Choosing Appropriate Empiric Therapy Based on Susceptibility & Resistance Rates

Ellie J C Goldstein, MD, director of RM Alden Research Laboratory, discusses how physicians need to rely on the data that is available when selecting an antibiotic.

Interview transcript: (modified slightly for readability)

“When it comes to selecting an antibiotic, physicians have to rely on the data that is available. Early on, it’s usually published studies which may or may not reflect what goes on locally. Later on, if your lab is able to do susceptibility studies, you can gather information on those specific isolates. It’s important because susceptibility and resistance vary from hospital to hospital, from location to location.

I go to 2 hospitals that are 5 blocks apart and the susceptibility and resistance rates are different for many of the organisms and many of the antibiotics. Depending on your patient demographic, depending on what’s available on formulary, that knowing what the susceptibility rates are helps you choose the best empirical therapy. And later, when you get the results back, [this] lets you decide on appropriate specific therapy for your patient so that you can choose wisely and choose an agent that is most appropriate with the best activity and chance of clinical success.

There’s a lag period for new antibiotics, and with new antibiotics often the susceptibilities are what we would call research use only, which are usually not published, or the hospital may not have the ability. And so, they have to go on to journals that do susceptibilities like the Journal of Antimicrobial Chemotherapy [and the Journal of] Diagnostic Microbiology and Infectious Diseases, and look at those susceptibilities and resistance rates to help guide therapy. But those are general, they’re not necessarily specific to your patient. And so, it’s based in the literature. The best thing is to have the susceptibility studies on your own institution and on your individual patient.

This is often difficult, so sometimes we have broad studies, but we don’t have real-time data of what is going on in our own locality, in our own facilities. Now, once the drugs are available then susceptibilities are part of the stewardship AMS mandate as well as regular infection control. They’re published at least annually in all hospitals as a requirement.

Many people don’t know where to find them even in their own hospitals. They’re online, they’re virtual, they’re in the computer, they’re not sure where to get them. And so, it becomes a problem, so they should be there for the older drugs and to update you, but they’re not always looked at or readily available. What infectious disease physicians do is they know their susceptibility rates or know at least where to find those annual antibiograms.

For newer drugs, it’s a bigger problem and that’s why reading studies as close to your institution that you can with the types of patients that you have are really important to help guide therapy.”