Japan's largest infectious disease
The main component of gastric juice is hydrochloric acid, so it is acidic. On an empty stomach, the pH is between 1 and 2, similar to the strong acid level of a car battery. When it drops to 4 to 5 after eating. Gastric juice helps absorb nutrients by digesting proteins, fats and carbohydrates, while preventing infection by killing disease-causing bacteria and viruses.
No one thought that there were still bacteria living in such a highly acidic environment. This bacterium is helicobacterpylo⁃ri, or "Helicobacter pylori" for short. Now, it has gained the status of "the largest infectious disease among the Japanese".
"helico" means "spiral" and is the same etymology as helicopter. "bacter" means "bacteria". And "pylo⁃ri" means the exit of the stomach "pylorus". Because its shape is twisted 2 to 3 times and has 4 to 8 flagella, it is called Helicobacter pylori.
Since the 19th century, bacteria with spiral tails have been found in the stomach, but are thought to be bacteria that happen to be "right in the field". University of Western Australia professors Robinwarren and Barryj. Marshall are two researchers who broke with that common sense.
They extracted Helicobacter from the stomach for culture, and after hard work, they finally succeeded in 1982. This bacterium grows much more slowly than ordinary bacteria, and culture and reproduction are difficult to confirm. It happened to be Easter break, so the Dish was left on for five days, and the bacteria began to proliferate.
Barry Marshall has experimented in his stomach to prove that drinking bacterial culture solution can cause gastritis, and that the use of antibacterial agents to remove bacteria can cure gastritis. At that time, the discovery of this bacterium attracted little attention, because gastritis and stomach ulcers were thought to be caused by stress. Later, it was clear that this bacterium was the culprit of stomach cancer, stomach ulcer, duodenal ulcer, and chronic gastritis. The two were awarded the Nobel Prize in Physiology or Medicine in 2005. In a physical exam, there should be many people who should be recommended to check and eliminate this bacterium.
The true face of Helicobacter pylori
In fact, the human body is full of microbes called "normal flora." Many of these strains have an older evolutionary history than humans. As the name suggests, normal flora are bacteria that live in the human body on a daily basis. It is almost everywhere in the human body.
In particular, parts exposed to the external environment, such as the skin, mouth, eyes, nose, airway, urinary tract, anus, and female genitalia, always have bacteria attached. When a person is in the mother's womb, he is in a sterile state, but at the same time as childbirth, he is exposed to bacteria, which increase in the body. Helicobacter pylori is one of these normal flora.
According to the analysis of Associate Professor Susan Hughes of Brown University in the United States, from the human body parts where the normal flora of the human body has been found so far, there are 7947 species on the tongue, 4154 species in the throat, 2359 species on the back of the ear, 33627 species in the large intestine, and 2062 species in the entrance of the female genitalia.
From the mouth to the anus, there are a large number of bacteria in the intestine, such as E. coli, lactic acid bacteria, butyric acid bacteria (also known as butyric acid bacteria), and Clostridium Wesperi (Clostridium gas-producing Clostridium) that produces stinky farts. Pneumococcus, pneumococcus, and pneumocycilli are present in the trachea from the throat to the lungs. On the skin, there are Propionibacterium acnes, which causes pimples (acne), Malassezia, which causes dandruff, Vitiligo, which causes beriberi. Among the bacteria that reside in the female genitalia, representative ones are Candida and Bifidobacterium.
It is estimated that there are 10 billion bacteria in the human mouth and more than 1 trillion bacteria on the skin, and in the human body, the total number is more than 10 times the number of cells that make up the human body, that is, tens of billions. The total weight of the normal flora is 1300 grams, which is equivalent to the weight of the brain.
Genetic deciphering in recent years has revealed that the microbiome in the gut has a total of 3.3 million genes, equivalent to 100 times the number of human genes. Some of them play a useful role for us in various forms.
Normal flora that coexist and thrive
Normal flora repels and symbiosis in the body, while maintaining a certain degree of harmony and coexisting and thriving. Animals develop a close relationship with normal flora. In particular, in the intestines where 100 trillion bacteria reside, compared to an amazingly developed plant ecosystem, it can be called an "intestinal bacterial flower bed". Because about half of the stool is intestinal bacteria or its corpse, it can be seen that its number is not ordinary.
Without E. coli, we can't survive. It helps break down polysaccharides and starches and produces vitamins and hormones associated with the accumulation of fat. It is also necessary for the development of the immune system and prevents the fulminant reproduction of harmful bacteria.
The world is studying "stool microbial transplantation", that is, transplanting intestinal bacteria from healthy people into patients with intestinal diseases and developing therapeutic drugs made from intestinal bacteria. It is said that it has a certain effect on the treatment of malignant enteritis, such as ulcerative colitis and allergic bowel syndrome.
