Germs

We use the alcohol based hand rub solutions in the intensive care unit. The major advantages are that they are effective, portable and because they are just at the bedside they are used more frequently. Its far easier to squeeze a bit of gel on your hands and rub it in as you walk to the next patient rather than going back and forth to the sink. I seem to remember our microbiologists saying there was evidence that they are more effective than handwashing, though that might be due to the increased use.
I can't see any reason to use them in a domestic setting though, where hand washing with soap is perfectly adequate.
 
Southwind17 said:
So, my missus gives me some Dettol hand wash, you know, the type that you just squeeze on and rub around without rinsing off, that claims to kill 99.99% of germs, and I'm wondering: is it cynical to wonder whether the 0.01% are the dangerous ones, and in any case wouldn't it be better to wash and rinse?
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Even if it kills all types at 99.99% efficiency, the 0.01% residue is going to consist mostly of those that are resistant to the antibacterial agents in the hand wash. It won't take them long to repopulate your hands, but now your little bacterial colony will be slightly harder to get rid of with the hand wash.

Rinse and repeat...
 
Remember this?

Take germs, for example. In the eighteenth century, no such thing, nada, nothing. No one ever imagined such a thing. No sane person, anyway. Ah! Ah! Along comes this doctor, uh, uh, uh, Semmelweis, Semmelweis. Semmelweis comes along. He's trying to convince people, well, other doctors mainly, that's there's these teeny tiny invisible bad things called germs that get into your body and make you sick. Ah? He's trying to get doctors to wash their hands. What is this guy? Crazy? Teeny, tiny, invisible? What do you call it? Uh-uh, germs? Huh? What? Now, cut to the 20th century. Last week, as a matter of fact, before I got dragged into this hellhole. I go in to order a burger in this fast food joint, and the guy drops it on the floor. Jim, he picks it up, he wipes it off, he hands it to me like it's all OK. "What about the germs?" I say. He says, "I don't believe in germs. Germs is just a plot they made up so they can sell you disinfectants and soaps." Now he's crazy, right? See?
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JHGRedekop said:
Even if it kills all types at 99.99% efficiency, the 0.01% residue is going to consist mostly of those that are resistant to the antibacterial agents in the hand wash. It won't take them long to repopulate your hands, but now your little bacterial colony will be slightly harder to get rid of with the hand wash.

Rinse and repeat...
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Bacteria and viruses are not able to build up resistance to chemical disinfectants. Alcohols, soaps and bleaches are effective at breaking down cell walls and fixing proteins and nucleic acids. The 0.01% that survive are those that usually need a longer exposure to the chemicals to kill them.

Are you confusing antibacterials with antibiotics?
 
JHGRedekop said:
Even if it kills all types at 99.99% efficiency, the 0.01% residue is going to consist mostly of those that are resistant to the antibacterial agents in the hand wash.
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If "resistance" is taken to refer to changes to the bacterial genome which constitute adaptations to the effects of the antibacterial agents in the hand wash, then no -- not if the active ingredient is alcohol. If the stuff is strong enough (the recommendation is for between 60 and 80 percent for ethyl, lower for isopropyl), and if it is applied thoroughly, there aren't going to be any survivors. Bacterial spores are another matter. These are "resistant" in a somewhat different sense, and killing them would require washing with chlorine bleach, in concentrations strong enough to burn your skin.
 
Dymanic said:
I carry alcohol gel hand sanitizer pretty much all the time during cold and flu season...
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Well that seems pointless. I don't see alcohol being that effective against viral infections.

Edit: Huh, what do you know, apparently it can "inactivate" them. Messes with their receptors or something I suppose.
 
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Capsid said:
Bacteria and viruses are not able to build up resistance to chemical disinfectants. Alcohols, soaps and bleaches are effective at breaking down cell walls and fixing proteins and nucleic acids. The 0.01% that survive are those that usually need a longer exposure to the chemicals to kill them.

Are you confusing antibacterials with antibiotics?
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Capsid- I've seen this argument elsewhere. I concur that these agents do not have an "antibacterial" action, any more than a cutting torch. They just destroy, (chemically in this case) the physical structure of the bacterium. There is no way this can encourage the growth of a resistant species through plasmid exchange with survivors.
Or is there?
Let's hypothesise a bacterium X that lives under fingernail cuticles. Call it "C.utie". We apply gel, which kills the bacteria on the hands- but probably does not penetrate under the nail cuticle to any distance. So, we selectively increase the population of Cuties on the fingers. Now ask WHY C.utie lives where it does. Perhaps because it is outcompeted on the great rolling veldt of the fingers? But now it has no competition...

