ABSTRACT:
Quinolone-resistant nontyphoidal
Salmonella
, one of the prominent pathogens causing acute gastroenteritis, has become a public health concern globally. The World Health Organization has ranked fluoroquinolone-resistant
Salmonella
as a high-priority pathogen for researching and developing new antibiotics. WQ-3034 and WQ-3154 are relatively new synthetic fluoroquinolones with distinctive structures. WQ-3034 has 6-amino-3,5-difluoropyridine-2-yl at R
1
, 3-hydroxyazetidinyl at R
7
, and the addition of chlorine atom at R
8
. WQ-3154 has a similar basic pharmacophore to WQ-3034 except for the modification at R
8
with a methyl group. In this study, the inhibitory effect and DNA cleavage effect against wild-type (WT) and mutant
Salmonella
Typhimurium DNA gyrases of WQ-3034 and WQ-3154 were examined along with WQ-3810 and ciprofloxacin by measuring the drug concentration that inhibits half of the enzyme activity (IC
50
) and the drug concentration that induces 25% of maximum DNA cleavage (CC
25
). The minimum inhibitory concentration (MIC) of the compounds was assessed against
Salmonella
Typhimurium and
Salmonella
Enteritidis. Among four compounds, WQ-3034 demonstrated the highest inhibitory effect against both WT and mutant
Salmonella
Typhimurium DNA gyrases with amino acid substitution at codon 83 and/or 87, while ciprofloxacin showed the lowest inhibitory effect. Remarkably, WQ-3034 and WQ-3154 exhibited a significantly higher inhibitory effect than ciprofloxacin against
Salmonella
Typhimurium DNA gyrase with double amino acid substitution, Ser83Phe-Asp87Asn. Similarly, CC
25
of WQ-3034 against mutant
Salmonella
Typhimurium DNA gyrase was lower than ciprofloxacin. Notably, MICs of WQ-3034 and WQ-3154 were higher than ciprofloxacin. In conclusion, this study revealed that WQ-3034 and WQ-3154 could potentially be effective therapeutic agents against quinolone-resistant nontyphoidal
Salmonella
.
IMPORTANCE:
Quinolone-resistant nontyphoidal
Salmonella
is a pressing public health concern, demanding the exploration of novel treatments. In this study, we focused on two innovative synthetic fluoroquinolones, WQ-3034 and WQ-3154. Our findings revealed that these new compounds demonstrate potent inhibitory effects, even against mutant strains that cause resistance to existing quinolones. Hence, WQ-3034 and WQ-3154 could potentially be effective therapeutic agents against quinolone-resistant
Salmonella
Typhimurium. Furthermore, the data obtained in this study will be baseline information for antimicrobial drug development.