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184 Cards in this Set

  • Front
  • Back
What is chemotherapy?
The science of selective toxicity.
Goal is to selectively destroy pathogenic microorganisms (or tumor cells) or with minimum side effects to the host
How does chemotherapy work?
it lowers the microorganism load so that the host defense system can rid the body of foreign organisms
Maintenance of constant blood levels is more important with what type of antimicrobial agents?
more important with bacteriostatic than bactericidal
What is a bacteriostatic agent?
a biological or chemical agent that stops bacteria from reproducing, while not necessarily harming them otherwise
What is a bactericidal agent?
a substance that kills bacteria and, ideally, nothing else
What is transduction?
occurs by the intervention of a bacteriophage that contains bacterial DNA incorporated within its protein coat. If this genetic material includes a gene for drug resistance, a newly infected bacterial cell may become resistant to the agent and capable of passing the trait on to its progeny
Which drugs does transduction confer resistance for?
penicillinase
erythromycin
tetracycline
chloramphenicol
What is transformation?
the incorporation of DNA that is free in the environment into the bacteria.
What is transformation the molecular basis of?
penicillin resistance in pneumococci and Neisseria
What is conjugation?
the passage of genes from cell to cell by direct contact through a sex pilus or bridge
What are the 2 sets of genes encoded in plasmids?
The first set codes for the actual resistance and is termed the R-determinant plasmid.
The second is termed the resistance tranfer factor or RTF and contains the genes necessary for bacterial conjugation.
What 3 strains of bacterial are known to be resistant to all known drugs?
Enterococci
Pseudomonas
Enterobacter
Which bactericidal agents are concentration dependent?
aminoglycosides
quinolones
Which bactericidal agents are time dependent?
beta-lactams
vancomycin
What is PAE (post-antibiotic effect)?
the length of time it takes for the culture to achieve log phase growth (after transferring from antibiotic containing medium to antibiotic free medium)
How do we treat enterococcal endocarditis?
penicillin + aminoglycoside
How do we treat pseudomonas infections?
penicillin + aminoglycoside
How do we treat Brucellosis?
doxycyclin + rifampin/aminoglycoside
How do we treat H. pylori?
bismuth + metronidazole + tetracycline
How do we treat Listeria?
ampicillin + aminoglycoside
Why do we treat M. tuberculosis and Pseudomonas aeruginosa with 2 drugs each?
preventing emergence of resistant microorganisms
How do we treat M. tuberculosis?
INH + rifampin
How do we treat Pseudomonas aeruginosa?
Gentamicin + Carbenicillin (resistance can develop in days!)
How do we treat intestinal candidiasis superinfection?
oral nystatin or amphotericin B
How do we treat staphylococcal enterocolitis?
oral vanco
How do we treat pseudomembranous colitis?
oral vanco or metronidazole
What is the DOC for surgical prophylaxis?
cefazolin
What is synergism?
when the inhibitory or killing effects of 2 or more antimicrobials used together are significantly greater than expected from their effects when used individually
Why is Methicillin only used for testing?
causes interstitial nephritis
What group of antibiotics are the DOCs for Stauph aureus (antistaphylococcal)?
Penicillinase Resistant Penicillins
- Nafcillin
- Cloxacillin
- Oxacillin
- (Methicillin)
What is the DOC for MRSA?
Vancomycin
What should be added to the anti-pseudomonal penicillins when treating pseudomonas?
Aminoglycosides
What is the relative rank of antipseudomonal activity of the anti-pseudomonal penicillins?
piperacillin > mezlocillin/ticarcillin >carbenicillin
How is Penicillin G excreted?
probably the most rapidly excreted drug by the normal kidney
What is the "ampicillin rash"?
occurs in 5-10% of children receiving ampicillin or amoxicillin and is a generalized dull red, maculopapular rash, generally appearing 3-14 days after teh start of therapy and is often mistaken for allergic reaction. This "rash" is not allergic and does not preclude future use of penicillin. Also a high percentage of pts with infectious mononucleosis (EBV) develop rash during therapy with ampicillin.
