Perils of over-sanitation

Abstract

The widespread practice of sanitation, once heralded as one of the biggest leaps medicine has ever had and saved millions of lives, resulted in a general averse towards microbes, and ultimately lead to over-sanitation in the latter half of 20th century. It was only recently that the biggest organ of human beings has discovered- human microbiome. Recent studies have revealed that changes in the human microbiome are associated with a large number of physiological and lifestyle diseases such as obesity, diabetes, heart disease, cancer, Alzheimer’s disease and even human behavioural diseases such as depression and autism. Like the rest of our organs, transplantation of human microbiome through faecal transplantation has various ethical and legal ramifications. Argued in this essay is what humans need is an evolution-informed fine balance; neither too much nor too little but just right sanitation for which original recommendation of Semmelweis still holds the key.

The term sanitation or personal hygiene might bring you mental images of Dettol and other antiseptic products. Importance of sanitation remained virtually unknown until Ignaz Philipp Semmelweis, the 19th-century Hungarian doctor, who introduced the simple practice of washing the hands of medical professionals to drastically reduce incidences of childbed fever- a lethal form of bacterial infection originating in the hospitals. The story behind that finding is indeed illuminating [1]. He noticed a very high mortality rate among women in the maternity ward of Vienna General Hospital where he worked. Women who went to the hospital for childbirth were far more likely to die from the puerperal sepsis-a lethal form of bacterial infection post-delivery- than the women who had childbirth in their homes. Even the homeless women who delivered on the streets were far more likely to survive than those who went to the hospital to give birth! He noticed the difference in death rates between different wards within the hospital; the wards in which doctors and medical students attended the delivery had almost five times mortality rates than the ward with midwives. When his own friend, a male pathologist, died of the same disease, he conjectured that the disease might have been spread by medical professionals who also attended post-mortem procedures. Note that during those days, the role of microbes in causing the disease was not known. According to Semmelweis, doctors transferred an invisible death particle from dead bodies to healthy women causing them to die, an approximation scientifically sound even today (what he was referring as the particle is the microorganism, especially bacteria). He instructed the medical professionals to wash their hands before attending the delivery, a simple practice that drastically reduced the mortality rates.

The term antisepsis refers to the practice of using antiseptics to ward off microbes that cause various diseases. Antisepsis came in existence with Semmelweis and since then hailed as a first-line defence against microbial infection; as Benjamin Franklin famously said: “​An ounce of prevention is better than a pound of cure”. Semmelweis’ contemporary, the British physician Joseph Lister is considered as the pioneer in antiseptic surgery and antisepsis, as he introduced various antiseptic compounds that are applied on the skin to reduce microbial infections. The mouthwash brand Listerine is inspired by Joseph Lister, indeed. Since then, the use of antiseptic compounds has tremendously increased throughout the world. While antiseptics are applied on the skin, an entirely new class of compounds produced by microbes to kill other microbes, the so-called antibiotics got serendipitously discovered by Scottish microbiologist Alexander Fleming. Antibiotics too became widely used throughout the world to fight the bacterial infections, and indeed saved millions of lives worldwide to herald its discovery as one of the most profound in the history of science. Yet another class of compounds, disinfectants, were also developed that can be used on surfaces to ward off the microbes. Alcohol-based antiseptic hand sanitizers appeared in the markets since the 1980s and its use have now become a quotidian affair among many of us around the world. Over these years words ‘microbe’ and ‘bacteria’ became synonymous with ‘germ’-with negative connotations. Overprotective parents restricted their children from playing with dirt and dirty surroundings. The children increasingly became living in their confinements of houses and schools with limited interaction with other children of diverse socioeconomic backgrounds. The impact of widespread use of antiseptics, antibiotics, disinfectants and the general averse with dirt were indeed profound.

It was only in the 20th century that a battery of studies revealed the gnotobiotic animals, animals that were grown in aseptic conditions (i.e., since birth, never exposed to microbes), were highly likely to get the infection and die when they were introduced to the outside world. Of course, we all know that expensive purebreds of cats and dogs could not survive when put on the streets; thousands of years of domestication made them adapted to human dwellings such that they became dependent on human beings for their life. The role of the immune system is known since the time of Edward Jenner who first introduced vaccination in the 18th century. The vaccination worked because it exposed our bodies to the sub-lethal doses of (or non-living remains of) the pathogens or its close relatives.

