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Epidemiological and clinical characteristics of hospitalized pediatric patients with Mycoplasma pneumoniae pneumonia before and after the COVID-19 pandemic in China: a retrospective multicenter study

BMC Infectious Diseases volume 25, Article number: 18 (2025) Cite this article

Abstract

Background

In China many respiratory pathogens stayed low activities amid the COVID-19 pandemic due to strict measures and controls. We here aimed to study the epidemiological and clinical characteristics of pediatric inpatients with Mycoplasma pneumoniae pneumonia (MPP) after the mandatory COVID-19 restrictions were lifted, in comparison to those before the COVID-19 pandemic.

Methods

We here included 4,296 pediatric patients with MPP, hospitalized by two medical centers in Jiangsu Province, China, from January 2015 to March 2024. Patients were divided into the pre-COVID (n = 1,662) and post-COVID (n = 2,634) groups. Their baseline characteristics, laboratory test results and radiological patterns were separately assessed and compared between the two groups to determine the substantial changes in the disease profile of MPP after the COVID-19 pandemic.

Results

Epidemiological results suggested a higher annual incidence of MPP after the COVID-19 pandemic when the outbreak reached a peak in October, two months delayed in seasonality compared to that in the pre-COVID era. For pediatric patients with MPP, there was no difference in their median ages, gender ratios, and severe case percentages between the two groups, where most patients were younger than 14 years old. With significance, the post-COVID group had more occurrences of cough and expectoration and higher incidences of influenza A/B virus (IAV/IBV) co-infection than the pre-COVID group. Many hematological parameters and radiological features between the two groups displayed alteration, but comparatively there demonstrated no worsened severity in hospitalized children with MPP after COVID-19 pandemic. Concurrently, the post-COVID group was administered with fewer antibiotics but more corticosteroids for effective treatment than the pre-COVID group.

Conclusion

Through the COVID-19 pandemic, the epidemiological and clinical characteristics of pediatric patients with MPP differed, but there was no evident change in the disease severity. After the COVID-19 pandemic, the increased incidence of IAV/IBV co-infection may contribute to the differences in clinical symptoms and hematological profiles, while the adding usage of corticosteroids might treat more effectively.

Peer Review reports

Background

Mycoplasma pneumoniae (MP) is a cell wall-free pathogen that infects humans in the respiratory tracts, causing mild to severe diseases, especially in children and adolescents [1]. It is responsible for about 30% of community-acquired pneumonia (CAP) cases in adults and 10%–40% in children, posing a substantial threat to public health [2]. Besides MPP, a wide array of extrapulmonary complications has been observed in children infected with MP, spanning the dermatological, neurological, cardiovascular and gastrointestinal systems [3]. Among the infected, 18% of children required hospitalization, although fatal cases were rarely reported [4]. Nevertheless, the number of MP positive adult patients that were transferred to the intensive care unit (ICU) upon hospitalization, has been found continuously increasing over the last decade, with elevated morbidity and mortality [5].

Epidemics of MP break out every 4–7 years [6]. The transmission of MP is mainly through aerosols and droplets in close contact, and the reproductive number during initial outbreak is estimated to be 1.4–1.7 [7]. Although a variety of vaccines against MP has been experimented with varying effects, including inactivated, live-attenuated and recombinant protein/DNA vaccines, there is yet immunization approved in the clinical settings [8]. Most MP infections are self-limiting, whereas the first-line antibiotic treatments are macrolides (e.g., azithromycin, clarithromycin) for pediatric patients and tetracyclines and fluoroquinolones for adult patients [9]. However, the macrolide-resistant MP (MRMP) began to emerge in 2001, mostly due to the A2063G mutation in the 23S rRNA of MP genome [10]. Globally, over the past two decades the proportion of MRMP infections has been climbing with the highest prevalence in Asia [11]. This resulted in an increasing number of refractory MPP (RMPP) cases, and their treatments are challenging. Alternatively, the administration of corticosteroids and other antimicrobials than macrolides was considered [12].

