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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Searching for drugs in new places

I mentioned that it’s microbiology week at fellow Scienceblog Deep Sea News. Today’s post over there is on “bioprospecting” in the sea–looking for naturally-produced chemicals that we can harness for employment as drugs or other uses. For example:

Over the last 20 years at Harbor Branch Oceanographic Institution we have developed a culture collection containing 17,000 bacteria and fungi from deep-water marine invertebrates and sediments. We have shown that the collection contains many unusual microbes which are not known from the terrestrial environment and are fermenting the isolates to produce extracts for screening as antibacterial or anticancer agents.

Click the link for more…

Ah, E. coli…is there any limit to your uses?

While E. coli typically makes the news as a food-borne pathogen, that’s only one facet of the bacterium. It can be deadly, sure, but it also helps us digest our food; it produces vitamin K for us; benign strains can even protect us from invading pathogens. It’s one of the most-studied bacterial species and a “workhorse” for research in microbiology and molecular biology. We use it as a marker of fecal contamination in water, and it can even be used to produce insulin for diabetes patients. So it may come as no surprise that it may one day be a cavity fighter as well:
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Marburg in bats: has the elusive reservoir species been found?

As I mentioned in the introductory post, we know incredibly little about the very basics of Marburg virus ecology and epidemiology. The sporadic nature of outbreaks of illness, their occurrence in remote areas of Africa lacking established medical research capabilities, and often in countries experiencing governmental strife and instability, compound the difficulty of determining the ecology of this particular virus. Often, the primary case (the first person in an outbreak known to be infected, and who likely acquired the virus from its wild reservoir) died before questions could be answered regarding his previous whereabouts, diet, and other activities; thus, it was difficult to determine where the case could have contracted the disease. Seasonality may also play a role; if a search for the virus is conducted during the dry season (as many ecological surveys have been), they may miss key pieces of the puzzle of Marburg virus ecology.

Nevertheless, scientists have attempted to make the most of outbreaks when they occur, and have undertaken studies between outbreaks in order to determine where the virus “hides” when it’s not infecting humans, and to find out how the virus moves from wherever it is maintained in nature into human populations. Is it simply airborne? Is it transmitted from butchering infected animals? Is it transmitted by an intermediate, such as an insect vector? The answer to these questions remains, despite years of investigation, a disappointing “we don’t know,” but some answers are slowly emerging. More after the jump…

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A few must-read posts

Today is the kids’ last day of school, and just happens to be an early dismissal as well, so I’ll be busy with them and not tied to the computer this morning/afternoon. However, there are tons of good things to read elsewhere.

First, Orac has a long-awaited update on the Tripoli Six: the group of nurses and doctors accused of killing children in Libya by deliberately infecting them with HIV. The science exonerated them, but that didn’t change the court outcome, and I’ve not seen updates until now.

Next, Revere writes about the H7N2 influenza outbreak in Wales, reminding us (as as I’ve mentioned before as well) that we need to keep an eye on all emerging influenza viruses, not just H5N1.

I mentioned I briefly ran into Chris Mooney at the American Institute of Biological Sciences meeting I attended a few weeks ago. Chris was there with Matt Nisbet to give their “Framing Science” talk, which unfortunately, I had to miss to attend another lecture. But now you can catch it via YouTube and see what the fuss has been about. (Note: if you only read their Science article, the talk goes into a lot of what you probably wanted to get from that, such as more concrete examples and ideas for change).

Janet of Germ Tales has a new two-part series on suburban wildlife: their encroachment, staying power, and ways we’ve come to live with them or try and keep their population in check (including a nice overview of wildlife contraception). Check out Part 1 here and Part 2 here.

Jennifer of Cocktail Party Physics has an excellent post up on John Snow, cholera, and other related issues.

And finally, MSNBC has an article on one of the areas I touched on yesterday in this follow-up TB post: border crossing and security, or more accurately, lack thereof when it came to the XDR-TB patient, and what implications that has for our response plans and terrorism in general.

Environmental change and infectious disease

Everyone knows about the “butterfly effect”: the idea that a butterfly flapping its wings in Brazil could eventually result in the formation of a tornado in Texas by virtue of very small alterations in the initial conditions of a system. Though this description of it is often decried by people who study chaos theory as an inaccurate oversimplification, it’s a useful illustration of the tiny perturbations that can have vast effects on a downstream chain of reactions.

When it comes to infectious diseases, climate change may be the beginning, but environmental effects extend much farther than just the weather. And while they may not be affected by the movement of a butterfly, even small environmental changes can mean large effects when it comes to microbiology. At a session Tuesday on Environmental Change and Disease, virologist Stephen Morse noted that “…environmental changes have always been associated with the appearance of new diseases, or the arrival of old diseases in new places. With more changes, we can expect more surprises.” I’ve mentioned this previously here, describing reasons why diseases “emerge”; the session today went much further, discussing infectious disease in terms of ecology, and how environmental changes have the capacity to alter much more than just our landscapes. More after the jump.

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Emerging Disease and Zoonoses #27: Rocky Mountain Spotted Fever

I had a strange worry as a kid. I was very scared of getting bit by a tick and developing Rocky Mountain Spotted Fever (RMSF). I know, weird–even for nerdy kids like me, who knows about Rocky Mountain Spotted Fever? How many readers are even familiar with it?

For those who aren’t, RMSF is a zoonotic rickettsial disease transmitted by several species of ticks. Though the disease is named after the geographical region where it was first described back in the late 1800s, the bacterium that causes it, Rickettsia rickettsii (an obligate intracellular pathogen), has been found in almost all US states and south to Mexico. The bacterium itself is related to Rickettsia prowazekii, the causative agent of louse-borne typhus, and RMSF is the most common rickettsial disease in the United States. Symptoms are non-specific initially (fever, muscle aches, nausea, vomiting, headache), making it difficult to diagnose. A rash starts to develop in most patients around 2-5 days after the fever presents, starting out faint and pinkish and typically getting redder and more “spotted” (hence the name) over time. More insidious, perhaps, are the cases where a rash doesn’t develop (“spotless fever,” ~10% of patients). Here, the physician may not have a reason to suspect RMSF, and therefore may not treat correctly.

Especially when untreated or treated late, infection can be severe, affecting the respiratory, central nervous, gastrointestinal, or renal systems. Those who have the worse infections also are more likely to suffer long-term damage, including hearing loss, loss of or reduction in bowel control, and paralysis, among others.

So how does a kid even learn about RMSF, a relatively rare disease (250-1200 cases reported annually according to the CDC), and why am I discussing it today? More below…
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Emerging Diseases and Zoonoses #26–Chimps at risk from antibiotic-resistant bacteria

When we think of the spread of antibiotic resistance between animals and humans, we tend to think of it going from Them to Us. For example, much of the research over the past 20 years on the sub-clinical use of antibiotics in animal feed has looked how this use of antibiotics as a growth promotant breeds resistant organisms in animals, which can then enter the human population via the food we eat. Along a similar line, I just mentioned Burt’s post post on cephalosporin use in cattle and the evolution of antibiotic resistance, where the worry is that use of these broad-spectrum antibiotics in animals will select for resistance that can then spread to humans. However, spread of resistant organisms is not a one-way street. For example, it has been suggested that transmission of methicillin-resistant Staphylococcus aureus (MRSA) has been transmitted both from horses to humans and vice-versa (see, for example, this Emerging Infectious Diseases paper). A new paper suggests that this phenomenon can happen even in animals that aren’t in such close contact with humans: chimpanzees.
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