Giardia Outbreak

Thanks for the clarification, Roger. That bar of soap you mention seems to be more effective than anything else and apparently trumps the alcohol-based hand sanitizers we have here provided that the hands are washed for a long enough time.

Hi again, Roger –

My main "reference" is an esteemed clinical microbiologist of some 30+ years of experience and education in the field, an author of some nationally recognized studies in the infection control area. I placed the question to him some time back after one of these discussions periodically surfaced on BPL, and at that time he seconded the ideas I relayed in my previous post. I trust the depth and breadth of his knowledge greatly. However, if you have references to the contrary I'd be interested in reading them, and passing them back his way.

My other reference would be any standard medical microbiology textbook. Unless something has changed since I studied the subject, there are two main mechanisms of gastrointestinal illness. One is by the ingestion of enteropathogenic bacteria which colonize the intestines and either produce enterotoxins (normal garden variety E. coli is not one of these, but the enteropathogenic O157:H7 serotype is, as are Salmonella and Vibrio cholerae) or penetrate the intestinal mucosa (Shigella and Campylobacter, for example). The other is to ingest food which has been overgrown with toxin-producing bacteria such as Staphylococcus or Clostridium; in those cases the bacteria don't directly infect the intestinal lining, but the toxins act upon your body in nasty ways.

I can find no reference to any mechanism of normal E. coli acting on the stomach, or causing problems from ingestion (other than the obvious "yuck" factor!).

It may be "simplistic", as you say, to assume that we are not normally consuming small amounts of bacteria on a daily basis, normal E. coli probably being one of the more common as you can find it nearly everywhere if you just set out a Petri dish. That, after all, is how we originally get our gut colonized after birth (from the top down), normally with no ill effects.

However, I am still in favor of vigorous hand washing, make no mistake about it; it is a fine way to avoid spreading disease, introducing pathogenic bacteria from the environment to one's system, or transferring bacteria to food where it may proliferate.

Cheers,
dk

dk,
I agree, though, I am not a microbiologist, just a couple years of study many years ago. The basic "you cannot catch something from yourself" rule is about what I follow. e.Coli is one that has thousands of strains, one of the reasons it is used for reseach. All of these are social diseases or from the enviornment.

But, as you say, keeping bacteria out of your food is always a wise precaution.

One thing you guys are forgetting is what happens if a general surgeon nicks the intestine during surgery? You guessed it…serious infection. Because the bacteria leaking out of the gut are not meant to be in other parts of the body.

Yes, you CAN infect yourself with your own intestinal bacteria.

Where's Dean the general surgeon when you need him?

Of course you can infect yourself with normal flora in normally sterile sites, like nicking the gut and leaking bacteria into the bloodstream. I'm not forgetting it, it's just not part of the hand-washing reasons.

E. coli is not uncommonly found in the mouth as normal flora (about 25% of individuals, according to http://textbookofbacteriology.net/normalflora.html).

Occasionally there is an E Coli outbreak. Like drinking water will be contaminated. A significant fraction of the people can die. Health departments react strongly. There are signs on restaurant bathroom walls telling people to wash hands after going to the bathroom. etc. Clearly, you can infect other people.

I've always wondered wether you can infect yourself. What Roger said makes sense. If you move E Coli upstream in your intestine it could be a problem. I would like to hear some more definitive data about this.

I think Purell kills E Coli. I've never heard any claims about using it to prevent Giardia.

The E. coli outbreaks referred to are of toxin-producing E. coli, not normal flora types. http://www.cdc.gov/ecoli/outbreaks.html

You'll find a totally mixed bag of results on whether Purell or any other alcohol based hand sanitizer actually kills e. coli. And that's probably why U. S. hospitals forbid that approach.

Randy,

I have a vague recollection that the infection control officer at our hospital passed around an article that said hand sanitizers were more effective on viruses than on bacteria, but my memory may be faulty, and/or there may be studies that say the opposite. And hand-washing is still the gold standard in the hospital environment.

Hi, Jerry –

" I would like to hear some more definitive data about this."

From the Merck manual at http://www.merckmanuals.com/professional/gastrointestinal_disorders/gastroenteritis/overview_of_gastroenteritis.html, see below (please note that all specific references to E. coli refer to pathogenic strains, not the normal flora, and that there are no references to E. coli garden variety acting on the upper digestive system to cause illness).

