Mycoplasma pneumonia, why are there so many cases suddenly?

Recently, many places in China are experiencing a high incidence of Mycoplasma pneumoniae infection. The number of patients with respiratory tract infections in major hospitals continues to rise, especially among teenagers and children. The demand for antibiotics such as azithromycin has increased. Among them, "Mycoplasma pneumonia" has become a high-frequency word in the parent circle.

Mycoplasma pneumoniae under a microscope. Source: Wikipedia

Mycoplasma is a prokaryotic organism that is similar to bacteria but not classified as such. This microorganism is not a common name and was first discovered only 120 years ago.

Bovine pleuropneumonia

In the early 18th century, Europe's livestock industry experienced significant growth and transformation through improvements in land use, livestock breeds, management practices, and market interventions, making an important contribution to Europe's food supply and economic growth.

In particular, the grazing of cattle, sheep and horses has diversified agriculture, which was once dominated by crop operations.

But during this period, cattle in Germany and Switzerland began to show symptoms such as fever, coughing, and reduced milk production. This disease, known as "bovine pleuropneumonia" or "lung rot," quickly spread and had a great impact on Europe's animal husbandry and economy. Infected cattle usually show acute respiratory infectious diseases, and autopsies show marbled lungs and serous fibrinous pleuropneumonia.

Because the symptoms of this disease are very similar to pneumonia, it is believed that there is the same pathogen. But strangely, people at that time did not observe the pathogen that causes bovine pleuropneumonia, nor were they able to successfully isolate and culture it.

It was not until 1898 that French microbiologists E. Nocard and ER Roux isolated a special microorganism from bovine lung tissue for the first time while studying bovine plague. This microorganism lacked a cell wall and was significantly different from ordinary bacteria.

Nocard also found that the microorganisms were able to grow and reproduce on non-living (cell-free) artificial culture media and that their diameters were relatively small, ranging from 50 to 300 nanometers. These findings sparked great interest in the scientific community.

They named these newly discovered microorganisms "pleuropneumonia-like organisms" (PPLO). The two microbiologists also observed that when these organisms were grown on culture media, they exhibited different morphologies.

However, the name of this type of organism was not determined at the beginning of its discovery. It was not until 1910 that Borrel et al. named it Asterococcus mycoides. However, as the research deepened, people found that this organism had unique biological characteristics, and they were more convinced that this microorganism was not an ordinary bacterium and needed to be reclassified and named.

In 1929, Nowak believed that these microorganisms had similar properties to fungi, so he used the name mycoplasma (myc comes from the Greek word mykes, meaning fungus or mold). Although it was later confirmed that it was a prokaryotic organism, which was very different from fungi, the name was still retained; and in the 1960s, the academic community reached a consensus and adopted this name to replace the earlier PPLO, which is translated into Chinese as mycoplasma.

Mycoplasma

In 1957, in the 7th edition of Bayle's Manual of Identification of Bacteriology, microbiologists classified these organisms into a new order Mycoplasmata. In 1967, Edward et al. proposed that these organisms should be classified into a new class, Mollicutes (Latin mollicutes, mollis means soft and flexible, and cutis means skin, because these organisms lack a clear cell wall).

More than 200 species of mycoplasma-like microorganisms have been found to be associated with sewage, plants, animals, insects, humus, hot springs and other high-temperature environments.

At least 11 serologically and biologically distinct mycoplasmas have been found in humans. For example, oral mycoplasma and salivarius mycoplasma can be found in almost every healthy adult; human mycoplasma accounts for a large proportion of sexually active adults; oral, pharyngeal, tonsil, urogenital tract inflammation and primary atypical pneumonia may all be caused by mycoplasmas.

Mycoplasma has been found to have the following characteristics:

Image source: Earth Knowledge Bureau

The pathogen that spread widely this time is Mycoplasma pneumoniae (M.Pneumonia) of the Mycoplasma genus. The disease may occur in all seasons of the year, but is more common in autumn and winter.

Mycoplasma pneumoniae is mainly transmitted through droplets, and infected people are the main source of infection. The incubation period of the disease is 1 to 3 weeks. The most common symptom after onset is tracheobronchitis, accompanied by dry cough or coughing up phlegm. Many patients also experience non-specific symptoms including headache, sore throat, flu symptoms and otitis media; a few patients will develop pneumonia or extrapulmonary complications.

The above symptoms are similar to those caused by a variety of bacteria or viruses. There are currently no specific symptoms that can be used to distinguish which microorganism is infected. To confirm mycoplasma infection, special laboratory tests (such as PCR, etc.) are required.

