[A multicenter retrospective study on the etiology of necrotizing pneumonia in children].

Objective: To investigate the etiology of necrotizing pneumonia (NP) in children and the clinical characteristics of NP caused by different pathogens in China. Methods: A retrospective, case-control study was performed in children with NP who were admitted to 13 hospitals in China from January 2008 to December 2019. The demographic and clinical information, laboratory data, etiological and radiological findings were analyzed. The data were divided into three groups based on the following years: 2008-2011, 2012-2015 and 2016-2019, and the distribution characteristics of the pathogens in different period were compared. Meanwhile, the pathogens of pediatric NP in the southern and northern China were compared. And the clinical characteristics of the Mycoplasma pneumoniae (MP) NP and the bacterial NP were also compared. T-test or Mann-Whitney nonparametric test was used for comparison of numerical variables, and χ2 test was used for categorical variables. Results: A total of 494 children with NP were enrolled, the median ages were 4.7 (0.1-15.3) years, including 272 boys and 222 girls. Among these patients, pathogens were identified in 347 cases and the pathogen was unclear in the remaining 147 cases. The main pathogens were MP (238 cases), Streptococcus pneumoniae (SP) (61 cases), Staphylococcus aureus (SA) (51 cases), Pseudomonas aeruginosa (13 cases), Haemophilus influenzae (10 cases), adenovirus (10 cases), and influenza virus A (7 cases), respectively. MP was the most common pathogen in all three periods and the proportion increased yearly. The proportion of MP in 2016-2019 was significantly higher than that in 2012-2015 (52.1% (197/378) vs. 36.8% (32/87), χ2=6.654, P=0.010), while there was no significant difference in the proportion of MP in 2012-2015 and that in 2008-2011 (36.8% (32/87) vs. 31.0% (9/29), χ²=0.314, P=0.575).Regarding the regional distribution, 342 cases were in the southern China and 152 in the northern China. Also, MP was the most common pathogen in both regions, but the proportion of MP was higher and the proportion of SP was lower in the north than those in the south (60.5% (92/152) vs. 42.7% (146/342), χ2=13.409, P<0.010; 7.9% (12/152) vs. 14.3% (49/342), χ2=4.023, P=0.045). Comparing the clinical characteristics of different pathogens, we found that fever and cough were the common symptoms in both single MP and single bacterial groups, but chest pain was more common (17.0% (34/200) vs. 6.1% (6/98), χ2=6.697, P=0.010) while shortness of breath and wheezing were less common in MP group (16.0% (32/200) vs. 60.2% (59/98), χ2=60.688, P<0.01; 4.5% (9/200) vs. 21.4% (21/98), χ2=20.819, P<0.01, respectively). The white blood cell count, C-reactive protein and procalcitonin in the bacterial group were significantly higher than those in the MP group (14.7 (1.0-67.1)×109/L vs. 10.5 (2.5-32.2)×109/L, 122.5 (0.5-277.3) mg/L vs. 51.4 (0.5-200.0) g/L, 2.13 (0.05-100.00) μg/L vs. 0.24 (0.01-18.85) μg/L, Z=-3.719, -5.901 and -7.765, all P<0.01). Conclusions: The prevalence of pediatric NP in China shows an increasing trend during the past years. MP, SP and SA are the main pathogens of NP, and the most common clinical symptoms are fever and cough. The WBC count, C-reactive protein and procalcitonin in bacterial NP are significantly higher than those caused by MP.目的： 了解我国儿童坏死性肺炎（NP）的病原学分布特点及不同病原学NP的临床特点。 方法： 病例对照研究，收集中国13家医院2008年1月至2019年12月共494例NP患儿的一般情况、临床表现、实验室检查和影像学检查等临床资料。根据年份分为2008至2011年、2012至2015年、2016至2019年3组，根据地域分为南方和北方，分别比较病原学的分布特点；根据感染的病原菌不同分为单一肺炎支原体感染组与单一细菌感染组，进行临床特征和炎症指标的比较。组间比较采用t检验、Mann-Whitney非参数检验、χ²检验。 结果： 494例NP患儿（男272例、女222例）年龄4.7（0.1~15.3）岁，其中494例NP中病原菌不明确147例，病原菌明确347例。常见的病原菌分别为肺炎支原体238例，肺炎链球菌61例，金黄色葡萄球菌51例，铜绿假单胞菌13例，流感嗜血杆菌10例，腺病毒10例，流感病毒A 7例。3个年份组最主要的病原均为肺炎支原体，2016至2019年组肺炎支原体比例高于2012至2015年组［52.1%（197/378）比36.8%（32/87），χ²=6.654，P=0.010］，2012至2015年组肺炎支原体比例与2008至2011年组［31.0%（9/29）］比较差异无统计学意义（χ²=0.314，P=0.575）。南方组与北方组患儿最主要的病原均为肺炎支原体，北方组肺炎支原体的比例高于南方组［60.5%（92/152）比42.7%（146/342），χ²=13.409，P<0.01］，而肺炎链球菌的比例则低［7.9%（12/152）比14.3%（49/342），χ²=4.023，P=0.045］。单一肺炎支原体组（200例）与单一细菌感染组（98例）均以发热（分别为197、98例）和咳嗽（分别为200、96例）为主要临床表现，单一肺炎支原体组较单一细菌感染组胸痛症状更常见［17.0%（34/200）比6.1%（6/98），χ²=6.697，P=0.010］，而气促、喘息症状更少见［16.0%（32/200）比60.2%（59/98），4.5%（9/200）比21.4%（21/98），χ²=60.688、20.819，均P<0.01］；单一细菌感染组的外周血白细胞计数、C反应蛋白、降钙素原均明显高于单一肺炎支原体感染组［14.7（1.0~67.1）×109/L比10.5（2.5~32.2）×109/L，122.50（0.5~277.6）比51.4（0.5~200.0）mg/L，2.13（0.05~100.00）比0.24（0.01~18.85）μg/L，Z=-3.719、-5.901、-7.765，均P<0.01］。 结论： 我国儿童NP病例逐年增多，肺炎支原体、肺炎链球菌和金黄色葡萄球菌是引起我国儿童NP的重要病原体。NP的临床症状以发热和咳嗽常见，细菌感染者外周血白细胞计数、C反应蛋白、降钙素原明显高于肺炎支原体感染者。.