Parasites, Pathogen of the Month

What are Mycoplasma Infections? What to Do About These Resistant Bacteria that Escape Our Immune Systems?

Author Chandana Balasubramanian , 22-Feb-2022

What are Mycoplasma Infections?

 

Mycoplasma is an entire category (genus) of gram-negative bacteria with over 100 different species. They are the smallest free-living organisms known today [1]. They belong to the class Mollicutes – the word is Latin for ‘soft skin’ – and are named so because they do not have a cell wall.

Mycoplasma bacteria can cause several types of infections that affect the respiratory pathway, skin, nerves, heart, joints, and blood [2]. The most common infections are the upper and lower respiratory tract, including the lungs. They are resistant to several antibiotics, infections are often persistent, and their lack of a cell wall makes them hard to detect and treat.  As a result, they are known as the “crabgrass” of cell cultures [3].

 

Types of Mycoplasma Bacteria: Mycoplasma Pneumoniae, Mycoplasma Genitalium, and More

 

The Mycoplasma bacterium, Mycoplasma pneumonia, was first discovered in 1898. It causes atypical pneumonia. Atypical pneumonia affects the lower respiratory tract and is often milder than regular or typical pneumonia. It is also known as ‘walking pneumonia’ since infected individuals are rarely hospitalized and can continue to perform their daily activities. Mycoplasma genitalium is another species of concern that causes sexually transmitted infections. Other commonly known Mycoplasma bacteria are Mycoplasma hominis, Mycoplasma fermentans, Mycoplasma penetrans, and Ureaplasma urealyticum. Ureaplasma is another species of Mollicutes that cause gynecologic infections [2].

 

Additionally, many species of Mycoplasma live harmoniously in human bodies and are not a risk for infection except in immune-compromised individuals. These bacteria are known as ‘commensals’ – they are parasitic and need to depend on the human host entirely to survive. If the host dies, they die. As a result, the survival of their hosts is often in their best interests. There are 14 human commensals and pathogens identified [4].

 

How Do You Get a Mycoplasma Infection? How is it Spread?

 

Common mycoplasma infections are transmitted from human to human. Zoonotic (or animal to human) transmissions are rare.

When a person infected by mycoplasma bacteria sneezes, talks, coughs or laughs, the mycoplasma infection is transmitted through droplets to another person. Here the bacteria attaches itself to the respiratory tract and begins to multiply [5].

Sexually transmitted mycoplasma infection, also known as a mycoplasma genitalium infection, is transmitted through sexual contact. It is a growing cause of concern and is the source of several types of inflammatory diseases in women and men [6]. 

 

Where are Mycoplasma Infections Found?

 

Mycoplasma infection has been documented worldwide and is endemic to all countries.

The most common infection caused by Mycoplasma pneumoniae is often associated with, and comprise, 10-30% of community-acquired pneumonia cases. Hospitals, schools, and other institutions that require people to live or stay close together are often at risk for the spread of community-acquired pneumonia. 15% of infected individuals remain asymptomatic [7] [8].

It is most prevalent in young children aged 5 – 15 years and rarely found in the elderly. It is also rare for children under five to develop pneumonia from M.pneumoniae. Epidemics of M.pneumoniae are found to occur every 3-7 years [8].

 

Biology of Mycoplasma

 

Since Mycoplasma bacteria are obligate parasites (depend entirely on a host for survival), they do not need a cell wall. Their cell membranes have evolved to be tough enough to protect them from damage or rupture. They have a limited genome since they do not need many enzymes for their nutrition and other functions. Due to their parasitic nature, they have a variety of plastic or flexible surface proteins designed to evade their host’s immune system – Mycoplasmas can stimulate and suppress lymphocytes. They also modulate cytokine and chemokine production and responses.

Many Mycoplasmas form membrane protrusions. For example, the M.pneumoniae has a special extension called the attachment organelle critical to its survival. The bacteria use their attachment organelles to connect with epithelial cells of their host’s respiratory tract firmly [9].

 

Symptoms

 

The most common symptoms of a respiratory Mycoplasma infection are a cough (initially dry), fever, sore throat, persistent headache, and fatigue. Sometimes, ear infections are also present. The incubation period is often 2-3 weeks after exposure, and symptoms can last from a few weeks to a month.

The symptoms of atypical pneumonia are different from typical pneumonia because patients do not exhibit shortness of breath and a cough that produces mucus or phlegm (productive cough) [2].

Early research shows that COVID-19 patients (SARS-CoV-2 virus) can have atypical pneumonia caused by M.pneumoniae as a co-infection. Since the symptoms of COVID-19 are similar to those of atypical and regular pneumonia, diagnosing a co-infection may be difficult unless the individual reaches out to a healthcare professional and gets tested [10].

Diagnosis

 

According to the CDC, M.pneumoniae infections pose different challenges from other bacteria during diagnosis. Mycobacteria pass through the standard filters used to separate bacteria. Also, light microscopy cannot detect it. The M.pneumoniae cultures need specialized media to grow cultures.

