Harnessing the combined effect of antivirulence agent trans-chalcone with bactericidal curcumin against sortase A enzyme to tackle Gram-positive bacterial infections

Gram-positive bacteria are responsible for a wide range of infections in humans. In most Gram-positive bacteria, sortase A plays a significant role in attaching virulence factors to the bacteria's cell wall. These cell surface proteins play a significant role in virulence and pathogenesis. Even though antibiotics are available to treat these infections, there is a continuous search for an alternative strategy due to an increase in antibiotic resistance. Thus, using anti-sortase drugs to combat these bacterial infections may be a promising approach. Here, we describe a method for targeting Gram-positive bacterial infection by combining curcumin and trans-chalcone as sortase A inhibitors. We have used curcumin and trans-chalcone alone and in combination as a sortase A inhibitor. We have seen ~78%, ~43%, and ~94% inhibition when treated with curcumin, trans-chalcone, and a combination of both compounds, respectively. The compounds have also shown a significant effect on biofilm formation, IgG binding, protein A recruitment, and IgG deposition. We discovered that combining curcumin and trans-chalcone is more effective against Gram-positive bacteria than either compound alone. The present work demonstrated that a combination of these natural compounds could be used as an antivirulence therapy against Gram-positive bacterial infection.

Sortase A: A chemoenzymatic approach for the labeling of cell surfaces

Sortase A, a transpeptidase enzyme is present in many Gram-positive bacteria and helps in the recruitment of the cell surface proteins. Over the last two decades, Sortase A has become an attractive tool for performing in vivo and in vitro ligations. Sortase A-mediated ligation has continuously been used for its specificity, robustness, and highly efficient nature. These properties make it a popular choice among protein engineers as well as researchers from different fields. In this review, we give an overview of Sortase A-mediated ligation of various molecules on the cell surfaces, which can have diverse applications in interdisciplinary fields.

Sortase A Mediated Bioconjugation of Common Epitopes Decreases Biofilm Formation in Staphylococcus aureus

Staphylococcus aureus is one of the most notorious pathogens and is frequently associated with nosocomial infections imposing serious risk to immune-compromised patients. This is in part due to its ability to colonize at the surface of indwelling medical devices and biofilm formation. Combating the biofilm formation with antibiotics has its own challenges like higher values of minimum inhibitory concentrations. Here, we describe a new approach to target biofilm formation by Gram positive bacteria. Sortase A is a transpeptidase enzyme which is responsible for tagging of around ∼22 cell surface proteins onto the outer surface. These proteins play a major role in the bacterial virulence. Sortase A recognizes its substrate through LPXTG motif. Here, we use this approach to install the synthetic peptide substrates onS. aureus. Sortase A substrate mimic, 6His-LPETG peptide was synthesized using solid phase peptide chemistry. Incorporation of the peptide on the cell surface was measured using ELISA. Effect of peptide incubation on Staphylococcus aureus biofilm was also studied. 71.1% biofilm inhibition was observed with 100 μM peptide while on silicon coated rubber latex catheter, 45.82% inhibition was observed. The present work demonstrates the inability of surface modified S. aureus to establish biofilm formation thereby presenting a novel method for attenuating its virulence.

Rule-based system for the fast identification of species of Indian Anopheline mosquitoes

In a developing country like India, classification and identification of the species of Anopheline mosquitoes in control operations of mosquito-borne diseases is of paramount importance. The WHO monograph, which describes the taxonomic data in the form of a pictorial key is generally difficult to understand by a non-taxonomist. Utilizing the principles of ID3 algorithm, a novel rule-based system, for the fast identification of unknown species of Indian Anopheline mosquitoes, is developed. The rule-based system is user-friendly, menu-driven and even a novice can make use of it in the identification of the unknown species with little practice. The above software is available on floppy disk and can be obtained with a minimum cost. This program can be ported on 5 1/4" or 3 1/2" floppy disk.

Vapour toxicity of aerosol formulation, allethrin on Culex quinquefasciatus (Diptera: Culicidae), Say & Musca domestica (Diptera: Muscidae) N

Studies on the toxicity of aerosol vaporizer formulation, allethrin were carried out on both male and female species of C. quinquefasciatus and M. domestica at different times of exposure. ANOVA models revealed significant differences in the mean values of the percentage mortalities in relation to sex and time-of-exposure for both the species.

A microcomputer FORTRAN program for rapid determination of lethal concentrations of biocides in mosquito control

Probit analysis calculations are highly useful in biology and related sciences. Since the statistical calculations and tests required are quite involved, the use of an automatic computer program is desirable. The description of the computational procedures and use of the computer program with suitable examples from mosquito control programmes are discussed.