Escherichia coli

The E. coli is one of the most common bacteria, and can be found abundantly in the human intestine (about 0.1% of all the bacteria in the intestine, based on Western diet). In each such bacterium there are only about 5,000 genes. This is the reason it is the first organism to have its genome mapped.

Under favourable conditions, a population of E. coli can double in number every 12.5 minutes. So if you start with one, in two hours you will have about 1000, and in four hours about a million. This is faster than the rate of human reproduction.

A bacteria can have a 1 in 200 chance of having a mutation in its genes. This is the reason that bacteria can adapt so quickly to changing environment (in your face proof of evolution). In four hours, one successful mutation has become one million.

This fast adaptation is one of the reasons for bacterias' success as an organism.

E. coli is an abbreviated form of the name Escherichia Coli. It is a naturally occurring bacterium that dwells inside a human’s large intestine. In exchange for the nutrients it gets, E. coli secretes Vitamins K and B-complex. Although an important dweller of our alimentary canal E. Coli only makes up 0.1% of the bacteria that lines an adult intestine. The relation between the human and the E. Coli bacterium is a symbiotic one. Humans provide the E. Coli with nutrients and, in turn they secrete necessary vitamins. The mutant form of E. Coli, E. Coli 0157:H7 is the strain that has given its nicer brothers a bad name. The most controversy seems to be surrounding uncooked beef, which became a nationwide problem with the “Jack in the Box” outbreak 1993. The mutant form, even though it is better known, is much rarer than normal E. coli.

The good form of E. coli could have transferred DNA with a virus or other sources (transduction possibly). This source possibly altered its make up and made the good E.coli into the mutant form. The mutant form is lethal for it secretes a toxin called Shiga-like toxin (SLT). A a result of the mutant E. coli releasing SLT, damage to the epithial cells of the intestine occurs. Due to injuries there is a loss of water and salts, bleeding, and hemorrhaging. This hemorrhaging can be lethal to small children.

The mutant E. coli (which will from here in be labeled as E. coli for reasons of convenience) can be transferred anytime a person comes in contact, more specifically ingests, any product that has been near animals. Most of the public is more concerned with getting it from undercooked hamburgers, but as in many cases it can even be transferred through beverages. Unless there is a cut in the meat below the surface it is usually sterile. If a knife cuts through the meat it can carry the E. coli down with it. Although it is rare infection can occur easily for it only takes about 10 bacterial cells for infection. The standard cooking rule of thumb is to cook the meat until all the juices run clear. The problem with hamburger meat is the fact that it is ground, for the once only surface dwelling bacteria plunge into every nook and cranny of the meat. A person who eats contaminated meat and gets infected, can spread the disease further through contaminated water. If any vegetables were washed in such water, or it was used to make a beverage, then it is likely to become a disease carrying entity. A case involving contaminated water occurred in July of 1993. Around 35,000 residents of New York City had to boil their water when it was discovered that somehow E. coli had made its way into the city’s water supply, despite the chlorination and filtration systems employed there.

Regarding treatment, the author of The Coming Plague , Laurie Garret, writes

“The Lederbergs [a research team] discovered tests that could identify streptomycin-resistant [E. coli] before the organisms were exposed to antibiotics. They showed that the use of antibiotics in colonies of bacteria in which even less than 1 percent of he organisms were generally resistant could have tragic results. The antibiotics would kill off the 99 percent of the bacteria that were susceptible, leaving a vast nutrient-filled petri dish free of competitor for the surviving resistant bacteria… the resistant bacteria rapidly multiplied and spread out, filling the petri dish within a matter of days with a uniformly antibiotic-resistant population of bacteria.”

Although that type of treatment was successful at first, the bacteria has grown, like others, resistant to many forms of antibiotics. What makes E. coli so resistant is that, like most bacteria roughly one out of every 10 million E. coli in a petri dish might randomly mutate to be resistant to, say penicillin. Then, if the drug were poured into the petri dish, 9,999,999 bacteria would die, but that one resistant E. coli would survive, and divide and multiply, passing its genes for resistance on to its progeny.

Because the rogue form of E. coli has gotten the majority of the press, many people don’t know that E. Coli in its natural form is actually a necessity. The future contamination and outbreaks will only proceed until people take proper precautions, and/or legislation regarding testing is passed. The problem does entail bacteria’s sped up evolution due to human’s role. It is a conundrum, if we try to cure it, it will evolve to break the cure.

Works Cited

“What the heck is an E. Coli?.” Bugs in the news. (7 October 2000)

Garrett, Laurie. The Coming Plague. New York: Farrar, Straus and Giroux, 1994.

So. E. coli 0157:H7. You've heard a bit about it, maybe read about an outbreak somewhere. You know you don't want to get it, but do you know why it's so bad, what it's like to have it? Probably not. Well, I do, and like I've done before, I'll let you know. Now, before we get started, some disclaimers: this is a personal account. YMMV. I'm not a doctor. I'm not even premed. Hell, I nearly failed freshman chemistry. Oh, and if you keep reading, I talk a lot about my shit. I warned you. Okay, now let's get into the good stuff.

