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Penicillins Flashcards

1
Q

What is among the most commonly used antibiotics in vet med?

A

Penicillins

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2
Q

Why are penicillins called Beta-lactam antibiotics?

A

Because of a ringlike structure in their chemical composition

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3
Q

What other group of antibiotics has a Beta-lactam ring?

A

Cephalosporins

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4
Q

What are the most commonly used penicillians?

A

Natural penicillins
Broad-spectrum aminopenicillins
Penicillinase-resistant or Beta-lactamase-resistant penicillins
Extended-spectrum penicillins

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5
Q

What is an example of a natural penicillin?

A

Penicillin G

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6
Q

What are examples of Broad-spectrum aminopenicillins?

A

Ampicillin

Amoxicillin

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7
Q

What are examples of Penicillinase-resistant or Beta-lactamase-resistant penicillins?

A

Cloxacillin
Dicloxacillin
Oxacillin
Methicillin

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8
Q

What are examples of Exteneded-spectrum penicillins?

A

Ticarcillin
Carbenicillin
Piperacillin

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9
Q

What are pencillins effective against?

A

Many gram-positive bacteria

Lesser number of gram-negative bacteria

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10
Q

Are penicillins bactericidal or bacteristatic?

A

Bactericidal

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11
Q

How do penicillins work primarily?

A

by attaching to & blocking the bacterial enzymes needed to assemble the cell wall during bacterial cell division

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12
Q

What does blocking the bacterial enzymes needed to assemble the cell wall accomplish?

A

Makes the resulting wall more structurally unstable

Makes the bacterium more prone to lysis from osmotic imbalances

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13
Q

What explains why one type of penicillin may be more effective against a bacterial population than another type?

A

Different penicillins affect different wall-building enzymes

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14
Q

What is a bacterial strain found on the skin and has acquired resistance to all penicillins?

A

Methicillin-resistant Staphylococcus aureus

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15
Q

How has MRSA become resistant to all pencillins?

A

The targeted wall-building enzymes to which penicillin attaches changes molecular shape making penicillins unable to dock & disrupt enzymes

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16
Q

Why should bacteriostatic antimicrobials not be used simultaneously with Beta-lactam antibiotics?

A

Because Beta-lactam antibiotics need the bacterial colony to be actively replicating and bacteriostatic antimicrobials inhoibit division of bacteria

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17
Q

Penicillins are well absorbed from where?

A

The injection site and GI tract

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18
Q

Which penicillin is inactivated by gastric acid and thus should never be given orally

A

Penicillin G

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19
Q

Because penicillin molecules are hydrophilic, it will not reach therapeutic concentrations where?

A

Globe of the eye
Brain
Prostate

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20
Q

Why are penicillin concentrations much higher in the urine than in the blood?

A

Because penicillin is actively transported by the renal tubules into the forming urine

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21
Q

Why are penicillins more commonly used to treat bacterial cystitis?

A

Because urine penicillins will exceed the MIC for many bacteria found in the kidneys, bladder or genitourinary tract

22
Q

What is the selection of particular antimicrobial drug before the results of a culture & sensitivity test are returned?

A

Empiric treatment

23
Q

Why are penicillins more effective against gram-positive bacteria?

A

Because they have a cell wall that is readily accessible to penicillin drug molecules

24
Q

Why are penicillins less effective against gram-negative bacteria?

A

Because they have an outer capsule that penicillins can only penetrate by slipping through porins

25
How do gram-negative bacteria become resistant to penicillin drugs?
By genetically decreasing the size of the porins
26
What particularly resistant gram-negative bacteria is commonly found in otitis externa or necrotic tissue?
Pseudomonas
27
What type of penicillins are likely to have much chance to be effective against Pseudomonas?
Only the most aggressive extended-spectrum penicillins Ticarcillin Carbenicillin
28
What is it called when a strain of bacteria that develops resistance to one type of penicillin, the bacteria will also be resistant to many of the other penicillins?
Cross-Resistance
29
What bacteria has acquire resistance to many penicillins because it produces an enzyme that attacks the penicillin's Beta-lactam rings?
Staphylococci spp
30
What group of penicilins are not affected by bacterial Beta-lactamase enzymes and are used in the treatment of bovine mastitis?
Oxacillin Dicloxacillin Cloxacillin Methicillin
31
What happens when a penicillin drug is combined with another compound, producing a strong modified penicillin resistant to the Beta-lactamase enzyme?
Pencillin drugs that are normally inactivated by Beta-lactamase can be chemically protected from the enzyme
32
What are two examples of compounds that are added to penicillins that produce a potentiated penicillin compound capable of withstanding bacterial lactamase enzymes?
Clavulanic acid (amoxicillin) and Sulbactam (ampicillin)
33
When Clavulanic acid or sulbactam combines with the Beta-lactamase enzymes, preventing the enzyme combining with and destroying the penicillin, what does it allow the penicillin to do?
Survive to attach to the cell wall enzymes and prevent normal cell wall formation
34
Why are penicillins considered quite safe?
Because their target bacterial cell walls & mammalian cells only have cell membranes, not cell walls
35
What is the most common type of adverse reaction seen with penicillins?
Hypersensitivity
36
What are the common signs of a hypersensitive reaction to penicillin?
``` Mild skin rash Hives Swelling of the lymph nodes Eosinophilia Neutropenia Fever ```
37
Life-threatening anaphylactic shock is more common with what kind of penicillin product?
Injectable
38
What happens when penicillin is given orally?
Penicillins may destroy beneficial gram-positive bacteria in the lumen of the intestinal tract, which allows more pathogenic, penicillin resistant bacteria to proliferate
39
What is the term to describe when penicillins destroy beneficial gram-positive bacteria and allow more pathogenic bacteria?
Superinfection or Suprainfection
40
Superinfection or Suprainfection causes diarrhea and death in what species?
Guinea pigs Ferrets Hamsters Rabbits
41
In what species should penicillins be used with caution in?
Snakes Birds Turtles Chinchillas
42
What group of pencillins are produced by mold and includes Penicillin G?
Natural penicillins
43
What penicillin has a narrow spectrum of activity and many bacteria are now resistant to?
Penicillin G
44
What are the 3 forms of penicillin G?
An aqueous solution Suspension form with procaine A longer-acting suspension combined with benzathine
45
What form of penicillin G contains a local anesthetic that may be prohibited in horses and last in the horse's system for 2 weeks?
Suspension combines with procaine
46
What group of penicillins include Ampicillin and amoxicillin, has a wider effective spectrum against gram-negative bacteria and is susceptible to destruction and inactiviation by Beta-lactamase?
Aminopenicillins
47
What can the injectable form of amipicillin and amoxicillin be formulated into that forms a slow-release suspension and prolongs the absorption of aminopenicillins?
Trihydrate
48
What group of penicillins are naturally resistant to the effects of the bacterial enzyme, has a low spectrum of activity?
Beta-lactamase-resistant penicillins
49
Why do Beta-lactamase-resistant penicillins have a low spectrum of antibacterial activity?
They do not penetrate the outer membrane of gram-negative bacteria
50
Beta-lactamase-resistant penicillins are used most commonly to treat what?
``` Staphylococcal osteomyelitis (bone infections) Staphylococcal pyoderma (skin infections) Staphylococcal mastitis ```
51
What group of penicillins have a wider spectrum than other penicillins, are expensive, able to penetrate the outer membrane of gram-negative bacteria and are susceptible to Beta-lactamase enzymes?
Extended-spectrum penicillins
52
What are extended-spectrum penicillins used to treat?
Severe, resistant gram-negative infections

Pharmacology (21 decks)

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