Staphylococcus aureus sarA regulates inflammation and colonization during central nervous system biofilm formation

Glutamate-dependent arginine biosynthesis requires the inactivation of spoVG, sarA, and ahrC in Staphylococcus aureus

Genome sequencing has demonstrated that Staphylococcus aureus encodes arginine biosynthetic genes argDCJBFGH synthesizing proteins that mediate arginine biosynthesis using glutamate as a substrate. Paradoxically, however, S. aureus does not grow in a defined, glutamate-replete medium lacking arginine and glucose (CDM-R). Studies from our laboratory have found that specific mutations are selected by S. aureus that facilitate growth in CDM-R. However, these selected mutants synthesize arginine utilizing proline as a substrate rather than glutamate. In this study, we demonstrate that the ectopic expression of the argDCJB operon supports the growth of S. aureus in CDM-R, thus documenting the functionality of this pathway. Furthermore, suppressor mutants of S. aureus JE2 putA::Tn, which is defective in synthesizing arginine from proline, were selected on CDM-R agar. Genome sequencing revealed that these mutants had compensatory mutations within both spoVG, encoding an ortholog of the Bacillus subtilis stage V sporulation protein, and sarA, encoding the staphylococcal accessory regulator. Transcriptional studies document that argD expression is significantly increased when JE2 spoVG sarA was grown in CDM-R. Lastly, we found that a mutation in ahrC was required to induce argD expression in JE2 spoVG sarA when grown in an arginine-replete medium (CDM), suggesting that AhrC also functions to repress argDCJB in an arginine-dependent manner. In conclusion, these data indicate that the argDCJB operon is functional when transcribed in vitro and that SNPs within potential putative regulatory proteins are required to alleviate the repression.IMPORTANCEAlthough Staphylococcus aureus has the capability to synthesize all 20 amino acids, it is phenotypically auxotrophic for several amino acids including arginine. This work identifies putative regulatory proteins, including SpoVG, SarA, and AhrC, that function to inhibit the arginine biosynthetic pathways using glutamate as a substrate. Understanding the ultimate mechanisms of why S. aureus is selected to repress arginine biosynthetic pathways even in the absence of arginine will add to the growing body of work assessing the interactions between metabolism and S. aureus pathogenesis.

Characterization of the Human Plasma Biofilm Model (hpBIOM) to Identify Potential Therapeutic Targets for Wound Management of Chronic Infections

The treatment of chronic wounds still represents a major challenge in wound management. Recent estimates suggest that 60-80% of chronic wounds are colonized by pathogenic microorganisms, which are strongly considered to have a major inhibiting influence on the healing process. By means of an innovative biofilm model based on human plasma, the time-dependent behavior of various bacterial strains under wound-milieu-like conditions were investigated, and the growth habits of different cocci species were compared. Undescribed fusion events between colonies of MRSA as well as of Staphylococcus epidermidis were detected, which were associated with the remodeling and reorganization of the glycocalyx of the wound tissue. After reaching a maximum colony size, the spreading of individual bacteria was observed. Interestingly, the combination of different cocci species with Pseudomonas aeruginosa in the human plasma biofilm revealed partial synergistic effects in these multispecies organizations. RT-qPCR analyses gave a first impression of the relevant proteins involved in the formation and maturation of biofilms, especially the role of fibrinogen-binding proteins. Knowledge of the maturation and growth behavior of persistent biofilms investigated in a translational human biofilm model reflects a starting point for the development of novel tools for the treatment of chronic wounds.

Interactions between the foreign body reaction and Staphylococcus aureus biomaterial-associated infection. Winning strategies in the derby on biomaterial implant surfaces

Biomaterial-associated infections (BAIs) are an increasing problem where antibiotic therapies are often ineffective. The design of novel strategies to prevent or combat infection requires a better understanding of how an implanted foreign body prevents the immune system from eradicating surface-colonizing pathogens. The objective of this review is to chart factors resulting in sub-optimal clearance of Staphylococcus aureus bacteria involved in BAIs. To this end, we first describe three categories of bacterial mechanisms to counter the host immune system around foreign bodies: direct interaction with host cells, modulation of intercellular communication, and evasion of the immune system. These mechanisms take place in a time frame that differentiates sterile foreign body reactions, BAIs, and soft tissue infections. In addition, we identify experimental interventions in S. aureus BAI that may impact infectious mechanisms. Most experimental treatments modulate the host response to infection or alter the course of BAI through implant surface modulation. In conclusion, the first week after implantation and infection is crucial for the establishment of an S. aureus biofilm that resists the local immune reaction and antibiotic treatment. Although established and chronic S. aureus BAI is still treatable and manageable, the focus of interventions should lie on this first period.

Host-pathogen interaction between macrophage co-cultures with Staphylococcus aureus biofilms

The ability of Staphylococcus aureus to form biofilms is an important virulence factor. During the infectious process, the interaction between biofilms and immune cells is determinant; however, the properties that make biofilms resistant to the immune system are not well characterized. In order to better understand this, we evaluated the in vitro interaction of macrophages during the early stages of S. aureus biofilm formation. Biofilm formation was evaluated by crystal violet staining, light microscopy, and confocal scanning laser microscopy. Furthermore, different activation on L-arginine pathways such as nitric oxide (NO^•) release and the arginase, the production of reactive oxygen species (ROS), the total oxidative stress response (OSR), and levels of cytokine liberation, were determined. Our findings show that the interaction between biofilms and macrophages results in stimuli for catabolism of L-arginine via arginase, but not for NO^•, an increase of ROS production, and activation of the non-enzymatic OSR. We also observed the production of IL-6, but not of TNFα o IL-10 in these co-cultures. These results contribute to a better understanding of host-pathogen interactions and suggest that biofilms increase resistance against immune cell mechanisms, a phenomenon that could contribute to the ability of S. aureus biofilms to establish mature biofilms.

Sapindus mukorossi Gaertn. and its bioactive metabolite oleic acid impedes methicillin-resistant Staphylococcus aureus biofilm formation by down regulating adhesion genes expression

Plants are boon to the mankind due to plenty of metabolites with medicinal values. Though plants have traditionally been used to treat various diseases, their biological values are not completely explored yet. Sapindus mukorossi is one such ethnobotanical plant identified for various biological activities. As biofilm formation and biofilm mediated drug resistance of methicillin-resistant Staphylococcus aureus (MRSA) have raised as serious global issue, search for antibiofilm agents has gained greater importance. Notably, antibiofilm potential of S. mukorossi is still unexplored. The aim of the study is to explore the effect of S. mukorossi methanolic extract (SMME) on MRSA biofilm formation and adhesive molecules production. Significantly, SMME exhibited 82 % of biofilm inhibition at 250 μg/mL without affecting the growth and microscopic analyses evidenced the concentration dependent antibiofilm activity of SMME. In vitro assays exhibited the reduction in slime, cell surface hydrophobicity, autoaggregation, extracellular polysaccharides substance and extracellular DNA synthesis upon SMME treatment. Further, qPCR analysis confirmed the ability of SMME to interfere with the expression of adhesion genes associated with biofilm formation such as icaA, icaD, fnbA, fnbB, clfA, cna, and altA. GC-MS analysis and molecular docking study revealed that oleic acid is responsible for the antibiofilm activity. FT-IR analysis validated the presence of oleic acid in SMME. These results suggest that SMME can be used as a promising therapeutic agent against MRSA biofilm-associated infections.

Staphylococcus aureus and the Cutaneous Microbiota Biofilms in the Pathogenesis of Atopic Dermatitis

Biofilm is the dominant mode of growth of the skin microbiota, which promotes adhesion and persistence in the cutaneous microenvironment, thus contributing to the epidermal barrier function and local immune modulation. In turn, the local immune microenvironment plays a part in shaping the skin microbiota composition. Atopic dermatitis (AD) is an immune disorder characterized by a marked dysbiosis, with a sharp decline of microbial diversity. During AD flares biofilm-growing Staphylococcus aureus emerges as the major colonizer in the skin lesions, in strict association with disease severity. The chronic production of inflammatory cytokines in the skin of AD individuals concurs at supporting S. aureus biofilm overgrowth at the expense of other microbial commensals, subverting the composition of the healthy skin microbiome. The close relationship between the host and microbial biofilm resident in the skin has profound implications on human health, making skin microbiota an attractive target for the therapeutic management of different skin disorders.

Staphylococcus aureus Biofilm-Conditioned Medium Impairs Macrophage-Mediated Antibiofilm Immune Response by Upregulating KLF2 Expression

Staphylococcus aureus infections associated with the formation of biofilms on medical implants or host tissue play a critical role in the persistence of chronic infections. One critical mechanism of biofilm infection that leads to persistent infection lies in the capacity of biofilms to evade the macrophage-mediated innate immune response. It is now increasingly apparent that microorganisms exploit the negative regulatory mechanisms of the pattern recognition receptor (PRR)-mediated inflammatory response to subvert host cell functions by using various virulence factors. However, the detailed molecular mechanism, along with the identity of a target molecule, underlying the evasion of the macrophage-mediated innate immune response against S. aureus infection associated with biofilm formation remains to be elucidated. Here, using an in vitro culture model of murine macrophage-like RAW 264.7 cells, we demonstrate that S. aureus biofilm-conditioned medium significantly attenuated the capacity for macrophage bactericidal and proinflammatory responses. Importantly, the responses were associated with attenuated activation of NF-κB and increased expression of Kruppel-like factor 2 (KLF2) in RAW 264.7 cells. Small interfering RNA (siRNA)-mediated silencing of KLF2 in RAW 264.7 cells could restore the activation of NF-κB toward the bactericidal activity and generation of proinflammatory cytokines in the presence of S. aureus biofilm-conditioned medium. Collectively, our results suggest that factors secreted from S. aureus biofilms might exploit the KLF2-dependent negative regulatory mechanism to subvert macrophage-mediated innate immune defense against S. aureus biofilms.

CSF inflammatory markers differ in gram-positive versus gram-negative shunt infections

Background

Cerebrospinal fluid (CSF) shunt placement is frequently complicated by bacterial infection. Shunt infection diagnosis relies on bacterial culture of CSF which can often produce false-negative results. Negative cultures present a conundrum for physicians as they are left to rely on other CSF indices, which can be unremarkable. New methods are needed to swiftly and accurately diagnose shunt infections. CSF chemokines and cytokines may prove useful as diagnostic biomarkers. The objective of this study was to evaluate the potential of systemic and CSF biomarkers for identification of CSF shunt infection.

Methods

We conducted a retrospective chart review of children with culture-confirmed CSF shunt infection at Children’s Hospital and Medical Center from July 2013 to December 2015. CSF cytokine analysis was performed for those patients with CSF in frozen storage from the same sample that was used for diagnostic culture.

Results

A total of 12 infections were included in this study. Patients with shunt infection had a median C-reactive protein (CRP) of 18.25 mg/dL. Median peripheral white blood cell count was 15.53 × 10³ cells/mL. Those with shunt infection had a median CSF WBC of 332 cells/mL, median CSF protein level of 406 mg/dL, and median CSF glucose of 35.5 mg/dL. An interesting trend was observed with gram-positive infections having higher levels of the anti-inflammatory cytokine interleukin (IL)-10 as well as IL-17A and vascular endothelial growth factor (VEGF) compared to gram-negative infections, although these differences did not reach statistical significance. Conversely, gram-negative infections displayed higher levels of the pro-inflammatory cytokines IL-1β, fractalkine (CX₃CL₁), chemokine ligand 2 (CCL2), and chemokine ligand 3 (CCL3), although again these were not significantly different. CSF from gram-positive and gram-negative shunt infections had similar levels of interferon gamma (INF-γ), tumor necrosis factor alpha (TNF-α), IL-6, and IL-8.

Conclusions

This pilot study is the first to characterize the CSF cytokine profile in patients with CSF shunt infection and supports the distinction of chemokine and cytokine profiles between gram-negative and gram-positive infections. Additionally, it demonstrates the potential of CSF chemokines and cytokines as biomarkers for the diagnosis of shunt infection.

