Micro - Antimicrobials Part 1 Flashcards
How do imipenem, aztreonam, and cephalosporins work?
They block cell wall synthesis by inhibiting cross-linking of peptidoglycans
How do bacitracin and vancomycin work?
They block peptidoglycan synthesis
What antibiotic works by disrupting bacterial/fungal cell membranes?
Polymyxins
Sulfonamides and trimethoprim work by blocking the synthesis of what molecules?
Nucleotides
How do fluoroquinolones exhibit their antibacterial effects?
DNA topoisomerase inhibition
Rifampin blocks the synthesis of what bacterial molecule?
mRNAs
Chloramphenicol works by what mechanism?
It binds to the 50S ribosomal subunit and blocks the synthesis of protein
Lincosamides work by what mechanism?
They bind to the 50S ribosomal subunit and block the synthesis of protein
Streptogramins work by what mechanism?
They bind to the 50S ribosomal subunit and block the synthesis of protein
Linezolid works by what mechanism?
It binds to the 50S ribosomal subunit and blocks the synthesis of protein
Macrolides work by what mechanism?
They bind to the 50S ribosomal subunit and block the synthesis of protein
Tetracyclines work by what mechanism?
They bind to the 30S ribosomal subunit and block the synthesis of protein
Aminoglycosides work by what mechanism?
They bind to the 30S ribosomal subunit and block the synthesis of protein
Name six antibiotics that are bacteriostatic.
Erythromycin, Clindamycin, Sulfamethoxazole, Trimethoprim, Tetracyclines, and Chloramphenicol (remember: were ECSTaTiC about bacteriostatics)
Name six antibiotics that are bactericidal.
Vancomycin, Fluoroquinolones, Penicillin, Aminoglocysides, Cephalosporins, and Metronidazole (remember: Very Finely Proficient At Cell Murder)
Penicillin _____ is administered intravenously; penicillin _____ is administered orally.
G; V
Penicillin is the prototype for which class of antibiotics?
β-Lactams
Penicillin blocks _____ to inhibit cross-linking and activates _____ enzymes as well.
Transpeptidase; autolytic
Which types of bacteria are killed by penicillin?
Gram-positive cocci and rods, gram-negative cocci and spirochetes; bacteria with penicillinase are resistant
What are the two major toxicities associated with penicillin treatment?
Hypersensitivity reactions and hemolytic anemia
Methicillin, nafcillin, and dicloxacillin have the same mechanism of action as what class of antibiotics?
Penicillins
What differentiates methicillin, nafcillin, and dicloxacillin from penicillin?
Methicillin, nafcillin, and dicloxacillin are resistant to penicillinase and are effective against bacteria like Staphylococcus aureus
Methicillin, nafcillin, and dicloxacillin are resistant to penicillinase as a result of what difference in their structure?
A bulkier R group
Methicillin, nafcillin, and dicloxacillin are narrow-spectrum antibiotics that are used clinically for the treatment of what conditions?
Staphylococcus aureus infections, except methicillin-resistant Staphylococcus aureus
(remember: naffor staph)
Why are nafcillin and dicloxacillin ineffective against methicillin-resistant Staphylococcus aureus?
Because of altered penicillin-binding protein target sites
What are the two major toxicities associated with methicillin treatment?
Hypersensitivity reactions and interstitial nephritis
Which drug can be administered with ampicillin to make it more effective against penicillinase-producing organisms?
Clavulanic acid, an inhibitor of penicillinase
Which has greater oral availability: amoxicillin or ampicillin?
AmOxicillin has better Oral availability
Which drugs have a wider spectrum of effectiveness: ampicillin/amoxicillin or penicillin?
Ampicillin and amoxicillin have a broader spectrum of effectiveness (remember: AMPicillin is Amped up penicillin)
What are the three major toxicities caused by ampicillin and amoxicillin?
Hypersensitivity reactions, rash, and pseudomembranous colitis
In addition to some gram-positive bacteria, which gram-negative rods are susceptible to ampicillin and amoxicillin?
