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Uropathogenic Escherichia coli (UPEC) are the most common cause of UTI, accounting for more than 90% infections in the normal and unobstructed urinary tracts. Multi-drug resistance (MDR) is an emerging threat to the mankind and hence, there is an urge to develop alternative therapies. Targeting quorum sensing (QS), a cell-cell communication process regulates various biofilm and virulence factors would be a most promising alternate which curbs the pathogenesis without killing the bacteria, unlike antibiotics. SdiA, a quorum regulator is well-known to control the behavioural changes of UPEC in establishing biofilm and virulence. Therefore, we have hypothesized that the SdiA-selective inhibitors derived from the plant, Melia dubia using the molecular docking would be a remarkable therapeutic candidate to down regulate the UPEC biofilm and virulence phenotypes. In this study, we have designed, synthesized and characterized the fructose-furoic acid ester by NMR and ESI-MS. In vitro studies revealed that the QSI-MD selectively inhibits UPEC adherence and confocal laser scanning microscopy (CLSM) analysis showed the effectiveness of QSI-MD to inhibit the UPEC biofilm. Genetic studies using qRT-PCR revealed the down-regulation of quorum sensing regulated genes (fimA, csgA, espA). Based on the findings, we could propose that the QSI-MD could possibly act through SdiA and show target-specific inhibition of biofilm and virulence. It is notable that more than 70 bacterial species execute their communication through the SdiA homologues (LuxIR system). Hence, the QSI-MD could be further developed as a broad-spectrum anti-infective drug.

Biofilm, the regulated complex behavior of bacteria pose serious threat to medical device associated infections and resist the action of antibacterial agents. Also, researchers have evidenced the chemical and physical properties of the non-biological surfaces that enhance the matrix-enclosed microbial accretions on them. In this context, it is a need of an hour to improve the non-adhesive nature of the medical devices against the adherence of microbial populations. So, in our present study, we have developed biocompatible coatings with TiO 2 -Ag thin film on stainless steel substrate (SS 304L) using DC reactive magnetron sputtering and Ag is doped by thermal evaporation technique. The XRD result indicates the formation of anatase TiO 2 films. FE-SEM micrograph showed the uniform deposition of nano-sized Ag and TiO 2 particles. Annealed TiO 2 film showed hydrophobic property and TiO 2 -Ag films showed hydrophilic property. Further, the improved material, TiO 2 -Ag thin films were also tested for its antibacterial and anti-biofilm properties. The data revealed significant reduction of bacterial counts and impairment of Staphylococcus aureus (S.aureus) biofilm in TiO 2 -Ag thin films when compared to SS 304L. Our results provide an insight onto a new perspective for the wide application of these thin film coatings on surgical tools, implant materials etc.

Antibiotic resistance is one of the most pivotal health menaces in the human population worldwide. Use of conventional antibiotics at high concentration for prolonged periods facilitates a selective pressure on the bacterial strain to develop resistance to these antibiotics. The ascent of multi-drug resistance in Vibrio cholerae strains is a key issue for alternative drug development against cholera. A drug that could curb the virulence of V. cholerae is an elective choice for treatment. A few research studies have been carried out to discover such alternative medication that has an anti-virulent property rather than antibacterial activity. Combinatorial antibiotic treatments along with anti-biofilm compounds have diverse effects on bacterial growth i.e. it can be additive, synergistic or antagonistic. In the present investigation, combinatorial action of 2,3-pyrazine dicarboxylic acid derivatives (QSIVc targeted against the quorum regulator, LuxO) along with antibiotics was evaluated. The results indicated that QSIVc could inhibit biofilm at a very low concentration (IC50 varying between 1 μM and 70 μM). The synergism of the compounds with the reported antibiotics (doxycycline, tetracycline, chloramphenicol and erythromycin) was evaluated by the checkerboard method. The fractional inhibitory concentration (FIC) values varied from 0.0 to 0.5 for each combination. The ΔE value (750–1900), according to the bliss independence model showed that the QSIVc synergistically enhanced the inhibitory effect of the reported antibiotics against the multidrug resistant clinical isolates of V. cholerae.