Unexpected eosinophilia in children affected by hydrocephalus accompanied with shunt infection

PURPOSE

The aim of the article is to describe an immunological reaction to shunt infection in children with hydrocephalus. The main cause of shunt infection involves methicillin resistant Staphylococcus epidermidis (Bhatia et al. Indian J Med Microbiol 35:120-123, 2017; Hayhurst et al. Childs Nerv Syst 24:557-562, 2008; Martínez-Lage et al. Childs Nerv Syst 26: 1795-1798, 2010; Simon et al. PLoS One, 2014; Snowden et al. PLoS One 8:e84089, 2013; Turgut et al. Pediatr Neurosurg 41:131-136, 2005), a bacterial strain which is responsible for the formation of biofilm on contaminated catheters (Snowden et al. PLoS One 8:e84089, 2013; Stevens et al. Br J of Neurosurg 26: 792-797, 2012).

METHODS

The study group involved 30 children with congenital hydrocephalus after shunt system implantation, whose procedures were complicated by S. epidermidis implant infection. Thirty children with congenital hydrocephalus awaiting their first-time shunt implantation formed the control group. The level of eosinophils in peripheral blood was assessed in both groups. Cerebrospinal fluid (CSF) was examined for protein level, pleocytosis, interleukins, CCL26/Eotaxin-3, IL-5, IL-6, CCL11/Eotaxin-1, CCL3/MIP-1a, and MBP. Three measurements were performed in the study group. The first measurement was obtained at the time of shunt infection diagnosis, the second one at the time of the first sterile shunt, and the third one at the time of shunt reimplantation. In the control group, blood and CSF samples were taken once, at the time of shunt implantation.

RESULTS

In the clinical material, the highest values of eosinophils in peripheral blood and CSF pleocytosis were observed in the second measurement. It was accompanied by an increase in the majority of analyzed CSF interleukins.

CONCLUSION

CSF pleocytosis observed in the study group shortly after CSF sterilization is presumably related to an allergic reaction to Staphylococcus epidermidis, the causative agent of ventriculoperitoneal shunt infection.

The Staphylococcal Biofilm: Adhesins, Regulation, and Host Response

The staphylococci comprise a diverse genus of Gram-positive, nonmotile commensal organisms that inhabit the skin and mucous membranes of humans and other mammals. In general, staphylococci are benign members of the natural flora, but many species have the capacity to be opportunistic pathogens, mainly infecting individuals who have medical device implants or are otherwise immunocompromised. Staphylococcus aureus and Staphylococcus epidermidis are major sources of hospital-acquired infections and are the most common causes of surgical site infections and medical device-associated bloodstream infections. The ability of staphylococci to form biofilms in vivo makes them highly resistant to chemotherapeutics and leads to chronic diseases. These biofilm infections include osteomyelitis, endocarditis, medical device infections, and persistence in the cystic fibrosis lung. Here, we provide a comprehensive analysis of our current understanding of staphylococcal biofilm formation, with an emphasis on adhesins and regulation, while also addressing how staphylococcal biofilms interact with the immune system. On the whole, this review will provide a thorough picture of biofilm formation of the staphylococcus genus and how this mode of growth impacts the host.

Staphylococcal Biofilms and Immune Polarization During Prosthetic Joint Infection

Staphylococcal species are a leading cause of community- and nosocomial-acquired infections, where the placement of foreign materials increases infection risk. Indwelling medical devices and prosthetic implants are targets for staphylococcal cell adherence and biofilm formation. Biofilm products actively suppress proinflammatory microbicidal responses, as evident by macrophage polarization toward an anti-inflammatory phenotype and the recruitment of myeloid-derived suppressor cells. With the rise in prosthetic hip and knee arthroplasty procedures, together with the recalcitrance of biofilm infections to antibiotic therapy, it is imperative to better understand the mechanism of crosstalk between biofilm-associated bacteria and host immune cells. This review describes the current understanding of how staphylococcal biofilms evade immune-mediated clearance to establish persistent infections. The findings described herein may facilitate the identification of novel treatments for these devastating biofilm-mediated infections.

