Unit 3: K43b.Beta-Lactams Flashcards
Beta-Lactams: how they work
Inhibit cell (peptidoglycan) wall synthesis OR break apart cell wall BY binding to enzymes in cell membrane causing autolysis and cell death
Beta-Lactams: what makes something a beta-lactam?
The beta-lactam ring (think: chemistry)
Penicillins: 3 Groups
- Penicillins: great against gram+ organisms, gram- cocci, and non-beta-lactamase-producing anaerobes; little activity against gram- rods
- Anyistaphylococcal penicillins: resistant to beta-lactamases
- Extended spectrum penicillins: antibacterial spectrum of penicillins, improved activity against gram- rods, susceptible to hydrolysis by beta-lactamases
Peptidoglycan is a…
cross-linked polymer of polysaccharides and peptides
Cross-links give the cell wall its…
RIGIDITY
Beta-lactam antibiotics kill bacterial cells only when…
they are actively growing and synthesizing cell wall
PBP
Penicillin binding protein
MOA
Mechanism of action
MOA of Penicillins
PCN binds to PBP that cross link the peptidoglycan layer. The wall breaks apart, and osmotic pressure causes the bacteria to swell and then rupture/lyse
How do bacteria become resistant to penicillins?
- Inactivation of antibiotic by beta-lactamase (most common mechanism)
- Modification of target PBPs
- Impaired penetration of drug to target PNPs
- Antibiotic efflux
Function of peptidoglycan
Allows cell to withstand osmotic pressure. If peptidoglycan gets destroyed, the is most pressure overwhelms the cell.
How does beta-lactamase work?
Breaks the beta-lactam ring, which is essential to the function of beta-lactam antibiotics
MSSA vs MRSA
Methicillin SENSITIVE staph aureus
vs
Methicillin RESISTANT staph aureus
What is interesting about oxacillin?
Used to test staph aureus to see if it’s MRSA or MSSA
Penicillins: Side Effects
Serious reactions are more rare
Important note for penicillins and mononucleosis
Ampicillin and amoxicillin can be associated with skin rashes when prescribed in the setting of viral illnesses. The patient can end up with an “allergy” on their chart, eliminating beta-lactams as a class (which is a huge blow in terms of what medications they can take for infections)—when they might not even have a true allergy
Cephalosporins: how they differ from penicillins
Similar, but are more stable/resistant to beta-lactamases —> broader spectrum
How many generations of cephalosporins are there?
Technically 4. 5th generation ceftaroline is the only one that covers MRSA.
Cefazolin can only be given …
IV
Cephalexin route is…
PO
Advantage of cefuroxime
Relatively active against organisms inhibited by 1st generation drugs, BUT ALSO has extended GRAM- coverage
Ceftriaxone is often used for …
CAP (community acquired pneumonia)
OR
UTI
Cefepime is good for _______ spectrum
OR ___________
Broad
pseudomonas pneumoniae
Why is ceftaroline special?
1st beta-lactam that covers MRSA
Side effects of cephalosporins
Can cause skin rash
Can irritate kidneys
Granulocytopenia
Monitoring for cephalosporins
CBC
BMP (kidneys)
Can a patient with a PCN allergy take a cephalosporin?
MINOR: yes
MAJOR/ANAPHYLAXIS: caution; should not receive 1st or 2nd generation cephalosporin; if cephalosporin really needed, patient may need to be hospitalized to be desensitized
Monobactams: a beta-lactam that DOES NOT cover _____
GRAM+ bacteria or anaerobes
The only monobactam available in the US
Aztreonam
What is special about beta-lactamase inhibitors?
By themselves, not very effective. But coupled with a penicillin, can inhibit beta-lactamase and make penicillin more effective
Claulvulanic acid gets added to ______ to make ________
Clavulanic acid + AMOXICILLIN = AUGMENTIN
Tazobactam gets added to ______ to make ________
Tazobactam + PIPERACILLIN = ZOSYN
Key toxicity to watch out for with vancomycin
Nephrotoxicity
Monitoring for daptomycin
Creatinine phosphokinase (risk of myopathy)
Fosfomycin is only used for _____
How many doses?
UTI
1
What ointment is a beta-lactam?
Bacitracin
Cycloserine is used primarily to treat …
tuberculosis caused by strains of Mycobacterium tuberculosis resistant to first-line agents.
Dose-related adverse effects of cycloserine
serious, dose-related central nervous system toxicity with headaches, tremors, acute psychosis, and convulsions
List major groups of beta-lactams
Penicillins
Cephalosporins
Carbapenems