Three epidemics of MP infections were documented in Europe during 2011/12 (6%−23% positive), 2014/15 (4%−23% positive), and 2015/16 (2%−20% positive), respectively [13]. One recent MP epidemic occurred in China and Korea between late 2019 and early 2020, showing a growing trend in the frequency of macrolide resistance and co-infection [14, 15]. Compared to an infection incidence of 8.61% estimated from 2017 to 2020 worldwide, the MP positive rates declined to 1.69% in 2020/21 and 0.70% in 2021/22 amid the COVID-19 pandemic, due to the implementation of non-pharmaceutical interventions (NPIs) such as mandatory mask, local lockdown and travel restriction [16, 17]. Along with the end of COVID-19 as a global health emergency, MP infections re-surged and outbroke in pediatric groups like many other respiratory diseases [18,19,20]. However, the epidemiological and clinical characteristics of pediatric patients infected with MP in the post-COVID-19 era and their comparisons to those before COVID-19 remain unexplored.

Herein we studied the epidemiological and clinical patterns of hospitalized children with MPP before and after the COVID-19 pandemic, by analyzing data extracted from January 2015 to December 2019 (pre-COVID) and from April 2023 to March 2024 (post-COVID) in two tertiary hospitals in Jiangsu Province, China. We examined the baseline profiles and laboratory parameters of MP-positive pediatric patients before and after the COVID-19 pandemic, to accent the evolving changes of this pathogenic infection impacted by COVID-19 measures.

Methods

Study design

This retrospective study included 4,296 pediatric inpatients with MPP, who were admitted to two tertiary hospitals, namely, Affiliated Hospital of Jiangsu University in Zhenjiang city, and Affiliated Hospital of Xuzhou Medical University, both in Jiangsu Province, China. Patients were hospitalized from January 1, 2015 to December 31, 2019 (pre-COVID) and from April 1, 2023 to March 31, 2024 (post-COVID), respectively. The inclusion and exclusion criteria of the patients were illustrated in Scheme 1. In brief, patients aged 1–18 years and diagnosed with MPP were enrolled, but those with serious underlying diseases that could affect the laboratory results were excluded, including hematological malignancies and immunocompromised conditions, etc. Pediatric patients aged < 1 year were excluded because their hematological reference ranges are distinctive from those aged 1–18 years [21].

Scheme 1
scheme 1

Inclusion and exclusion criteria of pediatric patients with MPP

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MPP diagnosis and MP detection

The MPP diagnosis in the pre-COVID era followed Expert Consensus on Diagnosis and Treatment of Mycoplasma Pneumoniae Pneumonia in Children (2015), where the pneumonia was diagnosed according to Guideline for Diagnosis and Treatment of Community-acquired Pneumonia in Children (2019) as previously reported [20, 22]. Briefly, the clinical symptoms of pediatric pneumonia consisted of fever and cough for ≥ 3 days, and increased respiratory rates and presence of rales, which could be further confirmed with chest radiographs showing patchy shadowing in the lungs. Concurrently, pathogenic detection of MP was confirmed by one or both of the following: (1) serum MP-specific IgM antibody titer ≥ 1:160 through microparticle agglutination test (e.g., colloidal gold assay), or a four-fold rising of MP-specific IgG antibody titer in the patients’ acute and convalescent sera; (2) positive results of MP DNA or RNA detected from oropharyngeal swabs or bronchoalveolar lavage fluid samples.

Upon hospital admission, the venous blood specimen was collected from the pediatric patients and the serological IgM was tested by indirect gold-labeled immunologic filtration assays (Kanghua Biotech Co., Ltd., Weifang, China), or by immunofluorescence assay kits against nine common pathogens in respiratory tract infection (VIRCELL, Granada, Spain), including MP, adenovirus, respiratory syncytial virus (RSV), influenza A/B virus (IAV/IBV), and parainfluenza, etc. Alternatively, real-time RT-PCR assays for the rapid in vitro qualitative detection of MP DNAs were conducted using oropharyngeal swabs (Roche Diagnostics, USA).

