Investigating geopolymer-mediated adsorption of methicillin-resistant Staphylococcus aureus cells and secreted proteins

131672-Thumbnail Image.png
Description
The rise in community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections and the ability of the organism to develop resistance to antibiotics necessitate new treatment methods for MRSA. Geopolymers (GPs) are cheap, porous materials that have demonstrated adsorptive capabilities. In this study,

The rise in community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections and the ability of the organism to develop resistance to antibiotics necessitate new treatment methods for MRSA. Geopolymers (GPs) are cheap, porous materials that have demonstrated adsorptive capabilities. In this study, GPs were investigated for their ability to adsorb whole MRSA cells and MRSA secreted proteins [culture filtrate proteins (CFPs)] as a complementary method of controlling MRSA infections. GPs have been synthesized with variable pore sizes (meso/macro scale) and further modified with stearic acid (SA) to increase surface hydrophobicity. Four GPs (SA-macroGP, macroGP, SA-mesoGP, and mesoGP) were incubated with whole cells and with CFPs to quantify GP adsorption capabilities. Following MRSA culture incubation with GPs, unbound MRSA cells were filtered and plated to determine cell counts. Following CFP incubation with GPs, unbound CFPs were separated via SDS-PAGE, stained with SYPRO Ruby, and analyzed using densitometry. Results indicate that macroGP was the most effective at adsorbing whole MRSA cells. Visual banding patterns and densitometry quantitation indicate that SA-mesoGP was the most effective at adsorbing CFP. Ultimately, GP-based products may be further developed as nonselective or selective adsorbents and integrated into fibrous materials for topical applications.
Date Created
2020-05
Agent

High-throughput screening and identification of synthetic peptides with Mycobacterium abscessus inhibitory activity

133000-Thumbnail Image.png
Description
The rise in the number of antibiotic-resistant bacteria, due in part to the widespread use of antibiotics, has spawned new technological approaches for identifying novel antimicrobials with narrow specificity. Current antibiotic treatment regimens and anti-tuberculosis drugs are not effective at

The rise in the number of antibiotic-resistant bacteria, due in part to the widespread use of antibiotics, has spawned new technological approaches for identifying novel antimicrobials with narrow specificity. Current antibiotic treatment regimens and anti-tuberculosis drugs are not effective at treating Mycobacterium abscessus; therefore, antimicrobial peptides have gained prominence as alternative antimicrobials due to their specificity towards anionic bacterial membranes, rapid action, and inability for the bacteria to develop resistance by acting against the cell membrane. Our group has developed a high-density peptide microarray consisting of 125,000 random synthetic peptides for rapid screening of antimicrobial peptides against M. abscessus. From the array screening, the peptides that interacted with the mycobacterial cell surface were synthesized and subsequent inhibitory, bactericidal, and toxicity assays were performed. Additionally, minimum inhibitory concentration assays were performed with these peptides against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli in order to determine if inhibitory activity was observed against Gram-positive and Gram-negative bacteria. Six peptides, out of the 125,000 peptides screened, had inhibitory activity against M. abscessus and low toxicity (< 10%) against human red blood cells. One peptide also exhibited inhibitory activity against S. aureus and E. coli. To determine combination effects, antimicrobial synergy assays will be performed with the six peptides and clarithromycin
Date Created
2019-05
Agent

Exchangeable Ions Are Responsible for the In Vitro Antibacterial Properties of Natural Clay Mixtures

129685-Thumbnail Image.png
Description

We have identified a natural clay mixture that exhibits in vitro antibacterial activity against a broad spectrum of bacterial pathogens. We collected four samples from the same source and demonstrated through antibacterial susceptibility testing that these clay mixtures have markedly

We have identified a natural clay mixture that exhibits in vitro antibacterial activity against a broad spectrum of bacterial pathogens. We collected four samples from the same source and demonstrated through antibacterial susceptibility testing that these clay mixtures have markedly different antibacterial activity against Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Here, we used X-ray diffraction (XRD) and inductively coupled plasma - optical emission spectroscopy (ICP-OES) and - mass spectrometry (ICP-MS) to characterize the mineralogical and chemical features of the four clay mixture samples. XRD analyses of the clay mixtures revealed minor mineralogical differences between the four samples. However, ICP analyses demonstrated that the concentrations of many elements, Fe, Co, Cu, Ni, and Zn, in particular, vary greatly across the four clay mixture leachates. Supplementation of a non-antibacterial leachate containing lower concentrations of Fe, Co, Ni, Cu, and Zn to final ion concentrations and a pH equivalent to that of the antibacterial leachate generated antibacterial activity against E. coli and MRSA, confirming the role of these ions in the antibacterial clay mixture leachates. Speciation modeling revealed increased concentrations of soluble Cu2+ and Fe2+ in the antibacterial leachates, compared to the non-antibacterial leachates, suggesting these ionic species specifically are modulating the antibacterial activity of the leachates. Finally, linear regression analyses comparing the log(10) reduction in bacterial viability to the concentration of individual ion species revealed positive correlations with Zn2+ and Cu2+ and antibacterial activity, a negative correlation with Fe3+, and no correlation with pH. Together, these analyses further indicate that the ion concentration of specific species (Fe2+, Cu2+, and Zn2+) are responsible for antibacterial activity and that killing activity is not solely attributed to pH.

Date Created
2013-05-17