Cell Wall Synthesis Inhibitors Flashcards
Describe the cell wall architecture of a gram-positive bacteria.
A thick murein wall outside the cytoplasmic membrain.
Describe the cell wall architecture of a gram-negative bacteria.
An outer lipopolysaccharide layer, outer membrane layer (both of these containing pores), a thin murein layer, and then an inner cytoplasmic membrane.
Describe the cell wall architecture of a mycobacteria.
From outside to in: extractable phospholipids, mycolic acids, and arabinogalactan (all three layers transversed by a pore), thin murein layer, and cytoplasmic mebrane.
Murein chains are cross-linked to one another by ___________ (__), also known as ________________.
transpeptidases; TP; penicillin-binding proteins
______________ (__) forms linkages between NAM & NAG residues.
glycosyltransferase; GT
Beta-lactams bind to & inhibit _____.
PBP (cross-linking)
Glycopeptides bind to terminal __________ residues, prevent cross-linking and polymerization.
D-alanine
What are the 4 major subclasses of beta-lactam antibiotics?
Penicillins
Cephalosporins
Carbapenems
Monobactams
Describe the structure of beta-lactam antibiotics and how this impacts the MOA.
They contain a “beta-lactam” ring which mimics the shape of the terminal D-alanine-D-alanine of peptidoglycan in the bacterial wall.
The antibiotic binds covalently (permanently) to the PBP.
Beta-lactam antibiotics are active only in ________ bacteria actively ________ cell wall.
growing; synthesizing
True/false: Highly hydrophobic agents have an increased ability to penetrate the outer membrane of GNB.
FALSE! Hydrophilic agents penetrate GNB via membrane pores. Hydrophilic and hydrophobic agents are able to penetrate the cell wall of GPB/GNB.
Name 3 types of beta-lactamases.
Penicillinases
Extended-Spectrum Beta-Lactamases (ESBLs)
Carbapenemases
What does a penicillinase inactivate?
Penicillins
What does an ESBL inactivate?
Penicillins, cephalosporins, and monobactams; they are produced by GNB.
What kind of bacteria produce ESBLs?
GNB
What do carbapenemases inactivate?
All beta-lactams and beta-lactamase inhibitors
Where do beta-lactamases distribute in GPB and GNB? Which is more problematic?
Outside the cell wall of GPB and around the cell wall between the membranes of GNB. The latter is more problematic because they are more concentrated and produce more of an effect.
What are the two types of beta-lactamase inhibitors?
Beta-lactam beta-lactamase inhibitors
Non beta-lactam beta-lactamase inhibitors
Name 3 beta-lactam beta-lactamase inhibitors
Clavulanic acid, sulbactam, tazobactam
Name 3 non beta-lactam beta-lactamase inhibitors.
Avibactam, vaborbactam, relebactam
True/false: Beta-lactamase inhibitors have extensive anti-bacterial activity.
FALSE! They are combined with certain beta-lactams to protect against beta-lactamases (rodeo clowns) but have limited to no antibacterial activity themselves.
Name 4 mechanisms of resistance to beta-lactams (besides beta-lactamases).
Penetration - inability to reach transpeptidases
Bacteria does not have cell wall (mycoplasma)
Bacterial efflux pumps (specifically GNB)
Transpeptidase (PBP) mutation - reduced binding (ex., MRSA)
Name the 4 classes of penicillins.
Natural penicillins
Anti-staph penicillins
Aminopenicillins
Anti-psudomonal penicillins
Name 2 natural penicillins.
Benzyl Penicillin (Pen G) Phenoxymethyl Penicillin (Pen V)
Name 4 anti-staph penicillins.
Dicloxacillin
Oxacillin
Methicillin
Nafcillin
Name 2 aminopenicillins.
Ampicillin
Amoxicillin
Name an anti-psudomonal penicillin.
Piperacillin
List the penicillin classes in order from more GPB activity to GNB activity.
Natural penicilins, anti-staph penicillins, aminopenicillins, anti-pseudomonal penicillins
Penicillins do NOT cover ____ or _______ bacteria.
MRSA; atypical
Describe the coverage of natural penicillins.
Streptococci, enterococci, GP anaerobes (mouth flora)
VERY LIMITED GP coverage: treponema pallidum (syphilis)
DO NOT cover staphylococci (resistance)
Describe the coverage of anti-staph penicillins.
Streptococci, MSSA
Do NOT cover enterococci, GNB, or anaerobes
Describe the coverage of aminopenicillins.
Streptococci, enterococci, GP anaerobes (mouth flora)
GNB - Haemophilus, Neisseria, Proteus, E. coli, Klebsiella (HNPEK)
With beta-lactamase inhibitor: MSSA, resistant HNPEK strains, and B fragilis (GN anaerobe)
Describe the coverage of anti-pseudomonal penicillins.
