MRSA and bedbugs?

An ahead-of-print paper in Emerging Infectious Diseases is generating some buzz in the mainstream media. While the findings are interesting, I’m honestly not sure how they got published, being so preliminary.

Like many areas, Vancouver, British Columbia has seen a jump in the prevalence of bedbugs. After finding impoverished patients infested with the bugs, researchers decided to collect some and test them for pathogens–specifically, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). So, they tested 5 bugs from 3 patients. That’s it–it doesn’t even appear to be 5 bugs apiece, but just 5 total. And the bugs were simply homogenized and streaked–not an uncommon way to test bugs for microbes, but one that has pretty severe limitations if you’re really looking at transmission via biting.

They did find MRSA (and VRE)–obviously, or it wouldn’t have made news. VRE was isolated from 1 bug each from 2 patients; MRSA was isolated from 3 bedbugs from the remaining patient. At first read, I thought they’d confirmed the MRSA strains were USA300, but they didn’t even do that–all they did was note the antibiotic susceptibility profiles of the isolates were consistent with USA300 (though headlines are already screaming “flesh eating bacteria isolated from bedbugs!” as you can see from the link up top). However, what we don’t know if whether the bedbugs were simply externally contaminated (perhaps from close contact with their human hosts), or if they were actually carrying the organisms in their salivary glands (as has been previously reported for S. aureus). If it’s the latter, an infection risk seems more plausible, although I suppose a bite from an externally-contaminated bedbug could also introduce organisms into an open wound.

Still, the paper is really, really, really sparse on data. I’ll sum up with words expressed in the newspaper story above:

Medical health officer Dr. Reka Gustafson said the St. Paul’s study is so small that no public health warning is necessary. She noted the superbug MRSA can be found on “doctors’ ties” and chairs in public places and that it’s more important to counsel people “to wash their hands thoroughly and use antibiotics wisely.”

Lowe CF, Romney MG (2011). Bedbugs as Vectors for Drug-Resistant Bacteria Emerging Infectious Diseases

Epidemiological studies–why don’t people participate?

Maryn McKenna was awesome enough to take some time out of her vacation to blog about our recent ST398 paper, finding “livestock-associated” S. aureus in a daycare worker. She raised one question I didn’t really address previously, regarding our participation by kids and workers at the facility (eight kids out of 168, and 24 out of 60 staff members).

(Staph screening is very non-invasive, by the way; it effectively involves twirling a long-handled Q-tip inside the front of your nostrils. Kinda makes you wonder why families would not have wanted to participate. On the other hand, since Iowa is the pig-growing capital of the U.S., they may have been motivated not to want to know.)

I thought I’d chat a bit about enrollment for this project, since getting people to participate is one of the most difficult parts of these types of studies. First, there really wasn’t any mention of MRSA and swine for this particular study, so I doubt protecting the pig industry was high on anyone’s list for reasons not to participate. However, anytime we do these type of studies, we’re relying on the generosity of individuals in the community–particularly when we didn’t really have participation incentives, as was the case in this project, which was done on a shoestring budget. (We passed out mini hand sanitizer bottles for adults, and had some little toys for the children).

We ran into several challenges for the research which limited our ability to enroll children. Along with a swab, we also had a questionnaire for parents and employees to fill out (as well as a third questionnaire for the director of the facility). For parents and employees, we asked about exposures: did they spend time in hospitals, around animals, at the gym? Had they recently had an infection? etc. For the directors, we asked about cleaning routines at the facility, as well as facility size (number of children and employees). So it wasn’t only the swabs, but also a decent amount of paperwork to fill out when you include the informed consent forms. We also had to do all of this at the facility; because of the way we were sampling, parents didn’t have a chance to take the questionnaire home to fill it out and then return it. So only parents (and employees) who had some spare time during either child drop-off or pick-up really had the chance to participate.

This particular study also started in roughly March 2009–right around the same time as the emergence of novel H1N1. There was a lot of news about the swabs that were taken to test for flu, which are more invasive than regular Staph swabs, so perhaps many potential participants had the mistaken assumption that the swab collection would be more uncomfortable than it really is. (When we were able to swab the child participants, most of them giggled and said that the swab tickled).

