Friday, April 03, 2026

Disinfectants influence microbes across hospital rooms

Hospital sink drains and airborne dust harbor disinfectant-tolerant bacteria

Northwestern University

Just because a topical antiseptic is swabbed on the skin doesn’t mean it stays on the skin.

In a new study, Northwestern University scientists studied how a powerful antiseptic, called chlorhexidine, affects bacteria in hospital environments. To prevent infections, hospitals heavily rely on chlorhexidine wipes to sterilize patients’ skin before procedures.

Through laboratory experiments, the researchers discovered that traces of chlorhexidine linger on surfaces much longer than previously known — long enough to help microbes build tolerance. By analyzing samples from a medical intensive care unit (MICU), the team also found chlorhexidine-tolerant bacteria spread throughout the hospital environment through touch — and, surprisingly, through the air.

The findings offer new insights into how disinfectants interact with microbes in indoor environments and could help inform strategies for preventing infection and antimicrobial resistance.

The study will be published on (Thursday) April 2 in the journal Environmental Science & Technology.

“Even though chlorhexidine is applied to patients’ skin, we saw evidence that it affects the microbes in the room all around the patients,” said Northwestern’s Erica M. Hartmann, who led the study. “Microbes and chemicals do not stay where we put them, and they can influence antimicrobial resistance. Our results suggest this is true for hospitals, but I have no reason to think there’s anything special about hospitals. I expect we would see the exact same thing if we looked at personal care products and microbes in homes, schools or anywhere else.”

An indoor microbiologist, Hartmann is a professor of civil and environmental engineering at Northwestern’s McCormick School of Engineering.

‘Keeping high-risk patients safe’

Widely used in healthcare since the 1950s, chlorhexidine is an important chemical for preventing infections in hospitals. Healthcare workers use products containing chlorhexidine in routine medical care, including the daily bathing of MICU patients, preparing skin before surgery or catheter insertion, sterilizing equipment and washing hands. It’s also commonly used in prescription mouthwashes for dental care and in veterinary clinics.

“Chlorhexidine is used in environments where patients are incredibly vulnerable, and physicians want to make sure microbial exposures are highly controlled,” Hartmann said. “It’s a well-regulated chemical and really important for keeping high-risk patients safe.”

But after chlorhexidine is applied to the skin, it appears to live a second life.

To track how chlorhexidine affects the environment, Hartmann and her team conducted a two-pronged study. First, the team designed laboratory experiments to simulate hospital cleaning. Then, they conducted an environmental survey inside a MICU.

Residue lingers for longer than 24 hours

In the laboratory, Hartmann’s team applied chlorhexidine to common materials — plastic, metal and laminate — often found in hospitals. Then, they cleaned those surfaces with chlorhexidine-free disinfectants typically used to sterilize hospital environments.

Even after these cleaning treatments, chlorhexidine residue lingered on surfaces after 24 hours. The residue levels were too low to kill bacteria but high enough to expose them to the chemical. In these conditions, surviving microbes can develop tolerance to the disinfectant.

To explore what happens under those sub-lethal conditions, the team exposed several clinically relevant bacteria, including Escherichia coli, to trace concentrations of chlorhexidine. Even after a full day of exposure, the microbes survived.

Sink drains are a hotspot

Next, Hartmann and her team conducted an environmental survey inside a MICU, collecting nearly 200 samples from hospital bed rails, keyboards, doorsills, light switches and sink drains. From those samples, they isolated more than 1,400 bacteria, and about 36% exhibited some level of tolerance to chlorhexidine.

While bacteria showed up all over the MICU, sink drains stood out as the biggest hotspot. Compared to dry surfaces, drains contained far higher levels of bacteria, including strains capable of tolerating much higher concentrations of chlorhexidine. According to Hartmann, hospital workers have long been concerned about sink drains because of the P-trap, the U-shaped pipe beneath the sink that traps a small amount of water to block sewer gas from escaping.

“Wherever there’s water, you will invariably have microbes,” Hartmann said. “Sink drains can be a reservoir for antimicrobial-resistant pathogens in hospitals. And the fear is that every time you run water, it generates aerosols. That has potential for re-exposures.”

Hitching a ride on airborne particles

In perhaps the most surprising finding, Hartmann and her team found bacteria with signs of chlorhexidine tolerance in samples collected from the top of doorsills.

“Our original hypothesis was that we’d find evidence of chlorhexidine in high-touch areas like light switches,” Hartmann said. “We included doorsills as a negative control.”

Because people rarely touch doorsills, the finding suggests bacteria might have hitched a ride on airborne particles, like dead skin cells. According to Hartmann, dust on doorsills can trap these particles circulating in the air.

“The point is not that we need to clean our doorsills,” she said. “The point is that we need to think about airflow pathways as a potential route of exposure or microbe transport within a built environment. Every time we walk around, we shed microbes, skin and chemicals that are on our skin. Some of that potentially floats around and deposits elsewhere in the room.”

Homes, offices do not need to be disinfected

While Hartmann emphasizes that chlorhexidine remains necessary and effective in clinical settings, she said the findings underscore the message that antimicrobial chemicals can have unintended consequences. Unless a person is actively sick or immune compromised, the environment around them does not need to be disinfected. To prevent antimicrobial resistance, Hartmann recommends using plain soap and water to clean our homes and offices.

“The MICU is an incredibly sensitive environment with incredibly vulnerable people,” she said. “But, elsewhere, we rarely need to disinfect. We don’t need to expose ourselves and our environments to these chemicals because those exposures are not necessarily benign.”

The study, “Hospital environments harbor chlorhexidine tolerant bacteria potentially linked to chlorhexidine persistence in the environment,” was supported by the Searle Leadership Fund.

