Repurposing Fenamic Acid Drugs To Combat Multidrug-Resistant Neisseria gonorrhoeae

Abstract

The rise of extensively drug-resistant and multidrug-resistant strains of Neisseria gonorrhoeae has occurred in parallel with the increasing demand for new drugs. However, the current methods of drug discovery are burdened with rigorous assessments and require more time than can be spared until gonococcal infections become difficult to control. To address this urgency, we utilized a drug-repurposing strategy and identified three clinically approved anthranilic acid drugs (tolfenamic acid, flufenamic acid, and meclofenamic acid) with potent antigonococcal activity, inhibiting 50% of the strains (MIC50) from 4 to 16 μg/ml. Furthermore, tolfenamic acid showed indifferent activity with antibiotics of choice for gonococcal infections, azithromycin and ceftriaxone, in checkerboard assays with a fractional inhibitory concentration index ranging from 0.75 to 1.5. Fenamic acids reduced a high inoculum of N. gonorrhoeae below the limit of detection within 12 h and exhibited a low frequency of resistance. Interestingly, the fenamic acids did not inhibit the growth of commensal Lactobacillus spp. that comprise the healthy female genital microbiota. Fenamic acids were also superior to ceftriaxone in reducing the burden of intracellular N. gonorrhoeae within infected endocervical cells by 99%. Furthermore, all three fenamic acids significantly reduced the expression of proinflammatory cytokines by infected endocervical cells. Finally, fenamic acids and other structurally related anthranilic acid derivatives were evaluated to ascertain a more in-depth structure-activity relationship (SAR) that revealed N-phenylanthranilic acid as a novel antigonorrheal scaffold. This SAR study will pave the road to repositioning more potent fenamic acids analogues against N. gonorrhoeae.

Structure–Activity Relationship Studies of Acetazolamide-Based Carbonic Anhydrase Inhibitors with Activity against Neisseria gonorrhoeae

“…Antibacterial activity of synthesized compounds against N. gonorrhoeae strains-The minimum inhibitory concentrations (MICs) of acetazolamide and analogs were determined using the broth microdilution assay, as previously described. [51][52][53] Briefly, N. gonorrhoeae strains were grown overnight on chocolate II agar plates. Bacterial cells were then suspended in phosphate-buffered saline (PBS) to achieve a turbidity equivalent to a 1.0 McFarland standard which was diluted in brucella broth supplemented with yeast extract, dextrose, proteose-peptone, NAD, pyrodixal, hematin and IsoVitaleX to reach a bacterial count of about 1 × 10 6 CFU/mL.…”

Epidemiology, Treatments, and Vaccine Development for Antimicrobial-Resistant Neisseria gonorrhoeae: Current Strategies and Future Directions

“…Several other antibiotics have shown promising in vitro studies in treating N. gonorrhoeae with similar or even superior antimicrobial activity in comparison to currently used antibiotics, including nitroxoline [ 77 ], salicylamide [ 78 ], mupirocin [ 79 ], fenamic acid derivatives [ 80 ], apramycin [ 81 ], and polyketides enacyloxin IIa and gladiolin [ 82 ]. Furthermore, several novel combinations of antibiotics including gentamicin with ertapenem, moxifloxacin with ertapenem, spectinomycin with ertapenem, azithromycin with moxifloxacin, and cefixime with gentamicin have been shown to have excellent in vitro activity against N. gonorrhoeae [ 83 ].…”

Auranofin exerts antibacterial activity against Neisseria gonorrhoeae in a female mouse model of genital tract infection

“…The MIC values of auranofin, azithromycin, and ceftriaxone against N . gonorrhoeae FA1090 were determined, as described previously [ 31 – 34 ]. Briefly, a bacterial suspension equivalent to a McFarland standard of 1.0 was prepared and diluted in Brucella Broth supplemented with yeast extract, dextrose, proteose-peptone, NAD, pyridoxal, and hematin to obtain a bacterial count of 1 × 10 6 CFU/mL.…”