2019.1 SAQ 13 – antibiotic prophylaxis

Outline the principles of antibiotic prophylaxis for surgical site infections using cefazolin in knee joint replacement surgery as an example.

BT_PO 1.131 Explain the principles of antibiotic prophylaxis.


Thanks to guest blogger Nic for contributing the following T/F statements.

T/F cefazolin is a third generation cephalosporin

T/F cefazolin is a broad spectrum antibiotic with good gram positive and gram negative cover *

T/F cefazolin is bacteriocidal

T/F beta lactam antibiotics disrupt bacterial cell wall synthesis

T/F prophylactic antibiotics are best given immediately prior to skin incision

T/F cefazolin should be administered in a dose of 15 mg/kg, up to 2 g

T/F cefazolin should not be used in a patient with penicillin allergy **

T/F during long operations, cefazolin should be re-dosed every 4 hours

T/F cefazolin should be re-dosed after blood loss > 1000 mL

*what is the main skin organism we are using cefazolin to cover?
** what is the incidence of allergic cross reactivity between penicillin and cefazolin, and why does it occur? (see reference 2)

1. any of the pharmacology books (Stoelting, Evers & Maze etc) have a chapter on antibiotics
2. Vorobeichik, etal. Misconceptions surrounding penicillin allergy: implications for anesthesiologists. Anesthesia & Analgesia, 2018; 127: 642-649.

What surgical antibiotic prophylaxis guidelines do you use in your hospital?


BT_PO 1.3 Describe the adverse effects of antimicrobial agents Discuss the role of antibiotic prophylaxis in preventing infection and the identification of patients requiring it.

I remember listening to a radio program a few years ago about the development of streptomycin. During WWII Sulfanilamide and (later) Penicillin were available, but there was no treatment for gram negative infections, which were obviously common after gunshot wounds to the abdomen. Selman Waksman was looking for such a drug amongst soil microbes, and found Streptomycin in 1943.


Here is a picture of someone making Streptomycin at a Merck Plant.

We don’t use streptomycin much now, but it sobering to think that it wasn’t that long ago that we couldn’t treat these infections at all.







T/F Antimicrobial effect of gentamicin is related to the area under the concentration time curve

T/F Clindamicin is effective against anaerobes

T/F Aminoglycoside ototoxicity is a dose dependent phenomenon

T/F If a patient has an anaphylactic reaction to penicillin there is a 15% chance they will also react to cefazolin

T/F Cefazolin is effective against most oral anaerobes