Inhibition of Salmonella Typhimurium adhesion, invasion, and intracellular survival via treatment with methyl gallate alone and in combination with marbofloxacin

Abstract

Salmonella enterica serovar Typhimurium infects intestinal epithelia and macrophages, which is prevented by inhibiting adhesion and cell invasion. This study aimed to investigate the role of methyl gallate (MG) in adhesion, invasion, and intracellular survival of Salmonella Typhimurium in Caco-2 and RAW 264.7 cells via a gentamicin protection assay, confocal microscopy, and quantitative reverse-transcription polymerase chain reaction. MG (30 µg/mL) inhibited adhesion and invasion of Salmonella Typhimurium by 54.01% and 60.5% in RAW 264.7 cells, respectively. The combination of MG with sub-minimum inhibitory concentration (MIC) of marbofloxacin (MRB) inhibited the adhesion, invasion, and intracellular survival by 70.49%, 67.36%, and 74%, respectively. Confocal microscopy further revealed reductions in bacterial count in Caco-2 cells treated with MG alone or with sub-MIC of MRB. Furthermore, MG alone or in combination with sub-MIC of MRB decreased the motility of Salmonella Typhimurium. Quorum sensing genes including sdiA , srgE , and rck were downregulated by 52.8%, 61.7%, and 22.2%, respectively. Moreover, rac - 1 was downregulated by 56.9% and 71.9% for MG alone and combined with sub-MIC of MRB, respectively, in mammalian cells. Furthermore, MG downregulated virulence genes of Salmonella Typhimurium including cheY, ompD , sipB , lexA , and ompF by 59.6%, 60.2%, 20.5%, 31.4%, and 16.2%, respectively. Together, the present results indicate that MG alone or in combination with a sub-MIC of MRB effectively inhibited the adhesion, invasion, and intracellular survival of Salmonella Typhimurium in vitro by downregulating quorum sensing and virulence genes. Electronic supplementary material The online version of this article (10.1186/s13567-018-0597-8) contains supplementary material, which is available to authorized users.

Pathogenicity of clinical Salmonella enterica serovar Typhimurium isolates from Thailand in a mouse colitis model

“…Gut epithelial invasion and macrophage intracellular survival of Salmonella were performed in Caco-2 and RAW264.7, respectively, using a gentamicin protection assay as described previously with some modifications. 36 Briefly, overnight cultures of Salmonella were subcultured in LB with 0.3 M NaCl, and incubated at 200 rpm, 37°C for 3 hr. The bacterial cultures were washed using 1× PBS, and added into the cell lines at MOI = 20.…”

Synergism of the Combination of Traditional Antibiotics and Novel Phenolic Compounds against Escherichia coli

“…It was demonstrated that the biofilms of Streptococcus mutans could be efficiently inhibited by the treatment of the phenolic compound, gallic acid (GA) [ 13 ]. A GA derivative, methyl gallate, was described in our recent reports for its inhibitory effects on the adhesion, invasion, and intracellular survival of Salmonella enterica serovar typhimurium , and for its interfering effects on Pseudomonas aeruginosa quorum-sensing regulatory genes [ 14 , 15 ]. These properties of bacteria play a vital role in increasing antimicrobial resistance and pathogenicity [ 16 ].…”

In vitro synergistic potentials of novel antibacterial combination therapies against Salmonella enterica serovar Typhimurium

“…The phenolic compound gallic acid (GA) demonstrated the potential to inhibit biofilms of S. mutans [15]. Recently, we also reported that methyl gallate, a GA derivative, can efficiently interfere with the QS regulatory pathways of P. aeruginosa, and inhibit the adhesion, invasion and intracellular survival of S. Typhimurium [16,17]. These properties of bacteria are known to have significant roles in increasing pathogenicity and antimicrobial resistance [18].…”