Abstract
Background: New strategies are needed to combat multidrug-resistant bacteria. The restriction of iron uptake by bacteria is a promising way to inhibit their growth. We aimed to suppress the growth of Vibrio bacterial species by inhibiting their ferric ion-binding protein (FbpA) using food components. Methods: Twenty spices were selected for the screening of FbpA inhibitors. The candidate was applied to antibacterial tests, and the mechanism was further studied. Results: An active compound, rosmarinic acid (RA), was screened out. RA binds competitively and more tightly than Fe3+ to VmFbpA, the FbpA from V. metschnikovii, with apparent KD values of 8 μM vs. 17 μM. Moreover, RA can inhibit the growth of V. metschnikovii to one-third of the control at 1000 μM. Interestingly, sodium citrate (SC) enhances the growth inhibition effect of RA, although SC only does not inhibit the growth. The combination of RA/SC completely inhibits the growth of not only V. metschnikovii at 100/100 μM but also the vibriosis-causative pathogens V. vulnificus and V. parahaemolyticus, at 100/100 and 1000/100 μM, respectively. However, RA/SC does not affect the growth of Escherichia coli. Conclusions: RA/SC is a potential bacteriostatic agent against Vibrio species while causing little damage to indigenous gastrointestinal bacteria.
Highlights
Vibrio is a genus of ubiquitous bacteria that inhabit a wide range of aquatic and marine environments and cause seafood contamination and infectious diseases in humans
Spectral Analysis of VmFbpA Interacting with rosmarinic acid (RA) To assess their dose-dependent effects on the inhibition of Fe3+ binding by VmFbpA, different concentrations (0, 0.9, 1.9, 3.8, 7.5, and 15 mg/mL) of cinnamon and rosemary extracts were subjected to inhibition assays using UV-visible absorbance spectroscopy (Figure 1b–e)
RA did not significantly inhibit E. coli growth (Figure 4c,d), nor did the combination of RA and sodium citrate (SC) (Figure 6c,d). These results indicate that E. coli uses a variety of iron sources and is resistant to RA and SC, but V. metschnikovii is more vulnerable to RA in the presence of SC
Summary
Vibrio is a genus of ubiquitous bacteria that inhabit a wide range of aquatic and marine environments and cause seafood contamination and infectious diseases in humans. More than 30 species of Vibrio have been discovered to date and V. cholerae, V. parahaemolyticus, V. alginolyticus, V. vulnificus, V. fluvialis, V. hollisaea, V. mimicus, and V. metschnikovii are among the most frequently isolated human pathogens. These bacteria are found in environments of moderate or high salinity, including in seawater and seafood, and they are agents of human vibriosis [1]. We aimed to suppress the growth of Vibrio bacterial species by inhibiting their ferric ion-binding protein (FbpA) using food components. The combination of RA/SC completely inhibits the growth of V. metschnikovii at 100/100 μM and the vibriosis-causative pathogens V. vulnificus and V. parahaemolyticus, at 100/100 and 1000/100 μM, respectively. Conclusions: RA/SC is a potential bacteriostatic agent against Vibrio species while causing little damage to indigenous gastrointestinal bacteria
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