Term
| 1. The penicillinase resistant penicillins were developed to overcome resistance to which organism? |
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Definition
| Staphylococcus aureus. Virtually all Staph produce penicillinase and are resistant to penicillins. (Except the antistaphylococcal/penicillinase- resistant penicillins). Penicillinase is a type of beta-lactamase but it does not break down all beta-lactams (ie cephalosporins and carbapenems are active vs. Staph aureus). |
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Term
| 2. The beta-lactamase inhibitor/penicillin combination productions provide enhanced coverage versus which organisms? |
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Definition
| Bacteria that produce beta-lactamase such as H. influenzae (approximately 50% produce beta-lactamase), Moraxella catarrhalis (approx. 90% produce beta-lactamase), certain anaerobes such as B. fragilis (virtually all produce beta-lactamase). Also provide coverage vs. Staphylococcus aureus. |
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Term
| 3. What antibiotics would you consider to treat an infection due to penicillin-resistant Streptococcus pneumoniae? |
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Definition
| Strains that are resistant to penicillin are also usually resistant to macrolides and sulfonamides. It is not due to the same mechanism of resistance but rather a multi-drug resistant gene that gets passed along. Agents that have activity against resistant S. pneumo nclude 3rd generation cephalosporins (ie. Ceftriaxone, cefotaxime), fluoroquinolones with enhanced gram-positive activity (ie. levofloxacin, moxifloxacin, gemifloxacin). High dose penicillins may work for intermediate strains. |
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Term
| 4. What is the mechanism of resistance of Streptococcus pneumoniae to penicillin? |
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Definition
| Altered penicillin binding protein. Therefore, amoxicllin/clavulanate (Augmentin) provides no better coverage vs. S. pneumoniae compared to plain amoxicillin. |
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Term
| 5. A patient reports an allergy to penicillin, when would you consider use of a penicillin or beta-lactam in this patient? |
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Definition
| First, you need to know what type of allergy the patient has. Many patients report nausea and diarrhea as allergies when they are really just side effects. If a patient experiences a rash, you may still use another beta- lactam (ie cephalosporin) under close supervision as only 5-10% of patients will have a cross reaction. If the patient reports a more severe reaction (ie. hives or anaphylaxis) you would generally stay away from all beta-lactams (penicillins, cephalsporins, carbapenems) if at all possible. However, depending on the infection and available alternatives, you still may consider under extremely close supervision (ie in the hospital setting). There are penicillin skin testing protocols to determine whether the patient has a true allergy. |
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Term
| 6. A patient presents with an uncomplicated skin and soft tissue infection, which class of cephalosporins would you use to treat this infection? |
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Definition
| 1st generation cephalosporins such as cefazolin or cephalexin |
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Term
| 7. The 2nd generation cephalosporin cefuroxime has enhanced activity compared to the 1st generation cephalosporin cephalexin versus which organism? |
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Definition
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Term
| 8. What would you recommend to prevent seizures secondary to penicillins? |
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Definition
| Appropriately reduce the dose for patients with renal dysfunction. Seizures are a dose-related adverse effect with the penicillins, cephalosporins. |
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Term
| 9. Which antibiotics have appreciable activity versus CA-MRSA (methicillin-resistant Staphylococcus aureus)? |
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Definition
| Vancomycin is considered the drug of choice for infections due to MRSA in the hospital setting. CA-MRSA infections are treated with TMP/SMX (Septra) or doxycycline in the outpatient setting. |
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Term
| 10. Which classes of antibiotics have appreciable activity versus atypical pathogens (i.e. Mycloplasma, Chlamydia, Legionella) and why? |
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Definition
Tetracylcines, macrolides, fluoroquinolones
Atypical pathogens generally lack an organized cell wall; therefore, cell- wall active agents (ie beta-lactams) do not provide reliable coverage against these organisms. |