In vitro antimicrobial activity of honokiol against Staphylococcus aureus in biofilm mode

Staphylococcus aureus (S. aureus) can attach to food, host tissues and the surfaces of medical implants and form a biofilm, which makes it difficult to eliminate. The purpose of this study was to evaluate the effect of honokiol on biofilm-grown S. aureus. In this report, honokiol showed effective antibacterial activity against S. aureus in biofilms. S. aureus isolates are capable of producing distinct types of biofilms mediated by polysaccharide intercellular adhesion (PIA) or extracellular DNA (eDNA). The biofilms' susceptibility to honokiol was evaluated using confocal laser scanning microscopy (CLSM) analysis. The transcript levels of the biofilm-related genes, the expression of PIA, and the amount of eDNA of biofilm-grown S. aureus exposed to honokiol were also investigated. The results of this study show that honokiol can detach existing biofilms, kill bacteria in biofilms, and simultaneously inhibit the transcript levels of sarA, cidA and icaA, eDNA release, and the expression of PIA.

IL-10 plays an important role in the control of inflammation but not in the bacterial burden in S. epidermidis CNS catheter infection

Background

Shunt infection is a frequent and serious complication in the surgical treatment in hydrocephalus. Previous studies have shown an attenuated immune response to these biofilm-mediated infections. We proposed that IL-10 reduces the inflammatory response to Staphylococcus epidermidis (S. epidermidis) CNS catheter infection.

Methods

In this study, a murine model of catheter-associated S. epidermidis biofilm infection in the CNS was generated based on a well-established similar model for S. aureus. The catheters were pre-coated with a clinically derived biofilm-forming strain of S. epidermidis (strain 1457) which were then stereotactically implanted into the lateral left ventricle of 8-week-old C57BL/6 and IL-10 knockout (IL-10 knockout) mice. Bacterial titers as well as cytokine and chemokine levels were measured at days 3, 5, 7, and 10 in mice implanted with sterile and S. epidermidis-coated catheters.

Results

Cultures demonstrated a catheter-associated and parenchymal infection that persisted through 10 days following infection. Cytokine analysis of the tissue surrounding the catheters revealed greater levels of IL-10, an anti-inflammatory cytokine, in the infected group compared to the sterile. In IL-10 KO mice, we noted no change in bacterial burdens, showing that IL-10 is not needed to control the infection in a CNS catheter infection model. However, IL-10 KO mice had increased levels of pro-inflammatory mediators in the tissues immediately adjacent to the infected catheter, as well as an increase in weight loss.

Conclusions

Together our results indicate that IL-10 plays a key role in regulating the inflammatory response to CNS catheter infection but not in control of bacterial burdens. Therefore, IL-10 may be a useful therapeutic target for immune modulation in CNS catheter infection but this should be used in conjunction with antibiotic therapy for bacterial eradication.

Targeting Staphylococcus aureus Toxins: A Potential form of Anti-Virulence Therapy

Staphylococcus aureus is an opportunistic pathogen and the leading cause of a wide range of severe clinical infections. The range of diseases reflects the diversity of virulence factors produced by this pathogen. To establish an infection in the host, S. aureus expresses an inclusive set of virulence factors such as toxins, enzymes, adhesins, and other surface proteins that allow the pathogen to survive under extreme conditions and are essential for the bacteria’s ability to spread through tissues. Expression and secretion of this array of toxins and enzymes are tightly controlled by a number of regulatory systems. S. aureus is also notorious for its ability to resist the arsenal of currently available antibiotics and dissemination of various multidrug-resistant S. aureus clones limits therapeutic options for a S. aureus infection. Recently, the development of anti-virulence therapeutics that neutralize S. aureus toxins or block the pathways that regulate toxin production has shown potential in thwarting the bacteria’s acquisition of antibiotic resistance. In this review, we provide insights into the regulation of S. aureus toxin production and potential anti-virulence strategies that target S. aureus toxins.

