Risk factors for antimicrobial resistance in cancer patients and survivors: an electronic health record study

Bloodstream infections occur when bacteria (which are germs that can cause disease) enter the blood and grow there. These infections are usually treated with antibiotics. However, bacteria can become resistant, meaning the antibiotics no longer work, and this is called antimicrobial resistance (AMR). It is a major worldwide health problem and people with cancer are especially at risk because both cancer treatments and the cancer itself weaken their immune systems (bodies own protection system).

We looked at what factors make antimicrobial-resistant bloodstream infections more likely (also called risk factors) in people experiencing cancer or with past cancer (survivors) using hospital health data. Knowing which patients are more likely to have resistant bloodstream infections, and which antibiotics they are resistant to, could help doctors choose better treatments sooner.

In this study we looked at 22 possible risk factors, including past infections, previous antibiotic use, age, sex, and cancer type. We looked at two common types of bacteria that cause bloodstream infections and seven antibiotics working against them. We worked out the impact of the factors on resistance of the bacteria to these drugs.

We found that the strongest risk factor for AMR in a current bloodstream infection was having had an infection with either a resistant or a sensitive bacteria (the antibiotic can kill or stop the bacteria growing) before. Patients who had bacteria resistant to an antibiotic in the past year were much more likely to have a bloodstream infection that was resistant to the same antibiotic. This was true across all the bacteria and antibiotics we studied. In contrast, if tests showed that a past infection was caused by a bacteria that was sensitive to an antibiotic, the current bloodstream infections was less likely to be resistant to that antibiotic.

We also found that previous antibiotic use increased the chance of a new bloodstream infection being resistant to the same antibiotic. Some groups of patients, including younger people and those with blood cancers, were also more likely to have resistant bloodstream infections overall, possibly because they are more likely to receive antibiotics regularly to reduce the risk of infection.

This work shows that information already collected during routine care can help identify which bloodstream infections are more likely to be resistant. This could help doctors choose the right antibiotics more quickly and improve outcomes for patients with cancer. In the future, we aim to use these findings to develop tools that help guide treatment decisions and reduce the impact of antibiotic resistance.

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Read the full paper here: https://www.medrxiv.org/content/10.64898/2026.04.17.26351097v1

Blog post written by Annie Hu.

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