Aim Ocular health greatly impacts the quality of life, and diabetes mellitus (DM) is a major caus... more 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 two main groups healthy nondiabetic (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 nondiabetic 41.8%, T1DM 50.6%, and T2DM 52.5%), besides Streptococcus (healthy nondiabetic 16%, T1DM 26.75%, and T2DM 29.20%) and Paracoccus (healthy nondiabetic 17%, T1DM 34.85%, and 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 significant...
Nano technology has emerged as a powerful field that enables the manipulation and control of matt... more Nano technology has emerged as a powerful field that enables the manipulation and control of matter at the nanoscale. One particular area of interest is the synthesis and application of silver nanoparticles (AgNPs) conjugated with chitosan, a biocompatible and biodegradable polysaccharide. This conjugate offers unique opportunities for various industries, particularly in biomedicine and environmental remediation. In the biomedical field, chitosan-silver nanoparticle conjugates exhibit significant potential as antimicrobial agents, wound dressings, and drug delivery systems. The combination of chitosan's biocompatibility and silver nanoparticles' antimicrobial activity provides an effective approach to combat infections and promote wound healing. Furthermore, the chitosan matrix can facilitate controlled release of therapeutic agents, enhancing their efficacy and reducing potential side effects. In environmental applications, chitosan-silver nanoparticle conjugates show promise for water purification, as they can effectively remove pollutants and disinfect water due to the antimicrobial properties of silver nanoparticles. Chitosan's ability to form gels and membranes further facilitates their use in filtration systems for wastewater treatment and environmental remediation. In conclusion, the conjugation of chitosan with silver nanoparticles represents a promising avenue in nano technology. This conjugate offers versatile applications in biomedicine and environmental remediation, leveraging the synergistic properties of both components. Further research and development are required to optimize the synthesis techniques, understand the mechanisms of action, and assess the long-term effects to ensure safe and effective utilization of chitosan-silver nanoparticle conjugates in various industries.
Bacterial cells in the natural environment and in infections are rarely found in a planktonic sta... more Bacterial cells in the natural environment and in infections are rarely found in a planktonic state. They are instead arranged in well-organized communities embedded in self-produced extracellular polymeric substances (EPS) called biofilms. The biofilm lifestyle confers a wide range of properties to the residing cells that allow efficient social interaction, permit nutrient availability, and ensure optimum usage of available enzymes and resources. The biofilm structure also permits a high level of tolerance to antimicrobials and host defense mechanisms. This creates a clinical milestone in treatment of biofilm-related infections. The medical consequences of biofilm formation and associated device-related infections (DRI) have been amplified with the widespread use of implanted medical devices. However, the biofilm structure itself represents a promising target in the development of novel antibacterial drugs. Therefore, this review represents an overview on the biofilm properties and the role of the EPS in the biofilm ecosystem. In addition, it emphasises the involvement of the biofilm structure as a therapeutic target in the development of novel antimicrobials and treatment of biofilm-related infections.
Antibiotic resistance is a universal warning to human health; by 2050, it is expected that the mo... more Antibiotic resistance is a universal warning to human health; by 2050, it is expected that the mortality rate due to antimicrobial resistance (AMR) will exceed 10 million. Heteroresistance (HR) is a phenomenon in which subpopulations of cells exhibit lower levels of antibiotic susceptibility compared to the main population. There are no standard methods to detect HR leading to inappropriate use of this expression. HR has been distinguished since 1947 and reported in Gramnegative and Gram-positive bacteria. Recently, HR is so prevalent in various bacterial species against the plethora of antibiotic classes. HR which has an unstable phenotypic character, having different mechanisms with non-standard methods to be determined, prevents recognition of the degree to which this phenomenon is precarious and its consequences. In 2009, World Health Organization (WHO) has defined antibiotic resistance (AbR) as a critical public health threat causing death rates more than that caused by cancer and such serious diseases. Consequently, understanding the novel and often under-recognized mechanisms of resistance that represent barriers to antibiotic efficacy is vital so as to combat resistance with new therapeutic approaches. Eventually, a fundamental issue is whether we can predict why some resistant clones have the ability to survive despite the perishing of the main population. In this review, we will assess the available literature on bacterial HR suggesting recommendations for the definition and determination criteria for antibiotic HR to help assess the treatment failure caused by heteroresistant bacteria.
