Antibiofilm and antipersister activity of acetic acid against extensively drug resistant Pseudomonas aeruginosa PAW1

Pseudomonas aeruginosa is an ESKAPE pathogen associated with difficult-to-treat burn wound and surgical-site infections. This study aimed to characterise an extensively drug resistant (XDR) P. aeruginosa isolate (designated PAW1) and to investigate the antibiofilm and antipersister effect of acetic acid on PAW1. PAW1 was identified using biotypic (VITEK) and genotypic (16S rDNA) analysis. Minimum inhibitory concentration (MIC) and disc susceptibility testing showed high level resistance against all antibiotics from classes including beta lactams, cephems, carbapenems and fluoroquinolones. It was therefore identified as extensively drug resistant (XDR), showing resistance to all antibiotics except for, aminoglycoside (gentamicin and netilmicin) and lipopeptides (polymyxin B). Time kill assays showed antibiotic tolerant, persister cell formation in presence of 100X MICs of gentamicin and polymyxin B. Other virulence traits such as ability to produce lipase, protease, haemolysin, and siderophores and to form biofilms were additional factors which may contribute to its pathogenicity. PAW1 showed promising susceptibility against acetic acid with MIC and minimum biofilm inhibitory concentration of 0.156% (v/v). Percent viability of PAW1 was dependent on dose and treatment time of acetic acid. 0.625% acetic acid treatment of 5 minutes was effective in killing >90% planktonic cells showing lesser toxicity to L929 cells (IC₅₀ = 0.625%). Biofilm disruption caused due to acetic acid was also dose dependent, showing 40.57% disruption after treatment with 0.625% acetic acid for 5 minutes. FESEM imaging and live dead staining of planktonic and biofilm forms of PAW1 confirmed that acetic acid treatment caused 19.04% of cell shrinkage and disruption of extracellular matrix resulting in killing of cells. Antipersister activity of acetic acid was demonstrated by showing complete killing of PAW1 at 4X MIC. Overall, this study characterised an XDR isolate P. aeruginosa showing resistance and tolerance to various antibiotics. Antipersister and antibiofilm effect of acetic acid demonstrates the importance of forgotten topical agents as an effective strategy to treat XDR pathogens.

In situ casting of rice husk ash in metal organic frameworks induces enhanced CO2 capture performance

Incorporation of rice-husk-ash (RHA), an agricultural waste, in situ during the synthesis of MIL-101(Cr) resulted in a significant improvement in the CO2 adsorption properties over the synthesized RHA-MIL-101(Cr). The newly synthesized RHA-MIL-101(Cr) composite exhibited an enhancement of 14-27% in CO2 adsorption capacity as compared to MIL-101(Cr) at 25 °C and 1 bar. The content of RHA incorporated in RHA-MIL-101(Cr) fine tuned the CO2 capture performance to achieve high working capacity (0.54 mmol g-1), high purity (78%), superior CO2/N2 selectivity (18) and low isosteric heat of adsorption (20-30 kJ mol-1). The observed superior CO2 adsorption performance of RHA-MIL-101(Cr) is attributed to the fine tuning of textural characteristics-enhancement of 12-27% in BET surface area, 12-33% in total pore volume and 18-30% in micropore volume-upon incorporation of RHA in MIL-101(Cr).

Multivalent Sialosides: A Tool to Explore the Role of Sialic Acids in Biological Processes

Sialic acids (Sias) are fascinating nine-carbon monosaccharides that are primarily found on the terminus of the oligosaccharide chains of glycoproteins and glycolipids on cell surfaces. These Sias undergo a variety of structural modifications at their hydroxy and amine positions, thereby resulting in structural diversity and, hence, coordinating a variety of biological processes. However, deciphering the structural functions of such interactions is highly challenging, because the monovalent binding of Sias is extremely weak. Over the last decade, several multivalent Sia ligands have been synthesized to modulate their binding affinity with proteins/lectins. In this Minireview, we highlight recent developments in the synthesis of multivalent Sia probes and their potential applications. We will discuss four key multivalent families, that is, polymers, dendrimers, liposomes, and nanoparticles, and will emphasize the major parameters that are essential for the specific interactions of these molecules with proteins in biological systems.