Serology tests are most commonly used to diagnose M.pneumoniae infections. Though commercially-available test kits exist, they lack specificity and can be cumbersome. Patients will need to provide samples multiple times.

For a culture test, growing mycobacteria in the lab can take a lot of time. This time delay means that test results may be too late to help guide treatment decisions.

In recent years, molecular tests have been used to detect mycobacteria because they have a high sensitivity and specificity to the bacteria. There are five FDA-approved assays currently available, with more being developed. The advantages of these tests are that they are fast and more accurate. However, they are also more expensive and need specialized knowledge. They are also new and have limited FDA approval [11].

 

Treatment

 

The lack of a cell wall makes Mycoplasma bacteria resistant to many antibiotics. M.pneumoniae infection is known to persist even after a treatment regimen because the bacteria can mimic the surface of their host cells [12].

However, antibiotics like azithromycin, fluoroquinolones in adults, and tetracyclines like doxycycline for older children and adults remain the standard treatment for M.pneumoniae infections. The lack of a cell wall makes them resistant to beta-lactam antibiotics.

According to the CDC, Asia presents the highest antibiotic resistance to M.pneumoniae, as much as 90%. The United States and Europe also experience M.pneumonia resistance [13]. 

Prevention

 

There is no vaccine to protect against Mycoplasma pneumoniae infection, and reinfections are possible. However, practicing general hygiene and safety protocols can help minimize risk. Covering the mouth during a sneeze or cough, coughing into the upper arm and not on hands, and washing hands properly with soap can help.

References
[1]J. E.Sykes, “Chapter 40 – Mycoplasma Infections,” in Canine and Feline Infectious Diseases, Elsevier Inc., 2014, pp. 382-389.
[2]A. E. Lanao, R. K. Chakraborty, and A. L. Pearson-Shaver, “Mycoplasma Infections,” Treasure Island (FL), StatPearls [Internet], 2022.
[3]S. Razin and (. B. S, “Mycoplasmas,” in Medical Microbiology. 4th edition., Galveston (TX), University of Texas Medical Branch at Galveston, 1996, p. Chapter 37.
[4]GIDEON Database (Global Infectious Diseases and Epidemiology Online Network), “GIDEON app,” 2022.
[5]Centers for Disease Control and Prevention, “Mycoplasma pneumoniae Infections: Causes and How It Spreads,” CDC, 05 06 2020. [Online][Accessed 16 02 2022].
[6]C. L. McGowin and C. Anderson-Smits, “Mycoplasma genitalium: an emerging cause of sexually transmitted disease in women,” PLoS Pathog, vol. 7, no. 5, 2011.
[7]J. Gomez, V. Banos, J. Ruiz Gomez, M. C. Soto, L. Munoz, M. L. Nunez, M. Canteras, and M. Valdes, “Prospective study of epidemiology and prognostic factors in community-acquired pneumonia,” European Journal of Clinical Microbiology & Infectious Diseases, vol. 15, p. 556–560, 1996.
[8]H. M. Foy, “Infections Caused by Mycoplasma pneumoniae and Possible Carrier State in Different Populations of Patients,” Clinical Infectious Diseases, vol. 17, no. Issue Supplement_1, p. S37–S46, 1993.
[9]S. Razin, D. Yogev, and Y. Naot, “Molecular Biology and Pathogenicity of Mycoplasmas,” Microbiol Mol Biol Rev., vol. 62, no. 4, pp. 1094-1156, 198.
[10]A. Oliva, G. Siccardi, A. Migliarini, F. Cancelli, M. Carnevalini, M. D’Andria, I. Attilia, V. C. Danese, V. Cecchetti, R. Romiti, G. Ceccarelli, C. M. Mastroianni, P. Palange and M. Venditti, “Co-infection of SARS-CoV-2 with Chlamydia or Mycoplasma pneumoniae: a case series and review of the literature,” Infection, vol. 48, p. 871–877, 2020.
[11]Centers for Disease Control and Prevention, “Mycoplasma pneumoniae Infections: Diagnostic Methods,” CDC, 05 06 2020. [Online] [Accessed 16 02 2022].
[12]S. Rottem, “Interaction of Mycoplasmas With Host Cells,” American Physiological Society: Physiological Reviews, vol. 83, no. 2, pp. 417-432, 2003.
[13]Centers of Disease Control and Prevention, “Mycoplasma pneumoniae Infections: Antibiotic Treatment and Resistance,” CDC, 05 06 2020. [Online][Accessed 16 02 2022].
Author
Chandana Balasubramanian

Chandana Balasubramanian is an experienced healthcare executive who writes on the intersection of healthcare and technology. She is the President of Global Insight Advisory Network, and has a Masters degree in Biomedical Engineering from the University of Wisconsin-Madison, USA.

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