Here, 210 healthy participants including community personnel (70), clinical students (68), and he... more Here, 210 healthy participants including community personnel (70), clinical students (68), and healthcare workers (HCWs) (72) from the eastern region of Saudi Arabia were studied. Sixty-threeStaphylococcus aureusisolates were obtained from the nares of 37% of the community personnel and 26% of the clinical students and HCWs. Methicillin-resistantS. aureus(MRSA) was found in 16% (10 isolates) of the 63 isolates; six were from HCWs. Molecular characterization revealed high clonal diversity among the isolates, with 19 differentspatypes, 12 clonal complexes (CCs), and seven sequence types (STs) detected. The most common strain type was USA900, CC15, and t084, seen in 11 methicillin-susceptibleS. aureus(MSSA) isolates. Moreover, three novelspatypes in six isolates and one novel ST in two isolates were identified, most from HCWs. Interestingly, 29 isolates weremecA positive by PCR, whereas only 10 isolates were MRSA by disk diffusion (cefoxitin resistant). Of the 19 MSSAmecA-positive isol...
Background: Sampling the microenvironment at sites of microbial exposure by dendritic cells (DC) ... more Background: Sampling the microenvironment at sites of microbial exposure by dendritic cells (DC) and their subsequent interaction with T cells in the paracortical area of lymph nodes are key events for initiating immune responses. Most of our knowledge of such events in human is based on in vitro studies performed in the absence of extracellular matrix (ECM) proteins. ECM in basement membranes and interstitial spaces of different tissues, including lymphoid organs, plays an important role in controlling specific cellular functions such as migration, intracellular signalling and differentiation. The aim of this study was, therefore, to investigate the impact of two abundant ECM components, fibronectin and laminin, on the phenotypical and functional properties of DC and how that might influence DC induced T-cell differentiation. Methodology/Principal Findings: Human monocyte derived DC were treated with laminin and fibronectin for up to 48 hours and their morphology and phenotype was analyzed using scanning electron microscopy, flow cytometry and real time PCR. The endocytic ability of DC was determined using flow cytometry. Furthermore, co-culture of DC and T cells were established and T cell proliferation and cytokine profile was measured using H 3-thymidine incorporation and ELISA respectively. Finally, we assessed formation of DC-T cell conjugates using different cell trackers and flow cytometry. Our data show that in the presence of ECM, DC maintain a 'more immature' phenotype and express higher levels of key endocytic receptors, and as a result become significantly better endocytic cells, but still fully able to mature in response to stimulation as evidenced by their superior ability to induce antigen-specific T cell differentiation. Conclusion: These studies underline the importance of including ECM components in in vitro studies investigating DC biology and DC-T cell interaction. Within the context of antigen specific DC induced T cell proliferation, inclusion of ECM proteins could lead to development of more sensitive assays.
Background Salmonella enterica serovar Typhimurium is an intestinal pathogen capable of infecting... more 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...
Background: Allergen uptake by DCs is central to allergic sensitization. Results: DC-SIGN recogni... more Background: Allergen uptake by DCs is central to allergic sensitization. Results: DC-SIGN recognizes major allergens from house dust mite and dog. However, silencing DC-SIGN leads to Th2 differentiation. Conclusion: DC-SIGN is a newly identified receptor for Der p 1 and Can f 1 that appears to support Th1 cell differentiation. Significance: Understanding of how allergic responses are selected and propagated is essential for developing novel therapies.
Objectives: Unraveling mechanisms whereby Pseudomonas aeruginosa becomes resistant to carbapenems... more Objectives: Unraveling mechanisms whereby Pseudomonas aeruginosa becomes resistant to carbapenems through testing 114 non-duplicate P. aeruginosa clinical isolates for their susceptibility to various classes of antibiotics and scrutinizing the production of metallo-β-lactamases (MBLs) by tested isolates. Methods: Susceptibility testing of P. aeruginosa to different antibiotics was determined by Kirby-Bauer disk diffusion method and MBLs production by tested isolates was studied phenotypically and genotypically and PCR products were confirmed by sequencing Results: All tested clinical isolates showed eminent resistance to the majority of tested antibiotics and 14 isolates were imipenem (IPM)-resistant. Furthermore, IPM-resistant isolates were verified to be MBLs-producers. MBLs-encoding genes blaSIM and blaSPM genes were detected by PCR where four isolates were found to harbor blaSPM gene while only one isolate harbored blaSIM gene. The correct size of PCR products of blaSIM and blaS...
Klebsiella pneumoniae is responsible for a plethora of infections involving multiple body systems... more Klebsiella pneumoniae is responsible for a plethora of infections involving multiple body systems. This study investigated K. pneumoniae clinical isolates for virulence-associated characters and antibiotic resistance. First, antibiotic sensitivity was determined for 40 K. pneumoniae clinical isolates. Some virulence and resistance-associated factors were studied phenotypically and genotypically. Multiple resistance profiles were observed (multidrug resistant [MDR; 42.5%], extensive drug resistant [XDR; 35%], and pandrug resistant [PDR; 5%]). Moreover, CTX-M-1, TEM, qnrS, and qnrA genes were detected in 70%, 30%, 60%, and 30% of selected isolates, respectively, and 40% of tested isolates were extended-spectrum β-lactamases (ESBLs) producers. Interestingly, all ESBLs producers harbored class 1 integrase gene (IntI1), while 60% of ESBLs producers harbored both CTX-M-1 and TEM. All tested isolates were capsulated while 87.5% were biofilm producers. Fimbriae were detected in 90% of tested isolates (all were biofilm producers and type 3 fimbriae adhesion gene [mrkD] positive). Sequence analysis of OXA-48, qnrS, and IntI1 revealed 100% identity with published sequences, while sequencing of qnrA, OmpK-35, and iron regulatory protein gene (irp2) showed minor variations in the form of one or few single-nucleotide polymorphism. Altogether, the current study revealed that all MDR, XDR, and PDR K. pneumoniae isolates were multivirulent and all harbored 3-5 virulence genes and 2-9 antimicrobial resistance genes and exhibited 8 and 10 different virulence and antimicrobial resistance profiles, respectively. In this study, we also report a positive correlation between some virulence genes and antimicrobial resistance genes among K. pneumoniae tested isolates.
Background: Salmonella enterica serovar Typhimurium is a common food-borne pathogen. S. enterica ... more 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 coexisting 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.
The fast progression of nanotechnology has led to novel therapeutic interventions. Antimicrobial ... more 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...
Multidrug resistance (MDR) in various kinds of cancers represents a true obstacle which hinders t... more Multidrug resistance (MDR) in various kinds of cancers represents a true obstacle which hinders the successes of most of current available chemotherapies. ATP-binding cassette (ABC) trasporter proteins have been shown to contribute to the majority of MDR in various types of malignancies. c-myc has recently been reported to participate, at least partly, in MDR to some types of cancers. This study aimed to test whether c-myc could play a role, solely or with coordination with other ABCs, in the resistance of HepG2 cells to doxorubicin (Dox). MDR has been induced in wild-type HepG2 and has been verified both on gene and protein levels. Various assays including efflux assays as well as siRNA targeting ABCB1 and c-myc have been employed to explore the role of both candidate molecules in MDR in HepG2. Results obtained, with regard to ABCB1 silencing on HepG2/Dox cells, have shown that ABCB1-deficient cells exhibited a significant reduction in ABCC1 expression as compared to ABCB1-sufficient cells. However, these cells did not show a significant reduction in other tested ABCs (ABCC5 and ABCC10) while c-myc silencing had no significant effect on any of the studied ABCs. Moreover, silencing of ABCB1 on HepG2 significantly increased fluorescent calcein retention in HepG2 cells as compared to the control cells while downregulation of c-myc did not have any effect on fluorescent calcein retention. Altogether, this work clearly demonstrates that c-myc has no role in MDR of HepG2 to Dox which has been shown to be ABCB1-mediated in a mechanism which might involve ABCC1.
Shigella sonnei is a bacterial pathogen and causative agent of bacillary dysentery. It deploys a ... more Shigella sonnei is a bacterial pathogen and causative agent of bacillary dysentery. It deploys a type III secretion system to inject effector proteins into host epithelial cells and macrophages, an essential step for tissue invasion and immune evasion. Although the arsenal of bacterial effectors and their cellular targets have been studied extensively, little is known about the prerequisites for deployment of type III secreted proteins during infection. Here, we describe a novel S. sonnei adhesin, SSO1327 which is a Multivalent Adhesion Molecule (MAM) required for invasion of epithelial cells and macrophages and for infection in vivo. The S. sonnei MAM mediates intimate attachment to host cells, which is required for efficient translocation of type III effectors into host cells. SSO1327 is non-redundant to IcsA; its activity is independent of type III secretion. In contrast to the up-regulation of IcsA-dependent and independent attachment and invasion by deoxycholate in S. flexneri,...
Allergens are initiators of both innate and adaptive immune responses. They are recognised at the... more Allergens are initiators of both innate and adaptive immune responses. They are recognised at the site of entry by epithelial and dendritic cells (DCs), both of which activate innate inflammatory circuits that can collectively induce Th2 immune responses. In an attempt to have a better understanding of the role of carbohydrates in the recognition and uptake of allergens by the innate immune system, we defined common glycosylation patterns in major allergens. This was done using labelled lectins and showed that allergens like Der p 1 (Dermatophagoides pteronyssinus group 1), Fel d 1 (Felis domisticus), Ara h 1 (Arachis hypogaea), Der p 2 (Dermatophagoides pteronyssinus group 2), Bla g 2 (Blattella germanica) and Can f 1 (Canis familiaris) are glycosylated and that the main dominant sugars on these allergens are 1-2, 1-3 and 1-6 mannose. These observations are in line with recent reports implicating the mannose receptor (MR) in allergen recognition and uptake by DCs and suggesting a major link between glycosylation and allergen recognition. We then looked at TSLP (Thymic Stromal Lymphopoietin) cytokine secretion by lung epithelia upon encountering natural Der p 1 allergen. TSLP is suggested to drive DC maturation in support of allergic hypersensitivity reactions. Our data showed an increase in TSLP secretion by lung epithelia upon stimulation with natural Der p 1 which was carbohydrate dependent. The deglycosylated preparation of Der p 1 exhibited minimal uptake by DCs compared to the natural and hyperglycosylated recombinant counterparts, with the latter being taken up more readily than the other preparations. Collectively, our data indicate that carbohydrate moieties on allergens play a vital role in their recognition by innate immune cells, implicating them in downstream deleterious Th2 cell activation and IgE production.
A group of 11 medicinal plants, including Lavandula pubescens, Trigonella foenugricium, Salsola s... more A group of 11 medicinal plants, including Lavandula pubescens, Trigonella foenugricium, Salsola schweinforthi, Calligonum comosum, Silene succulenta, Silene villosa, Bogonvillea glabra, Cakile maritime, Gomphrene celesoids, Mirabilis jalaba, and Silene nocturna growing in Egypt, were extracted and examined for their immunomodulatory and antioxidant activities. RAW 264.7 cells were recruited to investigate the immunomodulatory effect through multiple parameters analysis. First, the proliferation index of macrophages cells was evaluated revealing that Trigonella foenugricium, Silene succulenta and Silene villosa have a significant cytotoxic effect on RAW cells. Interestingly, we observed enhancement of macrophages phagocytic function of by all extracts except Cakile maritime, Gomphrena celosioides and Silene nocturna. Afterwards, macrophages were challenged by incubation with LPS and the effect of various extracts on inflammatory responses was investigated; the generation of NO from activated macrophage was substantially suppressed by 7 extracts namely, Trigonella foenugricium, Calligonum comosum, Silene succulenta, Bougainvillea glabra, Mirabilis jalaba, Gomphrena celosioides and Silene nocturna. TNF-a was decreased by percentage range from 3.8 to 85.8% and Trigonella foenugricium extract showed the highest inhibition of TNF-a release. All extracts except Trigonella foenugricium, Salsola schweinforthi, Silene succulenta and Mirabilis jalaba significantly inhibited COX-2 production from stimulated macrophage. Moreover, evaluating the potential antioxidant activity of these extracts showed that Trigonella foenugricium, Salsola schweinforthi, Calligonum comosum, Bogonvillea glabra and Mirabilis jalaba exhibited some antioxidant activities. Taken together, our results suggest that some of these extracts may have a considerable antinflammatory and antioxidant effects and may be a potential therapeutic choice in the treatment of inflammatory diseases.
Proceedings of the National Academy of Sciences, 2010
Surface Ig (sIg) of follicular lymphoma (FL) is vital for tumor cell survival. We found previousl... more Surface Ig (sIg) of follicular lymphoma (FL) is vital for tumor cell survival. We found previously that the Ig in FL is unusual, because the variable region genes carry sequence motifs for N -glycan addition. These are introduced by somatic mutation and are tumor specific. Unexpectedly, added glycans terminate at high mannose, suggesting a potentially important interaction of FL cells with mannose-binding lectins of the innate immune system. We have now identified mannosylated IgM at the surface of primary lymphoma cells. Recombinant lectin domains of the mannose receptor (MR) or DC-SIGN bind mannosylated Igs in vitro and bind to FL cells, signaling sIgM-associated increases in intracellular Ca 2+ . Lectins also bind to normal B cells but fail to signal. In contrast, anti-Ig signaled similarly in both FL and normal B cells. Mannosylation patterns were mimicked by FL Ig-derived single-chain Fvs (scFv), providing probes for potential receptors. Mannosylated scFv bound specifically to ...
The mannose receptor (MR) is a C-type lectin expressed by dendritic cells (DCs). We have investig... more The mannose receptor (MR) is a C-type lectin expressed by dendritic cells (DCs). We have investigated the ability of MR to recognize glycosylated allergens. Using a gene silencing strategy, we have specifically inhibited the expression of MR on human monocytederived DCs. We show that MR mediates internalization of diverse allergens from mite (Der p 1 and Der p 2), dog (Can f 1), cockroach (Bla g 2), and peanut (Ara h 1) through their carbohydrate moieties. All of these allergens bind to the C-type lectin-like carbohydrate recognition domains 4-7 of MR. We have also assessed the contribution of MR to T cell polarization after allergen exposure. We show that silencing MR expression on monocyte-derived DCs reverses the Th2 cell polarization bias, driven by Der p 1 allergen exposure, through upregulation of IDO activity. In conclusion, our work demonstrates a major role for MR in glycoallergen recognition and in the development of Th2 responses.