"Bacteria:

The bacteria most commonly implicated are

Salmonella
Campylobacter
Shigella
Escherichia coli (especially serotype O157:H7)
Clostridium difficile

Bacterial gastroenteritis is less common than viral. Bacteria cause gastroenteritis by several mechanisms. Certain species (eg, Vibrio cholerae, enterotoxigenic strains of E. coli) adhere to intestinal mucosa without invading and produce enterotoxins. These toxins impair intestinal absorption and cause secretion of electrolytes and water by stimulating adenylate cyclase, resulting in watery diarrhea. C. difficile produces a similar toxin (see Anaerobic Bacteria: Clostridium difficile–Induced Diarrhea).

Some bacteria (eg, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens) produce an exotoxin that is ingested in contaminated food. The exotoxin can cause gastroenteritis without bacterial infection. These toxins generally cause acute nausea, vomiting, and diarrhea within 12 h of ingestion of contaminated food. Symptoms abate within 36 h.

Other bacteria (eg, Shigella, Salmonella, Campylobacter, some E. coli subtypes) invade the mucosa of the small bowel or colon and cause microscopic ulceration, bleeding, exudation of protein-rich fluid, and secretion of electrolytes and water. The invasive process and its results can occur whether or not the organism produces an enterotoxin. The resulting diarrhea contains WBCs and RBCs and sometimes gross blood.

Salmonella and Campylobacter are the most common bacterial causes of diarrheal illness in the US. Both infections are most frequently acquired through undercooked poultry; unpasteurized milk is also a possible source. Campylobacter is occasionally transmitted from dogs or cats with diarrhea. Salmonella can be transmitted by consuming undercooked eggs and by contact with reptiles, birds, or amphibians. Species of Shigella are the 3rd most common bacterial cause of diarrhea in the US and are usually transmitted person to person, although foodborne epidemics occur. Shigella dysenteriae type 1 (not present in the US) produces Shiga toxin, which can cause hemolytic-uremic syndrome (see Thrombocytopenia and Platelet Dysfunction: Thrombotic Thrombocytopenic Purpura (TTP) and Hemolytic-Uremic Syndrome (HUS)).

Several different subtypes of E. coli cause diarrhea. The epidemiology and clinical manifestations vary greatly depending on the subtype: (1) Enterohemorrhagic E. coli is the most clinically significant subtype in the US. It produces Shiga toxin, which causes bloody diarrhea (hemorrhagic colitis). E. coli O157:H7 is the most common strain of this subtype in the US. Undercooked ground beef, unpasteurized milk and juice, and contaminated water are possible sources. Person-to-person transmission is common in the day care setting. Outbreaks associated with exposure to water in recreational settings (eg, pools, lakes, water parks) have also been reported. Hemolytic-uremic syndrome is a serious complication that develops in 2 to 7% of cases, most commonly among the young and old. (2) Enterotoxigenic E. coli produces two toxins (one similar to cholera toxin) that cause watery diarrhea. This subtype is the most common cause of traveler's diarrhea in people visiting the developing world. (3) Enteropathogenic E. coli causes watery diarrhea. Once a common cause of diarrhea outbreaks in nurseries, this subtype is now rare. (4) Enteroinvasive E. coli causes bloody or nonbloody diarrhea, primarily in the developing world. It is rare in the US.

In the past, C. difficile infection occurred almost exclusively in hospitalized patients receiving antibiotics. With the emergence of the hypervirulent NAP1 strain in the US in the late 2000s, many community-associated cases are now occurring.

Several other bacteria cause gastroenteritis, but most are uncommon in the US. Yersinia enterocolitica can cause gastroenteritis or a syndrome that mimics appendicitis. It is transmitted by undercooked pork, unpasteurized milk, or contaminated water. Several Vibrio species (eg, V. parahaemolyticus) cause diarrhea after ingestion of undercooked seafood. V. cholerae sometimes causes severe dehydrating diarrhea in the developing world and is a particular concern after natural disasters or in refugee camps. Listeria causes food-borne gastroenteritis. Aeromonas is acquired from swimming in or drinking contaminated fresh or brackish water. Plesiomonas shigelloides can cause diarrhea in patients who have eaten raw shellfish or traveled to tropical regions of the developing world."

I do at least somewhat know whereof I speak, at least on some subjects. :)

As far as moving normal E. coli directly upstream, it does happen in severe cases of vomiting, where the upper intestinal contents are vomited as well as stomach contents. But it apparently causes no problems above and beyond that which was already causing the individual to vomit so severely.

Many years ago (like 30? ugh) I was told by someone that Montezuma's revenge could be caused by "normal" E. coli that were "new" to the traveler's system, but I cannot find any reference to that on the web so it's likely that knowledge on the enteropathogenic strains of E. coli has just advanced over the years, replacing the older theory.

