Thursday, January 30, 2014

The usual suspects: Fluffy can make you sick

Large scale livestock production in conjunction with the widespread use of antibiotics to promote animal growth has resulted in the emergence of antibiotic resistant bacteria in farm animals. People who work on and live near such farms are exposed to the resulting pathogens. Smith et al observed that both pigs and the farm workers who raise them in the American Midwest can become colonized with MRSA. Voss et al reported MRSA prevalence among pig farmers that was more than 760 times higher than that among patients admitted to Dutch hospitals. Moreover, a recent study by Carrel and coworkers shows an association between people's proximity to concentrated animal-feeding operations and colonization with MRSA.

These studies, along with many others, illustrate the point that if we blast animals with antibiotics, then we should expect that the environment and people inhabiting it will be exposed to antibiotic resistant pathogens. Recognizing the risks involved, in 2006 the European Union banned the use of antibiotics to fatten farm animals. Denmark went even further and eliminated their use for disease prevention in livestock. In the US, the FDA recently described steps aimed at reducing antibiotic use in agriculture. Hopefully the proposed rules will be adopted and result in decreased use.

I think of the farm and antibiotics issue as being part of a larger thing: the nexus of animal and human health. This idea is often described as "One Health", which recognizes that human, animal, and environmental health are all linked.

And by "animal" we don't only mean livestock. I don't ordinarily think of Staph as a zoonosis, but it is. In fact, several studies have observed human infection associated with companion animals. A review by Day et al highlighted the remarkable spectrum of infectious diseases of dogs and cats that are shared by humans (including Staphylococcus spp.). More recently, Vincze et al described an alarming rate of MRSA in wound samples taken from companion animals in Germany.

It's important to realize that pets get antibiotics, too. Lots, it appears. Writing in 2005, Heuer et al observed that
 . . . a comparatively small number of companion animals (550,000 dogs and 650,000 cats) consume approximately the same amount of fluoroquinolones and cephalosporins as consumed annually in the much larger population of food animals in Denmark (23 million slaughter pigs, 130 million broiler chickens, and 1.2 million cattle and dairy cows). We do not believe that antimicrobial drugs are more generously prescribed for companion animals in Denmark than in other industrialized countries.
This is something that needs to be borne in mind. Overuse of antibiotics in companion animals also carries risks to human health, especially when you think about the frequent contact owners have with their pets.

So the next time Fluffy is feeling down, think twice before asking the vet for antibiotics.

(image source: David Hartley) 

Friday, January 24, 2014

The baggage of contact precautions

Contact precautions (CPs) have long been employed for breaking the chain of infection in hospitals. The basic idea is that by removing surfaces (e.g., gloves and gowns) contaminated in the course of patient-HCW interactions, mechanical transfer of infection between patients via care providers can be prevented. The theory makes sense, though a study by Morgan and Kirkland on how some physicians view the efficacy and impact of the approach is illuminating.

In fact, the recent literature has several studies illustrating issues surrounding contact precautions. Zahar et al suggest that, under certain circumstances, contact isolation of ICU patients is associated with increased rates of medical errors and adverse events and Karki et al show that patients under CPs have an increased risk of injuries and medication errors. Mehrotra et al demonstrate that patients under CPs are more likely to perceive problems with their care than those not under precautions.

Regardless of what you think about CPs, it's clear that they carry some baggage. One of my favorite blogs, Controversies in Hospital Infection Prevention, discussed the Morgan and Kirkland paper a year or so ago within the context of the plague doctor's outfit: the bizarre hats, waxed cloaks, and bird-beak masks stuffed with herbs and flowers worn by medieval doctors caring for plague victims. I've often thought about how terrifying the doctor's garb must have been to patients in the delirium of plague in the middle ages.

But has that changed for modern patients? Though familiar to HCWs, contact precautions surely can be terrifying to patients who are already upset from their condition. Consider the febrile patient in the fragile months following bone marrow transplantation. The incidence of infection in this patient population is often high, and these infections can be fatal. Having been rushed to the hospital late at night, say, such a patient -- a person, after all -- is typically surrounded by unrecognizable people in masks, gloves, and yellow gowns (hopefully properly worn and tied!) while being poked with needles for blood draws. Our clinical and research degrees aside, maybe the patient experience hasn't changed as much as we might have hoped from the days of plague masks and leeches. Food for thought.

(image source: Wikipedia)

Tuesday, January 21, 2014

A voice from the past, literally: Fleming himself week I wrote about Fleming's warning that microbes would become resistant if penicillin wasn't used properly. Through the wonders of the Twittersphere, I became aware a day or so ago that the Wellcome Library has a sound clip of him issuing the same warning (though this isn't his Nobel lecture) online. You can find it here.

(image source:Wikipedia)

Sunday, January 19, 2014

Life in a post-antibiotic era: A scary time global emergence of pathogens resistant to a range of antimicrobial treatment is a reality threatening the foundations of modern medicine. The WHO, CDC, ministries of health, and NGOs around the world now warn of a post-antibiotic era:
If current trends continue unabated, the future is easy to predict. Some experts say we are moving back to the pre-antibiotic era. No. This will be a post-antibiotic era. In terms of new replacement antibiotics, the pipeline is virtually dry, especially for gram-negative bacteria. The cupboard is nearly bare. . . A post-antibiotic era means, in effect, an end to modern medicine as we know it. Things as common as strep throat or a child’s scratched knee could once again kill. Some sophisticated interventions, like hip replacements, organ transplants, cancer chemotherapy, and care of preterm infants, would become far more difficult or even too dangerous to undertake.
The implications of this potential are astonishing, both in terms of health and economics. According to a recent CDC report, already each year in the US at least 2 million people acquire serious bacterial infections resistant to one or more antibiotics. More than 23,000 people die each year as a direct result of these infections, and many more succumb from conditions complicated by resistant infections. As resistance becomes more prevalent, these numbers will only increase.