Aim Ocular health greatly impacts the quality of life, and diabetes mellitus (DM) is a major caus... more 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 two main groups healthy nondiabetic (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 nondiabetic 41.8%, T1DM 50.6%, and T2DM 52.5%), besides Streptococcus (healthy nondiabetic 16%, T1DM 26.75%, and T2DM 29.20%) and Paracoccus (healthy nondiabetic 17%, T1DM 34.85%, and 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 significant...
Nano technology has emerged as a powerful field that enables the manipulation and control of matt... more Nano technology has emerged as a powerful field that enables the manipulation and control of matter at the nanoscale. One particular area of interest is the synthesis and application of silver nanoparticles (AgNPs) conjugated with chitosan, a biocompatible and biodegradable polysaccharide. This conjugate offers unique opportunities for various industries, particularly in biomedicine and environmental remediation. In the biomedical field, chitosan-silver nanoparticle conjugates exhibit significant potential as antimicrobial agents, wound dressings, and drug delivery systems. The combination of chitosan's biocompatibility and silver nanoparticles' antimicrobial activity provides an effective approach to combat infections and promote wound healing. Furthermore, the chitosan matrix can facilitate controlled release of therapeutic agents, enhancing their efficacy and reducing potential side effects. In environmental applications, chitosan-silver nanoparticle conjugates show promise for water purification, as they can effectively remove pollutants and disinfect water due to the antimicrobial properties of silver nanoparticles. Chitosan's ability to form gels and membranes further facilitates their use in filtration systems for wastewater treatment and environmental remediation. In conclusion, the conjugation of chitosan with silver nanoparticles represents a promising avenue in nano technology. This conjugate offers versatile applications in biomedicine and environmental remediation, leveraging the synergistic properties of both components. Further research and development are required to optimize the synthesis techniques, understand the mechanisms of action, and assess the long-term effects to ensure safe and effective utilization of chitosan-silver nanoparticle conjugates in various industries.
Bacterial cells in the natural environment and in infections are rarely found in a planktonic sta... more Bacterial cells in the natural environment and in infections are rarely found in a planktonic state. They are instead arranged in well-organized communities embedded in self-produced extracellular polymeric substances (EPS) called biofilms. The biofilm lifestyle confers a wide range of properties to the residing cells that allow efficient social interaction, permit nutrient availability, and ensure optimum usage of available enzymes and resources. The biofilm structure also permits a high level of tolerance to antimicrobials and host defense mechanisms. This creates a clinical milestone in treatment of biofilm-related infections. The medical consequences of biofilm formation and associated device-related infections (DRI) have been amplified with the widespread use of implanted medical devices. However, the biofilm structure itself represents a promising target in the development of novel antibacterial drugs. Therefore, this review represents an overview on the biofilm properties and the role of the EPS in the biofilm ecosystem. In addition, it emphasises the involvement of the biofilm structure as a therapeutic target in the development of novel antimicrobials and treatment of biofilm-related infections.
Antibiotic resistance is a universal warning to human health; by 2050, it is expected that the mo... more Antibiotic resistance is a universal warning to human health; by 2050, it is expected that the mortality rate due to antimicrobial resistance (AMR) will exceed 10 million. Heteroresistance (HR) is a phenomenon in which subpopulations of cells exhibit lower levels of antibiotic susceptibility compared to the main population. There are no standard methods to detect HR leading to inappropriate use of this expression. HR has been distinguished since 1947 and reported in Gramnegative and Gram-positive bacteria. Recently, HR is so prevalent in various bacterial species against the plethora of antibiotic classes. HR which has an unstable phenotypic character, having different mechanisms with non-standard methods to be determined, prevents recognition of the degree to which this phenomenon is precarious and its consequences. In 2009, World Health Organization (WHO) has defined antibiotic resistance (AbR) as a critical public health threat causing death rates more than that caused by cancer and such serious diseases. Consequently, understanding the novel and often under-recognized mechanisms of resistance that represent barriers to antibiotic efficacy is vital so as to combat resistance with new therapeutic approaches. Eventually, a fundamental issue is whether we can predict why some resistant clones have the ability to survive despite the perishing of the main population. In this review, we will assess the available literature on bacterial HR suggesting recommendations for the definition and determination criteria for antibiotic HR to help assess the treatment failure caused by heteroresistant bacteria.