The MPP diagnosis in the post-COVID era was following Guidelines for the Diagnosis and Treatment of Mycoplasma Pneumoniae Pneumonia in Children (2023), which was summarized below: (1) clinical presentation of fever and cough; (2) chest imaging with infiltrates; (3) positive detection of MP-specific DNA or RNA; (4) MP serum antibody titer ≥ 1: 160 or four-fold increase in acute and convalescent serum specimens [23]. Severe MPP (SMPP) was defined with worsened clinical symptoms and imaging features, including one or more of the following manifestations: 1) persistent high fever (> 39 ºC) for ≥ 5 days or fever for ≥ 7 days; 2) presence of symptoms such as wheezing, shortness of breath, dyspnea, chest pain and hemoptysis, etc.; 3) development of extrapulmonary complications, albeit not critically ill; 4) finger pulse oxygen saturation ≤ 0.93 when air inhalation at rest; 5) imaging features showing one of the following: lesions on ≥ 2/3 of one lobe, presence of uniform and consistent high-density consolidation or two or more lobes with high-density consolidation (regardless of sizes of lesioned lung involvement), possibly accompanied by moderate to large pleural effusion or manifestation of limited bronchiolitis; diffusive bronchiolitis in the single lung or bronchiolitis on ≥ 4/5 lobes in the bilateral lungs, possibly complicated with bronchitis and formation of mucus plug leading to atelectasis; 6) progressive aggravation of clinical symptoms and radiological images showing over 50% lesion progression within 24–48 h; 7) marked elevation of c-reactive protein (CRP), lactate dehydrogenase (LDH), or D-dimer [23]. The diagnosis standards were similar to those in the pre-COVID period, but with updated detection techniques of MP antibodies or antigens. MP-specific antibody was detected using Diagnostic Kit for Measurement of Antibodies to Mycoplasma Pneumonia (Livzon Pharmaceutical Group Inc., Guangdong, China), Mycoplasma Pneumonia IgM ELISA Kit (Beijing Beier Bioengineering Co., Ltd., China), or the immunofluorescence assay kit against nine common pathogens in respiratory tract infection (VIRCELL, Granada, Spain).

Statistical analysis

Data were summarized as the median and interquartile range (IQR) values for continuous variables and frequencies for categorical variables. For comparisons between the two groups, the Mann–Whitney U test was used for continuous variables. Categorical variables were examined by χ2 test. All calculated p values were two-sided, and p < 0.05 was considered statistically significant. Both data were subjected to binary logistic regression. All statistical analyses were performed using SPSS version 25.0.

Results

This retrospective study included 4,296 pediatric patients with MPP, divided into two groups; that is, 1,662 (38.7%) patients hospitalized between January 2015 and December 2019 as the pre-COVID group, and 2,634 (61.3%) patients hospitalized between April 2023 and March 2024 as the post-COVID group (Scheme 1). Given this fact, the annual incidence of MPP in hospitalized pediatric patients was much higher after the COVID-19 pandemic. Compared to the case in the pre-COVID group, the hospital admission of pediatric patients reached a peak about 2 months later in October and remained at higher levels from September to March in the post-COVID group (Fig. 1). As shown in Table 1, 16.0% of all confirmed diagnoses were based on RT-PCR for nucleic acid detection, while the rest (84.0%) were confirmed by antibody test. The proportions of diagnostic methods using RT-PCR or antibody test were comparable between the pre-COVID and post-COVID groups. The median age of patients was 6.0 years (IQR: 5.0–9.0), and it displayed no statistical difference between the two groups. Difference in the patient portion with ages between 14 and 18 was minimal in both groups. Moreover, the median hospitalization length was 7.0 days (IQR: 5.0–8.0), where the post-COVID group had longer hospital stays than the pre-COVID group. Of all patients, 48.3% were female. The occurrence of SMPP cases in our study was low, although the pre-COVID group displayed a higher incidence than the post-COVID group.

Fig. 1
figure 1

The proportion of hospitalized children with MPP in each month of the year

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Table 1 Baseline characteristics of pediatric patients with MPP
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The most common symptoms in the pediatric patients with MPP comprised of cough (99.1%), fever (75.7%) and expectoration (35.7%). Extrapulmonary symptoms were also observed, albeit infrequently, such as muscle pain and gastrointestinal symptoms exemplified by stomachache, diarrhea, and vomiting. Notably, compared to the pre-COVID group, the post-COVID group experienced more frequencies of coughing and expectoration but less occurrence of fever, sniffle, dyspnea and muscle pain (Table 1). Most patients were previously healthy, as the children with comorbidity were few. Upon hospital admission, a substantial portion of MP-positive patients was found to be co-infected with other respiratory pathogens, mainly IAV and IBV. Among them, the post-COVID group exhibited significantly higher incidences of IAV or IBV co-infection than the pre-COVID group where the patient ratio of sole MP infection was much higher.

