Carbonylacrylic Derivatives and Their Ability to Disrupt Biofi lm Formation

The rapid emergence of bacterial resistance to antibiotics has greatly pressed the need for novel therapeutics. One of the strategies bacteria use to enhance their resistance toward antibiotics is to embed themselves into polymeric matrices known as a biofi lm. Bacteria in a biofi lm state are highly resistant towards antibiotics and immune response, thereby more diffi cult to eradicate. Hence, antibiofi lm agents are considered an alternative strategy to unravel problems regarding bacterial antibiotic resistance. Our lab has focused on bacterial communication process called quorum sensing (QS), which is crucial for bacteria to conduct group behaviors such as biofi lm. Cysteine residue of LasR, key QS protein regulator, has been suggested to play an important role in QS-mediated biofi lm formation. In addition, cysteine-containing biomolecules have been implicated in bacterial pathogenesis. Herein, we explored the ability of thiol-reactive molecules for their ability to interfere with biofi lm formation in pathogenic Gram-negative Pseudomonas aeruginosa (P. aeruginosa). We hypothesized that the thiol-reactive molecules could potentially react with sulfhydryl group of cysteine residue of crucial QS enzyme or of cysteine-containing biomolecules that may lead to the reduce in the ability of the pathogen to form biofi lm. Carbonylacrylic compounds were previously reported to rapidly undergo thiol-Michael reaction with cysteine-containing proteins under physiological conditions. Total of three new carbonylacrylic derivatives were synthesized and tested for their anti-biofi lm activity. All synthesized compounds could inhibit biofi lm formation in a concentration-dependent manner without toxicity to bacteria. Derivative 1a exhibited the most potent antibiofi lm activity with IC50 of 85 μM.

Antibacterial activity evaluation of vinyl sulfones against global predominant methicillin-resistant Staphylococcus aureus USA300

The electrophilic potential of vinyl sulfone permits the rapid capture of cysteine-containing proteins under physiological conditions. These cysteine proteinases play vital roles in bacterial survival and pathogenesis of Staphylococcus aureus (S. aureus) and the global health threat methicillin resistant S. aureus (MRSA). Here in, total of 28 vinyl sulfones were synthesized and subjected to susceptibility testing of pathogenic bacteria, including global epidemic MRSA PFGE strain type USA300 (SF8300). Number of antibacterial vinyl sulfone derivatives were discovered. Among these, nitrile-substituted vinyl phenyl sulfones showed potent antibacterial activity. (E)-3-((4-methoxyphenyl)sulfonyl)acrylonitrile exhibited the strongest potency with MIC of 1.875 µg/mL against methicillin susceptible S. aureus and 3.75 µg/mL against MRSA USA300. Based on the structure-activity relationship analysis, the antibacterial activity of these compounds may involve sulfhydryl conjugation. In addition, the nitrile-substituted vinyl phenyl sulfone could also impair host cell adhesion. With their promising antibacterial activities, these vinyl sulfones have potential for S. aureus and MRSA therapeutics.

Alternative Sigma Factor B in Bovine Mastitis-Causing Staphylococcus aureus: Characterization of Its Role in Biofilm Formation, Resistance to Hydrogen Peroxide Stress, Regulon Members

This study examines treatments of the bacterial pathogen Staphylococcus aureus, namely, in the context of its being a major cause of subclinical bovine mastitis. Such infections caused by S. aureus among dairy cows are difficult to detect and can easily become chronic, leading to reduced productivity and large losses for dairy manufacturers. In this study, the role of alternative sigma factor B (σ^B), which has been shown to be a global regulator for S. aureus infections, was explored in a mastitis-causing S. aureus strain, RF122. For comparison with the wild-type strain, a sigB null (ΔsigB) mutant was constructed and analyzed for its phenotypes and transcriptome. Our study found that σ^B is essential for biofilm formation as the ΔsigB mutant strain produced significantly less biofilm than did the wild-type strain at 48 h. σ^B is involved in response to H₂O₂ stress. However, σ^B plays a minor or no role in resistance to antiseptics (e.g., povidone-iodine and chlorhexidine), resistance to tested antibiotics, hemolysin activity, and invasion ability. RNA sequencing identified 225 σ^B-dependent genes, of which 171 are positively regulated and 54 are negatively regulated. The identified genes are involved in stress response, pathogenesis, and metabolic mechanisms. Quantitative TaqMan RT-PCR was performed to verify the RNA sequencing results; i.e., σ^B is a positive regulator for asp23, sarA, katA, yabJ, sodA, SAB2006c, and nrdD expressions. In the RF122 strain, σ^B plays a role in biofilm formation, general stress response (e.g., H₂O₂), and regulation of virulence factors and virulence-associated genes.

Halogenated trimethoprim derivatives as multidrug-resistant Staphylococcus aureus therapeutics

Incorporation of halogen atoms to drug molecule has been shown to improve its properties such as enhanced in membrane permeability and increased hydrophobic interactions to its target. To investigate the effect of halogen substitutions on the antibacterial activity of trimethoprim (TMP), we synthesized a series of halogen substituted TMP and tested for their antibacterial activities against global predominant methicillin resistant Staphylococcus aureus (MRSA) strains. Structure-activity relationship analysis suggested a trend in potency that correlated with the ability of the halogen atom to facilitate in hydrophobic interaction to saDHFR. The most potent derivative, iodinated trimethoprim (TMP-I), inhibited pathogenic bacterial growth with MIC as low as 1.25 μg/mL while the clinically used TMP derivative, diaveridine, showed resistance. Similar to TMP, synergistic studies indicated that TMP-I functioned synergistically with sulfamethoxazole. The simplicity in the synthesis from an inexpensive starting material, vanillin, highlighted the potential of TMP-I as antibacterial agent for MRSA infections.

Unexpected enhancement in biological activity of a GPCR ligand induced by an oligoethylene glycol substituent

Polyethylene glycol (PEG) is widely used, and many biologically active molecules are modified with oligoethylene glycol substituents to enhance their half-lives in circulation. The pervasive use of PEG substituents is partly due to their presumed inertness. Our investigation of formyl peptide receptor (FPR)-mediated chemotaxis reveals that oligoethylene glycol substitution can enhance the ability of the peptide chemoattractant N-formyl-methionine-leucine-phenylalanine (fMLF) to activate signal transduction through FPR, a transmembrane G-protein-coupled receptor.