Repurposing Salicylamide for Combating Multidrug-Resistant Neisseria gonorrhoeae

Abstract

The U.S. Centers for Disease Control and Prevention (CDC) lists Neisseria gonorrhoeae as one of the most urgent antibiotic-resistant threats in the United States. This is due to the emergence of clinical isolates that have developed resistance to nearly every antibiotic used to treat gonorrhea and highlights the critical need to find new therapeutics. The present study discovered salicylamide, an analgesic and antipyretic drug, has antibacterial activity against 40 different antibiotic-resistant strains of N. gonorrhoeae (MIC, 8 to 32 μg/ml) with low frequency of resistance <2.4 × 10−9. Interestingly, salicylamide did not inhibit growth of bacterial species in the vaginal microflora involved in defense against gonococcal infections, such as Lactobacillus gasseri, Lactobacillus jensenii, Lactobacillus johnsonii, and Lactobacillus crispatus. A time-kill assay revealed that salicylamide is a rapidly bactericidal drug, as it eradicated a high inoculum of N. gonorrhoeae within 10 h. Salicylamide was superior to the drug of choice, ceftriaxone, in reducing the burden of intracellular N. gonorrhoeae by 97% in infected endocervical cells. Furthermore, salicylamide outperformed ceftriaxone in reducing expression of the proinflammatory cytokine interleukin 8 (IL-8) from endocervical cells infected with N. gonorrhoeae. A checkerboard assay revealed that salicylamide exhibited a synergistic interaction with tetracycline and additive relationships with azithromycin, ciprofloxacin, and ceftriaxone. A more in-depth investigation of the structure-activity relationship of derivatives of salicylamide revealed the amide and hydroxyl groups are important for antigonorrheal activity. In conclusion, this study identified salicylamide as a promising candidate for further investigation as a novel treatment option for multidrug-resistant gonorrhea.

Investigation of auranofin and gold-containing analogues antibacterial activity against multidrug-resistant Neisseria gonorrhoeae

“…The commensal vaginal bacterial strains were obtained from the Biodefense and Emerging Infections Research Resources Repository (BEI Resources) (Supplementary Table 2). All chemical compounds used in this study were obtained commercially from chemical vendors: auranofin (Chem-Impex International, Wood Dale, IL), sodium aurothiomalate, tetracycline and ciprofloxacin (Sigma-Aldrich, St. www.nature.com/scientificreports www.nature.com/scientificreports/ azithromycin was determined using the broth microdilution assay, as previously described 42 . Briefly, a 1.0 McFarland standard was prepared and diluted in Brucella Supplemented broth (BSB) (Brucella broth supplemented with yeast extract, dextrose, agarose, proteose-peptone, NAD, pyrodixal and hematin) to reach a bacterial count of 5 × 10 5 CFU/mL.…”

“…In order to investigate the ability of auranofin to enter human endocervical cells and reduce the burden of intracellular N. gonorrhoeae an intracellular bacterial clearance assay was utilized as previously described 42 . Briefly, a cell density of ~1 ×10 5 per well of human endocervical cells (ATCC CRL-2615, End1/E6E7) were seeded in 96-well tissue culture and then infected with N. gonorrhoeae strain194 at a multiplicity of infection of 100:1 for six hours at 37 °C and 5% CO 2 .…”

“…To investigate the anti-inflammatory activity of the gold compounds, IL-8, a pro-inflammatory cytokine, was detected in the supernatants of N. gonorrhoeae infected End1/E6E7 -human endocervix cells (ATCC CRL-2615) exposed to either the gold-containing drugs or ceftriaxone, as previously described 42,48 . In brief, N. gonorrhoeae strain 194 was allowed to infect the endocervical cells for two hours at 37°C with 5% CO 2 before initiating treatment with 0.5 × MIC of ceftriaxone, auranofin, sodium aurothiomalate, or aurothioglucose (tested in triplicates) and left for four hours.…”

Screening of Natural Products and Approved Oncology Drug Libraries for Activity against Clostridioides difficile

“…Translation of the current knowledge and technological advancements to a novel therapeutic is shackled by multifold challenges, including high costs, increased time, and risks of failure, thus making it a less preferable choice for investors. Drug repurposing, which involves identifying novel uses for drugs [30][31][32][33] that have already been approved or are in early stages of clinical trials, can be a lucrative alternative strategy, as it offers a reduced time frame for development, less costly investment, and lower risks of failure 18,34 .Thus, with this approach in mind, we screened two NCI libraries in an attempt to identify novel scaffolds exhibiting anti-clostridial activity.…”

N-(1,3,4-Oxadiazol-2-yl)Benzamides as Antibacterial Agents against Neisseria gonorrhoeae

“…The MICs of the tested compounds and control drugs; azithromycin, and tetracycline were determined using the broth microdilution as described previously [ 42 , 43 , 44 ]. Briefly, bacteria were grown overnight on chocolate agar II at 37° C in the presence of 5% CO 2 .…”