Here, 210 healthy participants including community personnel (70), clinical students (68), and he... more Here, 210 healthy participants including community personnel (70), clinical students (68), and healthcare workers (HCWs) (72) from the eastern region of Saudi Arabia were studied. Sixty-threeStaphylococcus aureusisolates were obtained from the nares of 37% of the community personnel and 26% of the clinical students and HCWs. Methicillin-resistantS. aureus(MRSA) was found in 16% (10 isolates) of the 63 isolates; six were from HCWs. Molecular characterization revealed high clonal diversity among the isolates, with 19 differentspatypes, 12 clonal complexes (CCs), and seven sequence types (STs) detected. The most common strain type was USA900, CC15, and t084, seen in 11 methicillin-susceptibleS. aureus(MSSA) isolates. Moreover, three novelspatypes in six isolates and one novel ST in two isolates were identified, most from HCWs. Interestingly, 29 isolates weremecA positive by PCR, whereas only 10 isolates were MRSA by disk diffusion (cefoxitin resistant). Of the 19 MSSAmecA-positive isol...
Background: Sampling the microenvironment at sites of microbial exposure by dendritic cells (DC) ... more Background: Sampling the microenvironment at sites of microbial exposure by dendritic cells (DC) and their subsequent interaction with T cells in the paracortical area of lymph nodes are key events for initiating immune responses. Most of our knowledge of such events in human is based on in vitro studies performed in the absence of extracellular matrix (ECM) proteins. ECM in basement membranes and interstitial spaces of different tissues, including lymphoid organs, plays an important role in controlling specific cellular functions such as migration, intracellular signalling and differentiation. The aim of this study was, therefore, to investigate the impact of two abundant ECM components, fibronectin and laminin, on the phenotypical and functional properties of DC and how that might influence DC induced T-cell differentiation. Methodology/Principal Findings: Human monocyte derived DC were treated with laminin and fibronectin for up to 48 hours and their morphology and phenotype was analyzed using scanning electron microscopy, flow cytometry and real time PCR. The endocytic ability of DC was determined using flow cytometry. Furthermore, co-culture of DC and T cells were established and T cell proliferation and cytokine profile was measured using H 3-thymidine incorporation and ELISA respectively. Finally, we assessed formation of DC-T cell conjugates using different cell trackers and flow cytometry. Our data show that in the presence of ECM, DC maintain a 'more immature' phenotype and express higher levels of key endocytic receptors, and as a result become significantly better endocytic cells, but still fully able to mature in response to stimulation as evidenced by their superior ability to induce antigen-specific T cell differentiation. Conclusion: These studies underline the importance of including ECM components in in vitro studies investigating DC biology and DC-T cell interaction. Within the context of antigen specific DC induced T cell proliferation, inclusion of ECM proteins could lead to development of more sensitive assays.
Background Salmonella enterica serovar Typhimurium is an intestinal pathogen capable of infecting... more 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...
Background: Allergen uptake by DCs is central to allergic sensitization. Results: DC-SIGN recogni... more Background: Allergen uptake by DCs is central to allergic sensitization. Results: DC-SIGN recognizes major allergens from house dust mite and dog. However, silencing DC-SIGN leads to Th2 differentiation. Conclusion: DC-SIGN is a newly identified receptor for Der p 1 and Can f 1 that appears to support Th1 cell differentiation. Significance: Understanding of how allergic responses are selected and propagated is essential for developing novel therapies.
Objectives: Unraveling mechanisms whereby Pseudomonas aeruginosa becomes resistant to carbapenems... more Objectives: Unraveling mechanisms whereby Pseudomonas aeruginosa becomes resistant to carbapenems through testing 114 non-duplicate P. aeruginosa clinical isolates for their susceptibility to various classes of antibiotics and scrutinizing the production of metallo-β-lactamases (MBLs) by tested isolates. Methods: Susceptibility testing of P. aeruginosa to different antibiotics was determined by Kirby-Bauer disk diffusion method and MBLs production by tested isolates was studied phenotypically and genotypically and PCR products were confirmed by sequencing Results: All tested clinical isolates showed eminent resistance to the majority of tested antibiotics and 14 isolates were imipenem (IPM)-resistant. Furthermore, IPM-resistant isolates were verified to be MBLs-producers. MBLs-encoding genes blaSIM and blaSPM genes were detected by PCR where four isolates were found to harbor blaSPM gene while only one isolate harbored blaSIM gene. The correct size of PCR products of blaSIM and blaS...