Which carbapenem is particularly active against enterobacteriaceae?
Ertapenem
Which carbapenem is rapidly inactivated by renal tubule dehydropeptidase and must be given with a dyhydropeptidase inhibitor?
Imipenem (give with cilastatin)
Which carbapenem is not inactivated by dehydropeptidases?
Meropenem
Which kind of lactamases are the Beta-lactamase inhibitors most active against?
plasma encoded lactamases
What are the 1st gen cephalosporins?
Cefazolin
Cephalexin
Cephradine
What are the 2nd gen cephalosporins?
Cefoxitin
Cefamandole
Ceaclor
Cefuroxime
Cefprozil
Loracarbef (Cefzil)
What are the 3rd gen cephalosporins?
Cefotaxime
Cefoperazone
Ceftazidime
Ceftriaxone
Cefixime
What are (is) the 4th gen cephalosporins?
Cefepime
What are the 1st generation cephalosporins the DOC for?
E. coli
Klebsiella pneumonia
Proteus mirabilis
What are the first generation cephalosporins active against?
good - Gram (+) and moderate - Gram (-)
Most gram (+) cocci except enterococci, MRSA and Staph epi.
What are the 2nd generation cephalosporins DOC for?
Moraxella catarrhalis
E. coli
Klebsiella
Proteus
What are the 3rd generation cephalosporins more active against than 1st and 2nd?
Enterobacteriaceae including penicillinase producing strains
Which 3rd generation cephalosporins have CNS penetration and therefore can be used for meningitis?
Cefotaxime Sodium
Ceftriaxone
Which 3rd generation cephalosporins have anti-pseudomonal activity?
Cefoperazone
Ceftazidime
Which cephalosporin is metabolized by the liver?
Cefoperazone (so don't drink alcohol while on this)
What is the DOC for Neisseria gonorrhoeae?
Ceftriaxone
What is another DOC for Neisseria gonorrhoeae?
Cefixime
What is the DOC for penicillin resistant Strep pneumoniae?
Ceftriaxone
What is the 4th generation cephalosporin (Cefepime) used for ?
better antipseudomonal activity and may be more active than ceftazidime against Enterobacter sp. due to the enhanced stability agianst beta-lactamases
What is the 4th generation cephalosporin NOT active against?
Enterococci or Bacteroides
None of the cephalosporins have activity against:
MRSA
Listeria monocytogenes
Enterococci
Atypicals (Chlamydia, Mycoplasma)
Which drug has 100% CNS penetration?
Chloramphenicol
What is the mechanism of action for all cephalosporins?
interference with the bacterial cell wall synthesis and an increase in autolytic enzymes that causes cell wall break-down in a manner analogous to penicillin.
Bactericidal!
What is the mechanism of resistance for Vancomycin?
If the terminal D-Ala-D-Alsa is replaced by D-Ala-D-Lactate - vancomycin cannot bind.
What can Vanco be combined with to increase bactericidal effects? What can this increase incidence of?
Aminoglycosides
increases possible nephro- and ototoxicity
What are the most notable adverse reactions to Vancomycin?
nephrotoxicity
ototoxicity
Red Man syndrome
What is the mechanism of action for Bacitracin?
Interferes with the final dephosphorylation step in the phospholipid carrier cycle, which causes impedence of mucopeptide transfer to the growing cell wall.
What is the mechanism of action for cycloserine?
Competes with D-alanine for 2 enzymes: L-alanine racemase and D-alanine synthetase, both of which are involved in the incorporation o D-alanine into the bacterial cell walls
What is Bacitracin used for?
active against Gram (+) bacteria
*commonly used in combo with neomycin and polymyxin which are active against Gram (-) bacteria*
Most commonly used topically to prevent superficial skin and eye infections following minor injuries
What is cycloserine used for?
