目的 探讨日龄<90 d婴儿细菌性脑膜炎（bacterial meningitis, BM）的病原学特征。 方法 回顾性分析5家协作单位2007年1月—2021年12月收治的日龄<90 d婴儿BM的病原学及转归。描述总体病原学特征，比较不同发病年龄、城市及年份的病原分布，以及常见病原菌BM的预后。 结果 共纳入197例细菌学阳性的BM婴儿，常见的病原菌为大肠埃希菌（Escherichia coli, E.coli）（72例，36.5%）、B组链球菌（group B Streptococcus, GBS ）（49例，24.9%）、单核细胞增多李斯特菌（Listeria monocytogenes, LM）（11例，5.6%）等。新生儿组E.coli检出率高于婴儿组（40.2% vs 18.2%，P<0.05）。北京和昆明以E.coli占首位，分别为31.7%、54.1%；深圳以GBS与E.coli并列首位，均为33.3%。2018、2019、2020、2021年E.coli检出率分别为46.4%、47.2%、45.2%及36.8%；GBS检出率分别为25.0%、27.8%、22.6%及31.6%。E.coli、GBS及LM所致BM的总并发症发生率比较差异无统计学意义（P>0.05），LM脑膜炎的脑室炎和脑积水发生率均高于GBS脑膜炎（P<0.017）。 结论 小婴儿BM以E.coli最常见，特别是新生儿；GBS在深圳市最常见，且呈上升趋势。LM脑膜炎也常见，不良预后发生率高。

Objective To investigate the etiological characteristics of bacterial meningitis (BM) in infants aged <90 days. Methods A retrospective analysis was conducted on the etiology and outcomes of BM in infants aged <90 days admitted to five collaborating hospitals between January 2007 and December 2021. The overall etiological profile was described, and pathogen distributions were compared across different age groups, regions, and years. The prognosis of BM caused by common pathogens was also evaluated. Results A total of 197 infants with bacteriologically confirmed BM were included. The most common pathogens were Escherichia coli (E. coli) (72 cases, 36.5%), group B Streptococcus (GBS) (49 cases, 24.9%), and Listeria monocytogenes (LM) (11 cases, 5.6%). The detection rate of E. coli was significantly higher in the neonatal group than in the infant group (40.2% vs 18.2%, P<0.05). E. coli was the predominant pathogen in Beijing (31.7%) and Kunming (54.1%), while GBS and E. coli were equally prevalent in Shenzhen (33.3%). From 2018 to 2021, the detection rates of E. coli were 46.4%, 47.2%, 45.2%, and 36.8%, respectively, whereas those of GBS were 25.0%, 27.8%, 22.6%, and 31.6%. No significant difference was observed in the overall complication rates among BM cases caused by E. coli, GBS, and LM (P>0.05). However, ventriculitis and hydrocephalus were more frequent in LM meningitis than in GBS meningitis (P<0.017). Conclusions E. coli is the most common pathogen in BM among young infants, particularly neonates. GBS is predominant in Shenzhen, with an increasing trend. LM meningitis accounts for a notable proportion of cases and is associated with poorer outcomes.