Professor Zhuang Peng
Medical PhD, Chief Physician, Director of the Department of Infectious Diseases of the Eighth Affiliated Hospital of Sun Yat-sen University, Master’s supervisor at Sun Yat-sen University. Member of the Infectious Diseases Physicians Committee of the Guangdong Medical Doctors Association, Member of the Infectious Diseases Branch of Guangdong Medical Association, Standing Committee Member of the Hepatology Professional Committee of the Guangdong Society of Integrated Traditional Chinese and Western Medicine, Deputy Chairperson of the Infectious Diseases Special Committee of Shenzhen Health Management Association, Standing Committee Member of the Internal Medicine Branch of Shenzhen Medical Association, Member of the Infectious Diseases Professional Committee of Shenzhen Medical Association, Member of the Hepatology Professional Committee of Shenzhen Medical Association.

Introduction: Immunity gap and periodic outbreaks are the main reasons contributing to mycoplasma pneumonia infections during the epidemic. Treatment strategies should be diversified in managing patients of varying age groups.

Mycoplasma pneumoniae pneumonia is characterized by lung inflammation resulting from an infection with mycoplasma pneumonia, affecting the bronchi, bronchioles, alveoli, and pulmonary interstitium¹. Recently, there has been a notable surge in mycoplasma pneumoniae infections, leading to a significant increase in patients compared to previous years. Once again, we extended an invitation to Professor Zhuang Peng from The Eighth Affiliated Hospital, Sun Yat-Sen University, to share his insights on the diagnosis, differential diagnosis, and anti-infective treatment of mycoplasma pneumoniae infection. We trust that his expertise will be valuable for your clinical practice.

The Causes of the Mycoplasma Pneumonia Epidemic: Immunity Gap and Periodic Outbreaks
As a common pathogen, mycoplasma manifests as a cyclical epidemic infection every few years. However, how is mycoplasma infection different this year? Professor Zhuang Peng pointed out that before the onset of the COVID-19 pandemic, mycoplasma pneumonia had always been a common cause of respiratory infections, often presenting a rising trend during the autumn and winter seasons, causing mild to moderate respiratory tract infection (i.e. bronchitis and pneumonia). Regional outbreaks of mycoplasma pneumonia typically occurred approximately every 4 to 7 years². Current data reveals that approximately 10% to 30% of community-acquired pneumonia cases in children result from mycoplasma pneumoniae infection.

After the outbreak of the COVID-19 pandemic, strict preventive measures, such as maintaining social distancing and wearing masks, were widely adopted. These measures resulted in a significant decline in various respiratory infectious diseases, including mycoplasma pneumonia infection. However, the low prevalence status may lead to a lack of immune stimulation in children, weakening their immunity to mycoplasma pneumonia. According to the latest data on mycoplasma pneumoniae infection from the Beijing Children’s Hospital, the most recent outbreak occurred between 2019 and 2020. After several years of dormancy, the gradual easing of the worldwide COVID-19 pandemic preventive measures led to expected emergence of mycoplasma pneumoniae infections in China this autumn.

Since October 2023, the incidence of influenza and mycoplasma pneumoniae infections in China been steadily on the rise. Mycoplasma pneumonia has gained prevalence in certain regions, giving rise to disease clusters within families or school classes. The cold winter itself marks the peak season for respiratory virus infections. Throughout the three-year pandemic, the public’s adherence to good hygiene practices and respiratory protection measures has mitigated the spread of COVID-19 and other pathogens, yet it has also potentially resulted in specific immunity gap in some children against mycoplasma. The combination of this immunity gap and the regional mycoplasma outbreak has contributed to the recent outbreak of the disease.

At present, mycoplasma pneumoniae infections shows only slight variation across different regions in China. Although children are the high-risk group for mycoplasma pneumoniae infections, adult infections also warrant attention, given that transmission among family members constitutes the main route of infection. Furthermore, the high resistance of mycoplasma pneumoniae infections to commonly used drugs like azithromycin warrants our attention.