Journal

Environmental Science & Technology

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Hospital environments harbor chlorhexidine tolerant bacteria potentially linked to chlorhexidine persistence in the environment

Article Publication Date

2-Apr-2026

Science confirms torpedo bat works as well as regular bat

Washington State University

Torpedo bat testing at WSU — video:
WSU researchers determined that torpedo bats and traditional bats performed equally well regarding hitting power.
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Credit: WSU Voiland College of Engineering & Architecture

PULLMAN, Wash. — The New York Yankees took the baseball world by storm with the newly designed torpedo bat last year, but the revolutionary design has ended up being no better than a standard bat for hitting the ball out of the park.

In the first-ever laboratory experiments done on the bat, a research team determined that the torpedo bat and traditional bat perform equally well in hitting power with only a slight difference in the location of the bat’s sweet spot. The researchers, including Lloyd Smith from Washington State University, Alan Nathan from University of Illinois and Daniel Russell from Penn State University, will present their work at the upcoming International Sports Engineering Association conference set for June 1–4 on the Pullman campus.

“Wood is wood,” said Smith, professor in WSU’s School of Mechanical and Materials Engineering and director of the university’s Sports Science Laboratory.

Smith said he wasn’t exactly surprised at the findings. He has been studying bats for a couple of decades and has seen lots of excitement over the years — as when people debated ash versus maple bats, for instance. The news about the torpedo bats confirms his theory that wood material just doesn’t have a lot of pizazz.

“When it comes to baseball, there’s not a lot you can do with wood,” he said. “If your goal is to keep the game steady and consistent and not have a lot of change, wood bats are good.”

The torpedo bat went viral, receiving worldwide attention in spring 2025 when the New York Yankees used the new type of bat for the first time in a game and set a team record, hitting nine home runs in that game.

Although the torpedo bat can be the same weight as a standard bat, it has a slightly different shape. The diameter of a traditional bat tapers from the handle to the barrel and then gradually increases to the tip of the bat. Researchers who made the torpedo bat removed wood from the barrel tip and added it to the sweet spot, so that the diameter tapers down from the sweet spot to the tip.

For the study, the researchers created two maple bats that were duplicates of a standard Major League Baseball bat. Two additional maple bats were made with a torpedo shaped barrel that gave them the same swing weight as the standard bat. To measure the bats’ ball-bat coefficient of restitution, or how much energy the bat returns to the ball, the researchers fired baseballs from an air cannon at a stationary bat and then used light gates and cameras to measure the speed of the incoming and rebounding ball.

The team found nearly identical performance for the torpedo and standard bats except that the sweet spot for the torpedo bat was a half inch farther from the bat tip than the standard bat.

“It was actually pretty phenomenal how close they were,” said Smith.

Of course, baseball players don’t care how much energy is lost — they just want to know how far the ball can be hit, said Smith.

In that case, the bats have the same swing weight, so that if a batter were blindfolded, he wouldn’t be able to tell the difference in how they felt. But because the ideal spot to hit the ball is closer in than on a standard bat, the torpedo bat will actually hit the ball a little bit slower than a standard bat would, he said.

“If you’re comparing both bats at the sweet spot, the ball hitting the torpedo bat is going to be traveling a little bit slower than the standard bat, so it will hit the ball not quite as fast or as far,” said Smith.

For some players who like to hit the ball closer in, the torpedo bat might be a better option for them, though, he added. And because the barrel is wider in a place where those batters do hit, they will be more likely to hit the ball more often — giving players a higher batting average.

In the first-ever laboratory experiments done on the bat, a research team determined that the torpedo bat and traditional bat perform equally well in hitting power with only a slight difference in the location of the bat’s sweet spot.

Credit

Photo courtesy of the Voiland College of Engineering and Architecture, WSU.

Article Title

Studies of the Torpedo Bat

Article Publication Date

1-Jun-2026

PediaBench: a comprehensive Chinese pediatric dataset for benchmarking large language models

Higher Education Press

Existing datasets for medical QA cannot comprehensively assess the proficiency of LLMs in pediatrics. To fill this problem, a research team led by Hui LI and Yanhao WANG published their new research on the benchmark of LLMs for pediatric QA in Frontiers of Computer Science co-published by Higher Education Press and Springer Nature.

The team introduced PediaBench, the first Chinese pediatric dataset encompassing 5 question types and 12 disease groups, and devised an integrated scoring scheme to thoroughly assess each LLM's proficiency across all types of questions in a unified manner. Finally validated the effectiveness of PediaBench with extensive experiments on 20 open-source and commercial LLMs.

In the research, they first introduced the construction process of the PediaBench dataset. The questions of PediaBench are collected from various public sources, including the Chinese national medical licensing examination, final exams of universities in medicine, pediatric disease diagnosis and treatment standards, and clinical guidelines. The questions are classified into five types: true-or-false (ToF), multiple choice (MC), pairing(PA), essay-type short answer (ES), and case analysis (CA). They use GLM to classify the questions into disease groups according to the International Classification of Diseases (ICD-11) standard issued by the WHO. Then they devise an integrated scoring criterion to evaluate the performance of each LLM. For ToF and MC questions, using accuracy as the basic measure. And assigning a weight to each question based on its difficulty level. For PA questions, using an equal weight of 3 and give a score of 1 for a partially correct result. And for ES and CA questions, using GPT-4o to score each LLM's answers. Finally, they assigned a fixed proportion to each type of question and calculated the integrated score.

The experimental results show that only a few LLMs achieve a passing score of at least 60. the high requirement for factuality in medical applications, there is still a significant gap when deploying LLMs as assistants for pediatricians.