H. influenzae, E. coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, enterococci (remember: ampicillin/amoxicillin HELPS kill enterocicci)
True or False? Ticarcillin, carbenicillin, and piperacillin are resistant to penicillinase.
False; but they can be used with clavulanic acid to give them resistance to penicillinase
Which bacteria are ticarcillin, carbenicillin, and piperacillin active against?
Gram-negative rods, including Pseudomonas(remember: Ticarcillin, Carbenicillin, and Piperacillin Takes Care of Pseudomonas)
What is a common toxicity of ticarcillin, carbenicillin, and piperacillin?
Hypersensitivity reactions
Cephalosporins belong to what class of drugs?
β-Lactams
Are cephalosporins more or less susceptible to penicillinase than other -lactams?
Less susceptible
Name two examples of first-generation cephalosporins.
Cefazolin and cephalexin
First-generation cephalosporins cover which organisms?
Gram-positive cocci, Proteus mirabilis, Escherichia coli, and Klebsiella pneumoniae. (remember: PEcK)
Name three examples of second-generation cephalosporins.
Cefoxitin, cefaclor, and cefuroxime
Second-generation cephalosporins cover which organisms?
Gram-positive cocci, Haemophilus influenzae, Enterobacter aerogenes, Neisseria, Proteus mirabilis, Escherichia coli, Klebsiella pneumoniae, and Serratia marcescens(remember: HEN PEcKS)
Name three examples of third-generation cephalosporins.
Ceftriaxone, cefotaxime, and ceftazidime
Third-generation cephalosporins cover which organisms?
Serious gram-negative infections that are resistant to other -lactams
Why are third-generation cephalosporins a good choice for treatment of meningitis?
Because they penetrate the blood-brain barrier
Which third-generation cephalosporin is used for Pseudomonascoverage?
Ceftazidime
Which cephalosporin is often used to treat gonorrhea?
Ceftriaxone
Name one example of a fourth-generation cephalosporin.
Cefepime
Fourth-generation cephalosporins are different from third-generation cephalosporins in that the fourth-generation drugs have increased activity against which organisms?
Pseudomonasand gram-positive organisms
True or False? Unlike penicillin, hypersensitivity reactions are not a major toxicity of cephalosporins.
False; hypersenstivity reactions are a potential toxocity of all cephalosporins
What is the likelihood that a penicillin-allergic patient is also allergic to cephalosporins?
There is cross-hypersensitivity in 5% to 10% of patients
What toxicity can occur in patients using cefamandole who drink alcohol?
A disulfiram-like reaction (applies to all cephalosporins with a methylthiotetrazole group)
Aztreonam is an example of what subclass of -lactam drugs?
Monobactams
Is aztreonam susceptible to -lactamases?
No; it is resistant to -lactamases because it is a monobactam
Aztreonam inhibits cell wall synthesis by binding to what substance?
Penicillin binding protein 3
Aztreonam is synergistic with what class of drugs?
Aminoglycosides
Does aztreonam have any cross-allergenicity with penicillins?
No
Aztreonam is used to treat infection with what type of organisms?
Gram-negative rods (Klebsiella, Pseudomonas, and Serratia)
Which gram-positive and anaerobic bacteria does aztreonam have activity against?
None!
Aztreonam is used in which two patient groups who have infections caused by susceptible organisms?
Penicillin-allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides
Aztreonams toxicity profile includes what side effects?
Aztreonam is usually nontoxic, although it may occasionally cause gastrointestinal upset
Imipenem is an example of what subclass of β-lactams?
Carbapenems
Imipenem is a _____(broad-/narrow-) spectrum, β-lactamase-_____ (resistant/susceptible) carbapenem.
Broad; resistant
Imipenem is always administered with _____ to reduce inactivation in the _____ _____
Cilastatin; it is given to reduce inactivation in renal tubules (remember: the “kill is Lastin with ciLastin)
Cilastatin is an inhibitor of what substance and thus given with imipenem?
