A new study has revealed the role that regular bugs play in spreading superbugs. A team from Aston University examined almost 20,000 insects collected from National Health Service (NHS) hospitals across the United Kingdom, and studied the kinds of bacteria they were carrying. The vast majority were found to host potentially harmful bacteria, more than half of which were resistant to some kinds of antibiotics.

The researchers began by collecting 19,937 individual insects from seven UK hospitals between March 2010 and August 2011, with about 75 percent of the final haul comprised of flies, 14 percent being "true bugs" like aphids, and the rest made up of ants, wasps, bees and moths. These were caught using UV light flytraps, bug zappers and sticky flypaper, placed throughout the facilities in wards, neonatal and maternity units, and food preparation areas.

Then, the team conducted microbiological analyses to determine the types and levels of bacteria the insects harbored, both in and on their bodies. Almost 90 percent of the insects tested were found to be carrying bacteria that can be harmful, and in some cases the levels were high enough to potentially cause infection in humans.

From those insects, the researchers isolated 86 different strains of bacteria, with the most common family being Enterobacteriaceae, which includes E. coli and Salmonella, at 41 percent. The second most common was the Bacillus family, which includes known food poison-associated bacteria like B. cereus, at 24 percent, and then the Staph family at 19 percent. The study showed that 53 percent of these bacterial strains were resistant to at least one class of antibiotics, with 19 percent showing multi-drug resistance.

"The results from this large-scale microbiological analysis show that a variety of flying insects collected from UK hospitals do indeed harbor pathogenic bacteria of different species," says Federica Boiochhi, lead author of the study. "What's quite interesting, though, is the high proportion of drug-resistant bacteria found in these samples. It's a vivid reminder of how our over-use of antibiotics in healthcare settings is making infections more difficult to treat."

Of course, it's important to consider this study in context. While the numbers themselves may sound alarming, the researchers point out that overall, insects would be responsible for a tiny portion of bacterial infections in hospitals. There are more important ways to fight multi-drug resistant "superbugs," such as developing new antibiotics and non-drug techniques like lights or materials.

That said, the researchers recommend that hospitals boost pest control measures to keep insects at bay. These might include using different types of traps, placing them in appropriate parts of facilities, and replacing them more regularly.

The research was published in the Journal of Medical Entomology.