Image source: Earth Knowledge Bureau

Unlike other bacteria, mycoplasmas do not have cell walls, so antibiotics that act on the cell walls are ineffective against mycoplasmas (such as the penicillin and cephalosporin that are familiar to the public).

Currently, the first choice of clinical treatment for mycoplasma pneumonia is macrolide antibiotics, mainly including erythromycin, azithromycin, etc. However, with the abuse of macrolide antibiotics, more and more cases of drug-resistant mycoplasma pneumonia have appeared in recent years, which has brought certain difficulties to treatment.

It’s the “big year” of mycoplasma pneumonia again

Mycoplasma can cause endemic or pandemic (crossing provincial and national borders or even continental borders to form a global epidemic in a short period of time): during endemic periods, mycoplasma pneumonia may account for 4% to 8% of community-acquired pneumonia. However, during pandemics, this proportion can be as high as 20% to 40%, and even up to 70% in closed groups.

It is estimated that there are about 2 million cases of mycoplasma pneumonia in the United States each year, resulting in about 100,000 hospitalizations among American adults. However, because the symptoms of mycoplasma infection and common bacterial infection are similar, many people with mycoplasma infection are not tested, and the actual number of cases may be higher.

In addition, the number of cases of Mycoplasma pneumoniae infection varies greatly in different years, with a peak of infection generally occurring every five years or so. This is vividly referred to as "big year and small year."

In my country, the number of Mycoplasma pneumoniae infections in Beijing reached a peak in 2007, 2011, 2014 and 2017, also known as the "big year". In peak years, the number of Mycoplasma pneumonia cases may exceed twice or even more than in normal years.

Since July this year, cases of Mycoplasma pneumoniae infection have appeared in many places in China . According to statistics from the Guangdong Provincial Women and Children's Health Care Hospital, the infection rate was 19.86% in June and rose to 27.16% in August . The majority of infected cases were school-age children.

Adolescents and children are susceptible. Image source: Earth Knowledge Bureau

Given that this year is another "big year" for mycoplasma pneumonia, if you have a high fever accompanied by severe coughing symptoms, you should seek medical help quickly, quickly identify the cause, and receive standardized treatment. Do not blindly take medication on your own. Improper mixed medication may lead to serious consequences and even endanger your life.

In particular, with the abuse of antibiotics, more and more cases of macrolide-resistant mycoplasma pneumoniae (MRMP) pneumonia have been found in clinical practice. In the United States and Europe, surveys show that the proportion of MRMP has reached 10%, while in the three East Asian countries (China, Japan and South Korea), the proportion of MRMP has exceeded half.

Even a survey in 2013 showed that the MRMP detection rate in children under 14 years old was 98.1%, while the MRMP detection rate in adolescents and adults was 83%, which means that antibiotics do not have a good effect in a considerable number of patients.

The best way is to avoid mycoplasma infection as much as possible, but there is currently no vaccine to prevent Mycoplasma pneumoniae infection, so it is crucial to cultivate personal hygiene habits in daily life .

In addition, you can also do the following:

Image source: Earth Knowledge Bureau

Although most people infected with Mycoplasma pneumoniae have relatively mild symptoms, there have been clear records of severe pneumonia caused by Mycoplasma in the past, as well as a small number of patients with complications involving multiple organs. This disease should not be taken lightly.

Similar infectious diseases may continue to strike in the future. While investing more in medical research and infrastructure, we should also strengthen public health education and popularization to raise public awareness and reduce panic.

References

[1] The peak season for mycoplasma infection is coming with the rise of influenza season. Be careful of superimposed infection. People's Daily Health Client Published on 2023-10-17.

[2] Waites KB, Xiao L, Liu Y, Balish MF, Atkinson TP. Mycoplasma pneumoniae from the Respiratory Tract and Beyond. Clin Microbiol Rev. 2017;30(3):747-809.

[3]Preksha Bhan. Learn about Mycoplasma (With Diagram). https://www.biologydiscussion.com/cell/mycoplasma/learn-about-mycoplasma-with-diagram/36777.

[4] Many children are infected! What exactly is Mycoplasma pneumoniae? Huashan Hospital Affiliated to Fudan University published on 2023-10-23.

[5] Zhao Shunying, Qian Suyun, Chen Zhimin, et al. Diagnosis and treatment guidelines for Mycoplasma pneumonia in children (2023 edition)[J]. Infectious Disease Information, 2023, 36(04): 291-297.

Planning and production

Source: Earth Knowledge Bureau (ID: diqiuzhishiju)

Author: Ziyu

Editor: Bai Li