Screening for superbugs in the era of antimicrobial resistance


Bacteria don’t usually come to mind as a leading threat to global health. Yet, in the not so distant future, infections caused by antibiotic-resistant bacteria are forecasted to result in more deaths than cancer and diabetes combined. You might ask why antibiotic-resistant infections are increasingly common. The rise of bacteria causing these outbreaks can be explained by the evolutionary concept of “survival of the fittest”. Antibiotic treatment wipes out most, but not all bacteria. The few survivors multiply and are more likely to survive further antibiotic exposure. Have you ever stopped taking an antibiotic prescription early? Not finishing prescriptions, and general overuse of antibiotics, in the healthcare sector and beyond, have sped up the natural development of antibiotic resistance.

Medically, these bacterial species are referred to as antibiotic-resistant organisms, but a more common term you might have heard is “superbugs”. Some superbugs are deadlier than others. Generally, the more drugs a superbug is resistant to, the greater risk it poses. Recently, scientists discovered the most frightening superbug yet — one resistant to all, even last resort, antibiotics. As our options for effective antibiotic treatments dwindle, common medical procedures that carry a risk of infection, including Caesarean sections and joint replacement surgeries, may become riskier. If you develop an antibiotic-resistant infection, there is a greater risk that treatment won’t work and that you will experience complications – which can be serious, even leading to death.

So how do we begin to address this problem? The most effective strategy to slow the spread of superbugs is reducing antibiotic use – and using them responsibly when they are absolutely necessary. But this is challenging, and other strategies are needed. Infection screening is one approach that aims to reduce the spread of infection amongst patients who are being admitted to hospital or other healthcare settings. When you undergo screening, swabs are taken from multiple body sites and sent for laboratory testing. If superbugs are detected, you might be moved to an isolated area to avoid transmission to others, and you might be provided with more intensive antibiotic treatment. Benefits of these precautionary measures may seem obvious, but they are not without risk. Screening could inadvertently identify some patients colonized with superbugs who may have never developed or transmitted an infection. Ironically, unnecessary treatment of these low-risk patients could further contribute to antibiotic resistance. Screening is also resource intensive and Canadian institutions spend millions of dollars to support laboratories, staff, and the cost of treatment. So who should be screened in order to reduce the spread of superbugs, but avoid potential harms and unnecessary costs? Should only high-risk patients — for instance, immunocompromised patients or patients in intensive care units — be screened? Is this too risky and should patients who have been in close proximity to outbreaks or who have been in hospital long-term also be included? Or, should healthcare facilities screen every patient (universal screening)?

To help resolve this uncertainty, the medical community turned to CADTH — an independent agency that finds, assesses, and summarizes the research on drugs, medical devices, tests, and procedures — to find out what the evidence says.

CADTH searched for evidence on the comparative clinical and cost-effectiveness of different screening strategies and found 21 publications — one systematic review, five clinical studies, and 15 economic evaluations. The decision to screen (versus no screening) is supported by clear evidence of clinical and cost-related benefits. But, what about the more complex issue of whether to use universal versus targeted screening? Targeted screening of higher risk patients may result in detection and prevention of a similar number of infections, and similar gains in patient quality of life compared to universal screening programs, at a lower cost. It may also be more feasible in facilities where there are limited resources. Another potential benefit could be reduced unnecessary antibiotic use. Overall, facilities may benefit from screening for superbugs, and there is more evidence to support targeted screening than universal screening.

Healthcare facilities often face the hard task of deciding on the best infection control strategies to invest in. To decide what type of screening is best for them, facilities will have to assess the feasibility of isolating patients, ability to provide timely lab tests, and availability of other infection control measures such as programs to support appropriate use of antibiotics, and staff education about infection prevention. However, the evidence identified by CADTH may help hospitals and healthcare authorities understand that testing every patient that comes through the doors of the facility is, in most cases, unnecessary. In fact, some health authorities in Canada have already removed universal admission screening for certain superbugs in favour of targeted strategies. Widespread screening may still be useful in some limited situations, for example, a cancer centre where patients are at high risk of infections. However, evidence suggests that in most circumstances, targeted screening for superbugs may help avoid unnecessary costs and antibiotic use, reduce inconvenience to patients, and help reduce the spread of infection and the larger threat of antibiotic resistance.

If you would like to learn more about CADTH and the evidence we have to offer to help guide healthcare decisions in Canada, please visit, follow us on Twitter: @CADTH_ACMTS, or talk to our Liaison Officer in your region: