If you work in the emergency department of a large city that has a significant rate of methicillin-resistant Staphylococcus aureus (MRSA) and a large bedbug problem — like New York, Washington, Los Angeles, or Atlanta — medical microbiologist Marc Romney, MD, has a suggestion for you. Do a study.
Several months ago, Dr. Romney and his colleagues at St. Paul's Hospital in Vancouver made headlines around the world when they found, for the first time, MRSA and other antibiotic-resistant bacteria on bedbugs taken from some of their patients. The idea of bedbugs as a possible vector for MRSA sent a shiver down the collective spines of many urban dwellers.
Dr. Romney said his study was only hypothesis-generating — and that there is much more to discover about the relationship between bedbugs and drug-resistant bacteria. That's where other urban EDs come in. “It would be nice to see if our findings could be replicated in another large city where there are big bedbug problems along with a lot of MRSA in the community,” he said. “If you suspect MRSA in an ED patient, be sure to submit specimens to the lab to try to understand transmission routes and if this is an issue in your community.”
The primary mode of transmission for MRSA is, of course, direct contact. But at St. Paul's, Dr. Romney and his colleagues were prompted to study the bedbug connection when they noticed a rise in MRSA infections at the same time bedbugs appeared to be surging in the area. “We wondered if there could be a link,” Dr. Romney explained. “We thought it would be interesting to culture and find out.”
So Dr. Romney's lab crushed up five bedbugs taken from three patients. Two patients each had one bedbug that was resistant to the antibiotic vancomycin, along with several other antibiotics; one patient carried three bedbugs that all were resistant to methicillin. (Emerg Infect Dis 2011;17:1132; http://1.usa.gov/MRSAbedbugs.)
“It had been previously stated definitively that bedbugs can't carry human pathogens, but most have looked at viruses like HIV and hepatitis B because bedbugs consume blood, and these are bloodborne pathogens,” Dr. Romney said. “That would make for an appealing hypothesis, yet very large studies looking into those theories have never proven that bedbugs can transmit human viruses such as HIV.”
No one had really looked at bacteria before, he said, and his results suggest a possibility of transmission from bug to human in a small percentage of cases. “If they can carry it, it's at least theoretically possible that they could transmit it from one bed to another,” he said.
Dr. Romney is the first to point out that his findings are preliminary. “We were never able to establish transmission,” he explained. Because the bedbugs were crushed for analysis, they can't even say where on or in the bedbugs the bacteria were being carried. “Was it in their salivary glands? Their digestive tracts? On the external surfaces of the bedbugs? We don't know. For that matter, it's possible that they still had skin cells attached to them from the patient.” But bedbugs do make people scratch, which can cause the skin breaks that could allow an infection to enter the bloodstream.
“It's an interesting theory,” said David Talan, MD, the chair of emergency medicine at Olive View-UCLA Medical Center. “But keep in mind that we've seen things like this before. We had a great suspicion that spiders transmitted MRSA. When there were outbreaks in the Los Angeles jail, they fumigated the jail because they didn't really understand what was going on, and of course, the infections continued. People tried to find it on spiders, and they couldn't.”
The difference here, of course, is that Dr. Romney did find the bacteria on bedbugs, but Dr. Talan pointed out that the bugs could have become colonized with MRSA from humans, rather than the other way around. “Do you suppose that if the bedbug community had its own Emergency Medicine News, they're writing headlines saying, ‘Oh, no, MRSA has been transferred from humans to bedbugs!’” he joked. “They may very well carry it. It doesn't take any great leap to think that bedbugs could be incidentally contaminated with MRSA just like the sheets, the pillow, or anything else that comes in contact with an infected human.”
Dr. Talan said strains of the bacteria can be typed to determine if the MRSA found on bedbugs is the same strain that humans get. “That would be the first step if someone wanted to do research in New York or another such city to see if bedbugs are at all implicated in MRSA outbreaks.”
But Drs. Talan and Romney stressed that the bedbug vector, even if real, is a minor element at best in the MRSA problem.”We have a pretty good idea of how MRSA is transmitted — through direct skin-to-skin contact with a colonized person and through poor hygiene practices such as sharing personal objects like towels and razors,” Dr. Romney said. “Even if there is a role for bedbugs, it probably only plays a limited role in unusual situations, such as areas where there is overcrowding, poor environmental and personal hygiene, bedbug infestation, and poor control measures.”
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