What is the Mycoplasma pneumoniae?
Affecting millions of people every year, bacterial pneumonia is a significant cause of morbidity and mortality around the world. Originally known as Eaton’s agent due to its initial discovery by Eaton et al. (1944), Mycoplasma pneumoniae is among the significant pneumonia-causing bacteria around the world. Despite the extensive collective knowledge of the pathogen, recent advancements in diagnostic methods, and improvements in available treatments, Mycoplasma pneumoniae remains a common cause of pneumonia and other extrapulmonary manifestations within adults and children worldwide. Read along to learn more about Mycoplasma pneumoniae, its microbiology, epidemiology, clinical presentation, and diagnosis.
What are the microbiological characteristics of Mycoplasma pneumonia?
Similar to other species of Mycoplasma, Mycoplasma pneumoniae is a self-replicating pleomorphic bacteria that can infect both the upper and lower respiratory tracts in humans. It is thought to originate from gram-positive bacteria. Given the lack of evidence for its sustainment within nature, Mycoplasma pneumoniae is thought to be principally a mucosal pathogen with a parasitical dependence on the epithelial surface of its host. Due to its minuscule genome size, it lacks a peptidoglycan cell wall and cannot be detected via light microscopy or gram stain. Its size also enables the bacteria to transmit through aerosol droplets. Following transmission, Mycoplasma pneumoniae connects to the ciliated cells within the respiratory epithelium of the host via its specialized tip organelles and efficiently extracts the nutrients necessary for its reproduction thanks to the absence of its cell wall. This link also protects the bacteria from mucilary clearance and leads to localized cytotoxicity, which accounts for the majority of the symptoms associated with Mycoplasma pneumoniae infection (Parrot et al., 2016).
How common are infections with Mycoplasma pneumoniae?
Mycoplasma pneumoniae has been observed to cause endemics and epidemics among adults and children around the world. According to Arnold et al. (2007), the Atypical Pathogens Reference Laboratory Database reports that Mycoplasma pneumoniae may be responsible for around 12% of the global incidence of community-acquired pneumonia worldwide. However, the estimated number of infections with Mycoplasma pneumoniae is highly variable and likely to be underestimated due to the abundance of patients with mild non-specific symptoms. Still, current data demonstrate that Mycoplasma pneumoniae causes a more significant burden on children in comparison to adults. In fact, according to Rogozinski et al. (2017), the pathogen is estimated to be responsible for up to 40% of pneumonia cases in children over the age of 5, which indicates that children may act as a potential reservoir.
What is atypical pneumonia?
Atypical pneumoniae is an unusual form of pneumonia that presents with many symptoms contrasting the classic symptoms observed in cases of bacterial pneumonia caused by Streptococcus pneumoniae. Atypical pneumonia can be caused by any one of the pathogens that is not commonly associated with the disease. One of the most common causative agents of atypical pneumonia is intercellular bacteria such as Mycoplasma pneumoniae. Indeed, according to Arnold et al. (2007), Mycoplasma pneumoniae was the most common atypical pathogen observed in 39 hospitals across 11 countries between the period 2001 and 2006.
Which symptoms should you watch out for?
The severity of disease caused by Mycoplasma pneumoniae can vary from mild upper respiratory tract infection to severe cases of atypical pneumonia. The incubation period for the infection may also vary from a few days up to three weeks. In adult patients, the pathogen often leads to a mild form of “walking pneumonia,” which typically causes initial symptoms such as persistent cough and low-grade fever. If atypical pneumonia develops, it may lead to prolonged symptoms associated with an upper respiratory infection, such as pharyngitis and sinus congestion, along with lower respiratory symptoms, such as the inflammation of the bronchi. Infection with Mycoplasma pneumoniae has also been observed to exacerbate other respiratory diseases such as bronchitis, asthma, a chronic obstructive pulmonary disorder, and cystic fibrosis. In severe cases, infected patients have been hospitalized due to decreased blood oxygen and difficulty of breathing.
How to test for infection with Mycoplasma pneumoniae?
There are various methods available for the diagnosis of infection with Mycoplasma pneumoniae. The laboratory diagnosis of the pathogen involves the use of serum antibody titers, culture, and PCR methods. Although the use of cold agglutinin testing and culture methods have previously found widespread use for the detection of Mycoplasma pneumoniae, recent advances in diagnostics have allowed for more efficient, convenient, and rapid methods with more accurate indicators such as serological tests, nucleic acid detection tests, and rapid diagnostic tests. Indeed, recent years have seen the development of rapid tests such as antibody-detecting microparticle agglutination assay (MAG) as well as two forms of antigen tests detecting L7/L12 ribosomal protein or P1 adhesion protein for the diagnosis of Mycoplasma pneumoniae (Parrot et al., 2016). In fact, early studies have found that the sensitivity of the ribosomal protein rapid antigen kit was approximately 60% (Miyashita et al., 2015) and 74% (Yamazaki et al., 2015) compared to real-time PCR. However, due to the limitation of data, the majority of M. pneumoniae cases continue to be diagnosed via serological methods detecting IgM and/or IgA antibodies or nucleic acid detection methods such as PCR and qPCR.
How to protect yourself against Mycoplasma pneumoniae?
Unfortunately, immunity induced by natural infection with Mycoplasma pneumoniae does not offer sufficient or long-lasting protection against the disease. Despite the ongoing efforts for its development, there is also no vaccine available against Mycoplasma pneumoniae. However, according to Parrot et al. (2016), antibiotic treatments that interfere with the synthesis of DNA or proteins, such as quinolones, macrolides, and tetracyclines, have demonstrated high levels of efficacy and are commonly utilized against the pathogen. Adherence to a healthy lifestyle and personal hygiene rules can also help reduce the risk of infection.
REFERENCES
Arnold, F. W., Summersgill, J. T., LaJoie, A. S., Peyrani, P., Marrie, T. J., Rossi, P., Blasi, F., Fernandez, P., File, T. M., Rello, J., Menendez, R., Marzoratti, L., Luna, C. M., & Ramirez, J. A. (2007). A Worldwide Perspective of Atypical Pathogens in Community-acquired Pneumonia. American Journal of Respiratory and Critical Care Medicine, 175(10), 1086–1093. https://doi.org/10.1164/rccm.200603-350oc
Miyashita, N., Kawai, Y., Tanaka, T., Akaike, H., Teranishi, H., Wakabayashi, T., et al. (2015). Diagnostic sensitivity of a rapid antigen test for the detection of Mycoplasma pneumoniae: comparison with real-time PCR. J. Infect. Chemother. 21, 473–475. doi: 10.1016/j.jiac.2015.02.007
Parrott, G. L., Kinjo, T., & Fujita, J. (2016b). A Compendium for Mycoplasma pneumoniae. Frontiers in Microbiology, 7. https://doi.org/10.3389/fmicb.2016.00513
Rogozinski, L. E., Alverson, B. K., & Biondi, E. A. (2017). Diagnosis and treatment of Mycoplasma pneumoniae in children. Minerva Pediatrics, 69(2). https://doi.org/10.23736/s0026-4946.16.04866-0
Yamazaki T, Kuroki H, Itagaki T, Iwata S, Tateda K. [Evaluation of a Rapid Antigen Detection Kit Targeting L7/L12 Ribosomal Protein for Mycoplasma pneumoniae]. Kansenshogaku Zasshi. 2015 May;89(3):394-9. Japanese. doi: 10.11150/kansenshogakuzasshi.89.394. PMID: 26552132.
