No abstract

Alpha-mangostin (α-MG) has been reported to be an effective antibacterial agent against planktonic cells of many Gram-positive bacteria. However, the antibiofilm potency of α-MG remains unexplored till date. In this study, the antibiofilm and mature biofilm eradication ability of α-MG against Staphylococcus epidermidis RP62A (ATCC 35984) biofilms were evaluated. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of α-MG against S. epidermidis RP62A were found to be 1.25 and 5 μg/mL, respectively. α-MG exhibited a phenomenal concentration dependent rapid bactericidal activity (>4-log reduction within 5 min). In a multi-passage resistance analysis using S. epidermidis, no development of resistance to α-MG as well as antibiotics was observed in its habituation. α-MG at its 1/2 MIC effectively inhibited the initial biofilm formation of S. epidermidis, which was further confirmed through scanning electron microscopic (SEM) analysis that portrayed a lucid reduction in the aggregation and the spread of biofilm. The crystal violet staining and viable cell quantification results confirmed the eradication of preformed immature and mature biofilms of S. epidermidis by α-MG in a concentration dependent manner. Besides, the biofilm eradication ability was also confirmed through SEM and live/dead BacLight staining using confocal laser scanning microscopy (CLSM). Thus, the present study exemplifies that α-MG could plausibly assist to eliminate biofilm infections associated with multidrug-resistance staphylococci.

Background: Alpha-mangostin (α-MG) is a natural xanthone reported to exhibit rapid bactericidal activity against Gram-positive bacteria, and may therefore have potential clinical application in healthcare sectors. This study sought to identify the impact of α-MG on Staphylococcus epidermidis RP62A through integrated advanced omic technologies.Methods: S. epidermidis was challenged with sub-MIC (0.875 μg/ml) of α-MG at various time points and the differential expression pattern of genes/proteins were analyzed in the absence and presence of α-MG using RNA sequencing and LC-MS/MS experiments. Bioinformatic tools were used to categorize the biological processes, molecular functions and KEGG pathways of differentially expressed genes/proteins. qRT-PCR was employed to validate the results obtained from these analyses.Results: Transcriptomic and proteomic profiling of α-MG treated cells indicated that genes/proteins affected by α-MG treatment were associated with diverse cellular functions. The greatest reduction in expression was observed in transcription of genes conferring cytoplasmic membrane integrity (yidC2, secA and mscL), cell division (ftsY and divlB), teichoic acid biosynthesis (tagG and dltA), fatty-acid biosynthesis (accB, accC, fabD, fabH, fabI, and fabZ), biofilm formation (icaA) and DNA replication and repair machinery (polA, polC, dnaE, and uvrA). Those with increased expression were involved in oxidative (katA and sodA) and cellular stress response (clpB, clpC, groEL, and asp23). The qRT-PCR analysis substantiated the results obtained from transcriptomic and proteomic profiling studies.Conclusion: Combining transcriptomic and proteomic methods provided comprehensive information about the antibacterial mode of action of α-MG. The obtained results suggest that α-MG targets S. epidermidis through multifarious mechanisms, and especially prompts that loss of cytoplasmic membrane integrity leads to rapid onset of bactericidal activity.

The present study highlights the potential of GE as a suitable candidate for the control of biofilm-mediated S. epidermidis infections.

The present study was designed to investigate the anti-biofilm potential of alpha-mangostin (α-MG) against Acinetobacter baumannii (AB). The biofilm inhibitory concentration (BIC) of α-MG against AB was found to be 2 μg ml. α-MG (0.5, 1 and 2 μg ml) exhibited non-bactericidal concentration-dependent anti-biofilm activities against AB. However, α-MG failed to disintegrate the mature biofilms of AB even at a 10-fold increased concentration from its BIC. Results from qRT-PCR and in vitro bioassays further demonstrated that α-MG downregulated the expression of bfmR, pgaA, pgaC, csuA/B, ompA, bap, katE, and sodB genes, which correspondingly affects biofilm formation and its associated virulence traits. The present study suggests that α-MG exerts its anti-biofilm property by interrupting initial biofilm formation and the cell-to-cell signaling mechanism of AB. Additional studies are required to understand the mode of action responsible for the anti-biofilm property.

