Interview with Katie Laird of De Montfort University, U.K.

What first drew you to study the laundering of healthcare textiles?

I’ve been researching the role of textiles in the transmission of infectious diseases for over a decade. My interest in this area was sparked by the fact that while hard surfaces have been extensively studied as potential sources of microbial cross-contamination, textiles, despite being high-touch items have not received the same level of attention or investigation.

What did you choose to investigate in this study, and why?

The U.K. is the only country in Europe where nurses’ uniforms are routinely laundered at home. A few years ago, I conducted a study which showed that microorganisms can survive 40°C washes and even transfer between textiles during laundering. This raised concerns about the risk of infection transmission between the home and healthcare settings. Despite the heightened awareness during the COVID-19 pandemic, domestic laundering policies for uniforms remained unchanged. With the increasing threat of antimicrobial resistance (AMR) and a growing understanding of the environment’s role in its spread, our research team felt it was essential to explore how home laundering practices might be contributing to this issue.

What are the key findings from your research?

We found that 50% of the domestic washing machines tested did not reach the 60°C temperature required to disinfect textiles, even when set to that temperature. Bacteria were able to survive a significant number of these washes, especially when rapid or eco cycles were used. We also discovered that many of these machines harboured antibiotic resistance genes, suggesting that they could act as reservoirs for the spread of resistance between microorganisms.

Additionally, we observed that bacteria exposed to non-biological detergent became resistant not only to the detergent itself but also exhibited cross-resistance to antibiotics. In one striking case, a previously antibiotic-susceptible Staphylococcus aureus strain developed antibiotic resistance effectively becoming MRSA without ever being exposed to antibiotics.

What most surprised or interested you about your findings?

The most surprising aspect was the poor performance of domestic washing machines, particularly those older than four years. I was also struck by how quickly bacteria developed antibiotic resistance after repeated exposure to sublethal concentrations of non-biological detergent.

You say you found increased bacterial tolerance to detergents used to clean healthcare worker uniforms, with some resistance to antibiotics as well. Can you tell us more about how this can cause problems in a healthcare setting?

The persistence of bacteria on textiles is well documented. When healthcare workers launder their uniforms at home, they risk bringing microorganisms into their household environment, an especially serious concern if they live with vulnerable individuals.

Although healthcare staff generally follow recommended laundering guidance, domestic machines often don’t reach the necessary temperatures for disinfection. Ensuring the correct detergent concentration for microbial kill without promoting resistance is complex, it requires precise knowledge of the machine’s water volume, the load weight, and more. These variables are difficult to control in the home setting. As a result, healthcare uniforms may carry bacteria back into clinical environments, bacteria that, due to suboptimal laundering, could now be resistant to antibiotics.

You suggest revising laundering guidelines to ensure domestic machines function more effectively. Can you tell us more about the steps healthcare providers can take to control antimicrobial resistance in their environments?

Ideally, all healthcare uniforms should be processed in on-site or industrial laundries, where disinfection procedures are validated, controlled, and regularly monitored. Our previous research on industrial laundering have shown no development of antibiotic cross-resistance at the disinfectant concentrations used. Where industrial laundering isn’t possible, healthcare providers should at least supply a standardised detergent proven to be effective at a range of temperatures and wash loads, accounting for the inconsistencies inherent in domestic machines. Machines less than four years old performed significantly better in our testing, so providing support or compensation to ensure healthcare workers have access to newer, higher-performing machines may also be necessary.

What do you hope your findings might lead to, and what are the next steps for your research?

I hope this study, alongside a growing body of related research, will lead to a reassessment of domestic laundering policies for healthcare uniforms. Our next steps involve investigating the actual transfer of microorganisms from textiles to human skin, as well as exploring how routine practices such as bed-making might contribute to the transmission of infectious diseases.

Interview edited by PLOS staff for clarity and concision.