Finally, I should note that this facility was one of the larger ones we sampled, and to do this, my grad student returned several times during the day to try and catch parents during common drop-off/pick-up times (and employees who worked different shifts). However, even with this, we certainly missed a number of children and employees, such as those who were part-time and simply didn’t attend or work the day that we were there. We did have higher participation rates at some of the other facilities.

So, I think timing and misinformation–rather than any kind of fear of finding out things they might not want to know–led to our lower participation rate at this facility.

Quick updates

The University of Iowa press office did a nice story on our recent article showing “livestock-associated” S. aureus in a daycare worker in Iowa. LabSpaces covers it here.

I started a new Facebook page for our research center, the University of Iowa Center for Emerging Infectious Diseases. Join up for research updates! We’ll have a lot coming up this summer.

And on that note, soon we’ll have a new Research Assistant starting at the Center: Megan Quick, who was featured today on in the “Photo of the Month” on the Association for Schools of Public Health website.

Have a few blog posts percolating but real life has been getting in the way; more next week!

New paper: Staphylococcus aureus ST398 in a childcare worker

One of the reasons I’ve not been blogging as much over the past 2 years or so is that it’s been just insane in the lab. As I was still living off start-up funds and pilot grants, I didn’t have anyone full-time to take care of everything, so all the work has been done by myself and a handful of excellent graduate & undergrad students. Happily, some of the initial projects are wrapping up, and publications are starting to come out (I’ll be blogging about others in the coming days/weeks). One of them was published yesterday in Emerging Infectious Diseases: Livestock-associated Staphylococcus aureus in Childcare Worker. More after the jump.
Continue reading “New paper: Staphylococcus aureus ST398 in a childcare worker”

MRSA and pets: should they get tested?

Over at the Worms and Germs blog, Scott Weese has a great post on MRSA testing. He notes the he’s frequently asked by human MRSA patients whether their pet should be tested as well, since several studies have documented transmission of MRSA between humans and their companion animals. His first response is always, “why?”

One big question I ask is ‘why do you want to know and what would you do with the results?’ Sometimes people want to know their pet’s status to see if the pet was the source of their infection. However, MRSA in pets is typically human-associated, and if a pet is carrying MRSA, it probably got it from the owner. Finding MRSA in a pet after someone was diagnosed with an MRSA infection doesn’t mean the pet was the source. More likely, the person got MRSA somewhere else and passed it on to their pet.

Sometimes, people want to know if their pet is at risk of an infection. Carrying MRSA presumably increases the risk of an MRSA infection, but likely only in animals already at risk of an infection because of underlying disease or other risk factors such as surgery. The risk to the average pet from short-term MRSA colonization is probably limited. Also, if the pet was identified as a carrier, we wouldn’t be doing anything to eliminate carriage, since we have no idea if we can do it and it doesn’t seem to be needed (since dogs and cats almost always get rid of it on their own). Therefore, it’s hard to justify screening for this reason. If the animal was getting ready to undergo surgery, then that might change my answer.

I think Scott makes great points. As he notes later in his post, his advice would be the same whether an animal was found to be colonized or not (since even if the animal is negative, that only means they were *negative at the time of the testing,* and they could become colonized later: practice good hygiene.

I’d add one addendum to his response, though. As he notes, his answer may change if the animal may be facing surgery. I’d add also from the human side that the carriage status of pet animals may be something important to know if there are recurring infections in the family. If this is an issue, then the entire family will need to be looked at as a unit, to see if one of them is a reservoir (potentially re-infecting others in the family)–and the family unit should include pets at this point. As Scott notes, typically pets become colonized from their owners, but once colonized, they do have the potential to pass it back to the other human family members like the world’s worst game of hot potato. As such, they may keep the MRSA transmission chain going, even if their humans are subjected to decolonization measures (as was described in this NEJM paper).

So, in special cases, it may be helpful to have your animals tested for MRSA–but for the vast majority of people, having that knowledge won’t do much one way or the other.

Emerging Disease and Zoonoses series

Part One: Introduction to Emerging Diseases and Zoonoses

Part Two: Introduction to Emerging Diseases and Zoonoses continued

Part Three: Bushmeat

Part Four: War and Disease

Part Five: Chikungunya

Part Six: Avian influenza

Part Seven: Reporting on emerging diseases

Part Eight: Disease and Domesticated Animals

Part Nine: The Emergence of Nipah Virus

Part Ten: Monkeypox

Part Eleven: Streptococcus suis

Part Twelve: Salmonella and fish

Part Thirteen: new swine influenza virus detected

Part Fourteen: dog flu strikes Wyoming.

