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Pharmacology 2. A topics > 17. Penicillins and beta-lactamase inhibitors > Flashcards

17. Penicillins and beta-lactamase inhibitors Flashcards

1
Q

Structure of penicillins

A

Beta-lactam ring (that can be cleaved by beta-lactamase) and thiazolidine ring. Two chains that are responsible for pharmacokinetics and antimicrobial spectrum.

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2
Q

How does structure influence pharmacokinetic properties of penicillins?

A
  • If Na/K -> water-soluble -> can be given IV. 2-3h
  • if procaine -> bad water solubility, relatively long action. Is not usually given alone. Up to 24h
  • Benzatine -> least water-soluble. Very long action. Up to 72 hours
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3
Q

What is the target of penicillins?

A

PBP - penicillin binding proteins: transpeptidase and carboxipeptidase - enzymes responsible for last step of bacterial cell wall synthesis - transpeptidation.

Beta-lactam drugs have similar structure to peptide chain -> PBP will bind beta-lactam drugs and not the bacterial peptide chain -> IRREVERSIBLE INACTIVATION of PBP -> cross-linking doesn’t happen -> weak cell wal -> collapsing of the cell wall and death

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4
Q

What is peptidoglycan? What is its structure?

A

= Murein. Layer of bacterial cell wall. Is important for cell wall integrity especially in Gram+ bacteria.
N-acetyl-muranic acid (NAM) and N-acetyl-glucose amine chain (NAG) make long chains that are connected to each other by transpeptide bonds. For formation of these bonds PBP (penicillin binding proteins) are responsible.

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5
Q

Mechanism of action of penicillins

A

Inhibition of synthesis of the peptidoglycan layer of bacterial cell wall. Irreversible inactivation if PBP (penicillin binding proteins) -> cross-linking (transpeptidation) does not happen -> collapse of cell wall and death of bacteria

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6
Q

Mode of action of penicillins

A

BACTERIACIDAL. Time-dependent. Also hav PAE (postantibiotic effect) 4-8h.

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7
Q

Why penicillins should NOT be used with bacteriostatic drugs?

A

Penicillins work against cell wall synthesis => against dividing bacteria.
Bacteriostatic drugs INHIBIT division of bacteria

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8
Q

Against what type of bacteria penicillins are most effective? Why?

A

Against Gram+ bacteria because

  1. huge part of their cell wall is peptidoglycan -> very sensitive to beta-lactam antibacterial drugs.
  2. PBPs are locate between cell wall and cell membrane an it’s much easier for drug to penetrate cell wall of Gram+ bacteria than Gram- (in gram- it can come only through PORINS)
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9
Q

Types of resistance against penicillins

A
  1. Ab ovo (primary). Never effective against pathogen: mycoplasma
  2. Beta-lactamase production
  3. PBP-gene mutation (e.g. MRSA, MRSP)
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10
Q

Examples of ab ovo resistance to penicilins

A
  • Mycoplasma - absence of cell wall. (resp tract infection in poultry and swine)
  • acid-fast bacteria - penicillin cannot penetrate and reach the target (Mycobacteria)
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11
Q

Against what bacteria were penicillinase stable penicillins created?

A

Against Staphylococcus. Gram+ bacteria that produces beta-lactamase

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12
Q

What bacteria produce beta-lactamase?

A

all gram– and Staphylococci

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13
Q

What are the ways to avoid beta-lactamase resistance?

A
  1. To use clavulonic acid
  2. To change structure of the drug
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14
Q

What happens if bacteria modifies its PBP? Can we apply penicillins?

A

If PBP is changed - NONE of beta-lactam antibacterial drugs will be efficient

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15
Q

MRSA - ?

A

Methicillin resistant Staphylococcus aureus.
Staphylococci produce beta lactamase -› penicilinase resistant penicillins were created with slightly different structure (methicillin, oxacillin, cloxacillin) -› PBPs mutated and changed structure -› none of beta-lactam antibacterial drugs is anymore resistant against MRSA

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16
Q

MRSP -?

A

Methicillin Resistant Staphylococcus pseudintermedius

17
Q

What are the types of antibacterial spectrum of penicillins?

