Molecular level understanding of resistance to nalidixic acid in Salmonella enteric serovar typhimurium associates with the S83F sequence type

Abstract

Nalidixic acid is an antibiotic drug used for treatment of Salmonellosis, a gastrointestinal infection. DNA gyrase subunit A (GyrA) of Salmonella typhimurium is the drug target for nalidixic acid. Resistance of GyrA to nalidixic acid, because of a point mutation in S. typhimurium, was recently reported. Substitution of Phe in place of Ser at locus 83 in GyrA of S. typhimurium has been experimentally associated with nalidixic acid resistance. Despite recent efforts, the mechanism of this resistance is not well understood. In this investigation we used computational techniques to address this shortcoming. Our results showed that contact with residue Arg 91 is certainly important for efficient binding of nalidixic acid to the target protein, and that mutation of this residue results in 180° rotation of the antibiotic in its binding pocket, around its own long axis. It is hoped these findings may enable development of new antibiotics against resistant forms of Salmonella.

Salmonellosis detection and evidence of antibiotic resistance in an urban raccoon population in a highly populated area, Costa Rica

“…Typhimurium/none‐identified strain). Since the mechanisms of resistance are closely related (DNA gyrase [gyrA and gyrB] and topoisomerase IV [parC and pare]; Preethi & Ramanathan, ), our results are not surprising.…”

“…In our study, one isolate was resistant to ciprofloxacin (S. Kentucky) and two were resistant to nalidixic acid (none-identified strain), and two isolates presented resistance to both antibiotics (S. Typhimurium/ none-identified strain). Since the mechanisms of resistance are closely related (DNA gyrase [gyrA and gyrB] and topoisomerase IV [parC and pare];Preethi & Ramanathan, 2016), our results are not surprising.…”

“…Remarkably, although S . Typhimurium is reported to demonstrate ciprofloxacin and nalidixic acid resistance in human studies by different authors (Oteo, Aracil, Alós, & Gómez‐Garcés, ; Preethi & Ramanathan, ; Roumagnac et al, ; Wain et al, ), Costa Rica´s national antibiotic resistance surveillance has not found S . Typhimurium with such AMR, as noted above.…”

Drug repurposing: An approach to tackle drug resistance inS. typhimurium

“…The E. coli strain was cultured in Luria‐Bertani broth (Titan Biotech Ltd., Azadpur, New Delhi, India) media until it reaches 0.5 McFarland units. Four different antibiotics; ciprofloxacin (Titan Biotech Ltd.), flufenamic acid (Sigma–Aldrich, Shivaji Marg, New Delhi, India), nalidixic acid (Himedia, Mumbai, Maharashtra, India), and sulfamethoxazole (Sigma–Aldrich), were used to estimate its MIC against E. coli ATCC 25922 strain . Fifty microlitres of the antibiotic solution with two‐fold serial dilution from 3600 to 0.054 μM were added in a sterile 96‐well microtitre plate.…”

“…Four different antibiotics; ciprofloxacin (Titan Biotech Ltd.), flufenamic acid (Sigma-Aldrich, Shivaji Marg, New Delhi, India), nalidixic acid (Himedia, Mumbai, Maharashtra, India), and sulfamethoxazole (Sigma-Aldrich), were used to estimate its MIC against E. coli ATCC 25922 strain. 46 Fifty microlitres of the antibiotic solution with two-fold serial dilution from 3600 to 0.054 μM were added in a sterile 96-well microtitre plate. Bacterial cell suspension with 5 × 10 5 CFU mL −1 was prepared and 50 μL was seeded to the wells along with this 100 μL blank and 100 μL growth controls was also maintained.…”