Objective To analyze the clinical characteristics, treatment course and genomic characteristics of a case of meningitis caused by erythromycin-resistant Listeria monocytogenes and provide evidence for clinical diagnosis, treatment and molecular epidemiology research of L. monocytogenes-caused meningitis.

Methods The basic clinical information of a 61-year-old woman admitted due to fever, headache and vomiting, icluding underlying disease history, clinical manifestations, white-blood-cell count (WBC), C-reactive protein (CRP), procalcitonin (PCT), blood culture results, cerebrospinal fluid culture results and metagenomic next-generation sequencing (mNGS) results, as well as antibiotic treatment course and prognosis, were collected for a retrospective analysis. The genomic analysis on the L.monocytogenes strain was performed by whole genome sequencing.

Results Laboratory results showed that the patient's WBC, CRP and PCT all elevated. The cerebrospinal fluid sample of the patient was identified as L. monocytogenes positive through bacterial culture and mNGS methods. The patient was diagnosed with meningitis caused by L. monocytogenes . After 34 days of treatment with ampicillin sodium and gentamicin, the patient was cured and discharged. The sequence type (ST) of the isolated L.monocytogenes strain was ST8, belonging to the CC8 clone group within multiple clone complexes (CCs), family II, and serogroup IIa. The strain carried the Listeria stress island 1 (SSI-1) and Listeria Pathogenicity Island 1 (LIPI-1), and had the complete InlA protein coding gene. Two special inherent drug resistance genes, mefA and msrD, were carried on the chromosome, which encoded the major facilitator superfamily efflux pumps (MFS), resulting in erythromycin resistance.

Conclusions For the clinical differential diagnosis of meningitis caused by L. monocytogenes infection, mNGS detection can identify the pathogen rapidly, sensitively and accurately, and traditional culture can be used for antibiotic susceptibility test and targeted antibiotic treatment to improve the clinical outcome.