In Vitro Activity of 3-Bromopyruvate, an Anticancer Compound, Against Antibiotic-Susceptible and Antibiotic-Resistant Helicobacter pylori Strains

Abstract

Helicobacter pylori (H. pylori) is a bacterium capable of inducing chronic active gastritis, which in some people, develops into gastric cancers. One of the substances that may be useful in the eradication of this microorganism is 3-Bromopyruvate (3-BP), an anticancer compound with antimicrobial properties. The aim of this article was to determine the activity of 3-BP against antibiotic-susceptible and antibiotic-resistant H. pylori strains. The antimicrobial activity was determined using a disk-diffusion method, broth microdilution method, time-killing assay, and checkerboard assay. The research was extended by observations using light, fluorescence, and scanning electron microscopy. The growth inhibition zones produced by 2 mg/disk with 3-BP counted for 16–32.5 mm. The minimal inhibitory concentrations (MICs) ranged from 32 to 128 μg/mL, while the minimal bactericidal concentrations (MBCs) for all tested strains had values of 128 μg/mL. The time-killing assay demonstrated the concentration-dependent and time-dependent bactericidal activity of 3-BP. The decrease in culturability below the detection threshold (<100 CFU/mL) was demonstrated after 6 h, 4 h, and 2 h of incubation for MIC, 2× MIC, and 4× MIC, respectively. Bacteria treated with 3-BP had a several times reduced mean green/red fluorescence ratio compared to the control samples, suggesting bactericidal activity, which was independent from an induction of coccoid forms. The checkerboard assay showed the existence of a synergistic/additive interaction of 3-BP with amoxicillin, tetracycline, and clarithromycin. Based on the presented results, it is suggested that 3-BP may be an interesting anti-H. pylori compound.

Transformation of Helicobacter pylori into Coccoid Forms as a Challenge for Research Determining Activity of Antimicrobial Substances

“…In a collection of eight articles [37][38][39][40][41][42][43][44] showing a morphological effect of antibiotics and other substances classically used in H. pylori therapies, microscopic and culture methods were used. In four of them [38,39,42,43], different staining techniques and fluorescence analysis were additionally included ( Table 1 and Figure 1).…”

“…In the next five analyzed articles [38][39][40][41]43], observations regarding a morphostructural effect of antibiotics come from publications primarily focusing on new compounds with a potential anti-H. pylori activity. Narayana et al [38,39] showed that AMX within 24 h reduced the viability of H. pylori by 3 log when treated with MIC.…”

Small Molecule Inhibitors of the Response Regulator ArsR Exhibit Bactericidal Activity against Helicobacter pylori

“…After 48 h of incubation at 37 • C under microaerobic conditions, microbial growth was colorimetric, revealed by the addition of 0.1 mg/mL resazurin (Sigma-Aldrich). The interaction between drugs was determined according to the fractional inhibitory concentration index (FICI): FIC A (MIC A in the presence of B/MIC A alone) + FIC B (MIC B in the presence of A/MIC B alone) [24].…”

“…We analysed the in vitro bactericidal effect of lithocholic acid in combination with other recognized anti-H. pylori substances including the conventional antibiotics clarithromycin, metronidazole and levofloxacin, as well as the flavonoid chrysin [16], by the checkerboard method [16,17,24,28]. According to this approach, when two antimicrobial substances are used together in a fixed concentration ratio against a certain microbial strain, and the combinatory action of both drugs noticeably increases the activity of each drug when they act separately against the same strain, we could infer that these substances exhibit a synergistic interaction in their antimicrobial action.…”

“…In those cases, we could observe a partial synergy known as an "additive effect", which occurs when the FICI value is >0.5 but ≤1. Hence, the term "synergy" implies that the resulting effect of a combination is significantly greater than the sum of its individual parts, while "additive effect" occurs when substances added together will improve or increase their efficacies, albeit not to the extent of a synergistic interaction [24,28]. As shown in Table 4, lithocholic acid showed additive (partial synergy) interactions with clarithromycin, levofloxacin and chrysin, but it did not interact with metronidazole.…”