Part Fifteen: Clostridium species.

Part Sixteen: The origins of HIV.

Part Seventeen: “Mad cow,” kuru, and prion incubation periods.

Part Eighteen: spread of H5N1 in Nigeria.

Part Nineteen: bats and emerging viruses.

Part Twenty: subclinical infections with avian influenza.

Part Twenty-one: West Nile virus outbreak…in Idaho squirrels?

Part Twenty-two: Popeye never warned you about this.

Part Twenty-three: Pets ain’t all they’re cracked up to be.

Part Twenty-four: Rift Valley Fever outbreak in Kenya.

Part Twenty-five: Rift Valley Fever update

Part Twenty-six: Chimps at risk of acquiring antibiotic-resistant infections

Part Twenty-seven: Rocky Mountain Spotted Fever.

Part Twenty-eight: Introduction to Marburg virus

Part Twenty-nine: Marburg virus: has the elusive reservoir species been found?

Part Thirty: swine flu in Ohio fairgoers?

Part Thirty-One: Newly discovered Ebola viruses: filling gaps in viral ecology

Part Thirty-Two: Chikungunya–in India, Italy, and Iowa

Part Thirty-Three: MRSA and swine: collision course

Part Thirty-Four: How far does religious freedom extend when it conflicts with public health?

Part Thirty-Five: What’s it like to work an Ebola outbreak?

Part Thirty-Six: Influenza meta-update: H5N1 spreading, new swine influenza virus found

Part Thirty-Seven: Where did syphilis come from?

Part Thirty-Eight: “One medicine, one health”

Part Thirty-Nine: What’s Google got to do with emerging disease?

Part Forty: Marburg hits Europe once again.

Part Forty-One: New Ebola subtype confirmed.

Part Forty-Two: Ebola in pigs!

Part Forty-Three: MRSA in US Swine

Part Forty-Four: Swine flu–a quick overview

Part Forty-Five: Swine flu and deaths in healthy adults–cytokine storm?

Part Forty-Six: Swine flu: 20 US cases now identified

Part Forty-Seven: Swine flu update: Europe and the bottom of the world

Part Forty-Eight: Swine flu–still spreading

Part Forty-Nine: Swine flu: Central & South America, Asia, New York update

Part Fifty: US up to 91 swine flu cases, including 1 death [Updated: New England confirmed cases]

Part Fifty-One: What does the WHO’s pandemic scale mean? And why is anyone worried about this?

Part Fifty-Two: Why I’ll be getting my kids their flu vaccines

Part Fifty-Three: MRSA and pets–should they get tested?

Part Fifty-Four: Staphylococcus aureus ST398 in a childcare worker

Part Fifty-Five: Staph in food–what does it mean?

Part Fifty-Six: MRSA and bedbugs–not so fast

Part Fifty-Seven: MRSA, Meat, and Motown

Part Fifty-Eight: Ebola in Uganda: current and past outbreaks

Part Fifty-Nine: Pigs with Ebola Zaire: a whole new can o’ worms

Part Sixty: When is MRSA not MRSA?

Part Sixty-One: E. coli O104:H4 in Europe–is it new?

Part Sixty-Two: E. coli update: sprouts as the culprit?

Part Sixty-Three: MRSA found in Iowa meat

Part Sixty-Four: Does bestiality increase your risk of penile cancer?

Part Sixty-Five: Castrating sheep with teeth–not a good idea (with video!)

Part Sixty-Six: MRSA in pork products–does the “antibiotic-free” label make a difference?

Part Sixty-Seven: The human origins of “pig” Staph ST398

Part Sixty-Eight: Influenza in bats

Part Sixty-Nine: The Emergence of Nodding Disease

Part Seventy: Poultry feather meal as a source of antibiotics in feed

Part Seventy-One: Ebola resurfaces in Uganda

Part Seventy-Two: Ebola: Back in the DRC

Related posts

Consumption of wild animals down in China

In the field

Pneumonic Plague outbreak

Also of interest: Infectious Animals, a National Geographic piece.