Flashcards
Antimicrobials (Rosser)
Cards in this deck (45)
- 1Define prophylaxisWhen a patient is given antimicrobials BEFORE exposure to PREVENT infection
- 2Define pre-exposure prophylaxisGiven to PREVENT infection but post-exposure
Eg) Rabies or HIV treatment - 3What is empiric therapy?When an antibiotic course is started without knowing what the pathogen that causes the disease is.
- 4What should you consider when prescribing EMPIRIC therapy?1. Organ System involved and commonly associated bacteria
2. AM susceptibility --> antibiograms
3. Activity of chosen AM AT THE SITE OF INFECTION (ie if you have a menigitis don't administer an AM that can't penetrate the CSF)
4. Host Factors (age, kidney and liver function, ALLERGIES) - 5What is definitive therapy?When you administer an AM course when you KNOW what the microbe is
- 6What is suppressive therapy?When LONGTERM AMs are administered to control residual infection
- 7What are some general principles regarding the administration of AMs?- choose the narrowest possible spectrum
- use the shortest duration
- opt for PO vs. IV
- choose the less expensive option - 8What is the MIC?Minimum Inhibitory Concentration
- specific to a drug/bug combination
MINIMUM CONCENTRATION OF DRUG TO INHIBIT LOGARITHMIC GROWTH - 9What is the MBC?Minimum Bacteriocidal Concentration
MINIMUM CONCENTRATION REQUIRED TO KILL BACTERIA DEAD (ie: 99.9% of bacteria are killed) - 10_____ are set by labs to define whether a bacteria is susceptible or resistant to a specific antimicrobial.Thresholds or Breakpoints
- 11What does the concentration of an organism have to be for it to be deemed susceptible to a particular antimicrobial?AT or BELOW the MIC
- 12What does the concentration of an organism have to be for it to be deemed RESISTANT to a particular antimicrobial?Above the MIC
- 13Contrast bacteriocidal and bacteriostatic.Bacteriocidal: kills microbes
Bacteriostatic: stops the growth and replication of microbes
Key: location and dosage can effect these properties.... terms are slightly misleading! - 14What are the 4 ways in which AMs can act on microbes?1. inhibit cell wall synthesis
2. inhibit protein synthesis
3. DISRUPT A METABOLIC PATHWAY (eg: folate metabolism)
4. Inhibit DNA synthesis - 15What are the 5 classes of drugs that effect cell wall synthesis?Penicillins
cephalosporins
glycopeptides
carbapenems
monobactams - 16Why are Penicillin Binding Proteins (PBPs) important to the action of B-lactam antimicrobials?PBPs are involved in cross linking PG subunts --> B-lactams bind PBPs and prevent this from occuring --> lose osmotic integrity --> LYSIS
- 17B-lactams are structural analogs of what part of peptidoglycan?D-ala-D-ala terminal repeat
- 18What are the 4 types of penicillins?Natural (Penicillin G)
Semi-Synthetic (anti-Staph) (cloxacillin --> can cross CSF)
Aminopenicillins (amoxicillin)
Ureidopenicillins (piperacillin) - 19What are the 2 beta-lactamase inhibitors and what drugs are they usually added to? Also how to they broaden the spectrum of the drug?Clavulanate and Tazobactam
Amoxicillin-Clavulanate
Piperacillin-Tazobactam
--> adds resistant Staph. aureus and many anaerobic bacteria, more gram (-) bacteria as well - 20How do beta lactamases work?B-lactams are inactivated if their ring is opened --> B-lactamases hydrolyze the ring and inactivate it!
