Bacteria account for nearly one third of the causes of community-acquired central nervous system infections, and traditional diagnostic methods are based on culture results, which are time-consuming and have a low detection rate leading to delayed diagnosis and treatment. Since metagenomic next-generation sequencing (mNGS) has the advantages of high timeliness and only detecting microbial trace gene fragments, it has been used more widely in recent years. Based on this, we explored whether the application of cerebrospinal fluid (CSF) mNGS is advantageous in patients with community-acquired purulent meningitis, especially in people who have already used antibiotics.This was a retrospective study of 63 patients with community-acquired purulent meningitis admitted to the Department of Neurology of Shanxi Bethune Hospital from March 2018 to November 2022. Data were systematically collected and classified into CSF culture group, blood culture group and CSF mNGS group according to different detection methods, and the total detection rate of each method was calculated. Each group of patients was divided into two subgroups according to whether antibiotics were used before sampling. The detection rates of the three groups were compared within and between groups to explore whether mNGS has advantages over traditional methods and the influence of antibiotic use on detection rates of the three methods.Among the 63 patients, the cases of CSF culture, blood culture and CSF mNGS were 56, 46, 44, respectively. The total detection rates of the three methods were 17.86%, 36.96%, 81.82%, with statistical differences (p < 0.05),suggesting that the detection rate of mNGS was higher than CSF culture (p < 0.05) and blood culture (p < 0.05),and the detection rate of blood culture higher than CSF culture (p < 0.05). Further grouping found that without antibiotics, the detection rates of CSF culture, blood culture and CSF mNGS were 28.57%, 56.25% and 88.89%, with statistical differences (p < 0.05), and the detection rate of CSF mNGS was higher than that of CSF culture (p < 0.05), but there was no statistical difference between CSF and blood culture (p > 0.05), nor between blood culture and CSF mNGS (p > 0.05). The detection rates of the three groups with antibiotics were 14.29%, 26.67% and 80.00%, with statistical differences (p < 0.05), and the detection rate of CSF mNGS was still higher than CSF culture (p < 0.05) and blood culture (p < 0.05). However, the detection rate of CSF mNGS also decreased after antibiotics were used for more than 3 days.The detection rate of CSF mNGS in patients with purulent meningitis is higher than traditional methods, especially in patients who have been given antibiotics, but the detection rate will decrease with the extension of antibiotic use.© 2023. BioMed Central Ltd., part of Springer Nature.