dThe emergence of ceftriaxone-resistant Neisseria gonorrhoeae is currently a global public health concern. However, the mechanism of ceftriaxone resistance is not yet fully understood. To investigate the potential genes related to ceftriaxone resistance in Neisseria gonorrhoeae, we subcultured six gonococcal strains with increasing concentrations of ceftriaxone and isolated the strains that became resistant. After analyzing several frequently reported genes involved in ceftriaxone resistance, we found only a single mutation in penA (A501V). However, differential analysis of the genomes and transcriptomes between pre-and postselection strains revealed many other mutated genes as well as up-and downregulated genes. Transformation of the mutated penA gene into nonresistant strains increased the MIC between 2.0-and 5.3-fold, and transformation of mutated ftsX increased the MIC between 3.3-and 13.3-fold. Genes encoding the ABC transporters FarB, Tfq, Hfq, and ExbB were overexpressed, while pilM, pilN, and pilQ were downregulated. Furthermore, the resistant strain developed cross-resistance to penicillin and cefuroxime, had an increased biochemical metabolic rate, and presented fitness defects such as prolonged growth time and downregulated PilMNQ. In conclusion, antimicrobial pressure could result in the emergence of ceftriaxone resistance, and the evolution of resistance of Neisseria gonorrhoeae to ceftriaxone is a complicated process at both the pretranscriptional and posttranscriptional levels, involving several resistance mechanisms of increased efflux and decreased entry.
Gonorrhea is one of the most prevalent sexually transmitted infections (STIs), and it is associated with many severe clinical symptoms such as prostatitis, seminal vesiculitis, pelvic inflammation, infertility, and ophthalmia neonatorum (1). Although epidemiological data show a decreased trend in gonorrhea incidence as a whole, in some countries, the incidence is increasing, especially in specific population groups (adolescents, men who have sex with men, or sex workers) or specific venues (brothels) (2-5). The pathogen responsible for this disease is Neisseria gonorrhoeae. According to worldwide surveillance reports, N. gonorrhoeae has developed resistance to several kinds of antibiotics over the past decades (6-10). Of increasing concern is the prevalence of ceftriaxone (CRO)-resistant N. gonorrhoeae (11), because CRO is the first-line empirical drug for gonorrhea treatment in dual therapy with azithromycin or doxycycline recommended by the WHO (covering the Western Pacific region and the Southeast Asian region) and the CDC (12-14). Several CRO-resistant gonococcal strains, such as H041 and F89, were isolated recently from patients who had a treatment failure with CRO (H041) and cefixime (F89) (15-18). Highlighting the seriousness of these resistant strains, Ohnishi et al. proposed the concept of an N. gonorrhoeae "superbug" in 2011 (17). Uncovering the mechanisms of CRO resistance is now a critical topic of N. gonorrhoeae research.Previous s...