Streptococci, enterococci, MSSA, GP anaerobes (mouth flora), HNPEK and HNPEK resistant strains
B fragilis
Other GNB: citrobacter, acinetobacter, serratia (CAPES), Pseudomonas aeruginosa
The natural penicillins, Benzyl Penicillin (Pen G) and Phenoxymethyl Penicillin (Pen V) are susceptible to ___________.
beta-lactamases
Pen G is unstable in ____________, necessitating administration by?
gastric acid; IV or IM
IV or IM Pen G comes in a ________ ______ formulation, therefore, monitoring which lab is important?
potassium salt; potassium
Which Pen G formulations are IM administration only?
Procaine (Wycillin) or benzathine (Bicillin L-A) salts
Which formulation of Pen G has a loner duration of action: procaine or benzathine?
Benzathine is more insoluble, producing a slow release; makes this formulation good for peds because they can get one shot and be done.
Which natural penicillin is stable in gastric acid, making it appropriate for oral administration?
Pen V
By what route is dicloxacillin taken?
Oral
By what routes is nafcillin taken?
IV & IM; a vesicant so give thru CVL
By what route is oxacillin taken?
IV
True/false: Anti-staphylococcus penicillins have GNB coverage.
False! They have none.
Anti-staphylococcus penicillins are resistant to _________ produced by _____________.
beta-lactamases; staphylococcus spp
Anti-staphylococcus penicillins are preferred for what 4 kinds of infections?
MSSA, bone and joint, endocarditis, and bloodstream
Anti-staphylococcus penicillins are primarily eliminated by what means? What is the implication?
Bile; no renal dose adjustment!
Compare/contrast the routes of administration for amoxicillin and ampicillin.
Amoxicillin is only given orally and has better PO absorption than ampicillin which is available PO, IV, and IM.
Amoxicillin is the drug of choice for what 3 conditions?
Acute otitis media, endocarditis prophylaxis (dental procedures), and H. pylori (ulcers)
How does the coverage of aminopenicillins compare to anti-staph penicillins?
Some GN coverage for aminopenicillins, but they are still susceptible to beta-lactamases, therefore they are combined with beta-lactamase inhibitors.
What are Augmentin and Unasyn?
Amoxicillin + clavulanic acid (a beta-lactamase inhibitor); PO
Ampicillin + sulbactam; IV
What is the drug of choice for acute otitis media and sinus infections?
Augmentin (amoxicillin + clavulanic acid)
What is the dose-related side effect of clavulanic acid?
Diarrhea
Piperacillin is always combined with what beta-lactamase inhibitor? Describe its activity.
Tazobactam (together as Zosyn); IV
Enhanced activity against GNB with increased resistance to GNB beta-lactamases; ACTIVE AGAINST PSEUDOMONAS AERUGINOSA!!!!!
Pencillins: static or cidal?
Bactericidal
Penicillins: time or concentration dependent?
Time-dependent: frequent dosing!
How are most penicillins eliminated? What is the exception?
Renally; anti-staph penicillins are eliminated in the bile.
What is the relative half-life of penicillins?
short; requires frequent dosing
Penicillins generally have poor CNS penetration, but what conditions can improve it?
Inflamed meninges
High doses
Reduced renal elimination (Prevenacid)
Name 6 potential side effects of penicillins.
Diarrhea Changes to gut flora Allergic interstitial nephritis Hematological reactions Neurotoxicity Seizures (antagonize GABA-A receptors)
Compare and contrast a type I and type IV allergic reaction/hypersensitivity.
Type I: Immediate, IgE mediated; within minutes to an hour; pruritis, flushing, urticaria, angioedema, wheezing, laryngeal edema, hypotension, anaphylaxis
Type IV: Delayed, T-cell mediated; appears after MULTIPLE doses of treatment, typically after days or weeks of administration; maculopapular cutaneous eruptions or delayed urticarial eruptions (as severe as SJS)
What is the rationale for attempting treatment with penicillin in patients who have had a previous reaction?
Less than 1% of reactions are IgE mediated; most patients lose their sensitivity after 10 years; other broad-spectrum antibiotics are more costly and put the patient at risk for resistance/suboptimal therapy.
What structural component increases the risk of cross-reactivity for patients with a penicillin/beta-lactam allergy?
Similar side chains
Name 5 types of drugs that have interactions with penicillins.
Anticoagulants/antiplatelets
Drugs that undergo renal tubular excretion
Methotrexate
Potassium sparing diuretics/drugs that increase potassium, or patients with renal dysfunction with potassium salt formulations
Aminoglycosides
Are cephalosporins bacteriostatic or bactericidal?
Bactericidal
Are cephalosporins time-dependent or concentration-dependent?
Time-dependent
Cephalosporins do NOT cover…(2)
Enterococcus and atypical
Name 2 drug classes that have cross-allergenicity.
Cephalosporins and penicillins
All cephalosporins are renally eliminated except?
Ceftriaxone (renal-biliary excretion)