Madeline King, PharmD, Recaps ECCMID Research on Pre-operative ASB and Aztreonam Usage

In a pair of posters presented at the European Congress of Clinical Microbiology and Infectious Disease (ECCMID 2019), Madeline King, PharmD, assistant professor of clinical pharmacy at Philadelphia College of Pharmacy who practices in infectious disease at Cooper Hospital, examined outcomes associated with pre-operative asymptomatic bacteriuria (ASB) and also the appropriateness of aztreonam usage and stewardship interventions.

Contagion® sat down with King, who is also a Contagion® Editorial Advisory Board Member, to discuss her research.

Interview transcript (modified slightly for readability):

Contagion®: What were the biggest takeaways from your 2 posters presented at ECCMID?Dr. King: I presented 2 posters this year, the first one being about the appropriate use of aztreonam in our institution at Cooper. The biggest takeaway from that poster, I think, is that aztreonam is being used inappropriately a good portion of the time, at least at our institution, and it seems to be that way kind of across the board just by talking to other people. I think the biggest takeaway is that we should really be thinking about if we're using aztreonam in the right patients and clarifying the penicillin allergies that a lot of people report.

The poster today is on treatment of asymptomatic bacteriuria prior to either a [coronary artery bypass grafting] CABG or a total joint arthroplasty and so we found that at our institution—and there's literature on this as well—it seemed like people were getting urine cultures taken prior to those types of procedures and maybe even being treated for that asymptomatic bacteriuria when it didn't really seem to matter, so I think the key takeaway there, in concordance with the new asymptomatic bacteriuria guidelines, is to stop doing that because, for the most part, it doesn't make a difference in the patient's outcome.

Contagion®: What can be done from a provider standpoint to better clarify and document allergies (particularly to beta-lactam antibiotics)?Dr. King: To clarify allergies for a patient who has a penicillin or beta-lactam reported allergy is really the main way to stop using aztreonam inappropriately, and the reason we even care is, for us especially, we don't have great susceptibility to aztreonam in a lot of our ESBL producers and a lot of our Pseudomonas, so using it empirically isn't really the best choice for the patient. It's also more expensive than a lot of the other agents that we might be using, and I hate to harp on cost but why not use a better drug that's less expensive basically?

The things we can do to clarify the allergies, I think providers, pharmacists, nurses can ask patients to specify exactly what their allergic reaction is and to exactly which drug it was and when it was because somebody who says they think they had an allergy as a child may not be allergic anymore or maybe it was an upset stomach and they just didn't know the difference. We see a lot of allergies that are listed that are not true allergies at all, and so in the poster I presented yesterday we looked at appropriateness based on if the patient had a history of an IgE-mediated allergy or if the patient had tolerated a beta-lactam in the past per our own medical administration record. And 40% of people who got aztreonam had tolerated a beta-lactam in the past, and over half of the people did not have an IgE-mediated allergy so just clarifying what that allergy was and talking to the patient about, you know, this isn't really a true allergy [and] the cross-reactivity between what you may have had an allergy to and a cephalosporin or a carbapenem is so low that even if you did have an allergy, you're not going to have a problem with these agents, so just really talking to the patient getting that information.

Contagion®: Your study identified the need for prospective measures to fully optimize aztreonam usage. What might some of those measures be?Dr. King: Some of the measures to better optimize aztreonam use... right now at our institution we have a 3-day restriction for aztreonam so you can use it for 72 hours but then you need ID approval. Something that we could do is either restrict it further and still do kind of a retrospective approval or every time the order is entered we could actually look and see, as the pharmacist verifying the order, "Hey, this is being put in but I see the patient's allergy was GI upset." So I can then call the provider and tell them, "Hey, actually you should order something else." Another way instead of having someone call a provider is in the order itself there can be kind of branching logic where they would have to select exactly why they need aztreonam, so IgE-mediated allergy documented, can't tolerate a beta-lactam, has failed beta-lactams recently, or something to that effect so really kind of catching it at the time of order entry.

Contagion®: Given your poster on pre-operative ASB, what is your reaction to the updated IDSA treatment guidelines for asymptomatic bacteriuria?Dr. King: The new guidelines for ASB kind of assure all of us in ID that we're doing the right thing, that we have the right mindset. For the patients that we looked at—our CABG patients and our patients with total joint arthroplasties—there's been plenty of literature that shows that the bacteria found in the urine and people who do get urine cultures pre-operatively doesn't correlate to the surgical-site infections that patients may get after. There was a study that showed patients who had asymptomatic bacteriuria without treatment may have had more surgical-site infections but it had nothing to do with the bacteria found in the urine. I discovered recently that this actually goes back to a study from the '70s where they saw an increase in post-op infections in patients who had bacteriuria, but it it doesn't correlate to the bacteriuria. The the new ASB guidelines talked about a lot of other things that are really nice. They kind of clarify that only if you're doing a urologic procedure do you really need to get those pre-operative urine cultures or in pregnant women obviously, but prior to other surgeries there's not really any benefit and if you give the patient antibiotics for this bacteriuria you may actually be doing harm [and] they may end up with adverse effects [such as] C diff being one of the worst ones of them.

The studies, "Appropriateness of aztreonam usage at a large academic medical centre: A retrospective analysis and stewardship intervention" and "Outcomes associated with pre-operative asymptomatic bacteriuria in patients undergoing joint arthroplasty or coronary artery bypass graft," were presented at ECCMID 2019.