On E. coli, super soil bacteria, and Hank Williams Jr.

Early this week, grant application; yesterday and today, IRB and IACUC for another project. But once again, fellow Sbers are keeping me busy reading about stories I’d like to be writing on; see yet again Mike on E. coli O157:H7–everything old is new again; Ed on a new study showing yet again how amazing bacteria are; and DrugMonkey discussing heroin addiction as a family legacy, and notes that this sad story again shows that Narcan saves lives.

Less is more when it comes to antibiotic use?

Over at Evolgen, RPM notes an interesting study in PNAS, looking at antibiotic use and how it serves to drive the emergence and maintenance of antibiotic-resistant strains. The current paradigm for antibiotic use is to prescribe relatively high doses of drugs for a few days to a few weeks (or months, in the case of tuberculosis), and patients are cautioned to stay on them until all the doses are finished. However, the new study RPM describes suggests this may be doing more harm than good, looking at what happens with Plasmodium species treated with antimalarials in a mouse model.

Do their results overturn the paradigm? I’m not convinced. First, RPM states that antibiotic resistance is a dichotomy: either sensitive, or resistant strains. But that’s not the case–those are simply the extremes of the spectrum, with many organisms that are some shade of partially resistant to various antibiotics. (For example, while penicillin resistance is rare in Streptococcus pyogenes, it takes much higher doses of the drug to kill them today than it did, say, 40 years ago; they have “intermediate” resistance or susceptibility). As noted in the comments, it’s not only the fully resistant organisms we’re worried about when it comes to antibiotic resistance: it’s also those for which it takes a lot of the drugs to kill, but they’ll die eventually (or at least, the drugs will inhibit their growth). This study doesn’t take those into account, which is a limitation–but then again, it seems designed to be more of a paper to get fellow scientists thinking about these ideas in general, rather than an exhaustive test of every potential hypothesis stemming from them.

Either way, antibiotic resistance is certainly a huge problem, and we need to find better ways to preserve the drugs we do have. Reducing their use in this manner (lower and shorter doses) is certainly worth a second look.

Fecal transplants to cure Clostridium difficile infection

Blogging on Peer-Reviewed Research In my field, many things that cause the average man-on-the-street to get a bit squeamish or squicked are rather commonplace. My own studies include two types of bacteria that are carried rectally in humans (and other animals), so I spend an absurd amount of time thinking about, well, shit, and the lifeforms that inhabit it and collectively make up our normal gut flora. The vast majority of these species don’t harm us at all, and many are even beneficial: priming our immune system; assisting in digestion; and filling niches that could be colonized by their nastier bacterial brethren.

It’s typically when there’s some disturbance in these flora that bad things happen. For example, you may ingest food contaminated with a foreign bacterial strain that may transiently colonize your intestines, resulting in cramping and diarrhea. Typically these infections are self-limited and your normal flora “resets itself” after a short time, but some pathogenic bacteria have a propensity for making themselves at home in your gut. How to get rid of these nasty invaders then? Antibiotics are one option, but they also kill your regular bacteria, potentially making the problem worse (especially if the nasty invader happens to be resistant to many antibiotics). There has been a large increase in the use of probiotics–formulations designed to add beneficial bacteria to your gut. However, these have largely not been rigorously tested or regulated, so it’s unsure how well they actually work.

What if, instead of re-constitituing healthy gut flora one species at a time, you could simply take the entire fecal contents from a healthy person and use it to re-colonize your own gut–in other words, undergo a fecal transplant? Yes, it’s like probiotics on steroids: getting an infusion of someone else’s gut flora in order to re-establish a healthy gut ecology of your own, and squeeze out some potentially harmful organisms along the way. A recent story discusses this treatment for patients suffering Clostridium difficile infections in Scotland, but it’s actually not brand-new, and has already surfaced in the peer-reviewed literature. More after the jump…
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MRSA and swine: collision course

Blogging on Peer-Reviewed Research Both Mike and Revere have new posts up documenting swine as a new threat to human health (beyond the pork chops and bacon), via carriage of methicillin-resistant Staphylococcus aureus in these animals. Several papers have been published recently documenting high rates of MRSA carriage in swine in the Netherlands, and also have documented transmission of this bacterium from swine to humans. However, even more worrisome to me than the Dutch publications is a new one out in Veterinary Microbiology, showing high rates of MRSA in Canadian swine–and guess where we import about 9 million hogs from every year?

More after the jump…
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Clostridium Marys

Clostridium difficile is an emergent bacterium. A close relative of the bacteria that cause tetanus and botulilsm (Clostridium tetani and Clostridium botulinum, respectively), C. difficile is an intestinal bacterium that can cause colitis. C. difficile has until recently been a fairly rare cause of disease, and then only typically within a hospital setting. However, the emergence of a new, highly virulent strain of the bacterium a few years ago, coinciding with an increase in the rate of serious infections it caused, put this pathogen on the map. And like methicillin-resistant Staphylococcus aureus, Clostridium difficile is no longer only found in hospitals: it’s spreading among the community as well.

While this is a concern, the bulk of cases still occur in medical settings, where the bacterium is the most common cause of health care-associated diarrhea. Why is this such an issue in these settings? Like its cousins, C. difficile can form hard, resistant spores–making it difficult to eliminate when contamination occurs. Therefore, infection control measures have been able to reduce C. difficile contamination, but not completely eliminate it. A recen study looks at another reason for the difficulty in eliminating the organism from hospitals and other care facilities: undiagnosed healthy carriers shedding the bacterium.
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