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INFECTION AND IMMUNOLOGY > Ian B Lec 1 Penicillins & Ceph > Flashcards

Ian B Lec 1 Penicillins & Ceph Flashcards

1
Q

How is penicillin G administered?

Why is this?

A

Injection only

Degraded in gastric acid due to low stability

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2
Q

What is the structural difference between penicillin G and V?

What does this mean?

A

Penicillin G has no polar O group on R group but V does!

Penicillin V is orally active (However not all of it is absorbed)

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3
Q

__% of patients who are allergic to penicillins are allergic to _____ too.

A

10%

Cephalosporins

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4
Q

Penicillins are peptide derived (cysteine & valine) so they can trigger an _____ response = anaphylaxis

A

Immune

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5
Q

Why was an acyl group aded to 6-acyl penicillins (derivatives of 6-APA (6-amino-penicillanic acid))?

A

To improve PK properties
Meant a lower dose was needed
Improved affinity for target

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6
Q

By finishing a course of penicillin you won’t kill 100% of the bacteria but kill the vast majority to reduce the ______.

Now _ and _ cells can kill the rest.

A

Bioburden

T & B cells

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7
Q

Methicillin is structurally ____.

This means that enzymes find it difficult to _____ it as it doesn’t fit their active site.

This makes it a powerful antibiotic.

A

Bulky

Metabolise

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8
Q

TRUE/FALSE?

1) Ampicillin can be taken orally
2) Ampicillin is active against both g+ve and -ves
3) Ampicillin can be used to treat Ps. aeruginosa infection

How many times is it give a day? OD, BD, TDS, QDS

A

1) TRUE
2) TRUE
3) FALSE

QDS

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9
Q

All penicillins show some degree of activity against Gram - ____.

A

Cocci

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10
Q

Ticarcillin can be used to treat Ps. Aeruginosa.

TRUE/FALSE

A

TRUE
Gram+ve, -ve and Ps. Aeruginosa

TDS-QDS

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11
Q

What is Flucloxicillin active against?

+ve, -ve, Ps. A?

A

ONLY G+ve

(some gram -ve cocci)

QDS

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12
Q

Flucloxicilin is stable towards B-lactamases from S.aureaus and gram-ves.

WHY?

A

Because it is bulky and doesn’t fit in the enzymes active site easily.

Bacteria can’t then cleave the B-lactam ring

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13
Q

Cefalosporin C is NOT used clinically.

It becomes clinical when you add ____ ____.

A

Side chains

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14
Q

Cefepime and Cefpirome are ___ generation cefalosporin.

A

4th

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15
Q

Cefamandole is a ____ generation cefalosporin.

How is it administered?

A

2nd

Orally

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16
Q

Ceftriaxone is a ____ generation cefalosporin

How is is administered?

A

3rd

Injection only

17
Q

As the cefalosporin generations progress, the trend is that they become more active against g_ve bacteria

They also become ____ resistant to beta lactamases

A

G-ve

More

18
Q

Activity of cefalosporins against g_ve bacteria depends on affinity for _ _ _s

Activity of cefalosporins against g_ve bacteria depends on penetration through the ___ ______.

A

G+ve bacteria
Penicillin binding proteins

G-ve bacteria
Outer membrane

19
Q

What are the 4 groups of drugs that contain a beta lactam ring?

A
  • Penicillins
  • Cefalosporins
  • Carbapenems
  • Monobactams
20
Q

What are the 4 ways resistance can occur?

A
  • Efflux pumps
  • Metabolise the drug
  • Decrease entry
  • Alter active site (e.g change Dala Dala to Dala Dlactate) This leads to VRE in Enterococci
21
Q

What might piperacillin be a better substrate mimic or PBPs?

