Harmful Bacteria Hitch A Ride On Houseflies

Scientists in Singapore have sequenced the genomes of flies and their associated bacteria to demonstrate that flies may be used for disease monitoring.

AsianScientist (Nov. 28, 2017) – An international research team led by Nanyang Technological University, Singapore (NTU Singapore) have proposed that swarms of flies can be used to help monitor disease outbreaks. They published their findings in Scientific Reports.

Flies are known to be carriers of disease, responsible for the spread of harmful microbes (pathogens). They are widely regarded as pests, but scientists may now have found a use for them.

In this study, scientists from NTU Singapore sequenced the genetic material of 116 houseflies and blowflies along with all the microorganisms found on the flies. They first baited the flies with a piece of rotting fish, then sedated the attracted flies by holding a container with dry ice close to the flies. The cold vapor from the dry ice sedated the flies and they fell into the cold container untouched and uncontaminated.

After the flies were defrosted in a sterile environment, the various parts were separated, then crushed, and the extracted DNA was put into a gene sequencing machine. A supercomputer was subsequently used to analyze the resultant data, separating the fly’s genes from that of symbiotic bacteria. The researchers thus discerned the fly’s microbiome by referencing a database of all known bacteria DNA and RNA.

The researchers discovered that each of these flies carried up to several hundred different species of bacteria, some of which may cause disease humans. Among the species of bacteria detected, the researchers identified Helicobacter pylori, a pathogen that can cause stomach ulcers in humans and is the strongest known risk factor for gastric cancer. Although known to be spread via body fluid and smear infections, this is the first time that H. pylori has been shown to be carried by flies in the environment.

“Our study has shown that bacteria can ‘fly’ by hitching a ride on common flies,” said Professor Stephan Schuster, a research director at the Singapore Centre for Environmental Life Sciences Engineering (SCELSE) at NTU Singapore. “They pick up the microbiome on their feet, spread them across their wings in a similar way like how we might comb our hair, and then proceed to disperse them on surfaces that they land on.”

The team believes that their new technique could put flies into service in public health surveillance programs. They suggest that germ-free flies, bred without any microorganisms in their microbiome, could pick up latent microbiomes in any environment they are released into since they are small enough to enter even the smallest of cracks and crevices.

When the flies are recaptured using bait traps, their microbiomes can be sequenced, giving clues to the type of bacteria they have encountered in the environment, thus acting as an early warning system.

“Such ‘autonomous bionic drones’ could be particularly useful in agriculture, if we want to detect a plant pathogen outbreak,” said Schuster. “Through regular monitoring, if we know that a particular pathogen is affecting the crops and is becoming an outbreak, then farmers could organize a targeted treatment that only eradicates that pathogen, leaving the other parts of the ecosystem intact.”

“To date, diseases transmitted by a mechanical vector like flies have been a major overlooked pathway by both the medical and academic community. This is a great example of how observations from basic research on how diseases spread might be translated into viable and useful applications, opening up new avenues for future technology,” he added.

The article can be found at: Junqueira et al. (2017) The Microbiomes of Blowflies and Houseflies as Bacterial Transmission Reservoirs.


Source: Nanyang Technological University; Photo: Shutterstock.
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