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Term
| 11. Which macrolide has the best activity versus Haemophilus influenzae? |
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Definition
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Term
| 12. What are the most common adverse effects of the macrolides? |
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Definition
| GI adverse effects (ie diarrhea, nausea). Erythromycin is the worst and this agent is also used to increase gut motility in patients with gastroparesis. |
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Term
| 13. Which fluoroquinolones have enhanced gram-positive activity? |
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Definition
| Levofloxacin, moxifloxacin, gemifloxacin |
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Term
| 14. A patient is prescribed doxycycline for an infection. What adverse effects may occur with this med and how would you counsel your pt to take this medication? |
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Definition
| Stay out of direct sunlight and use sunblock, the absorption of this agent is decreased when taken with Al, MG, CA, Fe products. Need to separate dosing by 4 hours. |
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Term
| 15. A 28 year old patient is started on ciprofloxacin for a UTI. How would you counsel the patient on taking this antibiotic? |
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Definition
| Take full course of antibiotics. Separate dosing from calcium-containing products (ie milk, yogurt), iron-containing products-take ciprofloxacin at least 1 hour before or 4-6 hours after these products. |
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Term
| 16. What is the spectrum of activity of clindamycin? In which conditions is this an alternative agent for? |
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Definition
| Gram-positive bacteria and anaerobes, particularly mouth anaerobes |
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Term
| 17. A 45 year old female is receiving cephalexin for a skin and soft tissue infection. One week day after starting therapy she develops severe diarrhea (10 watery loose stools per day). What do you think is the cause of the diarrhea and what do you recommend? |
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Definition
| Likely Clostridium difficle-associated diarrhea. Would send stool studies to test for C. dif antigen to confirm diagnosis. Treat with metronidazole and discontinue other antibiotics if at all possible. |
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Term
| 18. Which antibiotic is contraindicated in patients with CrCL < 40 mL/min due to inability to achieve adequate urinary concentrations and increased risk of toxicity? |
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Definition
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Term
| 19. Which class of antibiotics is contraindicated in pregnancy, lactation, and children < 8 years old? |
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Definition
Tetracyclines (pregnancy category D)
Fluoroquinolones should be used with caution and only when benefits out weigh the risk in pregnancy (category C) and lactation |
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Term
| Of the infections in the scenario listed below, list the most common bacteria causing the infection and the drug of choice and one alternative to treating the infection. |
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Definition
Acute otitis media in a 2 year old boy allergic to PCN
S. pneumo, H. flu, M. cat
Amoxil HD but with allergy not used. Depending on allergy can use cefdinir, cefuroxime or if type 1 allergy azithromycin.
Sinusitis in a 25 year old male
S. pneumo, H. flu. M.cat
If no allergies and no abx use, Amoxicillin, Augmentin, cefdinir.
Exudative pharyngitis (bacterial)
Caused by Group A beta hemolytic strep-DOC is PCN. Alternative agent is azithromycin if allergy present.
Acute exacerbation of chronic bronchitis in a 68 year old male with COPD
Viruses, S. pneumo, H. flu, M. cat. Possibly Mycoplasma
If decide to use abx, amoxicillin, doxycycline, TMP/SMX, more severe disease consider Augmentin, FQ.
Community Acquired Pneumonia (CAP) in a 56 year old female
S. pneumo, Mycoplasma, (H. flu, M. cat-to lesser extent if healthy)
Macrolide or doxycycline-DOC
UTI caused by E. coli in an 18 year old female (not pregnant)
E. coli-TMP/SMX (Septra) DOC
Chlamydia in a 16 year old female (pregnancy unknown)
Chlamydia trachomatis
DOC doxycycline, if pregnant or unknown azythromycin (Zithromax)
CA MRSA in a 3 year old girl
Methacillin resistant Staph Aureus-DOC TMP/SMX (Septra)
Diabetic foot infection in a 66 year old female
Polymicrobial-consider Staph, Strep, Klebsiella, Pseudomonas, E. coli- most often times requires culture
Empiric therapy can start with broad spectrum abx then change when culture results are available (consider Augmentin, FQ) |
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