Methicillin-Resistant Staphylococcus aureus Grown on Vancomycin-Supplemented Screening Agar Displays Enhanced Biofilm Formation

Brain heart infusion agar containing 3 mg/liter vancomycin (BHI-V3) was used to screen for heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA). There was markedly greater biofilm formation by isolates that grew on BHI-V3 than by strains that did not grow on BHI-V3. Increased biofilm formation by hVISA may be mediated by FnbA- and polysaccharide intercellular adhesin-dependent pathways, and upregulation of atlA and sarA may also contribute to enhanced biofilm formation by hVISA upon prolonged exposure to vancomycin.

Evidence for a Pneumocystis carinii Flo8-like transcription factor: insights into organism adhesion

Pneumocystis carinii (Pc) adhesion to alveolar epithelial cells is well established and is thought to be a prerequisite for the initiation of Pneumocystis pneumonia. Pc binding events occur in part through the major Pc surface glycoprotein Msg, as well as an integrin-like molecule termed PcInt1. Recent data from the Pc sequencing project also demonstrate DNA sequences homologous to other genes important in Candida spp. binding to mammalian host cells, as well as organism binding to polystyrene surfaces and in biofilm formation. One of these genes, flo8, a transcription factor needed for downstream cAMP/PKA-pathway-mediated activation of the major adhesion/flocculin Flo11 in yeast, was cloned from a Pc cDNA library utilizing a partial sequence available in the Pc genome database. A CHEF blot of Pc genomic DNA yielded a single band providing evidence this gene is present in the organism. BLASTP analysis of the predicted protein demonstrated 41 % homology to the Saccharomyces cerevisiae Flo8. Northern blotting demonstrated greatest expression at pH 6.0-8.0, pH comparable to reported fungal biofilm milieu. Western blot and immunoprecipitation assays of PcFlo8 protein in isolated cyst and tropic life forms confirmed the presence of the cognate protein in these Pc life forms. Heterologous expression of Pcflo8 cDNA in flo8Δ-deficient yeast strains demonstrated that the Pcflo8 was able to restore yeast binding to polystyrene and invasive growth of yeast flo8Δ cells. Furthermore, Pcflo8 promoted yeast binding to HEK293 human epithelial cells, strengthening its functional classification as a Flo8 transcription factor. Taken together, these data suggest that PcFlo8 is expressed by Pc and may exert activity in organism adhesion and biofilm formation.

An Essential Role for Coagulase in Staphylococcus aureus Biofilm Development Reveals New Therapeutic Possibilities for Device-Related Infections

High-level resistance to antimicrobial drugs is a major factor in the pathogenesis of chronic Staphylococcus aureus biofilm-associated, medical device-related infections. Antimicrobial susceptibility analysis revealed that biofilms grown for ≤ 24 hours on biomaterials conditioned with human plasma under venous shear in iron-free cell culture medium were significantly more susceptible to antistaphylococcal antibiotics. Biofilms formed under these physiologically relevant conditions were regulated by SaeRS and dependent on coagulase-catalyzed conversion of fibrinogen into fibrin. In contrast, SarA-regulated biofilms formed on uncoated polystyrene in nutrient-rich bacteriological medium were mediated by the previously characterized biofilm factors poly-N-acetyl glucosamine, fibronectin-binding proteins, or autolytic activity and were antibiotic resistant. Coagulase-mediated biofilms exhibited increased antimicrobial resistance over time (>48 hours) but were always susceptible to dispersal by the fibrinolytic enzymes plasmin or nattokinase. Biofilms recovered from infected central venous catheters in a rat model of device-related infection were dispersed by nattokinase, supporting the important role of the biofilm phenotype and identifying a potentially new therapeutic approach with antimicrobials and fibrinolytic drugs, particularly during the early stages of device-related infection.

Antibacterial activity of silver nanoparticles target sara through srna-teg49, a key mediator of hfq, in staphylococcus aureus

Attributed to its antimicrobial effect, Silver nanoparticles (AgNPs) is widely used in various fields, such as biomedicine, textiles, health care products and food, etc. However, the antibacterial mechanism of AgNPs in staphylococcus aureus (S. aureus) by regulating sRNA expression remains largely unknown.