2nd line, broad spectrum - Used in the tx o active pulmonary and extrapulmonary TB and UTI's
For action of the sulfonamides...what is essential for antibacterial action?
a free para amino group
What is the mechanism of action of the sulfonamides?
compete with PABA in the synthesis of bacterial folic acid. PABA is an integral part of Folic acid, which is necessary or purine and DNA synthesis by the bacteria.
What is special about the mechanism of action for sulfonamides?
Mammals require pre-formed folic acid since they do not synthesize their own. Thus a competitive antagonism between PABA and sulfa drugs is inconsequential in humans.
What are sulfa drugs the DOC for?
First UTI's
Nocardiosis
Toxoplasmosis
Trachoma
Pneumocystis jiroveci in kids and AIDS pts
What is the mechanism of resistance to sulfa meds?
decreased sensitivity of the target enzymes
increased formation of PABA
use of exogenous folate
What is special about sulfsalazine?
it is a prodrug used for the tx of ulcerative colitis
What is TMP-SMX used for?
P. jiroveci pneumonia
Shigellosis
Systemic salmonella infections
UTIs
Prostatitis
Some non-TB mycobacterial infections
What is TMP-SMX the DOC for?
uncomplicated UTIs
Moraxella catarrhalis infections
widely used for tx of otitis media
What is TMP-SMX the 2nd line drug for?
Listeria
What is Sulfadiazine + Pyramethamine used for ?
toxoplasmosis
What is the major side effect of Sulfadiazine?
crystalluria - limited use to serious infections
What is the mechanism of action of Trimethoprim?
folate antagonist - can inhibit purine metabolism
What can Trimethoprim (alone) be used for?
prophylaxis of uncomplicated UTI's
traveler's diarrhea
What can Trimethoprim combined with either dapsone or suflamethoxazole be used for?
prophylaxis and tx of P. carinii
What is the mechanism of Silver Sufladiazine?
Disrupts bacteria by damaging the cell membrane and the cell wall rather than by inhibiting folic acid synthesis.
What special situations can Silver Sulfadiazine be used?
when carbonic anhydrase inhibitors are contraindicated because it does not inhibit CA
What can Pyrimethamine + Sufladoxine cause? (major adverse side effect)
fatal toxic epidermal necrolysis
What is the mechanism of action of Sufladoxine + Pyrimethamine?
Pyremethamine inhbiits parasitic DHF reductase and Sulfadoxine antagonizes parasitic PABA
What are the Macrolides?
Erythromycin
Clarithromycin
Azithromycin
What is the mechanism of action for macrolides?
Inhibition of protein synthesis of susceptible bacteria (gram +) by binding reversibly to the 50S ribosomal subunits and interferes with the translocation step wherein the nascent peptide chain is moved from the A to the P site
Which other antibiotic should NOT be used in conjunction with Erythromycin?
Chloramphenicol - because the binding sites are situated close to each other and can interfere and antagonize each other
What is erythromycin the DOC for?
Legionella pneumophila pneumonia
How do bacteria become resistant to Erythromycin?
1. drug efflux by an active pump mechanism
2. ribosomal protection by inducible or constitutive production of methylase enzymes, mediated by expression of ermA, ermB, and ermC, which modify the ribosomal target and decrease drug binding.
3. macrolide hydrolysis by esterases produced by Enterobacteriaceae
4. chormosomal mutations that alter a 50S ribosomal protein
Erythromycin + what can cause serious QT prolongation and arrhythmias?
cisapride
pimoside
sparfloxacin/grepafloxacin
What is Clarithromycin used for?
MAC
H. pylori
CA-pneumonia in children
A single dose of what can treat STD's such as Chlamydia and Gonorrhea?
Azithromycin
IV dosage of what drug can treat PID?
Azithromycin
Describe the effect of food on Clarithromycin and Azithromycin.
