Maryn McKenna

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Almost Three Times the Risk of Carrying MRSA from Living Near a Mega-Farm

January 22, 2014 By Maryn Leave a Comment

Pig farms from the air. Image: Maryn McKenna

Pig farms from the air. Image: Maryn McKenna

In the long fight over antibiotic use in agriculture, one of the most contentious points is whether the resistant bacteria that inevitably arise can move off the farm to affect humans. Most of the illnesses that have been associated with farm antibiotic use — resistant foodborne illness, for example — occur so far from farms that opponents of antibiotic control find them easy to dismiss. So whenever a research team can link resistant bacteria found in humans with farms that are close to those humans, it is an important contribution to the debate.

A team from the University of Iowa, Iowa City Veterans Affairs, and Kent State University have done just that. In next month’s Infection Control and Hospital Epidemiology, they survey 1,036 VA patients who lived in rural Iowa and were admitted to the Iowa City facility in 2010 and 2011. Overall, among those patients, 6.8 percent were carrying MRSA, drug-resistant staph, in their nostrils. But the patients’ likelihood of carrying MRSA was 2.76 times higher if they lived within one mile of a farm housing 2,500 or more pigs.
[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: animals, antibiotics, colonization, food policy, hogs, MRSA, Science Blogs, ST398

MRSA research round-up: hospitals, vitamins, pets

March 15, 2010 By Maryn Leave a Comment

Because I’ve been so behind, there’s so much to cover! So let’s dive in:

In today’s Archives of Surgery, researchers from Seattle’s Harborview Medical Center report that one simple addition to the routine of caring for trauma patients made a significant difference to the patients’ likelihood of acquiring a hospital-associated infection:
bathing them once a day with the antiseptic chlorhexidine (in an impregnated wipe). Patients who were bathed with the antiseptic wipe, compared with patients wiped down with an inert solution, had
one-fourth the likelihood of developing a catheter-related bloodstream infection and
one-third the likelihood of ventilator-associated MRSA pneumonia. Cite: Evans HL et al. Effect of Chlorhexidine Whole-Body Bathing on Hospital-Acquired Infections Among Trauma Patients.
Arch Surg
. 2010;145(3):240-246.

How important are hospital-acquired infections? Here’s a piece of research from a few weeks ago that I sadly failed to blog at the time: Just
two categories of HAIs, sepsis and pneumonia, account for 48,000 deaths and $8.1 billion in health care costs in a single year. Writing in the Archives of Internal Medicine, researchers from the nonprofit project Extending the Cure analyzed 69 million hospital-discharge records issued in 40 states between 1998 and 2006. Hospital charges and number of days that patients had to stay in the hospital were
40% higher because of those infections, many of which are caused by MRSA — and all of which are completely preventable. Cite: Eber, MR et al. Clinical and Economic Outcomes Attributable to Health care-Associated Sepsis and Pneumonia.
Arch Intern Med.
2010; 170(4): 347-53.

 What else could reduce the rate of MRSA infections? How about Vitamin D? South Carolina scientists analyze data from the NHANES (National Health and Nutrition Examination Survey 2001-2004), a massive database overseen by the CDC, and find
an association between low blood levels of Vit. D and the likelihood of MRSA colonization. More than 28% of the population is Vitamin D deficient. MRSA colonization is increasing in the US. Can giving Vit. D decrease MRSA carriage? More research needed. Cite: Matheson EM et al. Vitamin D and methicillin-resistant Staphylococcus aureus nasal carriage.
Scand J Infect Dis

. 2010 Mar 8. [Epub ahead of print]

And finally: Who else carries MRSA? Some unlucky pet owners have found that animals can harbor human strains, long enough at least to pass the strain back to a human whose colonization has been cleared. So it makes sense to ask whether humans who spend time with pets are carrying the bug. Last month’s Veterinary Surgery reports that the answer is Yes.
Veterinarians are carrying MRSA in very significant numbers: 17% of vets and 18% of vet technicians at an international veterinary symposium held in San Diego in 2008. Cite: Burstiner, LC et al. Methicillin-Resistant Staphylococcus aureus Colonization in Personnel Attending a Veterinary Surgery Conference.
Vet Surg.
2010 Feb;39(2):150-7.

Filed Under: Science, Science Blogs, Superbug Tagged With: animals, colonization, Hospitals, infection control, medical errors, nosocomial, pets

MRSA and pets

June 24, 2009 By Maryn Leave a Comment

It’s been a while since we’ve focused on the presence of MRSA strains in pets, and the complications that can cause for the pets’ human owners/custodians/companions (or, in the view of my own two cats, abject servants. No, I will not post their pictures. I have some shreds of pride).

