Asymptomatic bacteriuria: Current management

Dominik Mertz, Roman Jaeschke

Dr Dominik Mertz, associate professor in the Division of Infectious Diseases at McMaster University and medical director of infection prevention and control at Hamilton Health Sciences, joins Dr Roman Jaeschke to discuss the current screening and treatment recommendations for asymptomatic bacteriuria.


Krzyzaniak N, Forbes C, Clark J, Scott AM, Del Mar C, Bakhit M. Antibiotics versus no treatment for asymptomatic bacteriuria in residents of aged care facilities: a systematic review and meta-analysis. Br J Gen Pract. 2022 May 6;72(722):e649-e658. doi: 10.3399/BJGP.2022.0059. PMID: 35940886; PMCID: PMC9377352.

Roman Jaeschke, MD, MSc: Good morning. Welcome to another edition of McMaster Perspective. The topic today is something that has been coming back periodically over my whole professional life, which is asymptomatic bacteriuria. And there’s a number of issues here including how to define it, how to screen for it, and how to treat it. The trigger for this interview with Professor Dominik Mertz from McMaster University was a recent publication in the British Journal of General Practice (doi: 10.3399/BJGP.2022.0059) specifically looking at asymptomatic bacteriuria in residents of long-term care facilities.

Professor Mertz, who should be screened, who should be treated, how should we behave? The floor is yours.

Dominik Mertz, MD, MSc: Good morning, Roman. I think the population that we should be screening and treating isn’t necessarily the population that they looked at, where we have even added evidence with this paper that you referred to that there’s no benefit of treatment or screening to start with. Screening is currently recommended, at least in the North American setting, for pregnant women—where we also can have an indication for treatment, as well as [prior to] urologic procedures—when bleeding is anticipated; and this, I would say, is a population where we unfortunately don’t do a good job with screening preinterventionally and have potentially preventable bacteremic episodes after those interventions, which probably could be, as I mentioned, largely prevented if we were to test them prior [to the procedure] and give them the appropriate antibiotics to prevent that bacteremia from happening.

Roman Jaeschke: It sounds like the message is very simple: no reason to screen people in long-term care facilities you consider asymptomatic and very few who should be treated—and these were the populations that you mentioned should [be treated] or we think it’s not a mistake if they are treated these days, who are pregnant women and [patients awaiting] urologic procedures. Is that as simple as that?

Dominik Mertz: It is as simple as that, based on the best knowledge that we have at this point. In different populations and the one that’s covered in this paper, we have multiple even randomized controlled trials (RCTs), which still aren't as common in infectious diseases (IDs), that showed no benefit whatsoever for testing and treating asymptomatic bacteriuria. The large number of different populations and long-term care residents is one example that is covered in this paper.

But it goes back to, I would say, a common principle that we have in medicine. Unless the test has an implication on management, we shouldn’t be doing the tests to start with. And I think it’s a great example for that what we do with asymptomatic bacteriuria because it’s always harder not to treat a positive culture once you have one, even if you didn’t want the tests, right? So, it’s best not to test when you already know priorly, “Well, I should not treat even if this culture was positive.”

Roman Jaeschke: Unless we decide that it’s difficult to decide what is asymptomatic and what nonspecific symptoms could be in the elderly population. Okay, well, if that is the case, this would be one of the shorter McMaster Perspectives reinforcing the previous idea and I thank you for it very much.

Dominik Mertz: Thank you, Roman.

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