Moreover, according to Guidelines for the Diagnosis and Treatment of Mycoplasma Pneumoniae Pneumonia in Children (2023), the pulmonary complications for pediatric patients with MPP include plastic bronchitis, pulmonary embolism, pleural effusion, necrotizing pneumonia, acute asthma, and bacterial or viral co-infection, while the extrapulmonary complications comprise of neurological/circulation/hematological system involvement, skin mucosal damage, and other non-pulmonary organ dysfunctions. Most of those pulmonary and extrapulmonary complications were not observed in our study here, except that the bacterial or/and viral co-infections in addition to MPP infections were noticeable with much higher incidences in the post-COVID group of pediatric patients than the pre-COVID one.

Next, the hematological analysis revealed leukocytosis, neutrophilia, lymphocytosis, monocytosis and anemia in a substantial proportion of patients, while thrombocytopenia was not commonly observed (Table 2). Although many biochemical indices were not significantly deranged, a portion of patients had noticeably abnormal values of several blood parameters, including elevated levels of CRP, procalcitonin (PCT), direct bilirubin, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and lowered concentrations of univalent electrolytes (i.e., K+ and Na+).

Table 2 Basic hematological profile of pediatric patients with MPP upon hospitalization
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As the radiological features remain gold standards for pneumonia diagnosis, chest X-ray imaging was performed on pediatric patients with MPP upon their hospital admission, and their radiological patterns were examined. As a result, 1.3% of patients did not show noticeable abnormality in chest radiographs upon hospitalization, while most patients exhibited the thickened lung texture (79.3%) and to a lesser extent patchy shadow (18.5%) and consolidation (10.3%) in the lungs (Table 3). The pathological lesions were most observed in both lungs (56.2%), followed by the right lung only (29.9%) and the left lung only (13.9%). The right lower lobe was found to be the location with the highest occurrence of lesions, and the left lower lobe was secondary to it, whereas the single lobe was infected most frequently. In terms of lesion type and location there was statistically different in the patient ratios with most characteristic X-ray features between the two groups. Compared to the pre-COVID group, the post-COVID group had more frequent patchy shadow, lesions in the right lung and right upper lobe, and single lobe infection, but less frequent thickened texture, consolidation, bilateral lung involvement, lesions in the left and right lower lobes, and multilobe infection. Representative images are also shown in Fig. 2.

Table 3 Chest X-ray findings in the pediatric patients with MPP
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Fig. 2
figure 2

Representative X-ray graphs of pediatric inpatients with MMP, taken upon hospital admission, demonstrating typical pathological changes in the lungs from the pre-COVID group (A-C) and the post-COVID group (D-F), respectively. A Image taken from a 5-year-old girl with fever and cough symptoms, showing the increased texture in both lungs (indicated by arrow); B Image taken from a 4-year-old girl having convulsion and fever, showing a patchy shadow in the right lower lobe (indicated by arrow); C Image taken from an 8-year-old boy with fever, cough and expectoration, showing the increased texture in both lungs and the high-density shadow in the right lower lobe (indicated by arrow); D Image taken from a 7-year-old girl with fever and cough, showing the increased texture in both right lower lobe and left upper lobe (indicated by arrow); E Image taken from a 12-year-old boy having cough and fever, showing a high-density shadow with blurred margins in the right middle lobe (indicated by arrow); F Image taken from a 10-year-old boy with fever and cough, showing flocculent shadows in both portal regions of the lungs and also in the right lower lobe (indicated by arrow)

Full size image

Parameters with significant differences between the two groups were further analyzed using multivariable regression (Table 4), deriving the substantial changes of clinical features in pediatric patients with MPP from the pre-COVID to the post-COVID era. Despite the noted differences in many blood parameters between the two groups, the results implied a comparable severity of MPP in terms of major blood cell counts and biochemical indicators within patients after the COVID-19 pandemic. Particularly, the symptoms of cough and expectoration and the co-infection with IAV and IBV held high odds ratios (ORs) for substantial alteration after the COVID-19 pandemic.