Klebsiella pneumoniae is responsible for a plethora of infections involving multiple body systems... more Klebsiella pneumoniae is responsible for a plethora of infections involving multiple body systems. This study investigated K. pneumoniae clinical isolates for virulence-associated characters and antibiotic resistance. First, antibiotic sensitivity was determined for 40 K. pneumoniae clinical isolates. Some virulence and resistance-associated factors were studied phenotypically and genotypically. Multiple resistance profiles were observed (multidrug resistant [MDR; 42.5%], extensive drug resistant [XDR; 35%], and pandrug resistant [PDR; 5%]). Moreover, CTX-M-1, TEM, qnrS, and qnrA genes were detected in 70%, 30%, 60%, and 30% of selected isolates, respectively, and 40% of tested isolates were extended-spectrum β-lactamases (ESBLs) producers. Interestingly, all ESBLs producers harbored class 1 integrase gene (IntI1), while 60% of ESBLs producers harbored both CTX-M-1 and TEM. All tested isolates were capsulated while 87.5% were biofilm producers. Fimbriae were detected in 90% of tested isolates (all were biofilm producers and type 3 fimbriae adhesion gene [mrkD] positive). Sequence analysis of OXA-48, qnrS, and IntI1 revealed 100% identity with published sequences, while sequencing of qnrA, OmpK-35, and iron regulatory protein gene (irp2) showed minor variations in the form of one or few single-nucleotide polymorphism. Altogether, the current study revealed that all MDR, XDR, and PDR K. pneumoniae isolates were multivirulent and all harbored 3-5 virulence genes and 2-9 antimicrobial resistance genes and exhibited 8 and 10 different virulence and antimicrobial resistance profiles, respectively. In this study, we also report a positive correlation between some virulence genes and antimicrobial resistance genes among K. pneumoniae tested isolates.
Background: Salmonella enterica serovar Typhimurium is a common food-borne pathogen. S. enterica ... more 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 coexisting 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.
The fast progression of nanotechnology has led to novel therapeutic interventions. Antimicrobial ... more 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...
Multidrug resistance (MDR) in various kinds of cancers represents a true obstacle which hinders t... more Multidrug resistance (MDR) in various kinds of cancers represents a true obstacle which hinders the successes of most of current available chemotherapies. ATP-binding cassette (ABC) trasporter proteins have been shown to contribute to the majority of MDR in various types of malignancies. c-myc has recently been reported to participate, at least partly, in MDR to some types of cancers. This study aimed to test whether c-myc could play a role, solely or with coordination with other ABCs, in the resistance of HepG2 cells to doxorubicin (Dox). MDR has been induced in wild-type HepG2 and has been verified both on gene and protein levels. Various assays including efflux assays as well as siRNA targeting ABCB1 and c-myc have been employed to explore the role of both candidate molecules in MDR in HepG2. Results obtained, with regard to ABCB1 silencing on HepG2/Dox cells, have shown that ABCB1-deficient cells exhibited a significant reduction in ABCC1 expression as compared to ABCB1-sufficient cells. However, these cells did not show a significant reduction in other tested ABCs (ABCC5 and ABCC10) while c-myc silencing had no significant effect on any of the studied ABCs. Moreover, silencing of ABCB1 on HepG2 significantly increased fluorescent calcein retention in HepG2 cells as compared to the control cells while downregulation of c-myc did not have any effect on fluorescent calcein retention. Altogether, this work clearly demonstrates that c-myc has no role in MDR of HepG2 to Dox which has been shown to be ABCB1-mediated in a mechanism which might involve ABCC1.
Shigella sonnei is a bacterial pathogen and causative agent of bacillary dysentery. It deploys a ... more Shigella sonnei is a bacterial pathogen and causative agent of bacillary dysentery. It deploys a type III secretion system to inject effector proteins into host epithelial cells and macrophages, an essential step for tissue invasion and immune evasion. Although the arsenal of bacterial effectors and their cellular targets have been studied extensively, little is known about the prerequisites for deployment of type III secreted proteins during infection. Here, we describe a novel S. sonnei adhesin, SSO1327 which is a Multivalent Adhesion Molecule (MAM) required for invasion of epithelial cells and macrophages and for infection in vivo. The S. sonnei MAM mediates intimate attachment to host cells, which is required for efficient translocation of type III effectors into host cells. SSO1327 is non-redundant to IcsA; its activity is independent of type III secretion. In contrast to the up-regulation of IcsA-dependent and independent attachment and invasion by deoxycholate in S. flexneri,...
Allergens are initiators of both innate and adaptive immune responses. They are recognised at the... more Allergens are initiators of both innate and adaptive immune responses. They are recognised at the site of entry by epithelial and dendritic cells (DCs), both of which activate innate inflammatory circuits that can collectively induce Th2 immune responses. In an attempt to have a better understanding of the role of carbohydrates in the recognition and uptake of allergens by the innate immune system, we defined common glycosylation patterns in major allergens. This was done using labelled lectins and showed that allergens like Der p 1 (Dermatophagoides pteronyssinus group 1), Fel d 1 (Felis domisticus), Ara h 1 (Arachis hypogaea), Der p 2 (Dermatophagoides pteronyssinus group 2), Bla g 2 (Blattella germanica) and Can f 1 (Canis familiaris) are glycosylated and that the main dominant sugars on these allergens are 1-2, 1-3 and 1-6 mannose. These observations are in line with recent reports implicating the mannose receptor (MR) in allergen recognition and uptake by DCs and suggesting a major link between glycosylation and allergen recognition. We then looked at TSLP (Thymic Stromal Lymphopoietin) cytokine secretion by lung epithelia upon encountering natural Der p 1 allergen. TSLP is suggested to drive DC maturation in support of allergic hypersensitivity reactions. Our data showed an increase in TSLP secretion by lung epithelia upon stimulation with natural Der p 1 which was carbohydrate dependent. The deglycosylated preparation of Der p 1 exhibited minimal uptake by DCs compared to the natural and hyperglycosylated recombinant counterparts, with the latter being taken up more readily than the other preparations. Collectively, our data indicate that carbohydrate moieties on allergens play a vital role in their recognition by innate immune cells, implicating them in downstream deleterious Th2 cell activation and IgE production.
