Washing Machines Could Be Home To Superbug Bacteria — And Detergent Might Make The Problem Worse

LEICESTER, England — Healthcare workers’ uniforms washed at home might be bringing dangerous bacteria back to hospitals, creating a breeding ground for drug-resistant superbugs. A new study from researchers in England reveals that most domestic washing machines fail to properly disinfect clothes, potentially endangering patients and contributing to the growing crisis of antibiotic resistance.

The study, published in PLOS One, revealed that more than half of household washing machines don’t reach high enough temperatures to kill dangerous bacteria, even when set to high temperature cycles. What’s worse, the bacteria surviving these washes can develop resistance to common antibiotics, creating potential superbugs that could make their way back into healthcare settings.

An Overlooked Infection Risk

Researchers at De Montfort University tested both the bacteria-killing ability of home washers and the microbes lurking inside them. While hospital linen and scrubs undergo carefully controlled industrial washing processes to eliminate microbes, healthcare worker uniforms often get laundered at home under much less rigorous conditions.

This is a blind spot in infection control efforts. While hospitals focus heavily on hand hygiene and surface disinfection, the textiles worn by healthcare workers receive less attention, despite evidence showing bacteria can survive for weeks on fabric.

The research team tested six different household washing machines with a biological indicator containing Enterococcus faecium, a common hospital-acquired infection. They ran both full-length and quick wash cycles at 60°C (140°F), the temperature recommended by UK health guidelines.

Only half of the machines achieved sufficient decontamination during full-length washes, and performance was even worse during quick cycles. One machine never exceeded 20°C (68°F) despite being set to a 60°C cycle.

The researchers found that only two machines maintained their peak temperature above 57°C (134.6°F) for the recommended 10 minutes, though even these fell short of the recommended 60°C threshold.

The Hidden Ecosystem Inside Your Washing Machine

But temperature issues aren’t the only problem. The team analyzed the microbial populations inside 12 different home washing machines and found they harbor potentially dangerous bacteria, including species of Mycobacterium, Pseudomonas, and Acinetobacter—all potential pathogens.

These bacteria also carried genes for antibiotic resistance. The researchers detected genes encoding for efflux pumps (which help bacteria push antibiotics out of their cells) and mechanisms that alter antibiotic targets, making the drugs ineffective.

To test whether the detergents themselves might contribute to antibiotic resistance, the team exposed common hospital pathogens—Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa—to increasing concentrations of laundry detergents.

The bacteria quickly adapted to survive higher and higher concentrations. S. aureus, for example, developed tolerance to liquid detergent concentrations almost 90,000% higher than what initially inhibited its growth. K. pneumoniae‘s tolerance increased by over 1.5 million percent.

Bacteria exposed to detergents developed cross-resistance to critical medical antibiotics. K. pneumoniae became resistant to carbapenems, often considered “last-resort” antibiotics. S. aureus developed resistance patterns resembling those of MRSA (methicillin-resistant Staphylococcus aureus), one of the most notorious hospital superbugs.

The combination of ineffective washing temperatures and bacterial adaptation creates a dangerous cycle: Healthcare workers’ uniforms can transport pathogens from hospitals to home washing machines, where inadequate cleaning allows these microbes to survive, contaminate the machine, spread to other clothes, and potentially return to healthcare environments.

This isn’t just a theoretical concern. Previous outbreaks have been linked to contaminated washing machines. In 2012, surgical scrubs contaminated by a healthcare worker’s home washing machine caused post-surgical infections in three patients. In 2019, an extended-spectrum beta-lactamase-producing Klebsiella oxytoca strain spread through a neonatal ward via knitted clothing washed in an on-site domestic machine.

Breaking the Cycle

Healthcare workers should avoid quick wash cycles, aim for temperatures above 70°C (158°F) to ensure reaching at least 60°C, clean their machines regularly, and replace them every four years. But the most effective solution might be moving away from home laundering altogether.

The researchers advise that professional commercial laundering services following proper standards would provide more reliable decontamination, improving the washing process and lowering infection transmission risks.

With antimicrobial resistance already causing over 1.2 million deaths annually worldwide, addressing every potential pathway for resistance development is crucial. This study suggests that something as seemingly innocent as washing work clothes at home might be contributing to one of healthcare’s most pressing crises.