Table 4 Multivariable regression analysis on differences between the clinical characteristics of children with MPP in the pre-COVID and post-COVID groups
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During hospitalization, antibiotics were administered based on the diagnosis of MPP and other possible bacterial co-infections. If the patient with MPP was co-infected with other bacteria, penicillin or cephalosporin in combination with macrolide might be given. The antibiotic types were similar between the two groups, but the percentage of patients taking those antibiotics was significantly lower in the post-COVID group (Table 5). Antiviral drugs were also given, if necessary, when viral co-infections other than MP infection were intensified in a small portion of patients. Compared to that in the pre-COVID group, the portion of patients administered with methylprednisolone was found much higher in the post-COVID group, although the usage of dexamethasone remained similar.

Table 5 The prescribed medications in the hospitalized pediatric patients with MMP
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Discussion

In this study we compared the epidemiological and clinical profiles of children with MPP before and after the COVID-19 pandemic, and concluded that many baseline characteristics, hematological parameters and radiological features of pediatric patients were substantially differing, signified by the clinical symptoms of cough and expectoration and the co-infection of IAV/IBV. With fewer antibiotics given, more corticosteroids (e.g., methylprednisolone) were administered to treat MPP in children with efficiency. Regardless of those alterations, comparable severity of MPP infection among pediatric patients was observed before and after the COVID-19 pandemic.

Being spindle-shaped with 1–2 µm long and 100–200 nm wide, MP is one of the smallest bacteria in absence of cell wall [24]. Lack of cell wall imparts them pleomorphism, so passable through 220-nm sterilizing filters, and conveys innate resistance to traditional β-lactam antibiotics which interrupt bacterial cell wall formation [25]. Although the pathogenesis of MP-induced illness remains inconclusive, it mainly stems from cytoadherence between surface P1 adhesins of MP and the receptors on airway epithelial cells of the host, producing peroxides that impose oxidative damage and cause local injury, as well as generating proinflammatory cytokines and provoking immune responses [26]. For this reason, variation in P1 adhesin structure, not only modifies the binding affinity to host proteins, but also renders macrolide resistance, so altering the epidemiological features of MPP [27].

In China, the annual MP-positive rates were recorded 18.33%−38.08% among patients with respiratory tract infections from 2014 to 2020 in one Southern regional hospital, with peak occurrence on April-June and September–November, most in children aged 4–14 years [28]. Particularly, MRMP was found greater than 90% of all MP infections, predominantly due to A2063G point mutation in domain V of 23 rRNA gene of MP [14]. During the COVID-19 pandemic period, the positive rates of MP infections were significantly reduced with a differing epidemic pattern from that in the pre-pandemic era, such as seasonality. Despite the significant diminution, the peak occurrence of MP infection took place in winter time between 2020 and 2022, while P1 type 1 remained the dominant MP genotype and the rate of MRMP was still as high as 96% among all MP specimens owing to A2063G mutation [29]. After the COVID-19 pandemic ended, a pronounced MP outbreak re-surged since July 2023 and maintained a high activity through November 2023, when a 10%−30% positive rate of MP infection was detected with 88.10% macrolide resistance, reported from two separate hospitals in Southern China [18, 30].

Globally, the re-emergence of MP epidemics after COVID-19 pandemic has been reported in many countries, offering several new epidemic patterns. Firstly, the post-COVID MP epidemic underwent a prolonged and non-seasonal outbreak [31]. Weather factors, such as mean temperature and relative humidity, can significantly affect the incidence of MPP [32]. This may explain the seasonal variations in the peak occurrence of MP infection in different regions. Simultaneously, the seasonality of MP epidemics, like many other respiratory pathogen infections, is susceptible to public health interventions in the region, such as travel restriction and mandatory masking amid the COVID-19 pandemic. Those NPIs greatly disrupted the seasonal peaks of respiratory pathogen infections, resulting in the ‘off-season’, ‘see-saw’, and ‘upsurge’ patterns in the post-COVID era once those NPIs were lifted [33]. Consistently, we here reported a postponed but rebound MP infection with peak occurrence in October 2023, about 2 months later than that in the pre-COVID time, corroborated by findings from others [31, 34].

