Background Salmonella enterica serovar Typhimurium is a common food-borne pathogen. S. enterica uses a type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1) to invade intestinal epithelial cells. A complex network of interacting transcription factors regulates SPI-1 gene expression. In addition, SPI-1 gene expression is coupled to flagellar gene expression. Both SPI-1 and flagellar gene expression are bistable, with co-existing populations of cells expressing and not expressing these genes. Previous work demonstrated that nutrients could be used to tune the fraction of cells expressing the flagellar genes. In the present study, we tested whether nutrients could also tune the fraction of cells expressing the SPI-1 genes through transcriptional crosstalk with the flagellar genes. Results Nutrients alone were not found to induce SPI-1 gene expression. However, when the cells were also grown in the presence of acetate, the concentration of nutrients in the growth medium was able to tune the fraction of cells expressing the SPI-1 genes. During growth in nutrient-poor medium, acetate alone was unable to induce SPI-1 gene expression. These results demonstrate that acetate and nutrients synergistically activate SPI-1 gene expression. The response to acetate was governed by the BarA/SirA two-component system and the response to nutrients was governed by transcriptional crosstalk with the flagella system, specifically through the action of the flagellar regulator FliZ. Conclusions Acetate and nutrients are capable of synergistically activating SPI-1 gene expression. In addition, these signals were found to tune the fraction of cells expressing the SPI-1 genes. The governing mechanism involves transcriptional crosstalk with the flagellar gene network. Collectively, these results further our understanding of SPI-1 gene regulation and provide the basis for future studies investigating this complex regulatory mechanism. Electronic supplementary material The online version of this article (10.1186/s12866-019-1583-7) contains supplementary material, which is available to authorized users.

The fast progression of nanotechnology has led to novel therapeutic interventions. Antimicrobial activities of silver nanoparticles (Ag NPs) were tested against standard ATCC strains of Staphylococcus aureus (ATCC 9144), Escherichia coli (O157:H7), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 90028) in addition to 60 clinical isolates collected from cancer patients. Antimicrobial activity was tested by disk diffusion method and MIC values for Ag NPs alone and in combination with N-acetylcysteine (NAC) against tested pathogens were determined by broth microdilution method. Ag NPs showed a robust antimicrobial activity against all tested pathogens and NAC substantially enhanced the antimicrobial activity of Ag NPs against all tested pathogens. Synergism between Ag NPs and NAC has been confirmed by checkerboard assay. The effect of Ag NPs on tested pathogens was further scrutinized by Transmission Electron Microscope (TEM) which showed disruption of cell wall in both bacteria and fungi. Ag NPs abrogated the activity of respiratory chain dehydrogenase of all tested pathogens and released muramic acid content from S. aureus in culture. The cytotoxic effect of Ag NPs alone and in combination with NAC was examined using human HepG2 cells and this revealed no cytotoxicity at MIC values of Ag NPs and interestingly, NAC reduced the cytotoxic effect of Ag NPs at concentrations higher than their MIC values. Taken together, Ag NPs have robust antimicrobial activity and NAC substantially enhances their antimicrobial activities against MDR pathogens which would provide a novel safe, effective, and inexpensive therapeutic approach to control the prevalence of MDR pathogens.

Cupressus sempervirens is an important medicinal plant in Egypt and the Eastern Mediterranean region. The aim of this work is to evaluate the chemical composition of cupressus leaves as medical plant. We used routine chemical analysis, chemical extractions (methanol and dichloromethane, steam distillation), and GC-mass methods to detect bioactive compounds. of cypress leaves. The results indicated that the percentage of fat was 9.55 %; moisture, 7.54%; protein, 9.24%; ash, 11.1%; fiber, 7.4%; and the percentage of carbohydrates was 55.17%. Alkaloids, flavonoids, phenols, saponin, terbines, tannins groups were detected, while ricin group was absent. Moreover, eighteen components were identified and measured. Sabinene was the main ingredient (67.46%), followed by 3-thujin (8.50%), cetronella (5.04%), 4terpinol (5.01%). Five essential oils were detected including citronella (5.04%), followed by D-limonene (2.94%), αcitronellol (1.88%), and terpinolene (1.12%). In conclusion, pilot extracted oil of cypress leaves could be used to control microbial activity against some fungi species such as Verticillium and Aspergillus.

