Antimicrobial Medications Flashcards
Resistance that develops due to genetic changes, including mutation and horizontal gene transfer.
Acquired Resistance
A compound naturally produced by molds or bacteria that inhibits the growth of or kills other microorganisms.
Antibiotic
An antibiotic or other chemical that kills microbes or inhibits their growth.
Antibiotic; also called an antimicrobial drug.
A chemical that is used to treat a viral infection and acts by interfering with the infection cycle of the virus.
Antiviral Medication; also called an antiviral drug.
Describes a chemical or other agent that kills bacteria.
Bactericidal
Describes a chemical or other agent that stops the growth of bacteria without killing them.
Bacteriostatic
An antibiotic that is effective against a wide range of bacteria, generally including both Gram-positive and Gram-negative bacteria.
Broad-Spectrum Antibiotic
A chemical used to treat disease.
Chemotherapeutic Agent
Resistance due to inherent characteristics of an organism.
Intrinsic (Innate) Resistance
An antibiotic that is effective against a limited range of bacteria.
Narrow-Spectrum Antibiotic
A plasmid that encodes resistance to one or more antimicrobial Medications.
R Plasmid
Who discovered that some chemicals could selectively kill microbes?
Paul Ehrlich (1854-1915)
What is the general formula for therapeutic index?
Lowest dose toxic / necessary thereby dose
Define therapeutic window.
The range between the dose used therapeutically and the toxic dose.
Which would be safer to use: an antimicrobial that has a low therapeutic index or one that has a high therapeutic index? Why?
A high therapeutic index because:
toxic dose / therapeutic dose
The higher the toxic dose and the lower the therapeutic dose, the larger the index.
In what clinical situation is it most appropriate to use a broad-spectrum antimicrobial?
Typically when specific species or group of bacteria is unknown, or when infection with multiple groups of bacteria is suspected.
Why would antimicrobials that have toxic effects be used at all?
Only when the alternative is worse. If there are no other options, it is sometimes worth risking serious injury instead of guaranteed death.
What does penicillins, Cephalosporins, carbapenems, and monobactams have in common?
A β-lactam ring structure
Target of β-lactam antimicrobial medications; their role in bacteria is peptidoglycan synthesis.
penicillin-binding proteins (PBPs)
How do some bacteria resist β-lactam drugs?
β-lactamse synthesis that breaks down the β-lactam ring, inactivating the medication.
How do glycopeptide antibiotics work?
By binding to the amino side chain of NAM molecules that connect peptidoglycan, blocking cross-linking between adjacent glycan chains.
When are glycopeptide antibiotics used?
They are typically reserved for serious infections by Gram-positive bacteria.
What kind of antibiotic is vancomycin?
Glyopeptide Antibiotic
How is vancomycin administered?
intravenously except when used to treat intestinal infections. It is poorly absorbed.
Name 2 glycopeptide antibiotics other can vancomycin. (There are many)
- telavancin
- dalbavancin
- oritavancin
How does bacitracin work?
By interfering with the transport of petidoglycan precursors across the cytoplasmic membrane.
How is bacitracin typically used?
Due to its toxicity, it is usually used in topical applications.
Why don’t antibacterial protein synthesis inhibitors affect human cells?
Bacterial 70S ribosomes are composed of a 50S and 30S subunit which is different enough from the 80S ribosome of human cells to not be affected.
What typically causes protein synthesis inhibitors to be toxic?
Mitochondrial ribosomes of eukaryotes are similar to bacteria, which contributes to the toxicity of some of these drugs.
Name 2 macrolide antibiotics. (there are many)
- erythromycin
- clarithromycin
- azithromycin
What are macrolides effective against?
Gram-positive bacteria
Why are macrolides used instead of penicillins?
When patients are allergic to penicillins.
Why is chloramphenical use generally limited even in very low doses?
In extremely rare cases, they can cause aplastic anemia–the inability for the body to form white and red blood cells.
What are lincosamides effective against?
A variety of gram-positive bacteria and some gram-negative anaerobes.
What are the risks of lincosamides?
C. diff infection risk is greater for people taking lincosamides.
What kind of antibiotic is clindamycin?
Lincosamide
What makes lincosamides useful?