One of the biggest factors limiting the use of orthopaedic implants in humans is the bacterial invasion and bio-film formation on the surface of the implants. Number of patients with infection continuously increases as the number of patients requiring such implants grows. Thus, the aim of our study is to identify the antibiofilm activity of potash alum by inducing infection of S. aureus. The films were tested for antibiofilm property using biofilm assay on clinically isolated S . aureus. Biofilm formation has been induced when we used alum and methylcellulose combination. But the biofilm has been reduced when we used alum without methylcellulose.

The expression of virulence genes in the human pathogen Staphylococcus aureus is strongly influenced by the multiple global regulators. The signal transduction cascade of these global regulators is accountable for recognizing and integrating the environmental cues to regulate the virulence regulon. While the production of virulent factors by individual global regulators are comparatively straightforward to define, auto-regulation of these global regulators and their impact on other regulators is more complex process. There are several reports on the production of virulent factors that are precisely regulated by switching processes of multiple global regulators including some prominent accessory regulators such as agr, sae and sar which allows S. aureus to coordinate the gene expression, and thus, provide organism an ability to act collectively. This review implicates the mechanisms involved in the global regulation of various virulence factors along with a comprehensive discussion on the differences between these signal transduction systems, their auto-induction and, coordination of classical and some comparatively new bacterial signal transduction systems.

With the alarming increase in the antibiotic resistance, there is an immediate need for alternative therapeutic strategies to combat this ever-changing bacterial battle. Combinatorial therapies have gained attention owing to their multiple targeted actions. The use of antibiotic is inevitable and antibiotics in combinations have been in use to treat drug resistant infections. Nevertheless, the multidrug resistant strains have found their own mechanisms to surpass such combinatorial treatments. Quorum sensing (QS) inhibition is considered to be the silver lining but is yet to find its way to commercial use. Hence, to combat the antibiotic resistance crisis, the synergy of QSIs and antibiotics is one of the possible revolutionary approaches. In this chapter, we have highlighted the importance and need for the synergy approach with the successful in vitro and in vivo studies that can possibly be extended to the commercial use.

Melatonin is a natural hormone found in a variety of living organisms, including plants, and possesses the potential to act as a growth promoter and stress alleviator. The present study aims in understanding the effect of melatonin in Catharanthus roseus (C. roseus; medicinal plant used in anticancer therapy) leaf extracts for enhanced silver nanoparticle synthesis. Our results indicated that the supplementation of 300 μM melatonin to C. roseus leaves improves silver nanoparticles (AgNPs) synthesis. The phytosynthesized AgNPs were characterized using UV-Vis spectroscopy, FE-TEM, Zetasizer, XRD, AAS and FTIR spectroscopy. Moreover, the AgNPs were found to be smaller in size (ranging from 10–25 nm) with potent antibacterial activity (MIC and MBC values against the most prevalent urinary tract pathogens, Escherichia coli and Staphylococcus aureus, being 15.6 ± 0.0 μg mL−1 and 31.25 ± 0.0 μg mL−1 respectively). Furthermore, LC-MS/MS analysis of the melatonin treated C. roseus leaf extracts indicated the presence of significant biomolecules; 6-acetyl morphine (used as an analgesic), rauwolscine and fisetin (anticancer compounds). Melatonin treatment of C. roseus leaves also enhanced its antioxidant potential and total chlorophyll content. Thus, melatonin serves as a potential agent to improve C. roseus growth and therapeutic potential.

Several conventional methods have been used for many years to accelerate the growth in decapod crustaceans but they are not suitable for aquaculture practices due to their harmful effects on the animals. Concern over water quality, environmental hazards, human health and food safety has led us to search for alternative targets, to design growth enhancers which can significantly improve the growth of crustaceans without harmful effects. Among such compounds is CGE-1, an amine compound which has shown excellent molt inducing property. Lobsters treated with CGE-1 exhibited a higher weight gain and greater increment in the carapace length post-molt as compared to the controls even without inhibiting the synthesis and secretion of molt-inhibiting hormone (MIH). This is a significant finding considering the fact that MIH binds specifically to the membrane receptor of y-organs, hence CGE-1 might interfere with this interaction allowing an incessant production of 20-hydroxyecdysone (20E). Here, we summarize our findings on CGE-1 and its effects with particular focus on inclusive growth and vitellogenesis. Our observations and findings suggest that CGE-1 could be a useful growth enhancer that could be used either alone or as a dietary supplement for the rapid growth of decapod crustaceans.