A group of 11 medicinal plants, including Lavandula pubescens, Trigonella foenugricium, Salsola s... more A group of 11 medicinal plants, including Lavandula pubescens, Trigonella foenugricium, Salsola schweinforthi, Calligonum comosum, Silene succulenta, Silene villosa, Bogonvillea glabra, Cakile maritime, Gomphrene celesoids, Mirabilis jalaba, and Silene nocturna growing in Egypt, were extracted and examined for their immunomodulatory and antioxidant activities. RAW 264.7 cells were recruited to investigate the immunomodulatory effect through multiple parameters analysis. First, the proliferation index of macrophages cells was evaluated revealing that Trigonella foenugricium, Silene succulenta and Silene villosa have a significant cytotoxic effect on RAW cells. Interestingly, we observed enhancement of macrophages phagocytic function of by all extracts except Cakile maritime, Gomphrena celosioides and Silene nocturna. Afterwards, macrophages were challenged by incubation with LPS and the effect of various extracts on inflammatory responses was investigated; the generation of NO from activated macrophage was substantially suppressed by 7 extracts namely, Trigonella foenugricium, Calligonum comosum, Silene succulenta, Bougainvillea glabra, Mirabilis jalaba, Gomphrena celosioides and Silene nocturna. TNF-a was decreased by percentage range from 3.8 to 85.8% and Trigonella foenugricium extract showed the highest inhibition of TNF-a release. All extracts except Trigonella foenugricium, Salsola schweinforthi, Silene succulenta and Mirabilis jalaba significantly inhibited COX-2 production from stimulated macrophage. Moreover, evaluating the potential antioxidant activity of these extracts showed that Trigonella foenugricium, Salsola schweinforthi, Calligonum comosum, Bogonvillea glabra and Mirabilis jalaba exhibited some antioxidant activities. Taken together, our results suggest that some of these extracts may have a considerable antinflammatory and antioxidant effects and may be a potential therapeutic choice in the treatment of inflammatory diseases.
Proceedings of the National Academy of Sciences, 2010
Surface Ig (sIg) of follicular lymphoma (FL) is vital for tumor cell survival. We found previousl... more Surface Ig (sIg) of follicular lymphoma (FL) is vital for tumor cell survival. We found previously that the Ig in FL is unusual, because the variable region genes carry sequence motifs for N -glycan addition. These are introduced by somatic mutation and are tumor specific. Unexpectedly, added glycans terminate at high mannose, suggesting a potentially important interaction of FL cells with mannose-binding lectins of the innate immune system. We have now identified mannosylated IgM at the surface of primary lymphoma cells. Recombinant lectin domains of the mannose receptor (MR) or DC-SIGN bind mannosylated Igs in vitro and bind to FL cells, signaling sIgM-associated increases in intracellular Ca 2+ . Lectins also bind to normal B cells but fail to signal. In contrast, anti-Ig signaled similarly in both FL and normal B cells. Mannosylation patterns were mimicked by FL Ig-derived single-chain Fvs (scFv), providing probes for potential receptors. Mannosylated scFv bound specifically to ...
The mannose receptor (MR) is a C-type lectin expressed by dendritic cells (DCs). We have investig... more The mannose receptor (MR) is a C-type lectin expressed by dendritic cells (DCs). We have investigated the ability of MR to recognize glycosylated allergens. Using a gene silencing strategy, we have specifically inhibited the expression of MR on human monocytederived DCs. We show that MR mediates internalization of diverse allergens from mite (Der p 1 and Der p 2), dog (Can f 1), cockroach (Bla g 2), and peanut (Ara h 1) through their carbohydrate moieties. All of these allergens bind to the C-type lectin-like carbohydrate recognition domains 4-7 of MR. We have also assessed the contribution of MR to T cell polarization after allergen exposure. We show that silencing MR expression on monocyte-derived DCs reverses the Th2 cell polarization bias, driven by Der p 1 allergen exposure, through upregulation of IDO activity. In conclusion, our work demonstrates a major role for MR in glycoallergen recognition and in the development of Th2 responses.
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Papers by Mohamed Emara