Thanks, interesting

My next question is can you get E Coli or other baceteria from your Poop, onto your hands, and back into your mouth which then causes symptoms.

Clearly you can infect other people

And that's interesting about Purell not being effective. You see it all over the place.

One thing is, yeah, maybe it kills the bacteria on your hands, but there's organic matter left there. The alcohol evaporates. Then, because there are bacteria all over, your hands will get reinfected.

Maybe better to wash most of the organic matter off your hands and don't worry so much about the bacteria. Most of them will get washed off with the organic matter. But then, since there isn't so much food left on your hands, the bacteria popluation will remain low.

Weird – the profanity filter requires that you capitalize the first letter of Poop : ) I thought the profanity filter was gone

Hi d k

I found the Merk reference very interesting – thank you.

I can understand that the reference comes at the question from the 'diagnosing gastro' point of view, rather than the 'can I reinfect myself' one. Should you or anyone else find any references which focus more on the latter, I would be very interested.

At this stage we will continue to wash our hands carefully, as there are two of us, but it would seem I (we?) need to find out a bit more before being quite so sure. Educational.

Cheers

"My next question is can you get E Coli or other bacteria from your Poop, onto your hands, and back into your mouth which then causes symptoms."

Not with normal flora, according to the teachings in medical microbiology at least over the last 30 years or so. At least to the best of my knowledge (and I studied it at the university level, worked as a microbiologist briefly and then for decades after that worked in close conjunction with an excellent microbiology department at a hospital with a high level of knowledge, experience and standards regarding infectious disease). Since I have not worked actively as a microbiologist for a while, and don't consider myself primarily a microbiologist any more, it's remotely possible that something new has come up but it does not appear that way from the sources I have contacted and searching I have done on the web. And apparently it would be new to the Merck manual as well.

In the absence of documented references to the contrary, it seems the current thinking in microbiology is that you can transfer your E. coli back to your gut or freshly to the gut of others, but unless it is a disease-causing strain (i.e., enteropathogenic or enterotoxin-producing) it will not normally cause the intestines any distress. If it is disease-causing, then it will have caused that disease in you first as well (unless you have immunological superpowers, I suppose, in which it's not going to get you the second time either).

If you introduce that bacteria to a sterile site (blood, bladder, spinal fluid, etc.), it may cause disease whether or not it is enteropathogenic (i.e. causing enteric – GI tract – illness).

And again, there is always good documented reason for hand-washing, even if it's not to prevent re-introduction of normal flora (or even if it is for that, since I doubt most of us here are keen on that general concept whether or not it causes illness).

Sorry to have gone off on this subject, but it's bothered me in the past when, for instance, people have responded to news items of people incapacitated in the wilderness with diarrhea/dehydration by saying in essence "oh well, he probably caused it himself by not washing his hands after pooping." Microbiologists are as persnickety about inaccuracy as, say, engineers :) After the last round of that, I consulted my sources, confirmed my viewpoint, and determined that the next time the issue came up (of causing disease by re-introducing one's own flora) I'd pipe up, if for no other reason than to offer someone a chance to educate me with documentation that it DOES happen.

Back to the original subject of Giardia and hand cleanser…

I thought that the subject of this thread was field hygiene in relationship to Giardia, which is a cystic protozoan (parasite).

Instead, the whole discussion seems to be about preventing problems of a bacterial or viral nature. These are all different organisms, and different topics. I agree that proper field hygiene will diminish problems of all three categories, but they are different kinds of critters (Aussie: "wogs").

–B.G.–

Thanks dk

Yeah, this subject has come up before but I haven't heard good answer

If you can't re-introduce bacteria, then what is the good documented reason for hand washing?

Maybe it doesn't matter – I should quit worrying about it and just wash my hands

(sorry about being persnickety engineer : )

Well, I am guilty of derailing the discussion of Giardia because I saw something posted attributing disease to re-introduction of E. coli normal flora and felt impelled to seek documentation of something that is contrary to what I have been taught on the subject, and to present what I understand to be the current academic and clinical view on that. I apologize for the detour.

"I agree that proper field hygiene will diminish problems of all three categories, but they are different kinds of critters (Aussie: "wogs")."

Perhaps the thread should be renamed poliwogs?

These things are microscopic in size, so perhaps they should be called microwogs.

–B.G.–

:) no need for apology, Jerry!

Good reasons for hand-washing:

1) Poop is yucky!