Diagnosis Should Not Solely Rely on Antibody Testing
Both influenza and mycoplasma pneumonia infections share common characteristics as respiratory infections, leading to symptoms such as fever, cough, and others. How can one differentiate between these common respiratory diseases? Professor Zhuang Peng pointed out that patients with influenza often experience more severe symptoms, including high fever, fatigue, headache, muscle soreness, and so on. Local symptoms such as sore throat, runny nose, and nasal congestion are relatively mild. On the other hand, patients with mycoplasma pneumonia infection may develop an intense and irritative dry cough, which differs from the influenza symptoms. In adults with mycoplasma pneumonia infection, the primary symptoms typically include fever and cough, with a lower risk of severe complications when compared with children.

In terms of laboratory tests, patients with influenza typically exhibit a normal total white blood cell count in peripheral blood. In severe cases, lymphocyte count may significantly decrease, and tests for influenza virus nucleic acid and/or antigen are positive. In contrast, mycoplasma pneumoniae infections are more prevalent in children and adolescents. Peripheral blood white blood cell count is generally normal, while C-reactive protein (CRP) may increase. Procalcitonin (PCT) levels are often normal as well. Differentiating the infection can be achieved through mycoplasma nucleic acid testing, serological antibody testing, and other methods.

It’s important to note that in the case of mycoplasma pneumoniae infection, the diagnosis is valuable only if there is a fourfold or greater change in antibody titers in both the acute and convalescent serum samples. Specific IgM antibodies typically emerge within 7 to 10 days post-infection, whereas it may take even longer for specific IgG antibodies to become detectable. Therefore, relying solely on specific antibody testing for mycoplasma pneumonia in clinical practice may not be conducive to early diagnosis. It is advisable to combine it with nucleic acid testing and other laboratory examinations for an early diagnosis.

Treatments for Mycoplasma Pneumoniae Infection Varies:  Medication Selection Based on Different Age Groups
Treatments for mycoplasma pneumoniae infection vary based on age groups. In routine clinical practice, macrolide antibiotics are the only available option for infected children under the age of 8. For children and adolescents aged between 8 and 18, tetracycline antibiotics (including doxycycline and minocycline) are effective, as there has been low resistance rates of mycoplasma pneumonia to tetracycline antibiotics. For people aged 18 and above, if the infection is confirmed to be caused by a drug-resistant strain, fluoroquinolone drugs such as levofloxacin and moxifloxacin can also be considered, apart from tetracycline antibiotics.

Summary
Over time and with climate change, the peak of mycoplasma pneumoniae infection will eventually subside. However, the prevention of mycoplasma pneumoniae infection remains a concern. At the end of the interview, Professor Zhuang Peng urged the public to cultivate good personal hygiene habits. During the epidemic, it is advised to avoid crowded and poorly ventilated public places and to wear face masks when necessary. When coughing or sneezing, individuals should cover the mouth and nose with a tissue, practice hand hygiene, and maintain cleanliness and disinfection. Schools, kindergartens, and other institutions should prioritize good ventilation and disinfection to prevent cluster infections. Let us collectively navigate through the mycoplasma pneumoniae infection epidemic safely with everyone’s joint efforts.

References:
1. Notice from the General Office of the National Health Commission on the Issuance of the Diagnosis and Treatment Guidelines for Mycoplasma Pneumonia in Children (2023 Edition) State Council Department Document _China Government Website (www.gov.cn)

2. Lenglet A, Herrador Z, Magiorakos AP, Leitmeyer K, Coulombier D; European Working Group on Mycoplasma pneumoniae surveillance. Surveillance status and recent data for Mycoplasma pneumoniae infections in the European Union and European Economic Area, January 2012. Euro Surveill. 2012 Feb 2;17(5):20075. doi: 10.2807/ese.17.05.20075-en. PMID: 22321134.

3. Diagnosis and treatment of community-acquired pneumonia in adults: 2016 clinical practice guidelines by the Chinese Thoracic Society. Chinese Journal of Tuberculosis and Respiratory Diseases. 2016.39(4):1-27.