Women with Severe Burns More Prone to Blood Infections than Men

The skin serves as a natural barrier that prevents bacteria from entering the body. In severe burns, this protective function is significantly impaired. Pathogens can more easily enter the bloodstream through the wounds. If the airways suffer burns or corrosions from inhaling hot and toxic substances, they too become gateways for infections.

Bacteria can multiply in the blood and spread throughout the body. In the worst case, this triggers blood poisoning—also known as sepsis— which leads to multiple organ failure. This is a common cause of death in burn victims. A study supported by the SNSF has now identified for the first time which patients are affected by such infections. This study was conducted before the catastrophe in Crans-Montana but generally contributes to a better understanding of the processes in the bodies of severely injured patients.

The study focused on gender differences. The analysis included 269 patients with severe burns treated at the Centre for Severe Burn Injuries at University Hospital Zurich between 2017 and 2021. The findings from the study aim to help prevent sepsis in those with severe burns or manage it early on.

**Female bodies usually handle infections better**

The study investigated when and if bacteria appeared in the blood of burn victims. Such bacterial presence in the blood, known as bacteremia, can develop into sepsis. The result: nearly a quarter of those affected experienced this between five and thirteen days following admission. Furthermore, the data showed that women were almost twice as likely to be affected.

"This result surprised us somewhat," says Silvio Brugger, senior consultant at the Clinic for Infectious Diseases and Hospital Hygiene at University Hospital Zurich. "Ordinarily, bloodstream infections are usually less frequent in women than in men."

It is known that there are gender differences in bacterial infections: for example, younger women are more prone to infections in the upper respiratory tract—throat, ears, and nose—while men are more often affected in the bronchi and lungs. Women are also more susceptible to bladder infections. Many of these differences can be attributed to body structure, hormonal factors, or external circumstances such as occupational exposure or risk behavior.

"Often, women's immune systems seem to handle pathogens better, and some studies have shown them to mount a stronger immune response," says Brugger. This does not appear to be the case with burn injuries, though. Why women with severe burns in this cohort developed bacteremia more frequently is a question researchers cannot yet answer.

Different pathogens are not likely to be the explanation: Men and women mostly had the same bacteria in their blood, those that naturally colonize the skin and mouth as part of the natural microbiome. They are usually harmless until they enter the bloodstream in large quantities.

**Estrogens might be key**

In a follow-up study, researchers plan to analyze the collected samples more closely for sex hormones and the composition of the skin and airway microbiomes. Sex hormones affect human immune cells, which are part of the body's defense mechanisms against infections. Female sex hormones like estrogen are commonly associated with a better response. "Burn injuries might alter hormone metabolism, weakening the immune response," Brugger speculates.

Alongside teams from intensive care and plastic surgery, researchers now aim to closely examine the biological mechanisms behind these results, as "Survival chances after burns have significantly improved in recent decades due to advances in burn medicine." Yet, bacterial infections in the blood remain a problem.

Though affected individuals usually receive antibiotics early on to combat bacteria, new infections recur due to the compromised barrier. Resistant strains can also quickly develop, for which there are few effective antibiotics available.

Better understanding these connections could lead to measures protecting all patients from bacteremia. Implementing these measures into medical guidelines could take some time.

(*) Nicole J.M. Schweizer et al.: Impact of sex on the development of bacteremia in critically ill burn patients: A retrospective cohort study. Burns (2026)

The text of this news and further information are available on the website of the Swiss National Science Foundation.

**Press Contact:**
Silvio Brugger
University Hospital Zurich
Tel. +41 44 255 33 22
silvio.brugger@usz.ch

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