Temperature-dependent control of Staphylococcus aureus biofilms and virulence by thermoresponsive oligo(N-vinylcaprolactam)

Poly(N-vinylcaprolactam)-Gold Nanorods-5 Fluorouracil Hydrogels: In the Quest of a Material for Topical Therapies against Melanoma Skin Cancer

Chemically crosslinked hydrogels based on poly(N-vinylcaprolactam) (PNVCL) were synthetized by a photoinitiated chemical method. A galactose-based monomer, 2-lactobionamidoethyl methacrylate (LAMA), and N-vinylpyrrolidone (NVP) were added with the aim to improve the physical and chemical properties of hydrogels. The effects of both comonomers on the swelling ratio (Q), volume phase transition temperature (VPTT), glass transition temperature (T_g), and Young's moduli by mechanical compression below and above the VPTT were studied. Gold nanorods (GNRDs) and 5-fluorouracil (5FU) were embedded into the hydrogels, to study the drug release profiles with and without the excitation of GNRDs by irradiation in the near-infrared region (NIR). Results showed that the addition of LAMA and NVP increased the hydrogels' hydrophilicity, elasticity, and VPTT. The loading of GNRDs in the hydrogels changed the release rate of 5FU when irradiated intermittently with an NIR laser. The present study reports on the preparation of a hydrogel-based platform of PNVCL-GNRDs-5FU as a potential hybrid anticancer hydrogel for chemo/photothermal therapy that could be applied against skin cancer for topical 5FU delivery.

Phytopigment Alizarin Inhibits Multispecies Biofilm Development by Cutibacterium acnes, Staphylococcus aureus, and Candida albicans

Acne vulgaris is a common chronic inflammatory skin disease involving Cutibacterium acnes with other skin commensals such as Staphylococcus aureus and Candida albicans in the anaerobic and lipid-rich conditions of pilosebaceous units. These microbes readily form multispecies biofilms that are tolerant of traditional antibiotics as well as host immune systems. The phytopigment alizarin was previously found to prevent biofilm formation by S. aureus and C. albicans strains under aerobic conditions. Hence, we hypothesized that alizarin might control C. acnes and multispecies biofilm development. We found that under anaerobic conditions, alizarin efficiently inhibited single biofilm formation and multispecies biofilm development by C. acnes, S. aureus, and C. albicans without inhibiting planktonic cell growth. Alizarin increased the hydrophilicities of S. aureus and C. albicans cells, decreased lipase production by S. aureus, diminished agglutination by C. acnes, and inhibited the aggregation of C. albicans cells. Furthermore, the co-administration of alizarin and antibiotics enhanced the antibiofilm efficacies of alizarin against C. acnes. A transcriptomic study showed that alizarin repressed the transcriptions of various biofilm-related genes such as lipase, hyaluronate lyase, adhesin/invasion-related, and virulence-related genes of C. acnes. Furthermore, alizarin at 100 µg/mL prevented C. acnes biofilm development on porcine skin. Our results show that alizarin inhibits multispecies biofilm development by acne-causing microbes and suggest it might be a useful agent for treating or preventing C. acnes-causing skin diseases.

Inhibition of Biofilm Formation of Foodborne Staphylococcus aureus by the Citrus Flavonoid Naringenin

Taking into consideration the importance of biofilms in food deterioration and the potential risks of antiseptic compounds, antimicrobial agents that naturally occurring are a more acceptable choice for preventing biofilm formation and in attempts to improve antibacterial effects and efficacy. Citrus flavonoids possess a variety of biological activities, including antimicrobial properties. Therefore, the anti-biofilm formation properties of the citrus flavonoid naringenin on the Staphylococcus aureus ATCC 6538 (S. aureus) were investigated using subminimum inhibitory concentrations (sub-MICs) of 5~60 mg/L. The results were confirmed using laser and scanning electron microscopy techniques, which revealed that the thick coating of S. aureus biofilms became thinner and finally separated into individual colonies when exposed to naringenin. The decreased biofilm formation of S. aureus cells may be due to a decrease in cell surface hydrophobicity and exopolysaccharide production, which is involved in the adherence or maturation of biofilms. Moreover, transcriptional results show that there was a downregulation in the expression of biofilm-related genes and alternative sigma factor sigB induced by naringenin. This work provides insight into the anti-biofilm mechanism of naringenin in S. aureus and suggests the possibility of naringenin being used in the industrial food industry for the prevention of biofilm formation.

