Study warns urban microbes evolve to resist cleaning products

By Stephen Beech via SWNS

Microbes in urban areas are evolving to resist the cleaning products used to eliminate them, warns new research.

New strains have also been discovered living in cities that were previously only found in Antarctic desert soil, say scientists.

Chinese researchers identified novel strains of microbes that have adapted to use the limited resources available in cities.

They also showed that our everyday behavior is changing the make-up of microorganisms in indoor environments.

Study lead author Dr. Xinzhao Tong, of Xi’an Jiaotong-Liverpool University , said: “Built environments offer distinct conditions that set them apart from natural and engineered habitats.

“Areas with many buildings are low in the traditional nutrients and essential resources microbes need for survival, so these built environments have a unique microbiome.

“Our use of cleaning and other manufactured products creates a unique setting that puts selective pressures on microbes, which they must adapt to or be eliminated, but the mechanisms by which microbes adapt and survive in built environments are poorly understood."

The research team collected 738 samples from a variety of built environments, including subways, residences, public facilities, piers and human skin in Hong Kong.

They then used a technique called shotgun metagenomic sequencing to analyze the microbes’ genomic content and understand how they have adapted to urban conditions.

The study, published in the journal Microbiome , identified 363 microbial strains that have not been previously discovered that live on our skin and the environment around us.

Some of the new strains’ genomes contained genes for metabolizing manufactured products found in cities and using them as carbon and energy sources.

This included the discovery of a strain of Candidatus phylum Eremiobacterota, previously only reported in Antarctic desert soil.

Dr. Tong said: “The genome of this novel strain of Eremiobacterota enables it to metabolize ammonium ions found in cleaning products.

"The strain also has genes for alcohol and aldehyde dehydrogenases to break down residual alcohol found in common disinfectants.

“Microbes possessing enhanced capabilities to utilize limited resources and tolerate manufactured products, such as disinfectants and metals, out-compete non-resistant strains, enhancing their survival and even evolution within built environments.

"They could, therefore, pose health risks if they are pathogenic.”

The Chinese researchers identified 11 unique, previously uncharacterized strains of Micrococcus luteus, typically non-pathogenic but capable of causing "opportunistic" infections in immunocompromised individuals.

Dr. Tong said: “The issue of their adaptation to our behavior becomes particularly critical in clinical settings where hospitals serve as hotspots for diverse pathogens that cause hospital-acquired infections, or HAIs.

"HAIs pose a significant threat, particularly in intensive care units where mortality rates can reach up to 30%."

The researchers also characterized two novel strains of Patescibacteria - known as “nanobacteria” - as they have tiny genomes that do not contain many genes for producing their own resources.

Dr. Tong said: “Some strains of Patescibacteria are considered parasitic as they rely on bacterial hosts to supply their nutrients.

"However, in this study, the researchers found that one of the nanobacteria strains, recovered from human skin, contains genes for the biosynthesis of carotenoids and ubiquinone."

She added: "These antioxidant compounds are vital to humans, and we typically acquire them, especially carotenoids, through our diets, suggesting a possible mutualistic relationship between bacteria and us as their hosts.”

The researchers are now investigating the transmission and evolution of resistance in pathogenic microbes within intensive care units that are exposed to stringent and extensive disinfectant practices.

They hope to improve infection control measures and increase the safety of clinical environments for healthcare workers and patients.

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