Saturday, June 23, 2012

Science Time!

I've got a bonus post for this week.  I've done really well so far not going overly science on most of my posts, but a friend of mine posted this really awesome article about a topic that is something of a soapbox for me.  As most of you know, my degree is in microbiology.  Honestly, it's hard to get me to shut up about bacteria even though I haven't worked with them for almost 4 years now.  I LOVE bacteria.  They make me happy and they do so many cool things.  I have favorites and they're almost all pathogens.  Any time I hear anything about the plague (Yersinia pestis), listeriosis (Listeria monocytogenes), or leprosy (Mycobacterium leprae) I go positively bonkers.  I can, and will if you give me half a chance, regale you with information, at great length, for all of them.  However, that is not what I mean to go on about today.

Before I go off on my usual bacterial tirade, here's the article that brought this whole thing on.  It's a New York Times article on the bacteria that live with people and it contains some of the best information I've seen outside scientific journals about the human microbiome (microbiome means the sum total of bacteria that live in and on us).  It's a really good read and it almost certainly does a better job explaining all the ways that bacteria are good for us than I ever could.  I highly recommend you read it, especially if you are a germaphobe; it might help you understand bacteria a little better and be less intimidated by them.

Just a bit of a heads up, the rest of this post will freak you out if you're a germaphobe.  Consider yourself warned.

As someone who very much adores bacteria it doesn't bother me that they are, in fact, everywhere.  There are exactly 2 places occuring in nature that are completely bacteria free (a condition called sterile in science talk).  The interior of the placenta and the circulatory system.  Microorganisms in either place is a recipe for disaster.  Bacteria in the blood is called sepsis and is nearly always lethal and infections that can cross the placenta (there are some organisms that can do that) are often damaging, if not deadly to the fetus.  Now, you can make stuff sterile with autoclaves (big, fancy sterilizers that work by using pressure and steam) but as soon as anything in an autoclave touches outside air it is no longer sterile.  There are bacteria (and fungi) in air.  There just are.  You can't do anything about it and you really don't want to.  But yeah, bleaching your counter-tops?  Not sterile.  Sanitary cycles on the dishwasher or washing machine?  Not sterile.  Using disinfectant?  Not sterile.  Anything along those lines is considered sanitized, which doesn't mean there are no bacteria.  If something has been sanitized it has had it's bacterial load greatly reduced but they are not all gone.  Which brings me to the point.

::Climbs on soap box::

I hate, HATE, antimicrobial soaps and hand sanitizers.  Hate, hate hate!

Antimicrobial soap and hand sanitizer are banned from my house and from my parents house. There are only two situations at home I can think of that I would consider acceptable for using those things and neither of them are very common.  If you have someone who is severely immunocompromised or if someone in your family has a MRSA, or similar, infection hand sanitizer starts being a good idea (antimicrobial soap never is).  At that point you're trying to protect a bunch of people and extra steps are necessary.  Other than that I feel very strongly that such things should only be used by health care workers and in hospitals.  They actually need them for the protection of patients and their own families and using hand sanitizer in a hospital protects you from other people's infections and them from yours.

The problem with antimicrobial soaps is that they contain antibiotic chemicals which kill bacteria indiscriminately and their use puts a low level of those chemicals into circulation where bacteria can get used to it and develop resistance.  When you use antimicrobial soap it kills a very large amount of the bacteria on your hands,which means that the ones that are supposed to be there can't do their job.   Unless, of course, you've used it so much that everything on you is resistant at which point there is no reason to use it anymore.  Think of your skin as a table with 16 chairs.  Normally each of those 16 chairs is occupied by one of your bacteria and no one else can sit down at the table.  Now we  add that antimicrobial soap; it kills the bacteria in 15 of the chairs.  The 1 bacterium that is left can eat as much as it wants now, so it grows at it's best rate.  Let's say it can double in 30 minutes.  In 30 minutes there are 2 chairs full, in an hour there will be 4, in an hour and a half there will be 8, and then by 2 hours all the chairs are full again.  But there is nothing holding those chairs specifically for your bacteria.  If you touch anything, and I do literally mean anything, there are other bacteria on it that can try to get at those spaces.  If you washed your hands at a gym, for instance, before going out to use the equipment anything on the equipment can infect you.  If the machine you went to use hadn't been wiped down well and a previous user had a staph infection your chances of getting that staph infection are a lot higher than it would be if you had just used regular hand soap.  What's more, pathogens can often grow faster than your own bacteria.  It's part of how they survive.  To put it back in our chair scenario, lets say we have 12 chairs which were full of our own organisms before using antimicrobial soap.  After the soap and touching something we'll say 1 seat has one of our own organisms in it and 1 seat has a pathogen.  Ours doubles it's number in 30 minutes, but the pathogen doubles it's number in 20.  After 30 minutes there are 4 chairs filled, 2 of each organism.  But in another 10 minutes (that would be the 40 minute mark) there are 6 chairs filled, the same 2 of our organism but now there are 4 of the pathogen.  At the 60 minute mark all the chairs are full but now 8 of them have the pathogen and only 4 of them have the organism we want.  You can see how that would be a problem. 

What's worse is that anything that survives the antimicrobial soap can easily get resistance to it and then it never has to worry about it again.  Hand sanitizer is safer in that respect because of how it works.  The active ingredient in hand sanitizer is usually alcohol.  Some have other antimicrobials in them, and so should be doubly avoided, but most anymore are typically just alcohol.  When alcohol hits a bacterial cell it sucks all the water out on contact and makes the cell die (think of it like alcohol poisoning in a person).  It kills indiscriminately, just like antimicrobial soaps, but it isn't something that bacteria can get used to so the resistance problem is greatly decreased.  However, the alcohol sucks the moisture our of our skin too, and that makes the skin more likely to be dry and cracked which provides a point of entry for anything that can infect us.  So that's both empty chairs at the table and a door to the party below that we didn't even know was there until it opened. That presents a new problem because some of the bugs that live naturally and happily on skin and protect you will be pathogens if they can get under your skin.   A large portion of what lives on people is a strain of staph, Staphylococcus epidermidis (it means Staph of the skin in Latin) to be specific.  It's pretty benign, but where one type of staph can live, so can others.  Like Staph. aureus.  That's the one that causes staph infections.  Hence the problem.

So, what do you do to protect yourself if antimicrobial soap and hand sanitizer can cause more problems than they solve?  The answer to that is laughably simple.  Rub your hands together under running water for a solid 20 seconds.  Sing "Happy Birthday" in your head twice if you need a timer.  You don't even need soap, though soap does help and should be used if it's available and not antimicrobial.  I wish I had pics of the experiment we did in microbiology lab where I proved just that to my students. Then I could show you real evidence and you wouldn't have to take my word for it.  What we did was this.  One student pressed a finger onto an agar plate (read-bacteria food) without doing anything to their hands.  Then they washed their hands without soap and pressed that same finger onto another agar plate.  Another student washed their hands with soap before putting a finger to an agar plate and a third student used hand sanitizer before touching their agar plate.  We labeled all of the plates and put them in an incubator until the next class period, 2 days later.  You know what we saw after those 2 days?  The unwashed finger plate was covered in bacteria, as you might expect.  The water only and soap plates had maybe 1 colony each (that means 1 cell made it to the agar plate) and the hand sanitizer plate had 3 or 4 colonies (meaning that 3 or 4 cells made it to the plate).  We had cold, hard evidence that plain old hand washing was just as effective as using something designed to kill bacteria.  You don't need antimicrobial soaps.











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