Drug-Resistant Hospital Infections May Sometimes Be Transmitted By Flying Insects: Study

Flies and other insects in hospitals often carry antibiotic-resistant bacteria that can sicken humans, according to the findings of a new study.

British researchers indicate that roughly nine out of 10 insects sampled in U.K. hospitals tested positive for bacteria that is potentially harmful to humans. The findings were published June 21, in the Journal of Medical Entomology,

It is well known flies and other flying bugs can carry bacteria. However, researchers wanted to determine the prevalence of bacteria on insects and if the bacteria posed a threat to humans. For that reason, researchers sampled flying insect populations of seven hospitals in the United Kingdom between March 2010 and August 2011.

Nearly 20,000 insects were collected, with samples taken from several species, including flies, aphids, ants, wasps, bees and moths.

Researchers then took cultures of bacteria from the various insects and performed an antibiotic resistance profile of the bacteria. A total of 68 bacterial strains were characterized for their antibiotic resistance profile.

Nearly 90% of insects had potentially harmful bacteria on or in their bodies. More than half were resistant to at least one type of antibiotic while about 20% were resistant to multiple antibiotics.

In some cases, the level of bacteria was enough to cause infections in humans.

Past research has shown some surfaces in hospitals can pose a risk to humans. Contaminated floors as well as hospital plumbing can lead to antibiotic resistant infections. Furthermore, roughly one in seven cases of infections acquired while a patient is in the hospital are resistant to antibiotics.

In the new study, most bacteria found belonged to Enterobacteriaceae. Nearly half of the positive samples contained this bacteria, which includes strains like E. coli and Salmonella. Other bacteria found included Bacillus spp., Staphylococcus spp., Clostridium, Streptococcus, and Micrococcus.

The resistance found was most commonly to penicillin, but some were also resistant to vancomycin and levofloxacin.

Staphylococcus represented the highest proportion of resistant strains with Bacillus app. as the next highest proportion of resistant strains.

Researchers noted samples were collected from various areas of the hospital including where food for patients, visitors and staff was prepared or stored. Other areas tested included patient rooms, neonatal units, and maternity wards. The highest number of insects were seen during spring or summertime.