I'd be interested to know if the range of bacterial species on an unwashed hand and the same hand after gel cleaning, then a day later, three days etc show significant differences.

Natural selection after all, operates on many creatures through non chemical means . Nobody used chemical warfare on mammoths, but they ain't so common as they were...
 
Soapy Sam said:
Let's hypothesise a bacterium X that lives under fingernail cuticles. Call it "C.utie". We apply gel, which kills the bacteria on the hands- but probably does not penetrate under the nail cuticle to any distance. So, we selectively increase the population of Cuties on the fingers. Now ask WHY C.utie lives where it does. Perhaps because it is outcompeted on the great rolling veldt of the fingers? But now it has no competition....
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Then, wouldn't your hypothetical bacteria be just as susceptible to the gel as the other bacterium? After all, it was sheltered from the gel while it lived under the cuticle - that's how it survived the gel treatment in the first place. A second treatment of gel would simply kill off any remaining bacterium on the hands.
 
~enigma~ said:
Next time you are in the hospital tell your doctor, nurse and tech not to sanitize their hands before touching you. Enjoy the nosocomial infection you acquire and hope it isn't MRSA.

ETA - Wonder why there is a term for an idea that is only held by me?
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:confused:

I think you might need to re-read both the posts you've responded to. The first one said nothing about medical professionals. It was talking about widespread use of sanitizers. And in the post I quoted above, you seemed to miss that the person you quoted was pointing out what I just pointed out...
 
Harpyja said:
Then, wouldn't your hypothetical bacteria be just as susceptible to the gel as the other bacterium? After all, it was sheltered from the gel while it lived under the cuticle - that's how it survived the gel treatment in the first place. A second treatment of gel would simply kill off any remaining bacterium on the hands.
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Harpyja- Yes it would- the bacterium has not acquired resistance from a few naturally resistant individuals, it has merely benefited short term by the removal of the competition-which is why most folk take the view that this is fundamentally not leading to selection.

But in the short term- hours, a day or so, that single survivor may expand into a significantly skewed population- and the larger than normal population of C.utie may then move onto other territory. If it's all over my hands six hours after I gelled them, I may be leaving it on door handles etc where it might not otherwise reach, because usually it's controlled by rivals and restricted to it's favoured sub cuticle niche.

Think fireweed on a burn site. Normally suppressed by other plants, but first in after a fire.


The point is, there's no change in the genome of C.utie, but it is given a chance to expand to new habitat by removal of natural controls.
 
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Soapy Sam said:
Harpyja- Yes it would- the bacterium has not acquired resistance from a few naturally resistant individuals, it has merely benefited short term by the removal of the competition-which is why most folk take the view that this is fundamentally not leading to selection.

But in the short term- hours, a day or so, that single survivor may expand into a significantly skewed population- and the larger than normal population of C.utie may then move onto other territory. If it's all over my hands six hours after I gelled them, I may be leaving it on door handles etc where it might not otherwise reach, because usually it's controlled by rivals and restricted to it's favoured sub cuticle niche.

Think fireweed on a burn site. Normally suppressed by other plants, but first in after a fire.


The point is, there's no change in the genome of C.utie, but it is given a chance to expand to new habitat by removal of natural controls.
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The door handle has its normal level of bacteria too so C. utie will have a far amount of competition and also will struggle to survive in its new envrionment. The fireweed analogy is not a good one because the fireweed is adapted to inhabit newly fire ravaged areas. C.utie is not adapted to door handles. Anyway surface inhabiting bacteria don't have a large food source and will not thrive.
 
As I recall from the last thread about hand sanitizers, there are no studies comparing HS to placebo.

The results of the most supportive study was that the more volume used, the less infections were transferred. But that didn't allow for the idea that those who use the most HS probably wash their hands more frequently too.

A DBPC study needs to be done before we even start arguing over viral susceptibility or even whether germs evolve to suit the HS environment.

Show me the DBPC !

eta: Perhaps the studies showing germ transfer via hands in the first place will show a valid connection. I'm sure food borne germs travel that way, along with 'food' for the germs. But what about respiratory germs? What kind of scientific proof is there of a connection of hands to infections anyhow?
 
