E. coli
mikethemadbiologist | April 8, 2008I've recently written a couple of posts about how evolution is used in medicine. Randolph Nesse and Stephen Stearns in Evolutionary Applications have written an article about evolutionary medicine. Here's one part that provides some additional examples (italics mine):
Some of the most useful applications of evolution often do not use evolutionary theory directly; instead they use technologies developed by evolutionary biologists. In particular, methods for reconstructing phylogenies are being applied to genetic data with very practical results. HIV is especially susceptible to such methods…
mikethemadbiologist | April 2, 2008Over at denialism blog, PalMD has two posts which, to me anyway, are related. The first has describes how sexually transmitted diseases (STDs) are actually treated with antibiotics:
After hours, we see walk-ins, and that's where the STD fun really begins. For whatever reason, I see STDs daily at the walk-in clinic, but almost never in my private practice. Most commonly, we see only one partner, and, at least in my state, treatment of the absent partner is prohibited. Basically, we only get one shot at folks, and we don't have access to rapid tests. So what do we do? We order a lot of "…
mikethemadbiologist | April 2, 2008When I started blogging, I never (EVAH!) thought I would describe the biology of E. coli with a Tolkein poem:
All that is gold does not glitter,
Not all those who wander are lost;
The old that is strong does not wither,
Deep roots are not reached by the frost.
From the ashes a fire shall be woken,
A light from the shadows shall spring;
Renewed shall be blade that was broken,
The crownless again shall be king.
I'm referring, of course, the spinach outbreak strain of E. coli O157:H7. You know, this one:
It turns out that this particular strain of E. coli O157:…
mikethemadbiologist | March 12, 2008I've written before about CTX-M-15 beta-lactamases which make bacteria resistant to most cephalosporin antibiotics--those antibiotics that begin with cef- (or ceph-) or end with -cillin. I've also discussed the role of clonal spread in the rise of antibiotic resistance: most (but obviously not all) resistant infections are not the result of a sensitive strain evolving resistance during the course of infections, but rather due to colonization by a previously resistant strain. A recent article in Emerging Infectious Diseases discusses the role of clonal spread in the dissemination of CTX-M-…
mikethemadbiologist | March 5, 2008
Yes, this is O157:H7, not ExPEC. Bully for you.
One thing regarding popular accounts of antibiotic resistance I've noticed is that there is an overemphasis on the evolution of resistance, and an underemphasis on the spread of resistant bacteria. While the evolution of resistance is important, most of what we see in a hospital is not the de novo change of a sensitive strain into a resistant one (i.e., evolution), but, instead, the survival and spread of already resistant bacteria in this antibiotic-laden environment.
What this means is that changes in the frequency of resistant organisms,…
mikethemadbiologist | February 29, 2008One piece of infection control legislation moving (slowly) through Congress is the Healthy Hospitals Act, H.R. 1174 (it's so slow that it's, erm, an act of 2007). H.R. 1174 would amend "the Social Security Act to require public reporting of health care-associated infections data by hospitals and ambulatory surgical centers and to permit the Secretary of Health and Human Services to establish a pilot program to provide incentives to hospitals and ambulatory surgical centers to eliminate the rate of occurrence of such infections."
There are many good provisions in this legislation:
Hospitals…
mikethemadbiologist | February 27, 2008And that includes the pets. Since I saw the 'TV version' while at the gym yesterday, that spurred me to get around to discussing this article about the transmission of E. coli within families.
In the article, the authors sampled at least seven isolates* of E. coli from 152 people and 76 pets, and then genetically typed them. Within households, pets were most likely to share genetically identical E. coli (58% of possible 'pet-pet' pairs), followed by adult-child (34%), child-child (33%), adult-adult (24%), adult-pet (18%), and child-pet (15%). What's interesting is that only 12% of shared…
mikethemadbiologist | February 13, 2008How antibiotic resistant your E. coli are has to do with where you've been, not what you eat.
A recent study isolated E. coli from 567 newly hospitalized patients and 100 vegetarians (one E. coli isolate per person), and screened them for resistance to X antibiotics, including ciprofloxacin, nalidixic acid, trimethoprim-sulfamethoxazole (the primary treatment for E. coli-related urinary tract infections), ceftriaxone, and ceftazidime (the last two indicate the presence of an extended-spectrum beta-lactamase, and can only be reliably treated with carbapenems).
The only significant risk factors…
mikethemadbiologist | January 28, 2008When I read Olivia Judson's post about hopeful monsters, I didn't think she used the term correctly (here are some good explanations why), but I was surprised by Jerry Coyne's response.
First, the personal attack on Judson is unwarranted: when we reach the point where the serious challenge to evolutionary biology is the misuse of a discredited decades-old idea, as opposed to the politically powerful anti-science creationist movement, we're in a pretty good place. She made a mistake--I don't think her motives were self-aggrandizing. Second, if you're going to launch an ad homeniem attack,…
mikethemadbiologist | January 21, 2008
(Yes, it's LOLFeral Pigs)
A recent article in Emerging and Infectious Diseases just made the explanation of the E. coli spinach outbreak much more complex.