Renal dehydropeptidase I
Imipenem is used to treat which kinds of infections?
Gram-positive cocci, gram-negative rods, and anaerobic infections
Imipenem/cilastatin and meropenem are the drugs of choice for infection by which bacteria?
Enterobacter
At what point during disease progression is imipenem or meropenem considered a treatment option? Why?
Only when other medications have failed or in life-threatening infections because of the significant adverse effects these two medications have
What are the toxicities associated with imipenem and meropenem?
Gastrointestinal distress, rashes, and seizures; adverse effects more commonly occur at high doses
Which has a higher risk of causing seizures imipenem or meropenem?
Imipenem
Why is meropenem not coadministered with cilastatin?
Because meropenem is stable to dehydropeptidase I
How does vancomycin work?
It binds the D-Ala D-Ala portions of cell wall precursors, thereby inhibiting cell wall mucopeptide formation
How do bacteria develop resistance to vancomycin?
Conversion of D-Ala D-Ala to D-Ala D-Lac
Vancomycin is used for multidrug-resistant gram-_____ (positive/negative) organisms.
Positive
Name two organisms for which vancomycin is commonly used.
Methicillin-resistant Staphylococcus aureus and Clostridium difficile(pseudomembranous colitis)
What types of toxicity are possible with vancomycin treatment?
Nephrotoxicity, ototoxicity, thrombophlebitis, and diffuse flushing (“red man syndrome”), but in general it does NOT cause many problems
“Red man syndrome” with vancomycin administration can largely be prevented with pretreatment with _____ and with the use of a _____ (slow/fast) infusion rate.
Antihistamines; slow
Which protein-synthesis-inhibiting antibiotics are bactericidal?
Aminoglycosides
Which mnemonic addresses which protein synthesis inhibitors are 30S subunit inhibitors and which are 50S subunit inhibitors?
Buy AT 30, CCELL at 50 (Aminoglycosides and Tetracyclines at 30, Chloramphenicol, Clindamycin, Erythromycin, Lincomycin and Linezolid at 50)
Name five aminoglycoside antibiotics.
Gentamicin, neomycin, amikacin, tobramycin, and streptomycin
Aminoglycosides block protein synthesis by the inhibition of _____ _____ formation, and they cause the misreading of _____.
Initiation complex; mRNA
Aminoglycosides require _____ for uptake and therefore are ineffective against _____.
Oxygen; anaerobes (remember: the aminoglycosides (Mean) gentamicin, neomycin, amikacin, tobramycin, and streptomycin (GNATS) canNOT(Nephrotoxicity, Ototoxicity and Teratogen) kill anaerobes
Are gentamicin, neomycin, amikacin, tobramycin, and streptomycin bactericidal or bacteriostatic?
Bactericidal
Aminoglycosides are used to treat severe infections by gram-_____ (negative/positive) _____ (cocci/rods).
Negative; rods
Aminoglycosides are synergistic with which class of antibiotics?
β-Lactams
Neomycin is commonly used as part of preparation for what procedure?
Bowel surgery
What toxicities are associated with aminoglycosides?
Nephrotoxicity and Ototoxicity; they are also Teratogenic (remember: mean GNATS canNOTkill anaerobes = Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin)
Aminoglycosides’ nephrotoxic potential is increased when it is used with what class of antibiotics?
Cephalosporins
Aminoglycosides’ ototoxic potential is increased when it is used with what class of drug?
Loop diuretics
Name four antibiotics that belong to the class tetracyclines.
Tetracycline, doxycycline, demeclocycline, and minocycline
What is the mechanism of action of tetracyclines?
Tetracyclines bind to 30S and prevent the attachment of aminoacyl-tRNA
Do tetracyclines have good central nervous system penetration?
No; tetracyclines have limited central nervous system penetration
Which tetracycline-family drug is safe to use in patients with renal failure?