Clarithromycin - food has no effect
Azithromycin - food decreases bioavaiability
what is azithromycin approved for tx of?
pediatric otitis media and pharyngitis
MAC prophylaxis
What is the mechanism of action of Ketek?
binds to a site on teh bacterial 23S ribosomal RNA of the 50S subunit
What does Ketek work against?
broad-spectrum:
Respiratory pathogens including erythromycin and penicillin resistant pneumococci. Activity against intracellular and atypical bacteria
What is the big adverse side effect of Ketek that lead to its FDA approval being withdrawn for URIs?
serious hepatotoxicity
What is the mechanism of action for Clindamycin?
binds to the 50S ribosomal subunits of the bacteria, which inhibits protein synthesis
What is the big indication for use of Clindamycin (+ pyrimethamine)?
treating toxoplasmic encephalitis in pts with AIDS
What is a major side effect of Clindamycin?
pseudomembranous colitis
What are the streptogramins used for?
Vanco-resistant Enterococcus faecium bacteremia and complicated skin/skin-structure infections due to Staph aureus
What is the mechanism of linezolid?
inhibits bacterial protein synthesis by interfering with translation. Binds to a site on the bacterial 23S ribosomal RNA of the 50S subunit. Prevents the formation of a functional 70S initiation complex, an essential step in the bacterial translation process
What is special about the mechanism of Linezolid?
reversile, non-selective inhibitor of monoamine oxidase (MAOI)
Which aminoglycosides are anti-pseudomonal?
gentamycin
tobramycin
amikacin
What is the mechanism of action of aminoglycosides?
inhibiting the function of 30S subunit of bacterial ribosomes. They first must be actively transported into susceptible bacteria by a transport mechanism requiring oxygen and bind irreversibly to the bacterial 30S subunit to produce nonfunctional 30S initiation complex that in turn inhibits the synthesis of bacterial cell protein.
What are the aminoglycosides effective against?
gram negative rods and pseudomonas (3 of them)
(gram negative enteric bacteria or when there is a suspicion of sepsis or endocarditis)
What are the 3 biggies for adverse side effects of aminoglycosides?
Ototoxicity
Nephrotoxicity
NMJ inhibition
What can't you mix in the same syringe?
beta-lactams (penicillins) and aminoglycosides
What are the aminoglycosides?
Gentamycin
Tobramycin
Amikacin
Streptomycin
Neomycin
Spectinomycin
Paromomycin
How is resistance to aminoglycosides conferred?
plasmid mediated (R-factor derived)
What is the mechanism of resistance to aminoglycosides?
chemical changes of enzymes that adenylate, phosphorylate, or acetylate the aminoglycoside drugs.
What is gentamycin + neomycin used for?
topical application of wounds and burns caused by gram (-) organisms
What is streptomycin used for?
Tularemia
Bubonic plague
TB
Endocarditis (when it is given along with other agents)
What is neomycin alone used for?
tx of hepatic encephalopathy
What is Neomycin + Kanamycin used for?
orally for pre-op suppression of enteric aerobic flora and also to control diarrhea caused by E. coli
What is spectinomycin used for?
uncomplicated gonorrhea by a single IM injection in pts who are allergic to ceftriaxone or to other beta-lactam antibiotics
What is Paromomycin used for?
intestinal amebiasis
(as well as cryptosporidium parvum and tapeworm)
What is the mechanism of chloramphenicol?
reversibly binds to the 50S subunit of the bacterial 70S ribosomes and prevents attachment of the amino acid containing end o the aminoacyl-tRNA to the acceptor site on the ribosome
What is the mechanism of resistance in chloramphenicol?
an enzyme, acetyl transferaisese produced by the resistant organisms acetylates and inactivates chloramphenicol.
How is resistance to chloramphenicol conferred?
can be passed from a resistant bug to another bug and transferred back and forth.
What is the body tissue distribution like in chloramphenicol?
distributed widely in body to all tissues including eyes and CNS!
What are the 3 biggies for adverse side effects of chloramphenicol?
Fatal aplastic anemia
Dose dependent bone marrow depression
Dose dependent gray baby syndrome (from the inhibition of protein synthesis in the host mitochondria)
What is chloramphenicol the DOC for?
NOTHING!!!!