Secondly, the coincident infection of MP with other respiratory pathogens in the post-COVID era became frequent. In fact, the bacterial and viral co-infections are commonly associated with MPP cases, whereas the higher occurrences of co-infections were found in the younger children with RMPP before the COVID-19 pandemic [22, 35]. The immune debt was similarly applicable to other respiratory pathogens rather than MP, since more than 3 years of NPIs adopted during the COVID-19 pandemic minimized the prevalence of many respiratory pathogens, so attenuating their immune stimulation. The relaxing of NPIs led to accelerated infections to populations, especially those with immunological vulnerability, such as children. This was mirrored by the fact that following the relaxation of COVID-19 NPIs, co-circulation of multiple respiratory pathogens increased the co-infection rate, leading to twindemic or tripledemic [36]. This also agreed with our results here that the elevated co-infection of IAV/IBV stood out in the post-COVID pediatric patients with MPP, which may contribute to the altered clinical manifestation of MPP (exampled by increased frequencies of cough and expectoration) and the raised administration of methylprednisolone for effective treatment.

Thirdly, two primary MP genotypes were found co-circulating amid the recent outbreak in post-COVID China, with decreasing portion of P1 type 1 (P1-1) but growing portion of P1 type 2 (P1-2), while more frequent macrolide resistance mutations (in the domain V of 23S rRNA, primarily A2063G) were acquired by P1 subtypes than pre-COVID time [19, 37]. The clinical samples taken from pediatric patients in central China were genotyped as 76.4% P1-1 and 23.4% P1-2 in 2019, and 50.0% P1-1 and 50.0% P1-2 in 2021, and all had A2063G mutations that resulted in macrolide resistance, showing no statistical difference in clinical characteristics between two P1 subtypes [37]. It is putative that the climbing trend of MRMP infections cross the world, with regional differences from 5.1% in European countries to 79.5% in China, may increase the risk of RMPP and SMPP, especially in children [11]. Patients with MRMP infection could have longer fever, medication course, and hospital stay, and higher levels of neutrophils, CRP and AST, and lower macrolide efficacy, than those with MSMP infection [4]. Nevertheless, systematic review and meta-analysis indicated the clinical difference between MRMP and MSMP infections was minimal. Similarly, compared to that in the pre-COVID era, no increased disease severity nor worsened clinical outcome has been recognized in the post-COVID era [34, 38]. Here our result revealed no substantial difference in clinical severity of pediatric patients with MPP before and after the COVID-19 pandemic, which stood in line with those findings.

For the increasing MRMP infection in China, the first-line treatment using macrolide antibiotics becomes challenging, given the fact that MRMP was 80% and 72% against erythromycin and azithromycin, respectively [39]. Azithromycin treatment, albeit resulting in longer febrile days in MRMP patients than in MSMP patients before they defervesced, remains the first choice of antibiotics against MPP mostly due to its anti-inflammatory effect aside from antimicrobial functions, while its combination with other drugs may synergize for a better outcome [12, 40]. In case that the patient with MPP has co-infection with other bacteria, non-macrolide antibiotics, mainly penicillin or cephalosporin, should be administered together with macrolides [41]. This was consistent with our study here. However, macrolide unresponsive MPP (MUMPP) is identified when fever is persistent over 3 days with unimproved or deteriorating symptoms after macrolide treatment, and 34.6% of pediatric patients with MUMPP were developing into RMPP without proper medication, where the risk factors included age, cell counts of leukocyte and neutrophil, serum levels of procalcitonin and LDH [42]. Therefore, a timely switch to another treatment regimen should be considered when RMPP is highly suspected. Although second-line medications, such as tetracycline (e.g., minocycline and doxycycline) and quinolones (e.g., moxifloxacin and fluoroquinolones) demonstrated no resistance, they were not preferred to treat young pediatric patients (< 8 years old), due to the dental damage and bone toxicity [43].

