Identification and expression analysis of ceftriaxone resistance-related genes in Neisseria gonorrhoeae integrating RNA-Seq data and qRT-PCR validation.

Objectives: The aim of the study is to identify ceftriaxone resistance-related genes in Neisseria gonorrhoeae.

Methods: Differences in gene expression were compared between ceftriaxone-susceptible N. gonorrhoeae isolates [minimum inhibitory concentration (MIC)=0.002-0.004mg/L] and isolates with decreased ceftriaxone susceptibility (MIC=0.125-0.5mg/L) using RNA-Seq (RNA sequencing).

Results: Total RNA of 10 clinical isolates was used to make libraries and generated an average of 24.07Mb reads per sample; these were assembled into 1871 mRNA genes. Moreover, 21 differentially expressed genes (DEGs) were found between the N. gonorrhoeae isolates with susceptibility and decreased susceptibility to ceftriaxone with a fold change of ≥2 (P<0.05), among which 11 were upregulated and 10 were downregulated. Furthermore, all DEGs were verified by quantitative reverse transcription PCR (qRT-PCR), which detected 25 clinical isolates with decreased ceftriaxone susceptibility and 21 ceftriaxone-susceptible isolates. In addition, seven DEGs revealed relative expression levels by 2Ct and showed a statistical significance (P≤0.05). Analysis of Gene Ontology (GO) terms and KEGG pathway for functional enrichment showed that six DEGs were related to the cellular component and one DEG was related to the biosynthesis of antibiotics, and these results might be related to ceftriaxone resistance.

Conclusions: Examining ceftriaxone resistance-related genes in N. gonorrhoeae is necessary owing to the high morbidity and antimicrobial resistance of N. gonorrhoeae, especially its eventual resistance to third-generation extended-spectrum cephalosporins (cefixime and ceftriaxone). Moreover, this report provides a new direction for the study and control of ceftriaxone-resistant N. gonorrhoeae.