Dental caries occurs as a result of disequilibrium between acid producing pathogenic bacteria and alkali generating commensal bacteria within a dental biofilm (dental plaque). S. mutans has been reported as a primary cariogenic pathogen associated with dental caries. Emergence of multidrug resistant as well as fluoride resistant strains of Streptococcus mutans due to over usage of various antibiotics is a rising problem and prompted the researchers worldwide to search for alternative therapies. In this perspective, the present study was aimed to screen selective inhibitors against ComA, a bacteriocin associated ABC transporter, involved in the quorum sensing of S. mutans. In light of our previous in silico findings, 1,3- disubstituted urea derivatives which had better affinity to ComA were chemically synthesized in the present study for in vitro evaluation of S. mutans biofilm inhibition. The results revealed that 1,3- disubstituted urea derivatives showed good biofilm inhibition. In addition, the synthesized compounds exhibited potent synergy with a very low concentration of fluoride (31.25 ppm to 62.5 ppm) in inhibiting the biofilm formation of S. mutans without affecting the bacterial growth. Further, the results were confirmed by confocal laser scanning microscopy. On the whole, from our experimental results we conclude that the combinatorial application of fluoride and disubstituted ureas has a potential synergistic effect which has a promising approach in combating multidrug resistant and fluoride resistant S. mutans in dental caries management.

Staphylococcus aureus is extensively acknowledged as an opportunistic pathogen because of acquisition and rapid spread of resistance to antibiotics. The temporal expression of many virulence genes is controlled by a major regulatory molecule, SarA that binds to the promoter region of target genes. Constitutive activation of the SarA proteins plays a critical role in the biofilm formation and proliferation of S. aureus. The investigation of SarA inhibitors as potential therapeutic agents is based on the fact that the highly conserved winged region participates in DNA binding and activation is expressed in various staphylococcal species. Computer-assisted drug design was employed to generate first specific low molecular weight compounds that interact with SarA and disrupt the quorum-sensing mechanism. Thirteen potential inhibitors of SarA are identified to improve the understanding of SarA biological function and to disclose future strategies for inhibition.

Cellular metabolism is a very complex process. The biochemical pathways are fundamental structures of biology. These pathways possess a number of regeneration steps which facilitate energy shuttling on a massive scale. This facilitates the biochemical pathways to sustain the energy currency of the cells. This concept has been mimicked using electronic circuit components and it has been used to increase the efficiency of bio-energy generation. Six of the carbohydrate biochemical pathways have been chosen in which glycolysis is the principle pathway. All the six pathways are interrelated and coordinated in a complex manner. Mimic circuits have been designed for all the six biochemical pathways. The components of the metabolic pathways such as enzymes, cofactors etc., are substituted by appropriate electronic circuit components. Enzymes are related to the gain of transistors by the bond dissociation energies of enzyme-substrate molecules under consideration. Cofactors and coenzymes are represented by switches and capacitors respectively. Resistors are used for proper orientation of the circuits. The energy obtained from the current methods employed for the decomposition of organic matter is used to trigger the mimic circuits. A similar energy shuttle is observed in the mimic circuits and the percentage rise for each cycle of circuit functioning is found to be 78.90. The theoretical calculations have been made using a sample of domestic waste weighing 1.182 kg. The calculations arrived at finally speak of the efficiency of the novel methodology employed.

