Bedbugs among homeless carry superbugs: study
Bedbugs are seen in a container from the lab at the National Pest Management Association, during the National Bed Bug Summit in Washington, Tuesday, Feb. 1, 2011. (AP / Alex Brandon)
The Canadian Press
Published Wednesday, May 11, 2011 6:45PM EDT
TORONTO - As if bedbugs aren't icky enough in their own right, researchers now wonder if the pesky little critters might also be a means of spreading so-called superbug infections.
Researchers discovered that a sample of the blood-sucking insects taken from three patients who live in Vancouver's gritty Downtown Eastside were carrying two types of drug-resistant bacteria.
Co-investigator Dr. Marc Romney, a medical microbiologist at nearby St. Paul's Hospital, said five bedbugs plucked from the patients or their belongings were carrying MRSA (methicillin-resistant Staphylococcus aureus) or VRE (vancomycin-resistant enterococci). Dubbed superbugs, the bacteria are resistant to many standard antibiotics.
While bedbugs have not been shown in previous studies to spread disease to people, it appears the night-feeding creepy-crawlies may at least cart around the microbes known to cause these often hard-to-treat infections.
"We can't state that bedbugs can transmit disease," Romney said from Vancouver. "What we can say is we found MRSA and VRE on these bedbugs and they might serve as potential vectors for MRSA and VRE, which may ultimately cause disease.
"But we haven't established that yet," he stressed, adding that the study analyzes only a small number of bedbugs from a few patients and they may only be carriers of the organisms.
Still, the discovery is of concern because infestations of Cimex lectularius Linnaeus, to give the bedbug its scientific name, have exploded in recent years.
"It's an important study with new information because no one has ever previously found that bedbugs can carry MRSA or VRE," said Dr. Stephen Hwang, a physician and research scientist at St. Michael's Hospital in Toronto's downtown core.
"The potential implications -- and I emphasize potential -- are quite significant, because if bedbugs do indeed transmit MRSA, or if they're vectors of transmission of MRSA and VRE, that would be a very significant health issue," said Hwang, who was not involved in the study.
"Because obviously these resistant bacteria are in health-care settings and they're in the community and we try very hard to control and limit the spread of these bacteria."
In fact, it was noticing a confluence of events among hospital patients that prompted Romney, in conjunction with co-author Christopher Lowe of the University of Toronto, to test out a theory about infection and the biting bugs.
"We noticed about three or four years ago that there was a big increase in MRSA infections, and many of these patients came from the Downtown Eastside of Vancouver. And around the same time, patients admitted to hospital were covered in bedbugs or their belongings were covered in bedbugs.
"And I thought, well, maybe there was a link, maybe bedbugs were playing a role in this big increase in MRSA infections in the Downtown Eastside."
Like other cities worldwide, Vancouver has seen an alarming increase in bedbugs, particularly in the Downtown Eastside, where 31 per cent of residents have reported infestations, he said. "The bedbugs are really coming from hotels and rooming houses."
MRSA is also a substantial problem in the community: it has been cultured from almost 55 per cent of skin and soft-tissue infections of patients seen at St. Paul's emergency department, the authors write. More recently, tests showed 43 per cent of wound infections among injection-drug users were colonized or infected with a community-linked strain of MRSA.
A high percentage of the neighbourhood's residents are also HIV-positive, and their weakened immune systems make them susceptible to other infections, Romney said. "Many of them inject drugs and their drug paraphernalia is contaminated with MRSA or they've recently been exposed to MRSA by sharing needles or skin contact."
To conduct the study, published Wednesday in the CDC journal Emerging Infectious Diseases, researchers collected the bedbugs, ground them up individually and tested them for disease signatures.
MRSA was isolated in three bedbugs taken from one patient, while VRE was present in two bedbugs, each taken from one of the other patients.
The MRSA found was typed as USA300, a community-transmitted strain that can cause skin and soft-tissue infections, severe pneumonia, and bloodstream and heart-valve infections.
Bites from the wingless, apple-seed-shaped insects can cause people to scratch excessively, causing skin breaks that act as portals for the MRSA bacteria to enter the body and cause potentially deadly infections.
"We were very surprised to find VRE because VRE isn't typically carried on individuals' skin -- it's carried in their (gastrointestinal) tract or their genital tract or urinary tract if they have an infection of their bladder," Romney said. "But I think it goes to show that these patients live in relatively unhygienic circumstances."
He said the study, which he described as small but intriguing, sheds no light on whether bedbugs pick up the infectious superbugs from people or vice versa, or whether the bacteria are carried externally on the insect or ingested after they take a blood meal.
While infestations have become a high-profile problem for big-city hotels, theatres and other venues, Romney believes superbug-carrying bedbugs aren't that widespread or even potentially hazardous for the broader population.
"It's probably not an issue for them. It's more of an issue for people who reside in impoverished inner-city neighbourhoods of large cities in North America where bedbugs are an issue."
Hwang said if bedbugs were a potential means to disseminate superbugs widely, "then that would be a significant threat."
But he cautioned that the study only demonstrates that superbugs can be isolated from bedbugs -- not that they are disease spreaders.
"This study show that it's theoretically possible -- and the next question is does transmission actually occur?"