Today the science informs us that the periodic exposure to the infectious agents are essential for our immune system to develop its own immunity against these microbes and allergens. In a sense, exposure to various microbes is very essential as microbes act as ‘teachers’ of the human immune system. Microbes educate our immune system to develop various antibodies that confer resistance against them. In one sense, this is similar to how bodybuilders increase their muscle mass; they periodically stress their muscles by resistance exercises. Astronomers who return to earth after spending a few months in International Space Station loses much of their muscle because virtually there are no stresses, not even gravity. Modern lifestyle with spending much of our times inside hermetically sealed spotless indoors made us similar to those gnotobiotic animals with decompensated immune systems; the moment we face the real world, even an innocuous infection (for example, a common cold) would turn out into a deadly and life-threatening tragedy. The so-called ‘hygiene hypothesis’ postulate that overly clean environments, especially during childhood, would lead to decreased immunity later in life. Today we know that not all bacteria are pathogenic. Our own body harbours a rich diversity of bacteria and other microbes. Estimates suggest bacteria outnumber cells in our bodies by almost ten times; total cells in the human body is around 10 trillion, while that of bacterias living on and inside our body is 100 trillion, the far majority of them live inside our gut (intestine). Human gut alone harbours around 1000 species of bacteria which together constitutes 100 times more genes than that of our own cells [2]. Many new species of bacteria are being discovered right from human bodies and many of which are being proven beneficial. For example, a new species of Lactobacillus found in human vaginal microbial communities yielded a novel antibiotic named lactocillin [3]. Scientists call these normally living bacteria as “microflora” (in a strict sense, microflora is a misnomer as flora refer plants, a vast majority of bacteria are non-photosynthetic), or “microbiome” or “microbiota”.

Prevalence of C-section (Cesarean) deliveries in modern times have led to associated problems as well. As children born out of C-sections had never been exposed to the mother’s own natural microbial environment of her vaginal canal, these children’s microbial constituents tend to be drastically different from their mothers. Studies indicate that the risk of developing various ailments such as obesity, autoimmune diseases such as type-1 diabetes and allergic diseases such as asthma are much higher for children born out of C-sections than the ones in normal deliveries [4]. Yet another problem of modern times is the unnecessary and prolonged use of antibiotics. The major impact of the usage of antibiotics is that it not only kills the pathogens, but also the normal microflora. While antibiotics are only effective in treating bacterial infections, many people take them during viral infections like common cold too, which is rather unnecessary and of no use. Injudicious antibiotic use led to the rampant issue of the emergence of drug-resistant microbes, for example, Multi-Drug Resistant Tuberculosis. In addition, as antibiotics kill the normal microflora, the true impacts of which remains unknown as of this writing.

Many recent studies suggest that microflora is essential to maintain normal physiology of human bodies. When these microflorae are impacted through, for instance, by injudicious use of antibiotics, we get a number of diseases. The surprising twist is that most of these diseases were previously thought to be physiological or lifestyle, with no involvement of bacteria. Recent research has revealed that change in gut microbiome constitution is involved with a number of human physiological and lifestyle diseases such as cancer, heart disease, Alzheimer’s disease and diabetes. Reason being these normal bacteria have protective roles, preventing the development of these diseases. When these microbes die, the protective effects are removed and we develop these diseases. The gut microbiome could change not only in response to antibiotic treatment but also in response to the kinds of food that we eat. For example, a landmark paper in 2014 published in nature revealed that when subjects take artificial sweeteners like aspartame (and beverages in which these sweeteners are used, like ‘diet coke’), it drastically changes the gut microbiome such that the subjects develop insulin resistance, the so-called Type-2 Diabetes [5]. In a sense, this paper revolutionized the way we understand our diseases and our own microbes that are living inside the guts- an association perhaps as old as the humanity itself. People substituted artificial sweeteners in place of natural sugar for preventing the chance of developing diabetes; ironically these same artificial sugars caused them to develop diabetes! New research suggests that fibrous foods are generally good for the gut microbiome, compared with processed foods and refined carbohydrates. Periodic and intermittent fasting is also proved to be beneficial to maintain a healthy human gut microbiome. Vermiform appendix, a pouch-like an organ in the human gut that previously thought to be a vestigial organ (useful in past, useless now), is now thought to function as a refuge for several useful gut microbes. Its unnecessary removal, for example, as practised by Antarctic expedition members before visiting Antarctica, might do us far more harm than benefits.

Perhaps you have heard the term ‘the gut feeling’, a feeling in our guts at times when we have anxiety or psychological stress; expecting bad news, during job interviews etc. But why gut? Common sense tells us that human emotions have more to do with our brains rather than guts. However, recent research has revealed a surprising connection between the gut microbiome and human behaviours [6]. Studies have revealed how a change in microbiome causes a number of behavioural and psychological diseases, including depression, ADHS (Attention Deficit Hyperactivity Disorder), amnesia, cognitive impairments, and autism. Signals from the human gut induced by its microbiome transmit directly to our brain via the vagus nerve.