A
  1. Narrow spectrum bacteria
  2. Penicilinnase stable penicillins
  3. Extended spectrum penicillins
  4. Penicillins acting against Pseudonomas spp.
18
Q

Narrow spectrum penicillins act against …

A

Most of gram+ bacteria, fastidious gram- + Leptospira, Borrelia, anaerobes

19
Q

What are the drugs belonging to narrow spectrum penicillins?

A
  • benzylpenicillin - Na/K (water-soluble)
  • benzylpenicillin - procaine
  • benzylpenicillin - benzathine
  • phenoxymethyl-penicillin (acid-stable, can be given orally)
  • penethamat (can cross blood-milk barrier)
20
Q

What bacteria are fastidious gram- ?

A
  • Pasteurella
  • Haemophilus
  • Actinobacillus
  • Mannheima

mainly cause respiratory tract infections

21
Q

Narrow spectrum penicilins are the first choice of trearment of: …

A
  1. swine erysipelas (diamond skin disease) Erysipelothrix rhusiopathiae
  2. anthrax - Bacillus anthracis
  3. tetanus - Clostridium tetani
  4. necrotic enteritis of poultry - Clostridium perfringens
  5. streptococcosis (mastitis, dermatitis, pharyngitis)

respiratory infections - not the first choice but can be treated

22
Q

What narrow spectrum penicillin can be absorbed orally?

A

phenoxymethyl-penicillin

23
Q

What is the distribution of narrow spectrum penicillins (PK)?

A

Distribution is poor. Hydrophilic. Can’t enter the cells -› not effective against intracellular organisms.

Most of penicillins can’t cross special biological barriers (exception: penethamat - can cross blood-milk barrier)

24
Q

What is the metabolism and excretion of narrow spectrum penicillins (PK)?

A

Metabolism is minimal. Can be given to patience with liver failure.

Excretion mainly via kidney. In active form and also concentrated.

25
Q

What are side effects of narrow spectrum penicillins?

A
  • allergy, non-immunological anaphylactic reaction (because of histamine release from mast cells). If adminestered IV then even more severe
  • dysbacteriosis (esp. in HORSES and RODENTS)
  • the most toxic nar. sp. pen. - procaine-penicilin (because of procaine) - restlessness, tremor. PIGLETS and FOALS are esp. sensitive. Doping drug.
26
Q

Can respiratory infections be treated by narrow spectrum penicillins?

A

Yes. But mostly not the first choice

27
Q

What narrow spectrum penicillins are often used together?

A

benzylpenicillin-procaine and benzylpenicillin-benzathine to increase duration of action

28
Q

Against what bacteria were penicillinase stable penicillins invented for?

A

Against Staphylococci and Streptococci mostly causing mastitis and dermatitis

29
Q

Are penicillinase stable penicillins effective against gram- bacteria?

A

NO

30
Q

What drugs belong to the penicilinase stable penicillins?

A
  • methicillin (now only historical significance. first kind of this kind)
  • Oxaciline
  • Cloxacillin
  • Dicloxacillin
  • Flucloxacillin

usually used as intramammary infusion in case of mastitis.

31
Q

Extended spectrum penicillins act against what type of bacteria?

A

Most of gram+ bacteria and several gram- bacteria

32
Q

Extended spectrum penicillins are important because they can act against…

A

E. coli and Salmonella

33
Q

Drugs belonging to broad spectrum penicillins

A
  • amphicillin (outdated: bad oral absorption, feed reduces it even more)
  • amoxicillin
34
Q

Why amphicillin considered outdated drug

A

Relatively bad oral absorption and fee reduces it even more. Instead amoxicillin is used

35
Q

Broad spectrum penicillins are used in case of:

A
  • same as narrow spectrum penicilllins and in case of respiratory infections are more effective
  • urinary tract infections - 1st choice
  • GI infection
  • Dermatitis, soft tissue infections
  • Lyme-disease
  • Osteomyelitis
  • Oral cavity infection, bite wounds
  • Septicaemia, bacteraemia
36
Q

Penicillins acting against Pseudonoas spp. Drugs:

A
  • Piperacillin (+tazobactam)
  • Ticarcillin (+ clavulonic acid)
37
Q

To what group of AMEG classification do penicillins acting against Pseudonomas spp. belong?

A

A. Avoid => only in small animals

Pharmacology 2. A topics (16 decks)

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