What is the mechanism of action for tetracyclines?
inhibition o bacterial protein synthesis by binding reversibly to 30S ribosomes and prevent the access of aminoacyl tRNA to the receptor site on the mRNA-ribosome complex. This prevents the addition of amino acids to the growing peptide chain.
Which organisms are resistant to tetracyclines?
B. fragilis
Proteus
Pseudomonas
How is resistance to tetracyclines conferred?
R-factors or plasmids play a role. Resistant mutants transport the drug out of the cell.
Describe the absorption of tetracyclines.
somewhat irregular partly because of low solubility and partly because of chelation with calcium, iron and aluminum
A tetracycline is the DOC for what?
infections with Mycoplasma pneumoniae, chlamydiae, ricketsiae, and some spriochetes
Which drug(s) cause stools to become softer, odorless, frothy and acquire a yellow color?
Tetracyclines
What are the big adverse side effects of tetracyclines?
GI side effects
Bone and Teeth issues (Dental discoloration)
Liver Damage (liver necrosis)
Renal Damage (Fanconi Syndrome - Renal tubular acidosis)
Photosensitization (esp with Demeclocycline)
Allergy (rare)
Which specific tissue does Doxycycline penetrate quite well?
prostate
What does demeclocycline do?
blocks ADH receptor function in the collecting tubules - used in SIADH
Which tetracycline is found in high concentrations in saliva and tears?
minocycline
What is special about Tigecycline?
has activity against MRSA, S. epi (MRSE), penicillin-resistant Strep pneumo (PRSP) and Vancomycin-resistant enterococci (VRE)
What do the fluoroquinolones all end in?
-floxacin
Which drug colors the urine brown?
Nitrofurantoin
What major side effect does Nitrofurantoin cause?
interstitial pulmonary fibrosis with chronic use (esp in elderly)
What is Nitrofurantoin good for?
UTIs (acute and chronic recurrent)
Gram negative and gram positive UTIs
What are some other adverse effects of NItrofurantoin?
Severe polyneuropathies and demyelination and degeneration of neurons.
GI issues (N/V/D)
Allergic reactions
What is the special mechanism of action of methenamine?
Decomposes to formaldehyde and ammonia in the acid medium of the urinary tract. Formaldehyde binds to amino groups, thereby inactivates proteins of the bacteria resulting in bactericidal action. May also have some antiseptic or antibacterial action in the Urinary tract
What is Methenamine used for?
chronic suppressive tx - especially of the UTI caused by E. coli. Also may be used prophylactically prior to urinary tract instrumentation and catheterization
What are some side effects of Methenamine?
GI distress, bladder irritations and other UT irriation (painful/frequent micturition, etc)
Crystalluria from mandelic acid may occur
What is the mechanism of action of Nalidixic acid?
inhibits DNA synthesis of many susceptible gram (-) bacteria but have no effect on Pseudomonas
Why does Nalidixic acid have limited usefulness?
because resistance develops in about 25% of cases
What is one major drug interaction for Nalidixic Acid?
Nitrofurantoin antagonizes the action of nalidixic acid if used simultaneously
Which drug can cause convulsions with high doses in pts with cerebral vascular insufficiency, parkinsonism, or epilepsy?
Nalidixic acid
Which drug can cause erosion of cartilage of weight bearing joints in young people?
Nalidixic acid
What is the mechanism of action for Cipro?
Inhibition of DNA gyrase of the susceptible bacteria.
DNA gyrase catalyzes the introduction of negative superhelical twists in the covalently closed circular DNAs.
What is the mechanism of resistance to Cipro?
mutation of the topoisomerase enzyme.
What is Cipro the DOC for?
post exposure prophylaxis and tx of anthrax.
What is special about the pharmacokinetics/drug interactions of Cipro?
antacids containing Mg2+ interfere with absorption
What are some shortcomings of Cipro?
limited activity against S. pneumoniae
Poor CNS penetration
not effective against anaerobes
Which drug can cause cartilage erosions in children and tendon rupture?
Cipro
When would you use Trovan (Trovafloxacin/Alatrofloxacin)?