OBJECTIVES

This study was performed to investigate the involvement of the antibacterial mechanism of AgNPs through sRNA-TEG49, a key mediator of Hfq, in S. aureus.

METHODS

Through the antimicrobial tests of AgNPs, its antibacterial laps and minimum inhibitory concentration was measured. A hierarchical cluster analysis of the differentially expressed sRNA in S. aureus was performed to investigate the relationship between AgNPs and sRNA. Expression of genes was analyzed by real-time PCR.

RESULTS

In the present study we found that at the concentrations higher than 1 mg/L, AgNPs could completely restrain bacteria growth, and the antibacterial activity of AgNPs apparently declined at the concentrations lower than 1 mg/L. S. aureus exposure to AgNPs, the expression of sRNA-TEG49, Hfq and sarA was significantly up-regulated in wild-type S. aureus. Moreover, Hfq loss-of-function inhibited the expression of sRNA-TEG49 in mutant-type S. aureus. Furthermore, sRNA-TEG49 loss-of-function associated with down-regulation the expression of sarA in mutant-type S. aureus.

CONCLUSIONS

It was reasonable that Hfq regulated a distinct underlying molecular and antibacterial mechanism of AgNPs by forming a positive feedback loop with sRNA-TEG49. These observations suggested that Hfq plays an important role in the antibacterial mechanism of AgNPs by regulating sRNA-TEG49 expression, via its target sarA.

Eugenol: a phyto-compound effective against methicillin-resistant and methicillin-sensitive Staphylococcus aureus clinical strain biofilms

Background

Inhibition and eradication of Staphylococcus aureus biofilms with conventional antibiotic is difficult, and the treatment is further complicated by the rise of antibiotic resistance among staphylococci. Consequently, there is a need for novel antimicrobials that can treat biofilm-related infections and decrease antibiotics burden. Natural compounds such as eugenol with anti-microbial properties are attractive agents that could reduce the use of conventional antibiotics. In this study we evaluated the effect of eugenol on MRSA and MSSA biofilms in vitro and bacterial colonization in vivo.

Methods and Results

Effect of eugenol on in vitro biofilm and in vivo colonization were studied using microtiter plate assay and otitis media-rat model respectively. The architecture of in vitro biofilms and in vivo colonization of bacteria was viewed with SEM. Real-time RT-PCR was used to study gene expression. Check board method was used to study the synergistic effects of eugenol and carvacrol on established biofilms. Eugenol significantly inhibited biofilms growth of MRSA and MSSA in vitro in a concentration-dependent manner. Eugenol at MIC or 2×MIC effectively eradicated the pre-established biofilms of MRSA and MSSA clinical strains. In vivo, sub-MIC of eugenol significantly decreased 88% S. aureus colonization in rat middle ear. Eugenol was observed to damage the cell-membrane and cause a leakage of the cell contents. At sub-inhibitory concentration, it decreases the expression of biofilm-and enterotoxin-related genes. Eugenol showed a synergistic effect with carvacrol on the eradication of pre-established biofilms.

Conclusion/Major Finding

This study demonstrated that eugenol exhibits notable activity against MRSA and MSSA clinical strains biofilms. Eugenol inhibited biofilm formation, disrupted the cell-to-cell connections, detached the existing biofilms, and killed the bacteria in biofilms of both MRSA and MSSA with equal effectiveness. Therefore, eugenol may be used to control or eradicate S. aureus biofilm-related infections.

Ventricular shunt infections: immunopathogenesis and clinical management

Ventricular shunts are the most common neurosurgical procedure performed in the United States. This hydrocephalus treatment is often complicated by infection of the device with biofilm-forming bacteria. In this review, we discuss the pathogenesis of shunt infection, as well as the implications of the biofilm formation on treatment and prevention of these infections. Many questions remain, including the contribution of glia and the impact of inflammation on developmental outcomes following infection. Immune responses within the CNS must be carefully regulated to contain infection while minimizing bystander damage; further study is needed to design optimal treatment strategies for these patients.