When the contaminated spinach story broke, there were a lot of accusations bandied about that this showed that either corporate factory farming was evil, or that organic farming (the farm was organic) was evil* (an aside: by now, it should be apparent to everyone that politicized public health and biological issues are often not discussed rationally or consistently). I'm no fan of corporate farming because the high densities of animals…
mikethemadbiologist | January 3, 2008Beta-lactam antibiotics, penicillin and all of its subsequent derivatives, are critical, life saving drugs. One way bacteria protect themselves from these antibiotics is by producing enzymes known as beta-lactamases that cleave the beta-lactam, rendering the beta-lactam antibiotic harmless. There are many different kinds of beta-lactams (such as CTX-M), and they differ in how common or rare they are.
A recent study examined looked at the role fitness might have in making TEM class beta-lactamases very frequent and found in many different species, and keeping SME class beta-lactamases rare…
mikethemadbiologist | December 27, 2007One of the lesser known microbiology facts is that the pathogen Shigella is actually E. coli. Since I'll be writing more about this cool bug soon, from the archives, here's an explanation (with a little modification).
As I mentioned in a previous post, Orac has two very good posts on MDs and creationism. In one of the posts, he links to a creationist medical student who writes the following:
Has anyone ever documented a plateful of Strep pneumo mutating into E coli? Or even into Strep pyogenes? I didn't think so. They mutate, and they exchange information. But they remain separate species…
mikethemadbiologist | August 23, 2007Forget smoking cessation. This is a patch everyone can use. From the August 10 edition of ScripNews (subscription only):
Iomai's traveller's diarrhoea vaccine patch shows promise
Iomai's investigational vaccine patch for traveller's diarrhoea has shown positive Phase II results in volunteers travelling to Mexico and Guatemala. If approved, it would become the first vaccine approved in the US for traveller's diarrhoea, says the company.
The patch is designed to treat traveller's diarrhoea associated with enterotoxigenic Escherichia coli (ETEC), which is responsible for most cases of the…
mikethemadbiologist | August 15, 2007One of the things that's hammered into your head as a baby scientist is the importance of running controls. Typically, you run a positive control--a 'gamed' experiment where you know what the outcome should be and which tells you that the experiment is working--and a negative control which should not give any results at all (e.g., a PCR reaction without any DNA) to make sure there's no contamination or other spurious results. It's always puzzled me why people don't like to run controls because if you don't do the controls, you'll have to redo the experiment, which is a lot more work than if…
mikethemadbiologist | August 9, 2007...the signal peptide? Interesting. I'll start at the beginning.
One of the few bright spots regarding the problem of antibiotic resistance is that resistance typically infers a fitness cost to the bacterium, at least initially. In other words, the resistant strain usually grows slower than a nearly identical sensitive strain*. While compensatory mutations can lower or eradicate this 'cost of resistance', it is thought that resistance can't increase initially without favorable selective conditions--antibiotic use--due to the cost of resistance.
We'll need a little background about…
mikethemadbiologist | July 19, 2007
Why can't you be nice to me?*
Look, I realize that Rick Perlstein's phrase 'E. coli conservatism' is a catchy way to describe the continuing breakdown of the national infrastructure. But that phrase bugs the crap out of me (pun intended).
I've noted before that most E. coli are harmless commensals--overwhlemingly, they do not cause disease. If they did, we would be sick all the time. Except immediately after certain kinds of antibiotic therapy, humans always have high concentrations of E. coli (around 1,000,000,000 per gram of poop, give or take a zero). Some cause disease, but there are…
mikethemadbiologist | June 21, 2007In the May edition of Evolution, Hopi Hoekstra and Jerry Coyne have an interesting commentary, "The Locus of Evolution: Evo Devo and the Genetics of Adaptation." They raise two points about "evo devo" (the fusion of developmental and evolutionary biology) that have always bothered me. From the abstract (boldface mine):
An important tenet of evolutionary developmental biology ("evo devo") is that adaptive mutations affecting morphology are more likely to occur in the cis-regulatory regions than in the protein-coding regions of genes. This argument rests on two claims: (1) the modular nature…
mikethemadbiologist | June 14, 2007The misuse of cefquinome has been a pet peeve of mine. Well, I have a commentary in ASM's Microbe about this topic: "Cefquinome: when Regulation Collides with Biology."
It might be boring because I don't use, erm, colorful, blogtopian language, but it still might interest you.
mikethemadbiologist | May 27, 2007From Monday to Friday, I attended the American Society for Microbiology meeting held in Toronto. Before I get to some of the interesting science, my apologies to all of the people who suggested we meet up. Unfortunately, I never look at the blog (or almost never) while I'm on the road, so I missed your messages (it's best to email me directly). Anyway, here's the list of random things:
The E. coli responsible for the spinach outbreak is found in many feral swine. Hence, feral swine are a possible reservoir of E. coli O157:H7. Of course, feral pigs roaming around California in…
mikethemadbiologist | May 22, 2007I'm giving a presentation today while I'm at ASM, and I'm using a picture of a wombat (one of the topics in the talk is E. coli from Australian mammals). So I have a question for you:
Which critter is cuter:
Pandas:
or Wombats:
Discuss. Inflammatory rhetoric is encouraged.