I'm a pretty healthy guy. I rarely get colds, and when I do, they barely affect me. (This may have to do with the fact that we have a lifetime supply of Cold-Eeze. Literally.) I haven't taken a sick day in years. But when something goes wrong, boy does it ever. The first thing I felt were the cramps. I was at the movies with some friends – The Patriot, actually – when they hit. They started mild – I shifted in my seat a bit. As they got worse, I was convinced that something was blocked up, so I left for the restroom to clear it out. That helped a bit, but the cramps came back. I repeated the process, though this time yielded fewer tangible results. All told, I spent 30 minutes of that film in the john, and to this day I believe it improved my moviegoing experience immeasurably.

When the movie let out, I asked to be dropped off at home, pleading discomfort. My friends dismissed my claims and headed for another friend's house, though after I spent most of my time there on the can (with an issue of Reform Judaism magazine), they agreed to take me home. At this point, the discomfort had subsided somewhat, and I had a few pieces of toast before heading upstairs to bed. Before I settled in, however, I made a final trip to the bathroom.

I didn't get up off that toilet for 14 hours.

After an hour, my mom said goodnight (my dad was already in bed). I said I had some diarrhea, and expected to go to bed soon. After another hour, I realized I was losing a lot of fluid and resolved to drink a Dixie cup or two of water every time I flushed (which was fairly often). I took two caps of Imodium AD. Another hour, and not only had they not helped, but I realized there was blood coming out (not much in the way of solids at this point). This was Not Good – I assumed I had burst some sort of vessel straining. As time went on, I was producing less and less, but I couldn't pass 5 minutes without the cramps making it feel imperative that I get back on the bowl and try again. My throat became drier and drier. First it hurt to swallow. Then I physically couldn't do it. I just tried to keep my tongue wet. I don't remember sleeping, but I know it doesn't go from 4 to 5 AM that fast. I s(h)at.

Around 9 my mom woke up and went out. My memory is fuzzy at this point. She came back around 1, and I finally told her that I thought I needed medical help. I explained everything, and we headed to my doctor's office. Off the toilet, the cramps hurt like hell, and I spent the ride doubled over. I waited in their bathroom. A brief interview was all they needed to ask for a stool sample (a quarter cup of reddish-brown muck was the best I could do) and send me off to the emergency room.

There, I waited in another bathroom, and when they moved me to a curtained intake room, waited in yet another. Eventually they gave me a commode, a metal chair with an integrated chamberpot that resembled nothing so much as a potty training apparatus for adults. At this point, my lips were not so much "chapped" as "encrusted", and I vomited for the first and only time during the whole experience, a small amount of thin, yellow bile. After some hours, my parents cornered a nurse and got her to process me. I was 12 pounds below normal weight, most of it dehydration. I was immediately given a drip of electrolyte solution, which is kind of like an IV of Gatorade, and a few swabs which looked like rock candy and tasted like hospital, but did wonders for my lips.

Later, a doctor came in and told me that no one was exactly sure what I had - it could be e. coli, could be salmonella, could be listeria, could be campylobacter or a variety of other food poisoning agents. They'd have to wait until the labs could make cultures from my stool sample. He gave me a prescription for antibiotics and Demerol to deal with the cramps, and told me that the delay in placing me was due to a shortage of beds, and eventually one was found for me, albeit in the rehab unit with a roommate recovering from a heart bypass. He was a nice enough guy, though I'm afraid I may have awakened him dragging my IV tree to the bathroom throughout the night, and I have to question the wisdom of pairing a patient recovering from major surgery with one carrying an infectious disease. Apparently I wasn't the only one, because next morning (I will never figure out why I was awoken each morning for a day of lying in bed and sitting on the can) I was moved to a single room.

Once there, I was again interviewed, this time by a gastroenterologist, and then left alone except for periodic checkups, IV bag replacements, cleanings, and intramuscular Demerol injections by a team of amiable though by no means attractive nurses. My days were uneventful – in bed or on the john. The Demerol didn't block out all the cramps, but it did mean that I'd spend an hour staring at my hand, thinking nothing. My doctor didn't like this, and by the second day ordered me off of it during the daytime – he feared it cut me off from reality and rendered me unable to communicate my situation to him, though when reality is a vise around your bowels and the best status update you could give is "Well, I'm still shitting blood", you'd think you'd be forgiven your indulgences.

On about the third day a group of friends came, bearing magazines. I entertained them for half an hour but had to hold court for the next hour through the bathroom door. Later, my doctor ordered me to stay off the toilet unless I was actually getting something done – he was afraid I'd get a hernia, and to tell the truth, for something people might sit on hours every day, it sure didn't seem to be designed for comfort. Absent the Demerol, just bearing the cramps was irritating, but luckily they had weakened some. I took a hot shower for the first time that afternoon.

