Antimicrobial activity of Mimosa caesalpiniifolia Benth and its interaction with antibiotics against Staphylococcus aureus strains overexpressing efflux pump genes

Chemical composition of Piper gaudichaudianum Kunth essential oil and evaluation of its antimicrobial and modulatory effects on antibiotic resistance, antibiofilm, and cell dimorphism inhibitory activities

Essential oils extracted from many plant species have different biological activities, among which microbial activity stands out. Species of the genus Piper have antimicrobial potential against different species of bacteria and fungi. In this sense, the present study aimed to determine the chemical composition of the essential oil from the leaves of Piper gaudichaudianum (EOPG), as well as to investigate their antimicrobial activity and their modulatory effect on the Norfloxacin resistance in the Staphylococcus aureus SA1199B strain overproducer of the NorA efflux pump. Furthermore, their inhibitory activities on the biofilm formation as well as on the cellular differentiation of C. albicans were evaluated. Gas chromatography analysis identified 24 compounds, such as hydrocarbon sesquiterpenes (54.8%) and oxygenated sesquiterpenes (28.5%). To investigate the antimicrobial potential of EOPG against S. aureus, E. coli, and C. albicans, a microdilution assay was performed, and no intrinsic antimicrobial activity was observed. On the other hand, the oil potentiated the activity of Norfloxacin against the SA1199B strain, indicating that EOPG could be used in association with Norfloxacin against S. aureus strains resistant to this antibiotic. EOPG also inhibited S. aureus biofilm formation, as evidenced by the crystal violet assay. In the dimorphism assay, EOPG was able to inhibit the cell differentiation process in C. albicans. Results indicate that EOPG could be used in association with Norfloxacin in the treatment of infections caused by resistant S. aureus strains overproducing the NorA efflux pump. Furthermore, its ability to inhibit the formation of hyphae by C. albicans suggests that EOPG could also be applied in the prevention and/or treatment of fungal infections.

An Update on Staphylococcus aureus NorA Efflux Pump Inhibitors

BACKGROUND

Methicillin-resistant and vancomycin-resistant Staphylococcus aureus are pathogens causing severe infectious diseases that pose real public health threats problems worldwide. In S. aureus, the most efficient multidrug-resistant system is the NorA efflux pump. For this reason, it is critical to identify efflux pump inhibitors.

OBJECTIVE

In this paper, we present an update of the new natural and synthetic compounds that act as modulators of antibiotic resistance through the inhibition of the S. aureus NorA efflux pump.

RESULTS

Several classes of compounds capable of restoring the antibiotic activity have been identified against resistant-S. aureus strains, acting as NorA efflux pump inhibitors. The most promising classes of compounds were quinolines, indoles, pyridines, phenols, and sulfur-containing heterocycles. However, the substantial degree structural diversity of these compounds makes it difficult to establish good structure- activity correlations that allow the design of compounds with more promising activities and properties.

CONCLUSION

Despite substantial efforts put forth in the search for new antibiotic adjuvants that act as efflux pump inhibitors, and despite several promising results, there are currently no efflux pump inhibitors authorized for human or veterinary use, or in clinical trials. Unfortunately, it appears that infection control strategies have remained the same since the discovery of penicillin, and that most efforts remain focused on discovering new classes of antibiotics, rather than trying to prolong the life of available antibiotics, and simultaneously fighting mechanisms of bacterial resistance.

Design, Overproduction and Purification of the Chimeric Phage Lysin MLTphg Fighting against Staphylococcus aureus

With the increasing spread of multidrug-resistant bacterial pathogens, it is of great importance to develop alternatives to conventional antibiotics. Here, we report the generation of a chimeric phage lysin, MLTphg, which was assembled by joining the lysins derived from Meiothermus bacteriophage MMP7 and Thermus bacteriophage TSP4 with a flexible linker via chimeolysin engineering. As a potential antimicrobial agent, MLTphg can be obtained by overproduction in Escherichia coli BL21(DE3) cells and the following Ni-affinity chromatography. Finally, we recovered about 40 ± 1.9 mg of MLTphg from 1 L of the host E. coli BL21(DE3) culture. The purified MLTphg showed peak activity against Staphylococcus aureus ATCC6538 between 35 and 40 °C, and maintained approximately 44.5 ± 2.1% activity at room temperature (25 °C). Moreover, as a produced chimera, it exhibited considerably improved bactericidal activity against Staphylococcus aureus (2.9 ± 0.1 log10 reduction was observed upon 40 nM MLTphg treatment at 37 °C for 30 min) and also a group of antibiotic-resistant bacteria compared to its parental lysins, TSPphg and MMPphg. In the current age of growing antibiotic resistance, our results provide an engineering basis for developing phage lysins as novel antimicrobial agents and shed light on bacteriophage-based strategies to tackle bacterial infections.