridine ring gives DHFR activity

Glutamate (POLAR) side chain for active transport by an amino acid carrier

52
Q

What is methotrexate used for?

A

Targets mammalian DHFR.
Anticancer in rapidly proliferating tumours
At low doses in IBD, rheumatoid arthritis and ectopic pregnancy.

53
Q

What is the disadvantage of using penicillin and methotrexate concomitantly?

A

Penicillin inhibits elimination of methotrexate making toxic effects more likely.

54
Q

What is the cause of TB?

A

Mycobacterium tuberculosis

55
Q

What are the symptoms of TB?

A

Mainly respiratory

90% of infected are asymptomatic and don’t transmit the disease

56
Q

What are the targets for TB treatment?

A

Mycobacteria have a cell wall rich in mycolic acids.

57
Q

What is streptomycin? How does it work?

A

First developed antibiotic cure for TB, actively transported into cells to inhibit ribosome function. Must be given IM and resistance is common.

58
Q

What is isoniazid? How does it act?

A

Prodrug for isonicotinamide, resembling NADH thus inhibiting desaturate in mycolic acid synthesis in TB. Highly active in rapidly dividing strains but not used alone due to resistance.

59
Q

What is the action rifamycins? What are they derived from?

A

Inhibit RNA polymerase by binding the the beta subunit, preventing nucleotide dimers from forming complexes with another nucleotide. Biosynthesised by Amycolatopsis mediterranei.

60
Q

What are rifamycins used for?

A

First line therapy for treatment of TB.

61
Q

What is the action of ethambutol?

A

Inhibits arabinogalactan synthesis via arabinosyl transferase, preventing cell wall formation in TB.

62
Q

What is a complication of ethambutol use?

A

Optic neuritis.

63
Q

What is the action of pyrazinamide? What is it used for?

A

Prodrug converted to pyrazinoic acid in TB by pyraziniamidase. Can be used for TB treatment in pregnancy.

64
Q

What is cycloserine?

A

TB treatment that inhibits alanine racemes and alanine ligase.

65
Q

What are meningococci?

A

Gram negative diplococci with 12 antigenically different capsular groups.

66
Q

Which menigococcal capsular group accounts for the most cases of meningococcal disease?

A

Meningococcal B

67
Q

What is the leading cause of community acquired pneumonia in adults?

A

Streptococcus pneumoniae

68
Q

How many pneumococcal subtypes are there?

A

Over 90 but only 7-10 considered pathogenic.

69
Q

What is Haemophilus influenzae?

A

Bacteria with 6 capsular serotypes, B being the most prevalent strain before vaccine was introduced.

Pharm Y2S1 (8 decks)

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