The problem with MRSA and pets is not the same as the problem of MRSA ST398 in food animals. Rather, pets tend to carry human strains, passed to them by their owners. The carriage is usually asymptomatic, but not always; there are cases in the medical literature of cats and dogs suffering serious skin and soft-tissue infections from community-strain MRSA, usually USA300. But the emerging consensus seems to be that pets carry the bug transiently — not long, but long enough to reinfect the person who passed the bacterium to the pet in the first place. (This can be, but is not always, the source of recurrent infections in humans: The human takes antibiotics and recovers, but the animal holds onto the bug long enough to pass it back to the now-clear human.)

For anyone who needs to go deeper on this, the current issue of Lancet Infectious Diseases has a good overview of the problem that community MRSA strains pose to pets and their humans. There’s a thorough review of the major papers:

  • Cefai, 1994: hospital outbreaks traced to two nurses and through them to their dog
  • Simoons-Smit, 2000: household epidemic of three humans, one cat, one dog
  • Manian, 2003; dog is source for owner’s recurrences
  • Vitale, 2006: owner is (apparently) source of cat’s MRSA.

(This is a good place to say that this entire history, including personal stories of human and animal infection, is covered in a chapter of SUPERBUG. Publication date coming soon!)

The Lancet paper incorporates reminders of some powerful and troubling trends. As with MRSA ST398, one thing can distinguish MRSA that has been in an animal is a resistance pattern that is slightly different from what we expect but that has arisen because the animals receive different drugs. In the case of pigs and ST398, the intriguing marker is tetracycline resistance; humans don’t usually get tetracycline for MRSA, but pigs do. In the case of companion animals, it tends to be fluoroquinolone resistance; pets are more likely to get that class of drugs for a skin/soft-tissue infection. But, the authors caution, that may mean that pets serve as a breeding ground for multi-drug resistant MRSA, with their fluoroquinolone treatment adding another resistance factor into the bug’s already potent arsenal.

The authors also remind us that MRSA can come from animals much more directly than through silent carriage: that is, in a bite. Both dog and cat bites have been found infected with MRSA, due to bacterial contamination of the wound either from the pet or from colonization on the human’s skin.

The cite is: Oehler RL et al. Bite-related and septic syndromes caused by cats and dogs. The Lancet Infectious Diseases, 9(7):439 – 447, July 2009. doi:10.1016/S1473-3099(09)70110-0.

Filed Under: Science, Science Blogs, Superbug Tagged With: animals, colonization, Community, MRSA, Science Blogs, ST398, zoonotic

More MRSA in pigs, in Portugal

April 14, 2009 By Maryn Leave a Comment

A brand-new report, in a letter to the International Journal of Antimicrobial Agents, indicates that ST398 “pig MRSA” has been found in Portugal for the first time.

Constanca Pomba and colleagues from the Technical University of Lisbon swabbed and cultured the noses of pigs and veterinarians on two pig farms in different regions of Portugal, and also checked the air at both farms.

What they found:

  • On Farm A: All pigs and the veterinarian positive for ST398, the pig-origin strain that has been found so far in Iowa, Ontario, the Netherlands, France, Denmark, Germany and Austria and has, depending on the country, caused human disease and/been found on retail meat. The veterinarian was transiently colonized, which is to say that he was not carrying the bug long-term.
  • On Farm B: All pigs — but neither of two veterinarians — positive for a different MRSA strain, CC (or ST) 30. This is very interesting, because CC30 is usually a drug-sensitive strain (MSSA, methicillin-sensitive S. aureus), and has been found in pigs primarily in Denmark and France. In Portugal, it is a human MSSA hospital-infection strain.

Strains from both farms were resistant to tetracycline; this is turning out to be a great marker for these strains having emerged due to antibiotic pressure in animals, because tetracycline is very commonly used in pigs. but not much used for MRSA in humans. The strains have the genes tetK and tetM, so they are resistant not just to tetracycline itself, but to the whole class of tetracyclines including doxycycline and minocycline. The Farm B strains also carried the gene ermC, which encodes resistance to erythromycin.

So what does this tell us?