Background Salmonella enterica serovar Typhimurium is an intestinal pathogen capable of infecting a wide range of animals. It initiates infection by invading intestinal epithelial cells using a type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1). The SPI-1 genes are regulated by multiple interacting transcription factors. The master regulator is HilD. HilE represses SPI-1 gene expression by binding HilD and preventing it from activating its target promoters. Previous work found that acetate and nutrients synergistically induce SPI-1 gene expression. In the present study, we investigated the role of HilE, nominally a repressor of SPI-1 gene expression, in mediating this response to acetate and nutrients. Results HilE is necessary for activation of SPI-1 gene expression by acetate and nutrients. In mutants lacking hilE, acetate and nutrients no longer increase SPI-1 gene expression but rather repress it. This puzzling response is not due to the BarA/SirA two component system, which governs the response to acetate. To identify the mechanism, we profiled gene expression using RNAseq in the wild type and a ΔhilE mutant under different growth conditions. Analysis of these data suggested that the Rcs system, which regulates gene expression in response to envelope stress, is involved. Consistent with this hypothesis, acetate and nutrients were able to induce SPI-1 gene expression in mutants lacking hilE and the Rcs system. Conclusions While the exact mechanism is unknown, these results demonstrate the HilE, nominally a repressor of SPI-1 gene expression, can also function as an activator under the growth conditions investigated. Collectively, these results provide new insights regarding SPI-1 gene regulation and demonstrate that HilE is more complex than initially envisioned.

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Infectious diseases remain one of the major health challenges worldwide due to the problem of antimicrobial resistance. Conventional antimicrobials have the disadvantage that bacteria rapidly acquire resistance to them, so alternatives must be developed to combat antibiotic resistance. Nanotechnology and the repurposing of existing drugs with known biological profiles are new approaches to replacing conventional antimicrobials. In this paper, we have tested the antibacterial activity of sodium acetate (NaA), vitamin C (VC), and zinc oxide nanoparticles (ZnO NPs) against Escherichia coli O157:H7 ATCC 51659 and Pseudomonas aeruginosa ATCC 27853. MIC values for tested compounds ranged from 0.08 to 6.5 mg ml−1, and the effect of combinations and safety profiles against HepG2 cell line of these compounds were also evaluated. At sub-MIC values, tested compounds had a potential antivirulence effect by inhibiting motility and reducing biofilm formation and maturation. Collectively, ZnO NPs and VC are considered safe alternatives to traditional antibiotics that are capable of reducing the development of antibiotic resistance in microbes. Graphical Abstract Graphical abstract representing the main aim and the final findings of our work. Spread of multidrug-resistant (MDR) bacterial strains created an urge for alternative safe antimicrobial agents. In this work, we found that ZnO NPs and vitamin C are potential candidates that could be used against MDR E.coli and P. aeruginosa.

Aim Ocular health greatly impacts the quality of life, and diabetes-mellitus (DM) is a major cause of several visual diseases. Likewise, microbiomes have a pivotal role in eye health. The aim was to study the effect of DM, both type-1 (T1DM) and type-2 (T2DM) on the ocular microbiome. Methods and results a total of 70 subjects were recruited for this study and divided into 2 main groups: healthy non-diabetic (n = 18) and diabetic (28 T1DM and 24 T2DM). The ocular surface (OS) microbiome was more diverse in the healthy group than in the diabetic one. Taxonomic analysis revealed Proteobacteria as the main phylum (healthy non-diabetic 41.8%, T1DM 50.6%, T2DM 52.5%), besides Streptococcus (healthy non-diabetic 16%, T1DM 26.75%, T2DM 29.20%) and Paracoccus (healthy non-diabetic 17%, T1DM 34.85%, T2DM 37.47%) as the main genera. No significant diversity was found between T1DM and T2DM on both phylum and genus levels; yet genera Brevundimonas and Leptotrichia were more significantly predominant in T1DM. Conclusion Two pathogenic genera, Streptococcus and Paracoccus, were more predominant in the DM group than in the healthy one.