While the total economic cost of antibiotic resistance to the US economy has been difficult to calculate, estimates quoted in the CDC report are as high as $20 billion in excess direct healthcare costs, with additional costs to society for lost productivity as high as $35 billion a year (in 2008 dollars). Other nations suffer similar or worse impacts. We can only expect that the costs will increase as infections resistant to antibiotics increase in incidence. 

I recently came across a report from the World Economic Forum, Global Risks 2013, that explores the issue of antibiotic resistance from a global economic perspective. The study frames many of the issues thoughtfully, and proposes some macro-level actions. Getting the issue before world leaders who have the power to do something in response to the threat, such as the members of the WEF, is a good first step. Although not a topic on the agenda for this week's meeting, hopefully, some of the conversation in Davos will include how to make progress against the threat of antibiotic resistance. A sustainable global approach might avert the looming disaster. A post-antibiotic era must be averted.    

(image source: Wikipedia)

Wednesday, January 15, 2014

Will the real hantavirus please stand up?

deer mousePeople often talk about "the" hantavirus. In the US, often they are referring to Sin Nombre virus, which was first recognized in connection with a 1993 outbreak of ARDS in the Four Corners region of the American Southwest. Infection occurs through contact with infected rodents, their urine and droppings, or the remains of infected rodents.

It's important to recognize, however, that SNV is one of several New World hantaviruses circulating in the US. Others include Bayou virus, Black Creek Canal virus, Monongahela virus, and New York virus.

Hantavirus pulmonary syndrome (HPS) is a reportable disease in the US. A recent study by Knust and Rollin showed that in two decades of surveillance, over 600 cases of HPS have been reported. More than 90% of those cases occurred in western states, and most cases were associated with SNV, though cases caused by these other viruses were also reported.

There is much information at the CDC site on hantaviruses and in the medical literature. The diversity and distribution of hantaviruses in South America and other parts of the world is also complex.

So, when you hear people talk about "the" hantavirus, perhaps you could capitalize on the teachable moment?

(image source: CDC)

Saturday, January 11, 2014

A voice from the past: I told you so

This picture circulated on Twitter recently. To many it may seem amusing, even quaint at this point nearly 70 years after the shot was taken, but it is also sobering.

The CDC's recent report on  Antibiotic resistance threats in the United States, 2013 lists drug resistant Neisseria gonorrhoeae as one of the three most "urgent" threats in terms of antibiotic resistance today (the other two being CRE and C diff), along with 12 other "serious" threats (including ESBLs, VRE, MRSA, and DR-TB) and 3 more merely "concerning" threats. The issue of drug resistance will only get worse unless something is done to counter it; unfortunately, it's a very complex problem at this point.

Curiously, and prophetically, Alexander Fleming, at the end of his Nobel lecture in 1945, warned that resistance would be a problem if administration wasn't managed carefully:
But I would like to sound one note of warning. Penicillin is to all intents and purposes non-poisonous so there is no need to worry about giving an overdose and poisoning the patient. There may be a danger, though, in underdosage. It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them, and the same thing has occasionally happened in the body.
He continued with a vignette:
The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant. Here is a hypothetical illustration. Mr. X. has a sore throat. He buys some penicillin and gives himself, not enough to kill the streptococci but enough to educate them to resist penicillin. He then infects his wife. Mrs. X gets pneumonia and is treated with penicillin. As the streptococci are now resistant to penicillin the treatment fails. Mrs. X dies. Who is primarily responsible for Mrs. X’s death? Why Mr. X whose negligent use of penicillin changed the nature of the microbe. Moral: If you use penicillin, use enough.
It seems he had remarkable clairvoyance. Although antibiotics can't be "bought by anyone in the shops" unless they have prescriptions, they are low cost and sometimes even free. They probably are very over-prescribed.

Just to bring things full circle, the annual CDC survey on STDs depicts increases between 2011 and 2012, with a large number of infections due to gonorrhea. The report notes that
With increased resistance to the fluoroquinolones and the declining susceptibility to cefixime, dual therapy with ceftriaxone and either azithromycin or doxycycline is now the only CDC recommended treatment for gonorrhea. (Emphasis added.)
(image source: Wikipedia)

Friday, January 10, 2014

Musings on infection: About the blog

Wikipedia defines "ecology" as the "scientific study of interactions among organisms and their environment" and "epidemiology" as the study of "the patterns, causes, and effects of health and disease conditions in defined populations." Ecology brings a key piece to the puzzle of infectious disease epidemiology: if we are to understand, in any meaningful way, the patterns, causes, and effects of infectious agents, we must understand the interactions of the agents themselves with their surrounding biotic and abiotic environments. Given an such an understanding, perhaps we can control infection.

This blog will explore such ideas, mostly (but not only) within the context of the hospital, community, and natural environments. Social, policy, and economic considerations will also be a theme. I suspect I’ll be blogging every couple weeks, but who knows. We'll see how that works out.