  • First, that (once again), every time people look for ST398, they find it; it is now a very widely distributed colonizing bug in pigs, and is repeatedly spreading to humans. What we don’t know, because all these studies are so new, is whether ST398 is actively expanding its range, or has been present in all these countries for a while. We have been anticipating its presence or spread (take your pick at this point) through the European Union because of open cross-border movement of food animals, meat, and agriculture and health care workers.
  • And second, it should tell us that it is really past time to start looking for this more systematically. Every finding of ST398 that we have (long archive of posts here) is due to an academic research team who decided to look for the bug. None of the findings, to date, have come from any national surveillance system. (NB: Except for the first human colonizations in the Netherlands, which were found as a result of the national “search and destroy” rules in hospitals.)

Of note, the European Union is running a study now that is supposed to report ST398 prevalence at any moment (as they have been saying since 2007). It is not expected to be comprehensive, since it was piggy-backed onto another study, but it is something. The US government has not been so enterprising.

The cite is: Pomba, C. et al. First description of meticillin-resistant Staphylococcus aureus (MRSA) CC30 and CC398 from swine in Portugal. Intl J Antimicrob Agents (2009), doi: 10.1016/j.ijantimicag.2009.02.019

Filed Under: Science, Science Blogs, Superbug Tagged With: animals, antibiotics, colonization, Europe, food, MRSA, pigs, Science Blogs, ST398

MRSA in a hospital nursery

April 13, 2009 By Maryn Leave a Comment

Via the Boston Globe and the blog of the hospital’s CEO comes work of an ongoing outbreak of community-associated MRSA in the newborn nursery at Beth Israel Deaconess Medical Center in Boston:

…between last November and March, BIDMC experienced several occurrences or “clusters” of methicillin-resistant Staphylococcus aureus, or MRSA, infections that have affected some of our patients (19 newborns and 18 mothers) days to weeks after discharge from our obstetrics and newborn services. These infections have been, for the most part, superficial skin infections and breast infections. It is important to note that no babies in our Neonatal Intensive Care Unit have been affected. (Paul Levy, president and CEO, BIDMC)

The paper and the blog post report that the Massachusetts Department of Public Health (DPH), the Boston Public Health Commission (BPHC), and the federal Centers for Medicare and Medicaid Services (CMS) are all investigating, and the Centers for Disease Control and Prevention (CDC) has sent epidemiologists to sort out transmission. Levy, the CEO, admits on his blog that in sorting out this outbreak, the hospital has found its staff’s infection-control procedures to be not-adequate.

By sheer chance, this occurs as I am writing a chapter on just this phenomenon of the blurring of the MRSA epidemics of hospital-acquired and community-associated staph. As constant readers know, the original MRSA strains arose in hospitals in the 1960s (1961 in the UK, 1968 in the US), and the separate community strain was first noticed in the 1990s. (Though there are intriguing hints about earlier cases that a few smart physicians noticed and no one else took seriously.)

But for about 5 years now, the community strain has been moving into hospitals and causing outbreaks there, particularly in mothers and newborns: first in New York City, and then in Houston, and now quite widely. The Globe article references some others.

Why this is important: Because CA-MRSA and HA-MRSA are different, and not just because they originally occurred in different settings or had different resistance profiles. CA-MRSA (which is a term that is obviously becoming much less useful than it once was) also appears, in newer research, to colonize the body in different ways — not just the nostrils, but also the armpit, groin, and genitals, possibly including vaginal colonization. So there may be an additional risk of transmission from mother to child during birth that has not been anticipated — or from mother to child to health care worker to another child to that child’s mother.

Now, mind you: Good infection control ought to anticipate all those posibilities, because good infection control does the right thing every time. But as we’re finding out, very few institutions manage to train their staff in such a way that they do the right thing every time or close to it (Novant Health Care, creators of the Soapacabana video, seem to have managed it, and won a major award for it). Most health care workers, even very well-intentioned ones, find themselves in time crunches or responding to unexpected emergencies, and make risk-based judgments about what they must do, and what they can afford to let slide.

If CA-MRSA is becoming a hospital organism, and its unique risks of colonization are not recognized by the hospital staff, then their judgments of relative risk will be off — and what would have been a relatively safe risk to take in one instance becomes a significantly unsafe risk in another.

That’s all speculation, of course: I’m not reporting on Beth Israel and have no inside knowledge of their outbreak. But it does describe a phenomenon that has been occurring in other medical centers, and it underlines one of the risks attendant on these epidemics blurring. When CA-MRSA moves into a hospital, the MRSA ecology changes, and the risks of transmission change. It is essential that staff training keep up with that, or additional mistakes will be made.

Filed Under: Science, Science Blogs, Superbug Tagged With: colonization, Hospitals, infection control, Science Blogs

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