Bacterial cell wall synthesis inhibitors Flashcards
Recall some of the key information covered in this topic on bacterial cell wall synthesis inhibitors
Name 2 classes of bacterial cell wall synthesis inhibitors.
Beta-lactams, Glycopeptide
Beta lactams bind to the active side of which enzyme?
Transpeptidase (penicillin binding protein)
Name 4 types of beta lactams
Penicillins, cephalosporins, carbapenems, monobactam
Name the 4 classes of penicillins
- natural penicillins (Pen G and Pen V),
- penicillinase resistant penicillins (cloxacillin, flucloxacillin),
- aminopenicillins (amoxicillin, ampicillin),
- antipseudomonal penicillins (piperacillin)
Which natural penicillin is administered parenterally?
Penicillin G
Syphilis caused by Treponema pallidum can be treated with which penicillin?
Penicillin G
Are natural penicillins commonly used against Staphylococcus aureus?
No
Which class of penicillin is commonly used against methicillin sensitive Staphylococcus aureus?
Penicillinase resistant penicillins
How does methicillin sensitive Staphylococcus aureus acquire resistance against the natural penicillins?
They produce penicillinases
Which bacteria is cloxacillin effective against?
Methicillin Sensitive Staphylococcus aureus (MSSA)
How are the penicillins mainly cleared?
Renal clearance
Name the 2 aminopenicillins
Ampicillin, amoxicillin
Are aminopenicillins effective against beta lactamase producing strains of bacteria?
No
Which of the aminopenicillins (amoxicillin or ampicillin) has better oral absorption?
Amoxicillin
Does aminopenicillins sufficiently cover Pseudomonas and Klebsiella?
No
How are aminopenicillins cleared?
Renal excretion
How is piperacillin administered?
Intravenously
Which class of penicillins has coverage against Pseudomonas, Proteus and Klebsiella?
Anti-pseudomonal penicillins (piperacillin)
Name 3 beta lactams-beta-lactamase inhibitor combination drugs.
- Augmentin (Amoxicillin + clavulanic acid)
- Unasyn (ampicillin + sulbactam)
- Zosyn (piperacillin + tazobactam)
How do beta-lactamase inhibitors work?
They either covalently bind at or near the active site of the β-lactamase and restructures it, permanently inactivating. In doing so, they protects other beta-lactam antibiotics from beta-lactamase catalysis.
Name a microbe that commonly causes nosocomial infections and is resistant to all penicillins.
MRSA (methicillin resistant Staphylococcus aureus)
Name at least 2 penicillins related life-threatening allergic reactions.
- Anaphylaxis
- Stevens Johnson syndrome
- Toxic epidermal necrolysis
Which generation of cephalosporins does cefazolin and cephalexin belong to?
First generation
Which generation of cephalosporins are primarily administered orally?
First and second generation cehalosporins. Cefazolin (first generation) is an exception.
How are the 3rd, 4th and 5th generation cephalosporins administered?
Parenterally
Name at least 3 types of microbes against which first and second generation cephalosporins are ineffective?
- Pseudomonas aeruginosa and
(LAME species)
- Listeria monocytogenes,
- Atypicals (Mycoplasma, Chlamydia, Legionella spp.),
- MRSA, and
- Enterococcus species
Ceftriaxone belongs to which generation of cephalosporins?
Third generation
Name one cephalosporin from the third and fourth generation each which is effective against Pseudomonas aeruginosa.
Third generation – Ceftazidime
Fourth generation - Cefepime
Which generation of cephalosporins has coverage against MRSA?
Fifth generation (ceftobiprole, ceftaroline)
How are most cephalosporins cleared?
Renal clearance
How is ceftriaxone cleared?
Hepatic clearance
Explain the mechanism of resistance underlying MRSA.
MRSA expresses an altered penicillin binding protein (PBP2a) with reduced affinity for the penicillins
Name 3 advantages the third generation and fourth generation cephalosporins have over the first and second generations.
- Higher activity against Gram-negative bacteria
- Greater resistance against the beta-lactamase producing strains
- Greater CSF penetration
Does cephalosporin have cross reactivity with penicillins?
Yes
Does cephalosporin have cross reactivity with penicillins?
Yes
Name the class of antibiotics that are commonly used against extended spectrum beta-lactamase (ESBL) producing bacteria?
Carbapenems
Name 3 carbapenems.
- Imipenem,
- meropenem,
- ertapenem
How are carbapenems administered?
Parenterally
Imipenem is combined with __________, which works by __________.
cilastatin,
inhibiting dehydropeptidase 1 (DHP1) found in the brush border of the proximal renal tubule. (DHP1 is necessary for the hydrolysis of imipenem. It is not a beta lactamase inhibitor.)
Can carbapenems be used to treat MRSA?
No
Which carbapenem has good CSF penetration?
Meropenem
Which of the following carbapenems is not effective against Pseudomonas aeruginosa?
Ertapenem
Which drug classes of beta lactams have cross reactivity with penicillins?
Cephalosporins, carbapenem
Which drug class does aztreonam belong to?
Monobactam
Aztreonam is effective against Gram-
negative bacteria (no activity against Gram positive and anaerobic microbes)
Does aztreonam have cross-sensitivity to penicillin?
No
What are some adverse effects related to the use of penicillins, cephalosporins and carbapenems?
GIT related symptoms (vomiting diarrhea), hypersensitivity (Symptoms range in severity, from a minor rash to life-threatening conditions like anaphylaxis)
Vancomycin is useful against Gram ___________
positives
How is vancomycin commonly administered?
Intravenously
When is oral vancomycin preferred?
Clostridium difficile-associated diarrhea (CDAD) or the more severe antibiotic-associated pseudo-membranous colitis.
What is the first line of antibiotics for CDAD?
Vancomycin
Vancomycin interferes with cell wall synthesis by inhibiting ___________
transglycosylation
Name 3 antibiotics that work by inhibiting bacterial cell wall synthesis, and are effective against MRSA?
- ceftobiprole (Fifth generation cephalosporins)
- ceftaroline (Fifth generation cephalosporins)
- Vancomycin
How is vancomycin cleared?
Renal clearance
Name 3 adverse effects related to vancomycin
- Nephrotoxicity,
- Ototoxicity,
- Red man syndrome