antibiotics

• Antibiotic

  naturally occuring agent produced by a microbe that inhibits or kills another.
• selective toxicity

  agent being used should inhibit or kill the intended pathogen without seriously harming the host
• empiric therapy

  treatment of an infection before specific culture information has been obtained
• targeted therapy

  treatment focused to known pathogen and susceptibility
• prophaylactic therapy

  administration of an antibiotic to prevent infection
• bacteriostatic

  inhibit the growth of susceptible bacteria rather than killing them immediately. Eventually leads to bacterial death. Immune defence plays a role in clearing the pathogen
• bactericidal

  kills susceptible bacteria. Important to use for immunocompromised patients and certain difficult infections
• Narrow spectrum antibiotics

  active against specific organisms, not causing damage to the normal flora
• Broad spectrum antibiotic

  active against many bacteria
• MIC

  minimum inhibitory concentration
• two methods for susceptibility testing

  disk diffusion and minimum inhibitory concentration
• goals of antimicrobial stewardship

  imporve patient outcomes, improve pateint safety, reduce resistance, reduce healthcare cost without compromising patient care
• COMS

  clinical improvement, oral route is not compromised, markers are trending down, specific indication
• prophylaxis

  treatment given or action taken to prevent disease
• adverse effects of antibiotics

  allergy - penicillin, altered normal flora, drug interactions, specific organ toxicity, antibiotic resistance
• what enzyme catalyses the builiding of cross linked chains?

  transpeptidases, aka penicillin binding proteins PBPs
• beta-lactams bind directly to transpeptidase preventing cross linking, bactericida
• four main types of beta-lactams

  1. penicillins
  2. cephalosporins
  3. carbapenems
  4. monobactams
• what enzyme catalyses the cross-linking of the cell wall peptides?

  transpeptidase, also known as penicillin-binding protein
• what antibiotics target transpeptidase?

  penicillin and other beta-lactams
• how do bata-lactam anitbiotics target transpeptidase?

  bind irreversibly to its active site. binding inhibits transpeptidase activity, prevents formation of cross-links between peptidoglycan strands. bacterial cell wall synthesis is disrupted, leading to weaked cell wall and eventual cell lysis. bactericidal.
• cell lysis


  cell death
• penicillinase-producing staphylococci


  penicillinase destroys penicilln and stops it from being an effective treatment
• penicillin is highly active against

  gram-positive cocci, gram-positive rods (listeria), most anaerobes, gram-negatives
• penicillin therapeutic use


  endocarditis, meningitis and pneumonia caused by susceptible bacteria. cellulitis and groupA strep infections. And Syphilis (gram neg)
• anti-staphylococcal penicillins are active against

  penicillinase-producing staphylococci. ex: flucloxacillin (oral or IV)
• therapeutic use of anti-staphylococcal penicillins

  endocarditis and BSI caused by staphylococci and septic arthritis caused by S. aureus
• anti-staphylococcal penicillins do not protect against MRSA, enterococci or Listeria
• penicillin G


  IM and IV
• Penicillin V

  acid stable so it can be given via the oral route
• co-amoxiclav is augementin with clavulanate

  inhibits Beta-lactamases so that amoxicillin remains active
• pip-tazo (IV only) tazobactam

  inhibts beta-lactamases of MRSA so that piperacillin remains active
• therapeutic use of borad spectrum penicillins with gram-positive activity

  provide cover for gram-positives in treatment of infections with mixed aetiologies. combination antibiotics
• vancomycin no good for gram-negatives
• flucloxacillin no use for MRSA
• cephalosporins (generally broad spectrum)
• 1st gen cephalosporins

  • good gram-pos activity, also some gram-neg activity
  • oral
  • respiratory infections and UTIs
• 2nd gen cephalosporins

  • gram pos and neg activity
  • oral and IV
  • respiratory infections, complicated UTIs and surgical prophylaxis
  • ex: cefuroxime
• surgical prophylaxis

  the use of antibiotics for the prevention of surgical site infections
• 3rd gen cephalosporins

  • good gram-neg activity
  • less staphylococcal activity + some streptococcal activity
  • IV