Humans and normal flora do not always coexist peacefully. These normal flora live in the original boarding area, and in a healthy state of the human body, it almost does not cause harm to people. However, even if there is no harm in the intestines of E. coli, when it enters the bladder site, it can cause cystitis. That is, E. coli has an ingenious mechanism of reconciliation, as long as it lives in the intestine, it is not considered a foreign body.
In addition, when unfamiliar "wild bacteria" enter the human body or the human body loses immunity and falls into an unprotected state, some normal bacteria will suddenly show their fierce appearance. These bacteria, which usually seem harmless but suddenly become frightening, are called opportunistic pathogens.
When older adults with weaker immunity contract the flu, bacteria in the respiratory tract can cause pneumonia. Patients who take anti-cancer drugs or antibiotics for a long time are often found to have abnormal growth of normal flora. Pneumocystis pneumonia, which is unique to AIDS patients, is caused by normal flora that is harmless in a healthy state.
More than 1 in 5 Japanese people suffer from "allergic dermatitis". There are various theories about why. There is some speculation that it is related to a protein produced by a bacterium in the normal flora of the skin. In addition, experiments have confirmed that antibiotics killing beneficial normal flora can suddenly make people fat. Over the past half century, the number of obese people in the United States has increased threefold. Some researchers claim that in addition to excessive intake of carbohydrates and lipids, it is also linked to antibiotics.
Discover some interesting things in recent years. The research team of Professor Cecil Lewis at the University of Oklahoma in the United States investigates the gut bacteria of mummies found in the Chilean desert. The results show that the normal flora in the human body between 8,000 and 1400 years ago was very similar to that of people in rural Africa today, but very different from modern people living in cities. This suggests that in the past everyone had a similar normal flora, but these normal flora have changed due to medication and diet.
The north-south problem of bacteria
Curiously, in Europe, the United States and African countries, there are many people who are infected with Helicobacter pylori like Japan, but there are very few stomach cancer patients. Even in East Asia, the further south you go, the lower the incidence of stomach cancer. According to the World Health Organization in 2008, the world average stomach cancer incidence is 14.1 per 100,000 people, compared with 30.0 in East Asia. That's overwhelming compared to 10.3 in Europe and 4.2 in North America.
Stomach cancer is concentrated in East Asia, with the worst 5 countries ranking 41.4 per 100,000 population in South Korea, 34.0 in Mongolia, 31.1 in Japan, 29.0 in China and 28.6 in Guatemala.
Professor Tohihiko Fujioka of Oita University School of Medicine and others have found that the gene types of Helicobacter pylori are different in Western and Asian countries, and the gene types of Helicobacter pylori in Asian countries are not necessarily the same. This difference is likely to lead to a difference in the incidence of stomach cancer.
More than 90% of helicobacter pylori, which resides in the stomachs of East Asians, has specific genes that cause inflammation or atrophy of the gastric mucosa leading to stomach cancer. However, in European and American Helicobacter pylori, the holding rate of this gene is only about 30% to 40%.
Helicobacter pylori, because it attacks the cells of the stomach wall, its damage accumulates and easily leads to stomach cancer. And, together with other risk factors, the risk of stomach cancer increases. People who were "bacteriaged and smoking" had an 11-fold higher risk of stomach cancer than those who were "sterile and non-smoking." Even compared to people who "smoke without sterility", the risk is 1.6 times higher. Similarly, people who are "carrier and have high blood sugar" have a 4 times higher risk of stomach cancer than people who are "sterile and have a normal blood sugar value", and even 2 times that of people who are "carrying bacteria and have a normal blood sugar value".
Helicobacter pylori tells the story of human migration
From the mutations in the Helicobacter pylori gene in different populations, human footprints can be inferred.
Bacteria grow fast, and genetic mutations take much less time than humans, making it easy to track their evolutionary footprints. A team of scientists from the University of Cambridge in the UK and the Max Planck Institute in Germany collected Helicobacter pylori from different races and ethnic groups to compare their genes and simulate their evolution with molecular clocks.
According to the simulations, the genetic diversity of Helicobacter pylori carried by Africans decreased with increasing distance from East Africa. In other words, the age of differentiation gradually becomes closer. Based on this, the hypothesis was made that the ancestors of Helicobacter pylori sneaked into the stomach of humans, set out from Africa, and spread to North and South America after passing through Central Asia, Europe and East Asia.
During the migration movement, Helicobacter pylori also underwent various genetic mutations, which can now be divided into seven subtypes. ●European type (Europe, Middle East, India, etc.) ●Northeast African type ● Africa type 1 (West Africa) ● Africa type 2 (southern Africa) ● Asian type (North India, Bangladesh, Thailand, parts of Malaysia, etc.) ● Sahur type (Australian Aboriginal, Papua New Guinea) ● East Asian type (Japan, China, Korea, South Pacific, American Aboriginal, etc.)
In North America, various subtypes were brought in, reflecting situations such as immigration and the slave trade from all over the world.