A
  • Forms more H bonds
  • More peptide bonds
  • Higher affinity
  • Better binding
22
Q

Carbapenem is a synthetic antimicrobial

- The _____ is replaced with a _____

A

Sulphur

Carbon

23
Q

Imipenem is ____ spectrum

  • Relatively _____ to beta lactamases
  • Poor in vivo ____
A

Broad
Resistant
Stability

24
Q

Aztreonam is a _____
It is highly active against most g_ve bacteria
Stable to most types of B lactamase

IV admin

A

Monobactam

G-ve

25
Q

Carbapenems, 3rd generation cefalosporins and Aztreonam synergise with _______.

E.g G_____ and T______

treat Pseudomonas lung infections in CF

A

Aminoglycosides

Gentamicin
Tobramycin

26
Q

Sulbactam, Brobactam, Tazobactam and _____ ___ are all what?

A

Clavulonic acid
Inhibitors of B lactamases

They remain bound once the B lactam ring is hydrolysed

27
Q

How do B-lactams work?
- Final stage of PG assembly is the ____-____ of the linear glycan strands assembled by trans_____ to the existing PG in the ___ ___.

  • Reaction catalysed by t______ enzymes, located on outer face of cell membrane.
  • They remove the terminal D-_____ residue from each stem peptide on the newly synthed glycan chain.
  • Energy released from breaking the peptide bond used in formation of new peptide bond between the remaining d-alanine on the stem peptide and free ____ group on the 3rd AA of the stem peptides in the existing cross linked PG.
  • Acceptor amino group supplied by amino acid L-lysine.

B LACTAM ANTIBIOTICS INHIBIT ______ (PBPs) by acting as alternative substrates (covalently bonding by mimicking D-alanyl-D-alanine)

THUS blocking _____-_____ of the PG.

A

Cross linking
Transglycosylation
Cell Wall

Transpeptidase

D-alanine

Amino group

TRANSPEPTIDASES

Blocks cross linking

28
Q

Porins are tr____ protein channels that B lactam drugs pass through.

Bacteria that have fewer channels are more _____

A

Trimeric

Resistant

29
Q

Bacteria that make more/less B lactamases are more resistant.

A

LESS - they are released into the inner and outer layer gaps

If more were made then they would be released and diffuse away quickly into the medium

30
Q

If a B lactam drug gains access to the bacteria then a pump can push it back outside the cell.

This is a mechanism of _______.

The efflux pump is a _ _ _ (_ ______) efflux pump

It works by binding the xenobiotic, inverting the protein in membrane which causes a change in _____ and the drug is released on the ex_______ side.

A

Resistance

PGP (P glycoprotein efflux pump)

Affinity

Extracellular

31
Q

Efflux pumps e.g…
PGP1 (MDR1)
ABCB1 (CD243)

Are all transporters that can cause the efflux of _-_____.

A

B-lactams

32
Q

Metabolism of drugs can cause resistance:

  • B-lactamases
  • Hydrolysis e.g to deactivate anti-____ in ___ acid mimetic antibiotics.
  • Oxidative demethylation catalysed CYP450
A
  • Anti-folate

- Folic acid mimetics

33
Q

VRE - _____ _____ _____

Become resistant by obtaining new _ _ _ in the form of ____ or _____ which encode genes that confer Vancomycin resistance.

High level Vanc resistant E.faecalis and E.faecium associated with outbreaks of hospital-acquired (______) infections

A

Vancomycin Resistant Enterococci

DNA

Plasmids/transposons

Nosocomial

34
Q

_ different types of Vancomycin resistance shown by Enterococcus.

Van-A VRE resistant to Vanc and T_____
Van-B VRE resistant to Vanc but sensitive to T____
Van-C VRE partially resistant to Vanc and sensitive to T___

A

6

Teicoplanin
Teicoplanin
Teicoplanin

35
Q

Mechanism of resistance to Vancomycin in Enterococcus:

Alteration of terminal AA residues of NAM/NA_ peptide subunits.

Normally Vanc binds D-Alanyl-D-alanine but D-Alanyl-D-____ mutation of O for NH results in loss of 1 _-_____ interaction.

A

NAM/NAG

D-Alanyl-D-Lactate

H-Bonding interaction

(1000-fold decrease in affinity)

INFECTION AND IMMUNOLOGY (14 decks)

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