Halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate K₂[B₃O₃F₄OH] inhibits emerging multidrug-resistant and β-lactamase-producing opportunistic pathogens

Abstract

Halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate, K₂[B₃O₃F₄OH] (boroxine) was previously shown to be very effective in inhibition of several carcinoma cell lines, including the skin cancer. Here, we investigated its antimicrobial potential by targeting the multidrug-resistant opportunistic pathogens associated with skin and wound infections. The antimicrobial testing against eleven bacterial and four fungal species revealed good activity of boroxine against pathogenic filamentous fungi Penicillium funiculosum and Aspergillus niger (MIC₅₀ 64 and 128 µg/ml), and a moderate bioactivity against the yeast Candida albicans (MIC₅₀ 512 µg/ml). Among the tested multidrug-resistant bacteria, the best antibacterial effect, stable over a 24-h period, was observed against the methicillin-resistant Staphylococcus aureus strain (MRSA) at MIC of 1024 µg/ml. The atomic force microscopy (AFM) used to investigate the morphology of S. aureus cells revealed indentations on its cell envelope after the boroxine exposure. These results show that in addition to the antitumor effect, boroxine exerts wide spectrum antimicrobial activity, thus may help preventing the development of skin and wound-related opportunistic infections.

Keywords:

• Atomic force microscopy
• boroxine
• membrane permeability
• MRSA
• multidrug-resistant pathogens

Acknowledgments

We thank Dr. Olga Schevchuk and anonymous reviewers for their suggestions on the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Croatian Science Foundation [grant no. IP-2014–09-6897] and Hrvatska Zaklada za Znanost.