In addition, Professor Yoshio Yamaoka of Oita University School of Medicine analyzed the Helicobacter pylori carried by different races. According to the distribution of Helicobacter pylori, the magnificent migration routes of humans are mapped. Based on this, Helicobacter pylori spread from 58,000 years ago when it left Africa and reached Asia 30,000 years ago. From there, it spread to Southeast Asia and the Pacific Ocean about five thousand years ago.
Another route runs from Asia through the Bering Strait, then a land bridge, stretching south from North America to South America. Among Africans and Japanese, the genetic sequence of Helicobacter pylori differs by 50%, while the Japanese and indigenous peoples of North America are very similar.
The age of human migration, calculated based on mutations in Helicobacter pylori, is quite consistent with the results of the study of human migration based on anthropology and the age of branches of different languages based on linguistics.
Helicobacter pylori of the European and African types is less pathogenic than the East Asian type. In general, when pathogens evolve with a parasitic host, they gradually weaken pathogenicity and seek a path to coexistence with the host.
However, with the migration of humans, the pathogenicity of Helicobacter pylori has become more intense. Originally, in the era when the East Asian type had just evolved, its pathogenicity should be weaker than that of Africa and Europe. The rationale for this is unclear.
Is it an infection or an allergy?
Professor Martin Brast of New York University believes that because Helicobacter pylori has long been parasitic in humans, it has some kind of existential significance. Originally, Helicobacter pylori was a normal flora that everyone has. In developed regions, the number of infections has decreased so much, and the reason is believed to be that people grow up in clean environments and receive antibiotic treatment from childhood.
It is said that during childhood, if you grow up in an unhygienic environment that may be infected with bacteria and parasites, it is difficult to develop allergies later on. Professor Joseph Lidler of the University of Salzburg in Austria proves this. For more than a decade, the professor has conducted a comparative study of the incidence of allergies in children of farmers and non-farmers.
Its results show that compared to children of non-farmers, the incidence of hay fever in children of farmers is only one-third, and the incidence of asthma is only one-in-four. Aspects such as living environment and diet were investigated, but there was not much difference. Studies have found that even children of non-farmers have a low probability of allergies if they have more exposure to livestock, and are less likely to occur if they are often exposed to bacteria in an environment like a livestock barn.
A study in the United States also found that children who had more contact with pets had a lower risk of allergies than children who had never kept a pet. However, some doctors believe that pets can aggravate allergies.
In other surveys, it has also been found that children who have experienced some kind of infection are less likely to have allergies. Epidemiological surveys have also pointed to this phenomenon, which has been discussed since the late 1990s. This is known as the "hygiene hypothesis", the English is "cleanhousesyndrome" (clean house syndrome), and the "friend loss hypothesis" (which means that there is no prevention of allergies to friends). While some are negative and skeptical, there has been a growing body of research findings in recent years supporting this hypothesis.
Professor Brast studied the relationship between childhood asthma and Helicobacter pylori. Based on its results, people infected with Helicobacter pylori were less likely to develop asthma, and evidence of Helicobacter pylori inhibiting other allergies was found. This phenomenon is common only in childhood and is difficult to see in adults. The professor noted that especially in childhood, Helicobacter pylori has great benefits for suppressing allergies.
Surge in allergies
Many people believe that "bacteria are bad". Japanese people, in particular, are surrounded by antibacterial products, disinfect what their hands touch, and encourage frequent hand washing. Japan is the most "hygienic" country in the world.
Helicobacter pylori originally coexisted with humans, and despite the risk of stomach cancer, it was not a big problem in an era when lifespan did not reach 50 years. However, because people live longer and create an overly hygienic environment, the symbiotic relationship with bacteria has changed.
In the first half of the 20th century, the three leading causes of death in Japanese people were infectious diseases such as "pneumonia", "gastroenteritis" and "tuberculosis". However, after the second half of the 20th century, with improvements in nutritional and hygiene conditions, treatment and advances in the medical system, these diseases rapidly declined, and the causes of death at the top of the ranking were replaced by "cancer" and "lifestyle diseases". In other words, inversely proportional to the prevention and treatment of infectious diseases, allergies are increasing dramatically.
According to the Allergic Disease Control Report (2011) of the Ministry of Health, Labor and Welfare of Japan, patients with allergic rhinitis, including hay fever, account for more than 47% of the national population, and allergic dermatitis (specific dermatitis) reaches about 10%. One in two people is allergic, and allergies become a national disease. The World Health Organization pointed out in the "Allergy White Paper" that there is a trend of increasing allergies worldwide, and 30% of the world's population has some kind of allergy.
Ironically, infections with infectious diseases have decreased, but this time they are suffering from allergies. The relationship between infection and allergy is like a seesaw, one side goes down, and the other side rises.
(This article is excerpted from "Don't BeReavement! Isn't it an Infectious Disease", shi hongzhi, translated by Wan Yi and Zhao Yifei, Shanghai People's Publishing House, January 2021, first edition, price: 68.00 yuan)
Source: China Reading Daily