Penicillins Flashcards
What is among the most commonly used antibiotics in vet med?
Penicillins
Why are penicillins called Beta-lactam antibiotics?
Because of a ringlike structure in their chemical composition
What other group of antibiotics has a Beta-lactam ring?
Cephalosporins
What are the most commonly used penicillians?
Natural penicillins
Broad-spectrum aminopenicillins
Penicillinase-resistant or Beta-lactamase-resistant penicillins
Extended-spectrum penicillins
What is an example of a natural penicillin?
Penicillin G
What are examples of Broad-spectrum aminopenicillins?
Ampicillin
Amoxicillin
What are examples of Penicillinase-resistant or Beta-lactamase-resistant penicillins?
Cloxacillin
Dicloxacillin
Oxacillin
Methicillin
What are examples of Exteneded-spectrum penicillins?
Ticarcillin
Carbenicillin
Piperacillin
What are pencillins effective against?
Many gram-positive bacteria
Lesser number of gram-negative bacteria
Are penicillins bactericidal or bacteristatic?
Bactericidal
How do penicillins work primarily?
by attaching to & blocking the bacterial enzymes needed to assemble the cell wall during bacterial cell division
What does blocking the bacterial enzymes needed to assemble the cell wall accomplish?
Makes the resulting wall more structurally unstable
Makes the bacterium more prone to lysis from osmotic imbalances
What explains why one type of penicillin may be more effective against a bacterial population than another type?
Different penicillins affect different wall-building enzymes
What is a bacterial strain found on the skin and has acquired resistance to all penicillins?
Methicillin-resistant Staphylococcus aureus
How has MRSA become resistant to all pencillins?
The targeted wall-building enzymes to which penicillin attaches changes molecular shape making penicillins unable to dock & disrupt enzymes
Why should bacteriostatic antimicrobials not be used simultaneously with Beta-lactam antibiotics?
Because Beta-lactam antibiotics need the bacterial colony to be actively replicating and bacteriostatic antimicrobials inhoibit division of bacteria
Penicillins are well absorbed from where?
The injection site and GI tract
Which penicillin is inactivated by gastric acid and thus should never be given orally
Penicillin G
Because penicillin molecules are hydrophilic, it will not reach therapeutic concentrations where?
Globe of the eye
Brain
Prostate
Why are penicillin concentrations much higher in the urine than in the blood?
Because penicillin is actively transported by the renal tubules into the forming urine
Why are penicillins more commonly used to treat bacterial cystitis?
Because urine penicillins will exceed the MIC for many bacteria found in the kidneys, bladder or genitourinary tract
What is the selection of particular antimicrobial drug before the results of a culture & sensitivity test are returned?
Empiric treatment
Why are penicillins more effective against gram-positive bacteria?
Because they have a cell wall that is readily accessible to penicillin drug molecules
Why are penicillins less effective against gram-negative bacteria?
Because they have an outer capsule that penicillins can only penetrate by slipping through porins
How do gram-negative bacteria become resistant to penicillin drugs?
By genetically decreasing the size of the porins
What particularly resistant gram-negative bacteria is commonly found in otitis externa or necrotic tissue?
Pseudomonas
What type of penicillins are likely to have much chance to be effective against Pseudomonas?
Only the most aggressive extended-spectrum penicillins
Ticarcillin
Carbenicillin
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
What bacteria has acquire resistance to many penicillins because it produces an enzyme that attacks the penicillin’s Beta-lactam rings?
Staphylococci spp
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
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
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)
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
Why are penicillins considered quite safe?
Because their target bacterial cell walls & mammalian cells only have cell membranes, not cell walls
What is the most common type of adverse reaction seen with penicillins?
Hypersensitivity
What are the common signs of a hypersensitive reaction to penicillin?
Mild skin rash Hives Swelling of the lymph nodes Eosinophilia Neutropenia Fever
Life-threatening anaphylactic shock is more common with what kind of penicillin product?
Injectable
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
What is the term to describe when penicillins destroy beneficial gram-positive bacteria and allow more pathogenic bacteria?
Superinfection or Suprainfection
Superinfection or Suprainfection causes diarrhea and death in what species?
Guinea pigs
Ferrets
Hamsters
Rabbits
In what species should penicillins be used with caution in?
Snakes
Birds
Turtles
Chinchillas
What group of pencillins are produced by mold and includes Penicillin G?
Natural penicillins
What penicillin has a narrow spectrum of activity and many bacteria are now resistant to?
Penicillin G
What are the 3 forms of penicillin G?
An aqueous solution
Suspension form with procaine
A longer-acting suspension combined with benzathine
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
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
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
What group of penicillins are naturally resistant to the effects of the bacterial enzyme, has a low spectrum of activity?
Beta-lactamase-resistant penicillins
Why do Beta-lactamase-resistant penicillins have a low spectrum of antibacterial activity?
They do not penetrate the outer membrane of gram-negative bacteria
Beta-lactamase-resistant penicillins are used most commonly to treat what?
Staphylococcal osteomyelitis (bone infections) Staphylococcal pyoderma (skin infections) Staphylococcal mastitis
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
What are extended-spectrum penicillins used to treat?
Severe, resistant gram-negative infections