Nights, I slept, pleasantly sedated. The bed had no integral bedpan, and a metal one wasn't feasible to sleep with, so a sort of pad was placed under my ass, a new one each night. Between years of social conditioning and basic mammalian fecal aversion, I did not like this one bit, but what could I do? After the fourth night, flow had ceased, and I went without it.

On the fourth day or so, I was taken for an Lower Gastro-Intestinal Series x-ray to determine if I suffered from any blockage, which means I was given a barium enema. On the plus side, this helped to clear out my bowels. On the negative side, it meant I had to lie with my butt in the air while a tube was put up my ass and I was pumped full of cold slime. I was found clear and taken back to my room. Later, the gastroenterologist came back with my test results, proclaiming it e. coli. He told me that he was taking me off the antibiotics, as they (counterintuitively) reduced the survival rate. To this point, I had considered this a major but nonthreatening annoyance, and was surprised that people were calculating my chance of survival. So, we would essentially wait the disease out, which would take another week or so. I had to cancel and reschedule a tour of West Coast colleges (little matter, I ended up at Cornell, in sunny upstate New York).

So, from here on it was mostly waiting. They started feeding me, three servings a day of juice, broth, and Jell-O, which was reasonably tasty, if by "tasty" you mean "not tasty in the least". On my last day before discharge, I was finally upgraded to solids. When the nurse came back to substitute noodles for my butter chicken (no dairy products, you see), I drew on some hindbrain instinct and hunched defensively over my plate until she let me be.

After around 9 days in the hospital, I went home. Confinement and sickness left me weak, straining to climb the stairs, though I recovered quickly. Oddly, after a week of little to no food, my fully hydrated weight had only dropped 3 pounds. Within 3 days, I was back up to full capability.

So, what caused all this? I still don't know. The CDC called me a week after I was discharged, trying to get a history of what I had eaten starting a week before I went to the hospital. My memory didn't really stretch beyond last night's dinner. That said, there are two major suspects - the first, which might appear to be the obvious cause, was a barbecue at my friend Steph's house. She had discovered an undercooked hamburger which I (against her objections) claimed and ate. (Even after all this, I still take my meat rare.) However, the timing's all wrong - this had occurred more than two weeks back, and e. coli has an incubation period of 3 to 9 days. The other candidate was a questionable-tasting chicken salad I had eaten the night before, which also trends past the incubation period, though in the other direction. While at first we thought my case might be related to other cases reported contemporaneously, those were all traced back to a petting zoo which I had never heard of.

Overall, while it certainly wasn't fun, I'm glad I had the experience. It was pretty interesting, and it helps you understand similar experiences in a way a "virgin" couldn't. (It also perfectly insulates me from any menstrual "as a guy, you can't understand" comments. Gee, uncomfortable cramps and bleeding from the nether regions. Why, I wonder what that might be like.) Further, it's quite the distinguishing mark - in the grand march of human history, damn few people can claim to have gone through a similar experience and lived to tell about it. I am progress incarnate. Can you say the same?

This node was originally hand-written at work, including pipelinks. 6 pages worth of legal pad.

A common bacterium that has been studied intensively by geneticists because it has a small genome and is usually harmless and easy to grow.

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From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.

Escherichia coli is a Gram-negative, non-spore-producing, rod-shaped bacterium that ferments lactose and lives in the intestines of many animals.

This bacterium produces a natural antibiotic called colicin. This chemical kills other bacteria by a variety of methods (depending on the type), such as blocking protein synthesis and degrading DNA. Colicins are encoded by a group of naturally-occurring E. coli plasmids such as Col E1.

E. coli has been widely studied by geneticists, who have created special strains for study:

1. HB101: This strain is unusually good at taking in introduced foreign DNA and incorporating it into its own genome. It is therefore commonly used as the host organism for growing recombinant DNA vectors.
   
   
2. C600 : this strain is used in genetics experiments as a host for foreign plasmids that have been cloned.

This bacterium is also interesting because contains many different DNA genes, which make proteins that are essential for DNA replication:

• dnaA gene: a defective gene which produces a defective protein that influences DNA replication in a variety of ways.
• dnaB gene: makes a protein that is involved in the formation of primer polynucleotide chains, which are precursors of DNA replication.
• dnaE gene (polC gene): makes some of the components of the DNA Polymerase III protein, an enzyme which plays an important role in DNA replication.
• dnaF gene (nrdA gene): codes for an enzyme (ribonucleotide reductase) which breaks down ribonucleotides.
• dnaG gene: makes the enzyme primase, an enzyme which helps make primers, which are precursors to DNA replication.
• dnaH gene (dnaZ gene): makes some of the components of the DNA Polymerase III protein, an enzyme which plays an important role in DNA replication.
• dnaJ and dnaK genes: helps the bacteria survive at high temperatures. They also play an important role in the replication of the DNA of bacteriophage lambda.
• dnaQ gene: also makes some of the components of the DNA Polymerase III protein.