Doxycycline (fecally eliminated and therefore can be used by patients with renal failure)
Which foods and drugs should not be taken with tetracyclines? Why?
Milk, antacids, and iron-containing preparations, because divalent cations inhibit the absorption of doxycycline
Tetracyclines are used to treat infections with which two organisms that are transmitted by ticks?
Borrelia burgdorferi and Rickettsia
Tetracyclines are used to treat which skin infection?
Acne
Tetracyclines are avoided for use in children for what three reasons?
They discolor teeth, inhibit bone growth, and cause gastrointestinal distress
What dermatologic adverse effect results from use of tetracyclines?
Photosensitivity
Which tetracycline is used as a diuretic in patients with the syndrome of inappropriate antidiuretic hormone secretion?
Demeclocycline, because it is an antidiuretic hormone antagonist (remember: Demeclocycline = Diuretic)
Name ten bacteria that tetracyclines are active against.
Vibrio cholerae, Acne, Chlamydia, Ureaplasma, urealyticum, Mycoplasma pneumoniae, Tularemia, Helicobacter pylori, Borrelia burgdorferi, Rickettsia(remember: VACUUM THe Bed Room)
Can pregnant women take tetracyclines?
No; tetracyclines are contraindicated in pregnancy
Name three examples of macrolide antibiotics.
Erythromycin, azithromycin, and clarithromycin
Macrolides inhibit protein synthesis by binding to the _____ rRNA of the _____ (30S/50S) ribosomal subunit.
23S; 50S
The binding of macrolides to the 23S rRNA of the 50S ribosomal subunit blocks what cellular process and inhibits protein synthesis?
Translocation of the peptide chain
Macrolides are used to treat infection with which organisms?
Gram-positive cocci, Mycoplasma, Legionella, Chlamydia, and Neisseria
What three types of infections are treated with macrolides?
Upper respiratory infections, pneumonia, and sexually transmitted diseases
Streptococcal infections in patients who are allergic to penicillin are treated with which drugs?
Macrolides
What is the most common cause of noncompliance with macrolide treatment?
Gastrointestinal discomfort
Macrolides increase the serum concentration of which drugs?
Theophyllines and oral anticoagulants
Other than gastrointestinal upset, what are four other adverse effects of macrolides?
Acute cholestatic hepatitis, eosinophilia, skin rashes, and prolonged QT interval
Which macrolide antibiotic is most likely to cause a prolonged QT interval?
Erythromycin
Chloramphenicol inhibits the enzyme _____, which is part of the _____ (30S/50S) ribosomal subunit.
Peptidyltransferase; 50S
Chloramphenicol is used to treat what type of infection?
Meningitis; it is considered a last resort because of significant toxicities
Chloramphenicol is used to treat meningitis caused by what three organisms?
Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae
What are the three major toxicities of chloramphenicol?
Dose-dependent anemia, dose-independent aplastic anemia, and gray baby syndrome
Chloramphenicol causes gray baby syndrome in _____ _____ as a result of the lack of the liver enzyme _____-_____ _____.
Premature infants, UDP-glucuronyl transferase
At the 50S ribosomal subunit, clindamycin inhibits protein synthesis by blocking the formation of what?
Peptide bonds
Clindamycin is primarily used to treat what type of organisms?
Anaerobes such as Bacteroides fragilis and Clostridium perfringens
What are the three major toxicities associated with clindamycin?
Pseudomembranous colitis, fever, and diarrhea
Why does pseudomembranous colitis often occur following treatment with clindamycin?
Because it kills normal flora and allows overgrowth of Clostridium difficile
Name three sulfonamide antibiotics
Sulfamethoxazole, sulfisoxazole and sulfadiazine
What are sulfonamide antibiotics and how do they work?
They are para-aminobenzoic acid antimetabolites that stop the activity of dihydropteroate synthetase, preventing DNA synthesis
Sulfonamides are active against what organisms?
Gram-positive organisms, gram-negative organisms, Nocardia, and Chlamydia