Urinary Tract Infection (UTI) is a globally widespread human infection caused by an infestation of uropathogens. Eventhough, Escherichia coli is often quoted as being the chief among them, Staphylococcus aureus involvement in UTI especially in gestational UTI is often understated. Staphylococcal accessory regulator A (SarA) is a quorum regulator of S. aureus that controls the expression of various virulence and biofilm phenotypes. Since SarA had been a focussed target for antibiofilm agent development, the study aims to develop a potential drug molecule targeting the SarA of S. aureus to combat biofilm associated infections in which it is involved. In our previous studies, we have reported the antibiofilm activity of SarA based biofilm inhibitor, (SarABI) with a 50% minimum biofilm inhibitory concentration (MBIC50) value of 200 μg/mL against S. aureus associated with vascular graft infections and also the antibiofilm activity of the root ethanolic extracts of Melia dubia against uropathogenic E. coli. In the present study, in silico design of a hybrid molecule composed of a molecule screened from M. dubia root ethanolic extracts and a modified SarA based inhibitor (SarABI(M)) was undertaken. SarABI(M) is a modified form of SarABI where the fluorine groups are absent in SarABI(M). Chemical synthesis of the hybrid molecule, 4-(Benzylamino)cyclohexyl 2-hydroxycinnamate (henceforth referred to as UTI Quorum-Quencher, UTI(QQ)) was then performed, followed by in vitro and in vivo validation. The MBIC50 and MBIC90 of UTI(QQ) were found to be 15 and 65 μg/mL, respectively. Confocal laser scanning microscopy (CLSM) images witnessed biofilm reduction and bacterial killing in either UTI(QQ) or in combined use of antibiotic gentamicin and UTI (QQ) . Similar results were observed with in vivo studies of experimental UTI in rat model. So, we propose that the drug UTI(QQ) would be a promising candidate when used alone or, in combination with an antibiotic for staphylococcal associated UTI.

Staphylococcus aureus is a common pathogen seen in prosthetic vascular graft, leading to high morbidity and mortality. The virulence genes for severity of infections are under the control of global regulators. Staphylococcal accessory regulator A (SarA) a known master controller of biofilm formation is an attractive target for the drug development. A structure based screening of lead compounds was employed for the identification of novel small molecule inhibitors targeted to interact to the DNA binding domain of the transcriptional activator, SarA and hinder its response over the control of genes that up-regulate the phenotype, biofilm. The top-hit SarA selective inhibitor, 4-[(2,4-diflurobenzyl)amino] cyclohexanol (SarABI) was further validated in-vitro for its efficacy. The SarABI was found to have MBIC50value of 200 μg/ml and also down-regulated the expression of the RNA effector, (RNAIII), Hemolysin (hld), and fibronectin-binding protein (fnbA). The anti-adherence property of SarABI on S. aureus invasion to the host epithelial cell lines (Hep-2) was examined where no significant attachment of S. aureus was observed. The SarABI inhibits the colonization of MDR S. aureus in animal model experiment significantly cohere to the molecular docking studies and in vitro experiments. So, we propose that the SarABI could be a novel substitute to overcome a higher degree of MDR S. aureus colonization on vascular graft.

Streptococcus mutans, a Gram positive facultative anaerobe, is one among the approximately seven hundred bacterial species to exist in human buccal cavity and cause dental caries. Quorum sensing (QS) is a cell-density dependent communication process that respond to the inter/intra-species signals and elicit responses to show behavioral changes in the bacteria to an aggressive forms. In accordance to this phenomenon, the S. mutans also harbors a Competing Stimulating Peptide (CSP)-mediated quorum sensing, ComCDE (Two-component regulatory system) to regulate several virulence-associated traits that includes the formation of the oral biofilm (dental plaque), genetic competence and acidogenicity. The QS-mediated response of S. mutans adherence on tooth surface (dental plaque) imparts antibiotic resistance to the bacterium and further progresses to lead a chronic state, known as periodontitis. In recent years, the oral streptococci, S. mutans are not only recognized for its cariogenic potential but also well known to worsen the infective endocarditis due to its inherent ability to colonize and form biofilm on heart valves. The review significantly appreciate the increasing complexity of the CSP-mediated quorum-sensing pathway with a special emphasis to identify the plausible drug targets within the system for the development of anti-quorum drugs to control biofilm formation and associated risks.

