Spontaneous Generation: The Life Cycle of Infection Control Rules


Let us be realistic: if microbes had not been so small, someone would have seen them long before, and Pasteur would not have founded modern science by discovering them. He would have been content to sterilize jams.

— Jean-Baptiste Botul, La métaphysique du mou (Éditions Mille et une Nuits, Paris, France; 2007)

I am a fundamental microbiologist because I was trained to be one. I have been teaching infection control, oral microbiology, immunology and, sometimes, what I consider philosophy since 1993. I like to think that was not so long ago, but my hair tells a different story! For the most part, I have lectured on infection control in Quebec, but I have also had the opportunity to do some teaching in the west as I try to make a modest contribution to the great guidelines fresco. You could say that I have helped contaminate dentistry with pain-in-the-neck microbiological facts.

One of my microbiology teachers, now a colleague and a dear friend, once told me that science is about facts, not about truth—something we forget all too often. We think that plain, solid facts give us absolute permission to go beyond them. There’s a rule of thumb in peer-reviewed scientific writing: do not make affirmations that are not supported by your data. As a reviewer, I am merciless in the application of this rule.

However, risk assessment sometimes insinuates itself into scientific facts. After all, the “precautionary principle” says that irrefutable scientific evidence of risk is not an absolute prerequisite for taking measures to protect individuals and society from that risk. It allows at least some side steps in the square dance of scientific writing.

Less than 200 years ago, many people thought that water, air and food contamination were the result of spontaneous generation of microbes. You left a piece of meat somewhere and, shazam!, microbes appeared from nowhere. No need for them to have a mother cell. Even some highly renowned scientists supported this view, until Louis Pasteur convincingly put the last nail in the coffin of this medieval belief.

I sometimes have the feeling that infection control rules have a life of their own. Once the engine is started, it seems to be unstoppable. We leave some manuscripts on the desk, surf the Internet a bit and, shazam!, a new rule spontaneously arises. “I don’t know what happened,” says the scientist, “I was writing something about the wonderful life of bacteria and suddenly a guideline took form.” Back in the 1960s, dentists would probably have laughed their heads off if someone had prophesized that one day they would have to sterilize everything, wear uncomfortable gloves and masks for hours and spend what seems like a lifetime bleeding waterlines like plumbers.

Our modern world is governed by laws. Most are probably of Murphy’s variety, but some are based on reasonable assumptions. I like to think that most infection control “laws” fit into this last category. Let’s take the sterilization paradigm, for example. Sterilizing every instrument that comes into contact with oral tissues, irrespective of the invasiveness of the procedure, is sound and reasonable. But, trying to adhere strictly to the Spaulding classification would be like separating letters in alphabet soup. Is this an A or a D? Critical or semi-critical?

We know that heat will damage materials in the long term, and we are well aware that sterilization and strict obedience to the “do-not-reuse-single-use-items” principle represent a significant burden on clinic finances. The rationale for sterilizing reusable items is based on science, not truth or bullet-proof demonstration. When I am asked to provide solid proof that a nonsterile handpiece will infect a patient, I don’t search frantically for a tailor-made paper on handpieces or 2-part dental mirrors. A few peer-reviewed papers on endoscopes or transrectal ultrasound prostate biopsy devices are more than sufficient to convince anyone that a sloppy job of cleaning or sterilizing can have uncomfortable consequences. These are raw facts, not truth. If it is truth we are interested in, we would be better off in a philosophy course. And even then.

Biological Indicators: How Good is a Police Endospore in a Bag if the Bad Guys are Playing Cards in a Private Club?

I have shown, and here is the proof sir, that I can achieve sterile status by squashing and ripping bacteria apart with my new sterilizer. The survivors will starve to death. My device is so effective that monitoring will be pointless.

— An inventor in my office (1996)

Biological indicators are not magic wands. They do not prove product sterility. No indicator can promise that. Sterility is a statistical calculation. The purpose of biological indicators is to verify whether a sterilizer can produce sterile conditions. If the user commits several sins during instrument processing (from cleaning through storage), sterilization or its preservation are deemed to fail no matter how good or expensive the sterilizer is. Failure to sterilize one pack in a full load may be the end result, even if you spore test your steam cooker 10 times a day.

For general dentistry, I see no rationale for daily spore testing. After all, the Association for the Advancement of Medical Instrumentation says that it is acceptable to do weekly testing, and the United Kingdom’s Medical Devices Agency does not even recommend routine biological indicator monitoring of the sterilization process. We have found that fewer than 5 in 100 spore tests fail. Eight out of 10 of these failures are the result of poor understanding of the sterilization process: overloading the sterilizer chamber to the point where one has to push on the door with all one’s might to shut it tightly or quickly close the door to prevent items from falling out is but one of these sins. Testing your sterilizer with a gazillion spores will not give you any useful information about the status of a soiled instrument you have decided to sterilize when you know that soil can prevent steam from reaching all the nooks and crannies of the instrument in question. In type N sterilizers (classic), steam has a harder time penetrating loads than in type B (pre-vacuum) models where the steam is sucked into every package, even into the small lumens of handpieces. Daily spore testing will be a poor indicator of this.

Routine daily testing may result in overconfidence. It is costly and offers no corresponding benefit to the user or patient. If quality assurance of the sterilization process is the concern—and I think it is—internal class 5 chemical integrators would be more cost- and time-effective, notably by providing results in real time. Weekly, or at the very least monthly, spore testing would still be required to check the sterilization “power” of your sterilizer, but integrators would give you more useful information on the ability of “quality” steam to penetrate each package in a given load, compared with a single spore strip randomly placed in the sterilizer.

Cherish a Circle and It Becomes Vicious: the Unexpected Drawback of Scientific Citations

It’s alive! It’s alive!

— Victor Frankenstein

Reverting to less-severe infection control guidelines is an almost impossible task. It sometimes seems that guidelines can only get stronger and unbearably unpleasant through generations of offspring. “Oops, I went a bit too far, sorry.” Once a guideline is published, it becomes common knowledge and, thanks to the Internet, it circles the earth 20 times in less than 48 hours. The citation cascade starts, inflates and ends up out of control. The guideline is conflated with common knowledge and becomes almost impossible to undo without incurring the wrath of the guardians of conventional wisdom.

For this reason, we must be excessively prudent when concocting a rule, law or guideline. Once it is in “the big book” you can be pretty certain that someone somewhere will use it without questioning it. In French, we say, nobody can be against virtue. Yet this is probably the biggest trap we can unknowingly fall into. Because we cannot oppose virtue, we may have the tendency to wash our hands of certain delicate matters and shovel the problem into someone else’s backyard. We all, myself included, do that once in a while.

Don’t get me wrong; I still strongly believe in the merits of infection control rules to protect both patients and practitioners. If this were not the case, I would not be teaching and obeying those rules. Nor am I about to start questioning all of them. But I believe that the precautionary principle should not be used automatically to justify new “laws” without carefully examining the potential drawbacks and consequences they may have, both inside and outside our immediate sphere.

You can tell whether a man is clever by his answers. You can tell whether a man is wise by his questions.

— Naguib Mahfouz, writer


Dr. Barbeau is professor of microbiology in the faculties of dentistry and medicine, University of Montreal, Montreal, Quebec.

Correspondence to: Dr. Jean Barbeau, Faculty of dentistry, University of Montreal, P.O. Box 6128, Station Centre-ville, Montreal, QC H3C 3J7. Email: jean.barbeau@umontreal.ca

The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the Canadian Dental Association.

This article has been peer reviewed.