Staphylococcus aureus Responds to Physiologically Relevant Temperature Changes by Altering Its Global Transcript and Protein Profile

Staphylococcus aureus is an opportunistic pathogen that colonizes the anterior nares of 30 to 50% of the population. Colonization is most often asymptomatic; however, self-inoculation can give rise to potentially fatal infections of the deeper tissues and blood. Like all bacteria, S. aureus can sense and respond to environmental cues and modify gene expression to adapt to specific environmental conditions. The transition of S. aureus from the nares to the deeper tissues and blood is accompanied by changes in environmental conditions, such as nutrient availability, pH, and temperature. In this study, we perform transcriptomics and proteomics on S. aureus cultures growing at three physiologically relevant temperatures, 34°C (nares), 37°C (body), and 40°C (pyrexia), to determine if small scale, biologically meaningful alterations in temperature impact S. aureus gene expression. Results show that small but definite temperature changes elicit a large-scale restructuring of the S. aureus transcriptome and proteome in a manner that, most often, inversely correlates with increasing temperature. We also provide evidence that a large majority of these changes are modulated at the posttranscriptional level, possibly by sRNA regulatory elements. Phenotypic analyses were also performed to demonstrate that these changes have physiological relevance. Finally, we investigate the impact of temperature-dependent alterations in gene expression on S. aureus pathogenesis and demonstrate decreased intracellular invasion of S. aureus grown at 34°C. Collectively, our results demonstrate that small but biologically meaningful alterations in temperature influence S. aureus gene expression, a process that is likely a major contributor to the transition from a commensal to pathogen.

IMPORTANCE Enteric bacterial pathogens, like Escherichia coli, are known to experience large temperature differences as they are transmitted through the fecal oral route. This change in temperature has been demonstrated to influence bacterial gene expression and facilitate infection. Staphylococcus aureus is a human-associated pathogen that can live as a commensal on the skin and nares or cause invasive infections of the deeper tissues and blood. Factors influencing S. aureus nasal colonization are not fully understood; however, individuals colonized with S. aureus are at increased risk of invasive infections through self-inoculation. The transition of S. aureus from the nose (colonization) to the body (infection) is accompanied by a modest but definite temperature increase, from 34°C to 37°C. In this study, we investigate whether these host-associated small temperature changes can influence S. aureus gene expression. Results show widespread changes in the bacterial transcriptome and proteome at three physiologically relevant temperatures (34°C, 37°C, and 40°C).

Biosurfactants of Lactobacillus helveticus for biodiversity inhibit the biofilm formation of Staphylococcus aureus and cell invasion

Aim: This study aimed to evaluate the differences of biosurfactants produced by two Lactobacillus helveticus strains against the biofilm formation of Staphylococcus aureus in vitro and in vivo. Materials & methods: Scanning electron microscopy, Real time-quantitative PCR (RT-qPCR) and cell assay were used to analyze the inhibiting effect of biosurfactants against biofilm formation. Results & conclusion: Results showed that the biosurfactants have anti-adhesive and inhibiting effects on biofilm formation in vivo and in vitro. The biofilm-formative genes and autoinducer-2 signaling regulated these characteristics, and the biosurfactant L. helveticus 27170 is better than that of 27058. Host cell adhesion and invasion results indicated that the biosurfactants L. helveticus prevented the S. aureus invading the host cell, which may be a new strategy to eliminate biofilms.