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Southwind17 said:
So, my missus gives me some Dettol hand wash, you know, the type that you just squeeze on and rub around without rinsing off, that claims to kill 99.99% of germs, and I'm wondering: is it cynical to wonder whether the 0.01% are the dangerous ones, and in any case wouldn't it be better to wash and rinse? It sure feels better - psychologically!
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You are correct to question anything claiming the number of "germs" killed as a product feature. It really depends on which "germs" they tested when they make those claims for commercial products and typically that is listed somewhere in fine print with an asterisk. "Kills 97%*" yadda yadda... "*In laboratory tests." And of course that means on the germs they tested which is not usually mentioned.

Regardless, this is a good example of considering closely just what is the implication of what is being measured. The true measure one is looking for is, was disease spread prevented, not how many organisms were killed. Sometimes we do measure overall decrease in number of organisms as an indication of the effectiveness of a disinfectant, but in the case of hand soaps, that only matters on things like nurse's hands.

For the public, what you want is infection prevented.


Regardless of the setting, handwashing with soap and running water is the best option. Disinfectant hand soaps all have Triclosan in them. The added benefit outside of the health care setting is negligible. But you can hardly find hand soap without it.

For the waterless hand cleaners, they have great benefit where sinks are not available. You need to use one with >60% alcohol. Those with less are not effective enough.

These hand cleaners work best on relatively clean hands. They aren't going to be effective if your hands are grossly contaminated. The disinfectant just doesn't get through all the biomass.

They are not effective against all organisms. They are effective against influenza, but they may not be effective against Norovirus. (Short story: the jury's still out; long story: I'll share if anyone is interested.)


My favorite antiseptic/disinfectant advertising lies are Listerine and Lysol. You cannot disinfect the air with a spray. UV light, yes, but not a spray. The reason is the disinfectant can't possibly even come in contact with organisms in the air, let alone do so in enough concentration for enough time.

Listerine claims to kill germs. First, that is not useful. The good organisms in your mouth prevent the bad ones from taking hold. And the makers of Listerine go to great lengths to conceal the fact the alcohol is listed as an inactive ingredient. The concentration is too low to be registered as an antiseptic. Next time you see a bottle, check it out. You'll find the Inactive Ingredients buried in the paragraph that starts out with Active Ingredients.
 
Southwind17 said:
So it's generally quantity not quality that matters? But then some types are worse, like salmonella, yes?
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The overwhelmingly vast majority of microorganisms are not human pathogens.

In other words, germs are mostly your friends and only a few of them are your enemies.

However, hands tend to carry those few enemies into your eye, nose and/or mouth, so keeping one's hands clean prevents infections. Keeping a wound clean and keeping organisms out of your food also prevents infection.
 
skeptigirl said:
False, there are many organisms not killed by alcohol.
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In what doses? Most organisms can tolerate some concentration, and various yeasts can obviously handle percentages into the teens (hence wine). But many of the hand sanitizers have concentrations up around 60%. What reliably survives those concentrations?
 
Bikewer said:
I've listened to a couple of microbiologists on Science Friday who don't think much of the whole idea.
First, ineffective. Our skins are host to a rather extensive fauna and flora, many living below the external layers that these washes might affect.
Secondly, with only a tiny portion of bacteria even remotely dangerous, they fear that broad-spectrum and constant "de-germing" just eliminates the good guys and may actually promote more lethal strains.
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This is a grossly oversimplified view.

Disinfectant/antiseptics are slower to induce resistance than antibiotics and antivirals. The difference is in the latter case the organisms are actively growing. In the former, you are merely decreasing the numbers of slowly dividing bacteria and viruses which are not dividing at all.

It's the same with vaccines. Do those same scientists think vaccines are only going to induce resistant strains?


It is true one does not need to waste time and resources on disinfectant/antiseptics in all cases. It's become a marketing gimmick. But this is no reason to shy away from waterless hand cleaners. If people washed their hands effectively, did it more often and prepared and cooked food properly, over 2/3s of all infections would be eliminated. (The other 1/3 of the big 3 are STDs.)

Hand washing has proven benefit. Unlike disinfectants in the soap when you are already washing with soap and water, waterless hand cleaners have much added benefit.
 
Ziggurat said:
In what doses? Most organisms can tolerate some concentration, and various yeasts can obviously handle percentages into the teens (hence wine). But many of the hand sanitizers have concentrations up around 60%. What reliably survives those concentrations?
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This Antimicrobial Spectrum of Disinfectants chart will give you an idea.

Ethyl and isopropyl alcohol regardless of concentration haven't been used as a cold sterilizers for decades because there are so many organisms they do not kill.
 
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