They are useful for treating infections from intestinal perforations because they inhibit Bacteroides fragilis, a member of the normal instestinal microbiota.
How do aminoglycosides work?
They irreversibly bind to the 30S ribosomal subunit, blocking translation and causing mRNA misreads.
What are the drawbacks of aminoglycosides?
They can cause severe side effects, including hearing loss and vertigo as a result of damage to sensory components of the inner ear.
They can also cause kidney damage.
When are aminoglycosides used?
Only when less toxic alternatives are not available or not an option for some other reason.
What are aminoglycosides generally not effective against? Why?
Against anaerobes, enterococci, and streptococci because they enter bacterial cells by a process that requires respiratory metabolism.
Name 2 aminoglycosides
- streptomycin
- gentamicin
- tobramycin
How to tetracyclines work?
They reversibly bind to the 30S ribosomal subunit, blocking the attachment of tRNA and preventing translation from continuing.
What antibiotics can cause discoloration in teeth when used by young children?
Tetracyclines and glycylcyclines.
Original penicillins produced by the mold Penicillium chrysogenum.
Natural penicillins
Scientists developed these in response to the problem of penicillinase-producing Staphylococcus aureus strains.
Methicillin and dicloxacillin.
Penicillinase-resistant penicillins
Active against not only penicillin-sensitive Gram-positive bacteria, but also many Gram-negative bacteria.
amipicillin
amoxicillin
Broad-spectrum penicillin
Name penicillinase-resistant penicillins
- methicillin
- dicloxacillin
Name 2 broad-spectrum penicillins
- amoxicillin
- ampicillin
These have greater activity against most of the Enterobacteriaceae as well as Pseudomonas aeruginosa.
Gram-negative bacteria are common causes of healthcare-associated infections and are often resistant to many other antimicrobial Medications.
ticaricillin
piperacillin
Extended-spectrum penicillins.
Name 2 extended-spectrum penicillins
ticarcillin
piperacillin
This is a combination of agents that protects penicillin against enzymatic destruction.
amoxicillin and clavulanic acid, for example.
Penicillins + B-lactamase inhibitor
Name 2 penicillinase-resistant penicillins
methicillin
dicloxacillin
Could penicillin be used to treat MRSA infections? Explain (critical thinking)
No, methicillin-resistant Staphylococcus aureus will not respond to a penicillinase-resistant penicillin like dicloxacillin or methiscillin.
Typically glycopeptide antibiotics are recommended for MRSA, like vancomycin.
What makes cephalosporins unique?
The chemical structure of cephalosporins protects them from destruction by certain B-lactamases.
What makes carbapenems unique?
- Carbapenems are effective against a wide range of Gram-negative and Gram-positive bacteria.
- They are not inactivated by extended-spectrum B-lactamases (ESBLs)
What type of bacteria produce extended-spectrum B-lactamases (ESBLs)?
certain Gram-negative bacteria
Name 2 carbapenems
imipenem
ertrapenem
meropenem
doripenem
What makes monobactams unique?
Monobactams are antibiotics each containing a B-lactam ring but lacking another ring fused to it.
What are monobactams used for?
Specifically for members of the family Enterbacteriacaea
_______ are synthetic compounds that inhibit one or more of a group on enzymes called topoisomerases, which maintain the supercooling of DNA within the bacterial cells.
Flouroquinolones
Flouroquinolnes used to be used widely in the past, why aren’t they anymore?
Severe side effects
name 2 flouroquinolones
ciprofloxacin
levofloxacin
moxifloxacin
ofloxacin
_______ are antibiotics that block bacterial RNA polymerase from initiating transcription.
Rifamycins
______ is a relatively new bactericidal antibiotic that interferes with transcription by binding to RNA polymerase. It passes through the intestinal tract without being absorbed and is particularly useful for treating C. diff.
Fidaxomicin
A synthetic compound that interferes with DNS synthesis and function, but only in anaerobic microorganisms.
Metronidazole (Flagyl)
Of the metabolic pathway antibacterials, which are most used as folate synthesis inhibitors?
solfonamides and trimethoprim
Explain how sulfa drugs (sulfanomides) work.
They are similar to para-aminobenzioc acid (PABA) which is found in folate synthesis pathways. Human cells lack this enzyme, making it selectively toxic to PABA binding proteins.