- 21What are the 3 classes of cephalasporins?First Generation
Second Generation
Third generation - 22What is the most common first gen cephalosporin?cefazolin (IV)
cephalexin (PO) - 23What is the most common second gen cephalosporin?Cefuroxime
- 24What are the 4 most common third gen cephalosporin?cefixime (PO)
cefotaxime
ceftriaxone
ceftazidime - 25As you go up generations of cephalosporins, how does the coverage change?First Gen (mostly gram +)
Third gen (more gram (-), some gram (+) at higher doses - 26Carbapenems have very ______ coverage.BROAD
- 27Carbapenems are all administered via _____.IV
- 28Imipenem is better with Gram ___. Meropenem is better with gram ____. Ertapenem is given ___ daily and does NOT cover ______ and ______.+
-
ONCE, Enterococcus, Pseudomonas - 29What are carbapenems typically used for?empiric therapy for SEVERE, healthcare-associated infections
Definitive therapy: good for extended spectrum B-lactam resistant GNB - 30What is vancomycin? What can it be used for?LARGE GLYCOPEPTIDE
not absorbed orally
ONLY targets GPB - 31How doe Vancomycin's mode of action differ from B-lactams?Vancomycin binds D-ala-D-ala precursors to interfere with cross linking
- 32What is important to keep in mind when dosing vancomycin?LONG half life --> requires loading dose
- 33What can vancomycin be used for?- MRSA and MSSA
- S. pneumoniae (resistant)
- given orally to treat C. diff
- Alt. therapy with B lactam allergy
BUT... vancomycin is not as bacteriocidal as B lactams --> B lactam preferred - 34Identify drug class and action: (all will be on the exam!) Piperacillin-tazobactam cefazolin ceftriaxone imipenem vancomycinP-T: Uriedopenicilllin
Cefazolin: First Gen Cephalosporin (covers PEK)
Ceftriaxone: Third Gen (covers HEN)
Imipenem: carbapenem; covers mostly gram +
Vancomycin: resistant bacteria but not as bacteriocidal as B lactams - 35What is a Type I allergic reaction?Immediate and Acute Hypersensitivity
(Anaphylaxis, urticaria (hives), angioedema, hypotension, bronchospasms) - 36What is a Type II allergic reaction?Delayed cytotoxic Ab-mediated hypersensitivity
(hemolytic anemai, thrombocytopenia, neutropenia) - 37What is a Type III allergic reaction?Ab complex-mediated Hypersensitivity
(serum sickness, glomerulonephritis, drug fever) - 38What is a Type IV allergic reaction?DTH (Delayed Type Hypersensitivity)
- contact dermatitis, pustulosis - 39If a patient has an anaphylactic reaction to penicillin what drugs should you avoid?1. all penicillins and cephalosporins with similar side chains
2. can give cephalosporins with different side chain
3. CEFAZOLIN (1st gen) --> does not share a side chain with ANY beta lactams - 40Which cephalosporin does not share a side chain with any B lactams?CEFAZOLIN
(good option if there is an allergy) - 41What should you document if a patient has a B lactam allergic reaction?- B-lactam used and route of admin
- date of rxn
- timing of rxn after admin
- description of reaction
- on any meds at time of rxn?
- exposure to any B-lactams since then? - 42You decide to treat the infection for six weeks intravenous vancomycin, to be followed by doxycycline 100 mg orally BID, for an indefinite period of time. This is an example of _______ therapy.Suppressive
- 43Appropriate EMERGENCY treatment for right leg cellulitis would be: 1. cefazolin 2g IV q8h 2. cephalexin 500 mg p.o. QID 3. ceftriaxone 2g IV daily 4. vancomycin 25 mg/kg IV loading dose, then 15 mg/kg twice dailyKey: we assume the infection is S. aureus... but it could be MRSA
1. good for regular S. aureus NOT MRSA
2. this is a pill, we need quick control
3. good, once a day but not the best for S. aureus OR MRSA
4. Good against S. aureus and MRSA
*BEST ANSWER = VANCOMYCIN** - 44A 44 year old woman comes to the Emergency Department with a 2-day history of fevers, rigors, dysuria, and right >>> left flank pain. Her urinalysis shows pyuria. Blood and urine cultures are pending. She claims an allergy to pencillin: it was 10 years earlier, the medication was for a sore throat and was three times daily (? amoxicillin?), and she developed hives/throat swelling/ difficulty breathing, requiring an emergency department visit. Which of the following is most true: 1. She can be safely given ceftriaxone, to treat a pyelonephritis. 2. She can be safely given vancomycin to treat a pyelonephritis. 3. She can be safely given piperacillin-tazobactam to treat a pyelonephritis. 4. She does not require empiric antimicrobial therapy - treatment should be withheld until culture results are available.Key: treat as if there is a penicillin allergy... therefore cannot give any B-lactams
also... pyelonephritis (kidney infection) is more likely to be cause by gram - over gram +.... VANCOMYCIN only covers gram +
Ceftriaxone is a B lactam but it does not share any side chains with penicillin therefore it is safe to use - 45Describe the "Eagle Effect." Why/how does clindamycin avoid the Eagle Effect?Clindamycin = lincosamide (50S inhibitor... prevents peptide bond formation)
The Eagle Effect is common in B-lactam AMs because they impair cell wall synthesis and therefore can only act when bacteria are ACTIVELY multiplying (in log phase of growth) --> This is called the Eagle Effect (bacteria remain at a stationary level- plateau)
Clindamycin acts via inhibiting protein synthesis and therefore is not subject to the Eagle Effect.