This study was intentionally focused on cyclo(l-leucyl-l-prolyl) (CLP), a cyclic dipeptide with myriad pharmaceutical significance, to explore its antivirulence efficacy against the predominant foodborne pathogen,Listeria monocytogenes(LM). Minimum inhibitory concentration (MIC) of CLP against LM ATCC 19111 was found to be 512 μg mL(-1) CLP at sub-MICs (64 128, 256 μg mL(-1)) demonstrated a profound non-bactericidal dose-dependent antibiofilm efficacy (on polystyrene and glass) against LM, which was further confirmed through confocal and scanning electron microscopic analysis (on stainless steel surface).In vitrobioassays divulged the phenomenal inhibitory efficacy of CLP towards various virulence traits of LM, specifically its overwhelming suppression of swimming and swarming motility. Data ofin vivoassay usingCaenorhabditis eleganssignified that the plausible mechanism of CLP could be by impeding the pathogen's initial adhesion and thereby attenuating the biofilm assemblage and its associated virulence. This was further confirmed by significant decrease in extracellular polymeric substance, autoaggregation, hydrophobicity index and extracellular DNA of the CLP-treated LM cells. Collectively, this study unveils the antivirulence efficacy of CLP against the Gram-positive foodborne pathogen and the strainBacillus amyloliquefaciensaugurs well to be a promising probiotic in controlling infections associated with LM.

In plant soft-rotting bacteria Pectobacterium, quorum sensing (QS) regulates the secretion of an arsenal of plant cell wall degrading extracellular enzymes (PCWDEs) and flagella-mediated motility via two different signaling molecules such as 3-oxohexanoyl-Lhomoserine lactone (3-oxo-C6-AHL) and 3-oxooctanoyl-L-homoserine lactone (3-oxo-C8-AHL). In the present investigation, the phytochemical compound curcumin was assessed for its QS inhibitory potential against AHL-dependent PCWDEs production and motility in P. wasabiae SCC3193, P. carotovorum subsp. Carotovorum Pcc21 and P. carotovorum subsp. Carotovorum Pcc. Interestingly, curcumin at sub-MIC effectively inhibited the production of PCWDEs as well as the swimming and swarming motility of all tested pathogens in a non-bactericidal fashion. Subsequently, the in vitro root pathogenicity assay in Arabidopsis thaliana unveiled the rescuing efficacy of curcumin against the pathogenicity of tested plant pathogens by attenuating its QS mediated virulence factors production. Besides, studies with QS mutant strain Pcc21-M10 also evidenced the QSI property of curcumin.

The global poultry industry has grown to the extent that the number of chickens now well exceeds the number of humans on Earth. Escherichia coli infections in poultry cause significant morbidity and economic losses for producers each year. We obtained 94 E. coli isolates from 12 colibacillosis outbreaks on Saskatchewan farms and screened them for antimicrobial resistance and biofilm formation. Fifty-six isolates were from broilers with confirmed colibacillosis, and 38 isolates were from healthy broilers in the same flocks (cecal E. coli). Resistance to penicillins, tetracyclines, and aminoglycosides was common in isolates from all 12 outbreaks, while cephalosporin resistance varied by outbreak. Most E. coli were able to form biofilms in at least one of three growth media (1/2 TSB, M63, and BHI broth). There was an overall trend that disease-causing E. coli had more antibiotic resistance and were more likely to form biofilms in nutrient-rich media (BHI) as compared to cecal strains. However, on an individual strain basis, there was no correlation between antimicrobial resistance and biofilm formation. The 21 strongest biofilm forming strains consisted of both disease-causing and cecal isolates that were either drug resistant or susceptible. Draft whole genome sequencing indicated that many known antimicrobial resistance genes were present on plasmids, with disease-causing E. coli having more plasmids on average than their cecal counterparts. We tested four common disinfectants for their ability to kill 12 of the best biofilm forming strains. All disinfectants killed single cells effectively, but biofilm cells were more resistant, although the difference was less pronounced for the disinfectants that have multiple modes of action. Our results indicate that there is significant diversity and complexity in E. coli poultry isolates, with different lifestyle pressures affecting disease-causing and cecal isolates.