2) to prevent introducing enteric bacteria to your hands where it could get into cuts on the skin, scratching mosquito bites, blisters, burns from that flaring stove, etc., and cause an infection

3) to keep from introducing bacteria (either from your gut or from the environment) to your food that may multiply there and produce toxins that could make you ill. This probably is less common in backpacking, where much of your food is dry and not likely to foster bacterial proliferation, and what food you have that's moist usually is consumed immediately. But cheeses, salami, etc., would still be susceptible.

4) to keep from spreading any pathogenic bacteria you may have to others, in case you are either an asymptomatic chronic carrier of a pathogenic enteric, or about to start manifesting symptoms from the Salmonella you consumed at that restaurant the night before hitting the trailhead :)

5) to keep from transferring any viruses (cold, flu, enteric, etc.) you are carrying from your gut to other people, either directly or via surfaces

There may be others, I'm giving up now…

Pure speculation: With regards to #3, I am wondering why the toxin-producing strains of organisms such as Staph aureus and Clostridium perfringens, which can be normal inhabitants of the gut, apparently only produce these toxins in food and not while living in your gut, apparently unlike the pathogenic forms of E. coli??? Perhaps the other flora keep them in check inside us, but not so in food. I'd never really considered that point until composing this post, and may need to research that. Hmmm…

Hi d k

> Pure speculation: With regards to #3, I am wondering why the toxin-producing strains of organisms such as Staph aureus and Clostridium perfringens, which can be normal inhabitants of the gut, apparently only produce these toxins in food and not while living in your gut, apparently unlike the pathogenic forms of E. coli??? Perhaps the other flora keep them in check inside us, but not so in food. I'd never really considered that point until composing this post, and may need to research that. Hmmm…

Can I make a suggestion (following on from my re-education)?
If you transfer some bacteria from your hands to your mouth, the number of cells involved is likely to be small. Perhaps your system can handle that – very likely I imagine.

Ah, but if you transfer those same few cells to wet food where they can multiply, then you eat that food, you could be hitting your system with a dose 1000x bigger. It is possible that could overwhelm your defenses.

What then happens when you ingest a few cells of a strain completely unknown to your immune system? Bit of chaos there for a while I would imagine. That new strain might be labeled 'seriously toxic' when in fact it is little different from the ones to which you have immunity from previous exposure.

Please – keep us up to date!

Cheers

Agreed on the idea of "some" bacteria on hands vs. " lots" in food, what I'm not sure about is why a strain like S. aureus that can colonize your gut normally (i.e. "lots") apparently won't produce the enterotoxins in your gut that it will if it's just growing in the tuna salad that sat out all day. Either they are different strains and that's just not spelled out clearly online where I've been looking, or there is something about growing in the presence of lots of other diverse flora that inhibits toxin production, or ??? This is the part that will require further digging on my part… give me a few days and I'll ask around.

maybe growing in the presence of lots of other diverse flora inhibits growth of the bad bacteria?

on a tuna sandwhich, they are free to grow prolificly?

> apparently won't produce the enterotoxins in your gut …
> or there is something about growing in the presence of lots of other diverse flora
> that inhibits toxin production, or ???

My guess is that your gut has evolved some (chemical) means of suppressing the toxin production of the S aureus – which is why both you and it can coexist. I haven't the faintest idea what the suppressor chemical might be, but it is probably in very short supply in a tuna salad.

Does our current state of knowledge tell us what that chemical is? I would not be surpised if that remains an 'unknown'.

Cheers

Trawled from the net ….

We have about 5 pounds of bugs in our gut.

“The bacterial inhabitants of the human gastrointestinal tract constitute a complex ecosystem that includes both aerobic and anaerobic microorganisms. Four hundred to five hundred bacterial species are estimated to be present in the human fecal flora at concentrations of up to 1012 viable microorganisms per g of stool (29). The total number of bacterial cells of the intestinal flora is estimated to approximately 1014. According to conventional culture, the indigenous flora is relatively stable and consists of the four major bacterial groups Bacteroides, Bifidobacterium, Eubacterium, and Peptostreptococcus at concentrations of approximately 1010 to 1011 CFU/g, also called the dominant flora. The subdominant flora consists of bacteria belonging to the genera Streptococcus, Lactobacillus, and, to a lesser extent, Enterococcus, Clostridium, Bacillus, and yeasts at concentrations of 106 to 108 CFU/g. “

More Here

They probably self-regulate under normal circumstances.

Cheers
Roger

"what I'm not sure about is why a strain like S. aureus that can colonize your gut normally (i.e. "lots") apparently won't produce the enterotoxins in your gut that it will if it's just growing in the tuna salad that sat out all day."

Is it possible that the tuna salad, being a different substrate than what is found in the gut, might result in enterotoxins when metabolized by S. aureus?