Cholera, a known diarrheal disease is associated with various risk factors like hypovolemic shock, rice watery stools, and death in developing countries. The overuse of antibiotics to treat cholera imposed a selective pressure for the emergence and spread of multi-drug resistant Vibrio cholerae strains. The failure of conventional antimicrobial therapy urged the researchers to find an alternative therapy that could meddle the cholera murmurs (Quorum Sensing). It seems to effectively overcome the conventional cholera therapies in parallel to decrease the morbidity and mortality rate in the developing countries. The paramount objective of this review essentially focuses on the different Quorum Sensing (QS) regulatory switches governing virulence and pathogenicity of Vibrio cholerae. This review also provides an insight into the plausible QS targets that could be exploited to bring about a breakthrough to the prevailing cholera therapy.

The first set of competitive inhibitors of molt inhibiting hormone (MIH) has been developed using the effective approaches such as Hip-Hop, virtual screening and manual alterations. Moreover, the conserved residues at 71 and 72 positions in the molt inhibiting hormone is known to be significant for selective inhibition of ecdysteroidogenesis; thus, the information from mutation and solution structure were used to generate common pharmacophore features. The geometry of the final six-feature pharmacophore was also found to be consistent with the homology-modeled MIH structures from various other decapod crustaceans. The Hypo-1, comprising six features hypothesis was carefully selected as a best pharmacophore model for virtual screening created on the basis of rank score and cluster processes. The hypothesis was validated and the database was virtually screened using this 3D query and the compounds were then manually altered to enhance the fit value. The hits obtained were further filtered for drug-likeness, which is expressed as physicochemical properties that contribute to favorable ADME/Tox profiles to eliminate the molecules exhibit toxicity and poor pharmacokinetics. In conclusion, the higher fit values of CI-1 (4.6), CI-4 (4.9) and CI-7 (4.2) in conjunction with better pharmacokinetic profile made these molecules practically helpful tool to increase production by accelerating molt in crustaceans. The use of feeding sub-therapeutic dosages of these growth enhancers can be very effectively implemented and certainly turn out to be a vital part of emerging nutritional strategies for economically important crustacean livestock.

Staphylococcus aureus pathogenesis is an intricate process involving a diverse array of extracellular proteins, biofilm and cell wall components that are coordinately expressed in different stages of infection. The expression of two divergent loci, agr and sar, is increasingly recognized as a key regulator of virulence in S. aureus, and there is mounting evidence for the role of these loci in staphylococcal infections. The functional agr regulon is critical for the production of virulence factors, including α, β and δ hemolysins. The sar locus encodes SarA protein, which regulates the expression of cell wall-associated and certain extracellular proteins in agr-dependent and agr-independent pathways. Multidrug-resistant S. aureus is a leading cause of morbidity and mortality in the world and its management, especially in community-acquired methicillin-resistant S. aureus infections, has evolved comparatively little. In particular, no novel targets have been incorporated into its treatment to date. Hence, these loci appear to be the most significant and are currently at the attention of intense investigation regarding their therapeutic prospects.

Quantum dots (QDs) play a vital role in anti-bacterial activity. Cadmium Telluride (CdTe) QDs were synthesized by wet chemical method. Synergistic interactions of CdTe and antibiotic (Ampicillin (amp)) were studied towards the adhesion activity of S.aureus strains (ATCC 25923, Clinical Isolate 762) and we found that significant biofilm inhibition was obtained at maximum concentration of CdTe.

Zinc oxide (ZnO) thin films have been deposited onto thoroughly cleaned stainless steel (AISI SS 304) substrates by reactive direct current (dc) magnetron sputtering and the films were doped with silver (Ag). The prepared thin films were analyzed using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) to investigate the structural and morphological properties. The thickness values of the films were in the range of 194 to 256[Formula: see text]nm. XRD results revealed that the films were crystalline with preferred (002) orientation. Grain size values of pure ZnO films were found to be 19.82–23.72[Formula: see text]nm. On introducing Ag into ZnO film, the micro-structural properties varied. Adhesion test was carried out with Staphylococcus aureus (S. aureus) in order to know the adherence property of the deposited films. Colony formation units (CFU) were counted manually and bacterial adhesion inhibition (BAI) was calculated. We observed a decrease in the CFU on doping Ag in the ZnO films. BAI of the film deposited at – 100 V substrate bias was found to be increased on Ag doping from 69 to 88%.