Use restricted to certain life- or limb-threatening infections for which the need for the antibiotic outweighs the potential risk of hepatic disease
What is the mechanism of action for Moxifloxacin?
inhibits bacterial topoisomerase II and topoisomerase IV
How is Moxifloxacin metabolized?
through glururonide and sulfate conjugation in the liver
Which drug should be avoided in those pts taking Class IA or III antiarrhythmics?
Moxifloxacin
What is Levaquin used for?
sinusitis
chronic bronchitis
CAP
skin and skin structure infections
Complicated RTI's
Acute pyelo
What is Gatifloxacin used for?
ocular application only
What is Gemifloxacine used in?
active against penicillin resistant S. pneumoniae, CAP
What is the mechanism of action for Daptomycin?
Bind to bacterial membranes and cause rapid depolarization of membrane potential. They do NOT penetrate the bacterial cytoplasm. Loss of the membrane potential leads to inhibition of protein, DNA, and RNA synthesis and eventually bacterial cell death
What do we use Bactroban for?
tx of impetigo caused by Staph aureus and GABHS including Strep pyogenes.
Intranasal application to pts who carry MRSA
What is the mechanism of Bactroban?
bacterial protein and RNA synthesis are inhibited when it binds reversibly to bacterial isoleucyl-tRNA synthetase. This enzyme normally promotes the conversion of isoleucine and tRNA to isoleucyl-tRNA.
What is the mechanism of Polymyxin B?
binds to gram (-) bacterial cell membrane phospholipids. This increases the permeability of the cell membrane, which results in loss of metabolites essential to bacterial existence.
What is the mechanism of Isoniazid?
inhibits biosynthesis of mycolic acid (how? idk)
How is Isoniazid metabolized? What does this mean?
acetylation inactivates the drug --> fast vs slow acetylators (dosage)
What should you give to pts along with Isoniazid therapy? Why?
Vitamin B6 to prevent the peripheral neuritis
What is the mechanism of rifampin?
Inhibits the DNA-dependent RNA polymerase activity of most susceptible organisms w/o affecting the mammalian enzyme system in therapeutic doses
What is the mode of resistance for Rifampin?
mutations in the rpoB gene
What is the major side effect of Rifampin?
Turns sweat, pee, tears, contacts ORANGE!
Instead of Rifampin, what should be used in HIV pts?
Rifabutin
What is the mechanism of action for Ethambutol?
Inhibits arabinosyl transferases involved in cell wall biosynthesis; bacteriostatic
What is the mode of resistance for Ethambutol?
mutation in embCAB operon
What is a major side effect (though luckily reversible) of Ethambutol?
Decrease of visual acuity and loss of Green-Red perception suggesting retrobulbar neuritis.
What is the mechanism of action or Pyrazinamide?
prodrug - requires conversion into active form, pyrazinoic acid by Mtb PZase (pncA). Inhibits trans-translation in non-replicating bacilli
What is the mode of resistance for Pyrazinamide?
mutation in pncA
What are the side effects of Capreomycin?
Kidney damage (most serious)
Nitrogen retention
CN VIII damage, deafness and vestibular disturbances
What are the side effects of Rifabutin?
Rash
GI upset
Neutropenia
Urine discoloration (like Rifampin)
Thrombocytopenia
What are the side effects of cycloserine?
peripheral neuropathy
CNSy dysfunction
psychotic reactions
What is the mechanism of Dapsone?
similar to sulfonamides: PABA antagonist
What are some adverse side effects of Dapsone?
Methemoglobinemia
Leukopenia
Nasal obstruction
Hemolysis
Peripheral neuritis
What is the mechanism of action for Clofazimine?
Phenazine dye - used as an anti-inflammatory agent.
Binds preferentially to mycobacterial DNA and inhibit reproduction and growth.
What is Thalidomide the DOC for?
erythema nodosum leprosum
What is the mechanism of action or Thalidomide?
Accelerates the degredation of TNF-alpha mRNA encoding protein