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Antibiotics-basics
- 3. Choosing an antibiotic  Know the group of bacteria: Gram positive, negative or anaerobic  Know which antibiotics are effective (including in allergic patients)  Know which diseases require specific knowledge: pneumonia, meningitis  Consider patient factors: renal failure, discharge to home?
- 4. Bacteriology • Staphylococci • Streptococci • Enterococci • Pseudomonas • Escherichia coli • Clostridium • Bacteroides fragilis
- 5. Penicillins Interfere with bacterial cell wall synthesis. Poor CSF penetration. Excreted in urine. 1. Original penicillins 2. Enteric active penicillins 3. Anti-staphylococcal penicillins 4. Anti-pseudomonal penicillins 5. Penicillins with beta lactamase inhibitors
- 6. Penicillins Class Examples Spectrum Notes Original penicillins Benzylpenicillin (PO/IM/IV), phenoxymethylpenicillin Streptococcus, enterococcus, some anaerobes Gram –ves and staph. are mostly resistant Enteric active penicillins Amoxicillin (PO/IV), ampicillin (IV) Enterococcus, streptococcus (rash if EBV), some anaerobes Gram –ves are mostly resistant Antistaphylococca l penicillins Flucoxacillin/ dicloxacillin (PO/IV) Exclusive Gram +ve: Staph & strep. Antipseudomonal penicillin Piperacillin/ ticarcillin (IV) Broad spectrum gram –ve & +ve Expensive: Use only when serious gram neg. sepsis Penicillin + beta lactamase inhibitor Amoxycillin + clavulanic acid (PO), ticarcillin + CA (IV) Broad spectrum gram –ve & +ve and anaerobes Useful if wide range of pathogens
- 7. Penicillins Side Effects  Hypersensitivity: 1-10% of exposed individuals, only 0.05% get anaphylaxis. Some cross reactivity with cephalosporins and beta-lactams.  Encephalopathy: Rare – more likely in severe renal failure  Common: Diarrhoea and antibiotic associated colitis
- 8. Review questions  Name some penicillins that would work for staphylococcal infection.  What don’t they work on?  What do original penicillins work best on?  What is the drug of choice in enterococcus?  What drug should only be used if serious gram negative sepsis is suspected?  Which penicillins are active against MRSA?
- 9. Cephalosporins  Four generations: As you increase the generation, there is less staph/strep coverage and more gram negative.  1st generation: Cephazolin IV, cephalexin PO  2nd generation: Mostly used in ENT  3rd generation: Cephtriaxone IV/IM or cefotaxime IV  4th generation: Covers pseudomonas and staphylococcus  Indications: Penicillin allergy, gram negative cover in renal impairment or pregnancy & meningitis. Useless for enterococci.
- 10. Review Questions  What are first generation cephalosporins used for?  What is the name of the oral first generation?  What organisms are ceftriaxone effective against?
- 11. Carbopenems  Imipenem and meropenem (IV)  Insanely broad spectrum (except MRSA and ampicillin resistant enterococci)  Expensive, last resort
- 12. Glycopeptides  Vancomycin  Narrow spectrum: First line for MRSA and ampicillin resistant enterococci
- 13. Aminoglycosides  Gentamicin (IV or IM), neomycin, streptomycin  Gram negatives including pseudomonas  Renal toxicity(excreted by kidney) and ototoxicity  Use for a maximum of 7 days as side effects are dose related  Can measure serum concentration
- 14. Macrolides  Erythromycin, roxithromycin, clarithromycin & azithromycin  Spectrum: Staph/Strep and atypical organisms (chlamydia, legionella)  Good for allergic patients
- 15. Tetracyclines  Doxycycline PO  Spectrum: Mainly atypicals (malaria prophylaxis, chlamydia, rickettsia)  Deposits in teeth and bones – caution in children under 12  Caution: Hepatic impairment, myasthenia gravis, SLE  Side effects: N/V, diarrhoea, oesophageal irritation
- 16. Lincosamide  Clindamycin PO/IV  Spectrum: Staph (not MRSA), strep and anaerobes – particularly used for staphylococcal joint and bone infection
- 17. Quinolones  Ciprofloxacin PO/IV  Spectrum: Gram negative and atypicals  Newer quinolones (i.e. moxifloxacin) have better gram positive activity
- 18. Trimethoprim and Sulphas  Trimethoprim PO has limited gram positive and negative – it’s used mainly for UTIs  Trimethoprim w/ sulphamethoxazole (PO/IV) = Bactrim  Drug of choice for Pneumocystis carinii pneumonia and chest sepsis
- 19. Chloramphenicol  Not used in Australia as it suppresses bone marrow – used commonly in the third world as very broad spectrum ad penetrates the BBB  Exception: eye drops
- 20. Nitroimidazoles  Metronidazole PO/IV  First line: Anaerobes **Clostridium difficile colitis
- 22. Pneumonia  What are the common organisms in community acquired pneumonia?  Which antibiotic would you use?  How would you classify the severity?
- 23. Answers  Common pathogens:  Strep pneumonia, mycoplasma pneumonia, chlamydia, staph, h.influenza, legionella
- 25. SMART-COP  0-2: Low risk of needing intensive respiratory or vasopressor support  3-4: Moderate risk (1 in 8)  5-6: High risk (1 in 3)  >7: Very high (2 in 3)  Score of >3 is 92% sensitive for IRVS
- 26. CURB 65  Risk of death at 30 days increases as score increases.  0-1: Tx as outpatient (0.7-3.2% risk)  2-3: Consider short stay in hospital or hospital in the home (13-17% risk)  4-5: Req. hospitalisation, consider ICU (41.5-57% risk)
- 27. Hospital Acquired Pneumonia  What are the common pathogens?  What is empirical treatment?
- 28. HAP  Suspect if purulent sputum, persistant infiltrate on CXR, increased oxygen requirement, febrile or leukocytosis/leukopenia.  Colonisation of the oropharynx w/ aerobic gram negative bacilli and multidrug resistant hospital pathogens: MRSA, drug-resistant Enterobacteriaceae, Pseudomonas aeruginosa etc.  Can occur due to atypicals: Legionella, Aspergillus, respiratory viruses
- 31. Answers  Staphylococcus, streptococcus  Dicloxacillin/ flucloxacillin
- 32. UTI  Organisms?  Treatments?  Pyelonephritis
- 33. Answers  E. Coli mostly, then klebsiella, protease  Trimethoprim or cephalexin (don’t know why) or amoxyl/clavulanic acid  Pyelonephritis – higher dose or gentamicin and amoxy/amp
- 34. Meningitis  Know this algorithm!
Hinweis der Redaktion
- Bold + italics = drug of choice