Scientists these days refer to human gut microbiome as a forgotten organ of human bodies, the largest organ indeed [7]. Although remained essentially unknown until recently, the gut microbiome virtually affects all facets of human life and physiology; perhaps one of the most crucial organs in our body. Reinstating lost microbiomes (for instance, in response to long-term antibiotic usage) is an active area of research in contemporary science. Probiotics such as curd and other supplements containing good bacteria had been proposed as one way to replenish the microbial flora, however, recent research suggests these are not as effective as earlier thought them to be. A newer development is the introduction of the fecal transplant; a transplant like any other organs. Faecal transplant is transplanting a compromised patient’s gut with faeces from a healthy donor. The faeces could be implanted via the anus or orally as a capsule. Faecal transplantation could prove to be an effective therapeutic intervention in lifestyle diseases; for example, a diabetic patient can take capsules containing faeces from non-diabetic donors. Legal and ethical ramifications of this procedure could be enormous. For example, how legal for an athlete ‘take’ the faeces from a top athlete to increase her or his performance? Would it be regarded as a form similar to doping and deemed illegal? Not only faecal transplantations, but the physiological function of a number of human behaviours also become significant in light of our invisible microbiome. For example, a handshake not only functions as a goodwill gesture but also act as a social mechanism that exchanges our microbiomes. A 10-second kiss exchanges 80 million microbes between the partners, as revealed in a 2014 study published in the journal Microbiome [8]. Even seemingly simple conundrums such as “who am I?” would become significant in light of human microbiome that far outnumbers our own cells, and leads to existential crises! The moment we die, human gut microbiome progressively gets replaced with ‘necrobiome’ as the time goes. Gut microbial community structure could reveal the time of death with great precision such that this procedure is now employed in forensic medicine.

All these findings point the finger in the same direction; over-sanitation is indeed highly detrimental to our bodies. As microbes do us more good than harm, blindly killing them all would remove many beneficial species, leading to the development of diseases such as cancer and heart diseases and behavioural conditions such as depression and autism. Bathing in a Dettol solution or using a disinfectant soap would remove many good bacteria from our skin and thereby does us more harm than good. However, adopting a lifestyle with no sanitation would effectively pull us back to the time of Semmelweis; those dark days of infectious diseases and high mortality rates. What we need is a fine balance; not too much a sanitation, not too little too, but just right, as in the Goldilocks fable. A good rule of thumb is to stick with Semmelweis’ original recommendation, good old handwashing with a bar of soap (studies have revealed 30 second-hand washing with a soap to be more effective than hand sanitizers), and drying the hands on a towel (studies have revealed that hand drying on a towel- paper or cloth- be more effective than drying with electric hand dryers). We should also periodically emulate the life our great ancestors in African savannah had to go through; for example, barefoot running, intermittent fasting and so on. That would also mean we better increase our social interactions by visiting public places often; such as a crowded train, coffee shops and so on rather than spending our lives in social isolation under the comfort of the air-conditioned indoors and cars. After all, most of the microbes are our friends; we should get back those long lost friends through more social amalgamation.

Suggested Reading

1. Carter, K. C., & Carter, B. R. (2017). Childbed fever: a scientific biography of Ignaz Semmelweis. Routledge.
2. Huttenhower, C., Gevers, D., Knight, R., Abubucker, S., Badger, J. H., Chinwalla, A. T., … & Giglio, M. G. (2012). Structure, function and diversity of the healthy human microbiome. Nature, 486(7402), 207.
3. Donia, M. S., Cimermancic, P., Schulze, C. J., Brown, L. C. W., Martin, J., Mitreva, M., … & Fischbach, M. A. (2014). A systematic analysis of biosynthetic gene clusters in the human microbiome reveals a common family of antibiotics. Cell, 158(6), 1402–1414.
4. Arrieta, M. C., Stiemsma, L. T., Amenyogbe, N., Brown, E. M., & Finlay, B. (2014). The intestinal microbiome in early life: health and disease. Frontiers in immunology, 5, 427.
5. Suez, J., Korem, T., Zeevi, D., Zilberman-Schapira, G., Thaiss, C. A., Maza, O., … & Kuperman, Y. (2014). Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature, 514(7521), 181.
6. Dinan, T. G., Stilling, R. M., Stanton, C., & Cryan, J. F. (2015). Collective unconscious: how gut microbes shape human behavior. Journal of psychiatric research, 63, 1–9.
7. Baquero, F., & Nombela, C. (2012). The microbiome as a human organ. Clinical Microbiology and Infection, 18, 2–4.
8. Kort, R., Caspers, M., van de Graaf, A., van Egmond, W., Keijser, B., & Roeselers, G. (2014). Shaping the oral microbiota through intimate kissing. Microbiome, 2(1), 41.

The article appeared in Dream2047