In Japan, the occurrence of MRMP infection in children remained high between 2008 and 2012 but declined rapidly afterwards. The reason can be attributed to the use of respiratory fluoroquinolone/tosufloxacin and the changing distribution of P1 genotypes [44, 45]. The excessive prescription of macrolides may influence the selection and increase the macrolide-resistant strains, so the appropriate use of macrolides and their alternatives becomes a key in reducing MRMP infection rates. In addition to antimicrobials, immunomodulators such as corticosteroids can alleviate the inflammatory reactions associated with MPP without adverse effects [40]. The pathogenesis of MPP was reported to be associated with the proinflammatory cytokine production and immune cell activation [26], while corticosteroids have been administrated during the COVID-19 pandemic to treat SARS-CoV-2 infection, due to their inhibition of cytokine release and suppression of T-cell immunity [46]. Irrespective of antibiotic use, early corticosteroid therapy was suggested to reduce the disease severity of pediatric patients with MPP [47]. Simultaneously, glucocorticoid add-on treatment for MRMP in children might significantly lower the morbidity [48].

This study has several limitations. First, most of the pediatric patients in the post-COVID group were not tested for SARS-CoV-2 infection at the time of hospitalization, and the possibility of co-infection with SARS-CoV-2 cannot be excluded, albeit the SARS-CoV-2 remained a relatively low activity since April 2023 and the population immunity to COVID-19 was already boosted. Second, there was no information available with regards to the therapeutic measures of pediatric patients taken before they were hospitalized, as many of them might have self-administered medications at home or local clinics. This would underestimate the patients’ conditions upon their hospital admission. Finally, a series of data for patients during their hospital stays were missing. We could otherwise assess the disease courses until they were discharged and compare the dynamic data before and after COVID-19 pandemic, for a better understanding towards the complete disease profile of MPP over time.

Conclusion

We reported and compared the clinical characteristics of hospitalized pediatric patients with MP infections in two hospitals in Jiangsu Province, China, before and after the COVID-19 pandemic. While the epidemic patterns of pediatric MPP were substantially changed after the COVID-19 pandemic, the clinical severity revealed no evident mitigation or aggravation, although the patients’ baseline characteristics, radiological features, and laboratory parameters showed measurable variations.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding authors (JZ or ZT) on request.

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Acknowledgements

We thank the financial supports from Jiangsu University and Xuzhou Medical University.

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Authors and Affiliations

  1. Department of Emergency Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212001, China

    Yuqian Zhang, Jianguo Zhang & Zhimin Tao

  2. Department of Emergency Medicine, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, China

    Chenglei Su & Xianliang Yan

  3. Department of Emergency Medicine, Suining County People’s Hospital, Xuzhou, Jiangsu, 221200, China

    Yang Zhang & Xianliang Yan

  4. Department of Emergency Medicine, Fengxian County People’s Hospital, Xuzhou, Jiangsu, 221700, China

    Shuo Ding

  5. Jiangsu Province Key Laboratory of Medical Science and Laboratory Medicine, Department of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, 212013, China

    Zhimin Tao

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  1. Yuqian Zhang
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  2. Chenglei Su
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  3. Yang Zhang
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Contributions

JZ and ZT conceived the idea and designed the study. YQZ, CS, YZ, SD, XY and JZ contributed to the data processing and CT graph reading. YQZ and ZT prepared all tables and figures. YQZ, CS and ZT contributed to the statistical analysis. All authors wrote and revised the manuscript and approved the manuscript submission.

Corresponding authors

Correspondence to Jianguo Zhang or Zhimin Tao.

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Ethics approval and consent to participate

The study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committees of Affiliated Hospital of Jiangsu University and Affiliated Hospital of Xuzhou Medical University, respectively. The informed consents of patients were waived by both Research Ethics Committees due to the retrospective nature of this study.

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The authors declare no competing interests.

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Zhang, Y., Su, C., Zhang, Y. et al. Epidemiological and clinical characteristics of hospitalized pediatric patients with Mycoplasma pneumoniae pneumonia before and after the COVID-19 pandemic in China: a retrospective multicenter study. BMC Infect Dis 25, 18 (2025). https://doi.org/10.1186/s12879-024-10370-8

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BMC Infectious Diseases

ISSN: 1471-2334

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