Comparative Study on the Evaluation Methods for Mycoplasma pneumoniae Infection

doi:10.13560/j.cnki.biotech.bull.1985.2024-0464

Abstract

Abstract:

【Objective】In this study, mice were used as animal models to analyze the characteristics of Mycoplasma pneumoniae infection（MPI）and to compare and analyze the evaluation criteria of lesions, aiming to provide a reference for the development of a unified evaluation method for MPI.【Method】BALB/c mice were infected with the M. pneumoniae M129 strain at a concentration of 5×10⁷ CCU twice via nasal drip. After 14 d, the weight, gross lung lesions, pathological changes of lung tissue and two quantitative analysis methods, pathogenic load of lung tissue, T lymphocyte subsets in peripheral blood and the expressions of IL-6 in serum were detected. The infection characteristics of M. pneumoniae were analyzed and the evaluation criteria of lesions were compared and analyzed.【Result】After 14 d of infection with M129 strain, the level of IL-6 in BALB/c mice serum increased; significant consolidation occurred in the lungs, a large number of neutrophil infiltrates were observed in lung tissue sections, and alveolar septal thickening was observed. Two methods were used to compare the degree of lung lesions in lung pathological sections, and it was found that the pathological scoring system for lung injury proposed by the American Thoracic Society（ATS）reflected lung lesions more finely and objectively than the 26-score method. Infection led to the development of inflammatory responses in mice and eventually caused a significant reduction in mice body weight. On the other hand, the results of lung pathogen load showed that the lung pathogen load of mice infected with M129 strain was very low after 14 d. Flow cytometry analysis of T cell subsets showed that the body produced immunity biased towards CD4⁺ T cells, suggesting that M. pneumoniae infection and body immunity play a mutual game, and the body's immune response may gradually clear the lung pathogen.【Conclusion】M. pneumoniae causes systemic inflammation via nasal drip in BALB/c mice. ATS lung injury pathology scoring system is more precise and objective than the 26-score method for the evaluation of lung tissue lesions, which is conducive to the comparative analysis of different studies.

Key words: Mycoplasma pneumoniae, mouse infection model, lung lesions, pathology scoring system, immune clearance

LI Zhi-qiang, WANG Ji-ying, YUAN Ting, WANG Jia, WEI Yan-na, WANG Yu-ge, LI Shao-li, SHAO Guo-qing, FENG Zhi-xin, YU Yan-fei. Comparative Study on the Evaluation Methods for Mycoplasma pneumoniae Infection[J]. Biotechnology Bulletin, 2025, 41(1): 110-119.

Figures/Tables 14

References 38

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指标 Parameter	每视野得分Score per field
指标 Parameter	0	1	2
A.肺泡腔内的中性粒细胞 Neutrophils in the alveolar space	无None	1-5	>5
B.间隙内的中性粒细胞 Neutrophils in the interstitial space	无None	1-5	>5
C.透明膜Hyaline membranes	无None	1	>1
D.充满空气空间的蛋白 Proteinaceous debris filling the airspaces	无None	1	>1
E.肺泡间隔增厚 Alveolar septal thickening	<2×	（2-4）×	>4×

指标 Parameter	每视野得分Score per field
指标 Parameter	0	1	2
A.肺泡腔内的中性粒细胞 Neutrophils in the alveolar space	无None	1-5	>5
B.间隙内的中性粒细胞 Neutrophils in the interstitial space	无None	1-5	>5
C.透明膜Hyaline membranes	无None	1	>1
D.充满空气空间的蛋白 Proteinaceous debris filling the airspaces	无None	1	>1
E.肺泡间隔增厚 Alveolar septal thickening	<2×	（2-4）×	>4×

评价指标Evaluating indicator	评价标准Evaluation criterion	得分Score
A.细支气管/支气管周围浸润 Peribronchiolar/bronchial infiltrates	无 None	0
	少量：<25% Few: <25%	1
	很多：25%-75% Many: 25%-75%	2
	大部分：>75% Majority: >75%	3
B.细支气管/支气管周围浸润的定性 Quality of peribronchiolar/ bronchial infiltrates	无：偶见极少量渗出物或大的支气管周围淋巴样肿物 None: Occasional minimal infiltrates or large peribronchial lymphoid	0
	轻度：异常，常有间断的环 Mild: Abnormal, often with interrupted collar	1
	中度：完整的环或新月形的环，小于5个细胞的厚度 Moderate: Complete collar or crescent collar with the thickness of < 5 cells	2
	重度：完整的环，大于5-10个细胞厚度 Severe: Complete collar with the thickness of > 5-10 cells	3
C. 细支气管/支气管腔渗出 Peribronchiolar/ bronchial luminal exudate	无 None	0
	轻度：≤25%腔闭合 Light: ≤25% lumen occlusion	1
	重度：>25%腔闭合Heavy: >25% lumen occluded	2
D.血管周围浸润 Perivascular infiltrate	无 None	0
	少量：<10% Few: <10%	1
	很多：10%-50% Many: 10%-50%	2
	大部分：>50% Majority: >50%	3
E.实质性肺炎 Parenchymal pneumonia	无 None	0
	轻度：斑块状实质性浸润 Light: Patchy parenchymal infiltrates	3
	重度：斑块状和融合的实质性浸润 Heavy: Patchy and confluent parenchymal infiltrates	5

评价指标Evaluating indicator	评价标准Evaluation criterion	得分Score
A.细支气管/支气管周围浸润 Peribronchiolar/bronchial infiltrates	无 None	0
	少量：<25% Few: <25%	1
	很多：25%-75% Many: 25%-75%	2
	大部分：>75% Majority: >75%	3
B.细支气管/支气管周围浸润的定性 Quality of peribronchiolar/ bronchial infiltrates	无：偶见极少量渗出物或大的支气管周围淋巴样肿物 None: Occasional minimal infiltrates or large peribronchial lymphoid	0
	轻度：异常，常有间断的环 Mild: Abnormal, often with interrupted collar	1
	中度：完整的环或新月形的环，小于5个细胞的厚度 Moderate: Complete collar or crescent collar with the thickness of < 5 cells	2
	重度：完整的环，大于5-10个细胞厚度 Severe: Complete collar with the thickness of > 5-10 cells	3
C. 细支气管/支气管腔渗出 Peribronchiolar/ bronchial luminal exudate	无 None	0
	轻度：≤25%腔闭合 Light: ≤25% lumen occlusion	1
	重度：>25%腔闭合Heavy: >25% lumen occluded	2
D.血管周围浸润 Perivascular infiltrate	无 None	0
	少量：<10% Few: <10%	1
	很多：10%-50% Many: 10%-50%	2
	大部分：>50% Majority: >50%	3
E.实质性肺炎 Parenchymal pneumonia	无 None	0
	轻度：斑块状实质性浸润 Light: Patchy parenchymal infiltrates	3
	重度：斑块状和融合的实质性浸润 Heavy: Patchy and confluent parenchymal infiltrates	5

组别 Group	编号 Numbering	D0体重 D0 Weight/g	D14体重 D14 Weight/g	体重变化 Weight change/g
M129	B59	19.0	15.4	-3.6
	B60	18.5	15.8	-2.7
	B70	18.0	14.7	-3.3
	B72	17.7	13.9	-3.8
	B73	19.2	16.5	-2.7
NC	B56	18.8	20.4	1.6
	B57	17.2	20.5	3.3
	B58	17.8	21.3	3.5
	B69	18.1	20.8	2.7
	B71	18.0	20.6	2.6