Choosing the right antimicrobial is a most difficult task. There are many factors to consider. Most antibiotic prescribing (~75%) is "empiric" before you know the organism that is causing the infection. Therefore getting the choice right on the front end is critical to ensure appropriate treatment while limiting toxicity.

For years I have taught my students the triangle approach that addresses 3 primary areas that you have to consider when selecting an antibiotic:

1. Patient: Patient characteristics are important to consider when choosing an antibiotic. For example, what allergies does the patient have? Are they pregnant? Is this a pediatric patient?
2. Bug: Where is the infection? Choosing an antibiotic depends on where the infection is originating. A skin/soft tissue infection will often involve gram positive organisms such as Streptococcus pyogenes or even MRSA while a urinary tract infection will most often involve gram-negative organisms such as E. coli. In addition some infections like diabetic foot infections, involve multiple organisms together termed "polymicrobial".
3. Drug: Sometimes there are many right answers for treating a patient when the organism is very susceptible. But sometimes a potential toxicity (e.g. nephrotoxicity from vancomycin) or multidrug resistance may lead you to choose a different agent.

Choosing an appropriate antibiotic involves asking the appropriate questions from each of these 3 parts of the triangle.

At teachmepharm.com, we have many videos devoted to helping you choose the correct antibiotic using these principles. Feel free to try us out here: https://www.teachmepharm.com/subscribe.

Have a great weekend!

Chris