Thiazolidione derivatives targeting the histidine kinase YycG are effective against both planktonic and biofilm-associated Staphylococcus epidermidis

Abstract

Aim: To evaluate the efficacies of six derivatives of Compound 2, a novel YycG histidine kinase inhibitor with the thiazolidione core structure in the treatment of medical device-related biofilm infections. Methods: The minimal inhibitory concentration (MIC) of the derivatives was determined using the macrodilution broth method, and the minimal bactericidal concentration (MBC) was obtained via sub-culturing 100 μL from each negative tube from the MIC assay onto drug-free Mueller-Hinton agar plates. Biofilm-killing effect for immature (6 h-old) biofilms was examined using a semiquantitative plate assay, and the effect on mature (24 h-old) biofilms was observed under a confocal laser scanning microscope (CLSM). Results: The derivatives potently suppressed the growth of Staphylococcus epidermidis. The MIC values of the derivatives H2-10, H2-12, H2-20, H2-29, H2-27, and H2-28 on S epidermidis ATCC 35984 were 24.3, 6.5, 6.2, 3.3, 3.1, and 1.5 μg/mL, respectively. The MBC values of these derivatives were 48.6, 52.2, 12.4, 52.6, 12.4, and 6.2 μg/mL, respectively. The derivatives killed all bacteria in immature (6 h-old) biofilms and eliminated the biofilm proliferation. The derivatives also displayed strong bactericidal activities toward cells in mature (24 h-old) biofilms, whereas they showed low cytotoxicity and hemolytic activity toward Vero cells and human erythrocytes. Conclusion: The bactericidal and biofilm-killing activities of the new anti-YycG compounds were significantly better than the parent Compound 2.

Inactivation of Multiple Bacterial Histidine Kinases by Targeting the ATP-Binding Domain

“…Furthermore, the aminothiazole of 11 and 12 , the urea of 13 , and the aminotriazole of 14 are consistent components of GHL inhibitory compounds, and several also appear in other HK studies ( Supporting Information Figure 26b ). 23 , 27 , 46 , 48 − 51 Evidence of these successes in proteins with similar ATP-binding domains validate the scaffolds identified in our studies and will provide guidance in future inhibitor development.…”

“… 18 , 19 , 21 , 22 Small molecules exploiting the same conserved residues that bind ATP may enable the targeting of multiple HKs (Figure 1 c). 13 In silico screens targeting the ATP-binding domain from a specific HK have led to the identification of molecules that inhibited these proteins in vitro , possessed antibacterial activity, 23 , 24 and in several cases, they showed promise in animal infection models. 25 − 27 Examples of ATP-competitive compounds that more broadly affect HKs have also been reported.…”

Nh125 Kills Methicillin-Resistant Staphylococcus Aureus Persisters by Lipid Bilayer Disruption

“…Further, the WalK/R system is known to regulate biofilm formation and cell wall synthesis [57]. Thiazolidione derivatives targeting WalK show bactericidal activity on Staphylococcus epidermidis biofilms where persisters exist [58]. Based on previously published studies of NH125, we hypothesized that the WalK/R system would be a target for killing persisters through membrane permeabilization.…”

“…Essential TCS are considered to be promising targets for the development of antibiotics due to their indispensability for bacterial survival and their absence in mammalian cells [16]. In particular, the WalK/R system, which is highly conserved in low GC content Gram-positive pathogens such as S. aureus, Streptococcus pneumonia and Enterococcus faecalis, has been exploited as a target for developing new antibiotics [19][20][21][22][23][24][25][26]. Indeed, the WalK inhibitors NH125 [19,20], signermycin B [25], walkmycin B [22] and waldiomycin [26], as well as the WalR inhibitors walrycin A [23] and walrycin B [23], have been shown to have antimicrobial activity against S. aureus or MRSA.…”

Conformational dynamics of the essential sensor histidine kinase WalK

“…The crystal packing of lpWalK in the closed state was completely different from that in the open state (Table 1). Several thiazolidione WalK inhibitors, which are predicted to bind to the WalK active pocket (Huang et al, 2012), did not induce lpWalK to crystallize under the same conditions as used for the lpWalK fragment. Importantly, selective crystallization of one specific conformation of target molecules often occurs.…”