One particle, two targets: A combined action of functionalised gold nanoparticles, against Pseudomonas fluorescens biofilms

Attempts to deal with the problem of detrimental biofilms using nanoparticle technologies have generally focussed on exploiting biocidal approaches. However, it is now recognised that biofilm matrix-components may be targets for the disruption or dispersion of biofilms. Here, we show that the functionalization of gold nanoparticles with the enzyme, proteinase-K (PK) led to both biocidal and matrix disruption effects within Pseudomonas fluorescens biofilms and released cells. This study highlights the potential mechanisms underpinning the properties of Proteinase-K functionalized gold nanoparticles. With the emergence of biocide-resistant biofilm-forming organisms, novel nanoparticle strategies may provide the ideal solution for disrupting and inactivating biofilm cells, thereby minimising the use of biocides or antibiotics.

Recent Nanotechnology Approaches for Prevention and Treatment of Biofilm-Associated Infections on Medical Devices

Bacterial colonization in the form of biofilms on surfaces causes persistent infections and is an issue of considerable concern to healthcare providers. There is an urgent need for novel antimicrobial or antibiofilm surfaces and biomedical devices that provide protection against biofilm formation and planktonic pathogens, including antibiotic resistant strains. In this context, recent developments in the material science and engineering fields and steady progress in the nanotechnology field have created opportunities to design new biomaterials and surfaces with anti-infective, antifouling, bactericidal, and antibiofilm properties. Here we review a number of the recently developed nanotechnology-based biomaterials and explain underlying strategies used to make antibiofilm surfaces.

Calcium-chelating alizarin and other anthraquinones inhibit biofilm formation and the hemolytic activity of Staphylococcus aureus

Staphylococcal biofilms are problematic and play a critical role in the persistence of chronic infections because of their abilities to tolerate antimicrobial agents. Thus, the inhibitions of biofilm formation and/or toxin production are viewed as alternative means of controlling Staphylococcus aureus infections. Here, the antibiofilm activities of 560 purified phytochemicals were examined. Alizarin at 10 μg/ml was found to efficiently inhibit biofilm formation by three S. aureus strains and a Staphylococcus epidermidis strain. In addition, two other anthraquinones purpurin and quinalizarin were found to have antibiofilm activity. Binding of Ca²⁺ by alizarin decreased S. aureus biofilm formation and a calcium-specific chelating agent suppressed the effect of calcium. These three anthraquinones also markedly inhibited the hemolytic activity of S. aureus, and in-line with their antibiofilm activities, increased cell aggregation. A chemical structure-activity relationship study revealed that two hydroxyl units at the C-1 and C-2 positions of anthraquinone play important roles in antibiofilm and anti-hemolytic activities. Transcriptional analyses showed that alizarin repressed the α-hemolysin hla gene, biofilm-related genes (psmα, rbf, and spa), and modulated the expressions of cid/lrg genes (the holin/antiholin system). These findings suggest anthraquinones, especially alizarin, are potentially useful for controlling biofilm formation and the virulence of S. aureus.

Streptomyces-derived actinomycin D inhibits biofilm formation by Staphylococcus aureus and its hemolytic activity

Staphylococcus aureus is a versatile human pathogen that produces diverse virulence factors, and its biofilm cells are difficult to eradicate due to their inherent ability to tolerate antibiotics. The anti-biofilm activities of the spent media of 252 diverse endophytic microorganisms were investigated using three S. aureus strains. An attempt was made to identify anti-biofilm compounds in active spent media and to assess their anti-hemolytic activities and hydrophobicities in order to investigate action mechanisms. Unlike other antibiotics, actinomycin D (0.5 μg ml(-1)) from Streptomyces parvulus significantly inhibited biofilm formation by all three S. aureus strains. Actinomycin D inhibited slime production in S. aureus and it inhibited hemolysis by S. aureus and caused S. aureus cells to become less hydrophobic, thus supporting its anti-biofilm effect. In addition, surface coatings containing actinomycin D prevented S. aureus biofilm formation on glass surfaces. Given these results, FDA-approved actinomycin D warrants further attention as a potential antivirulence agent against S. aureus infections.