Mini-review: Staphylococcus epidermidis as the most frequent cause of nosocomial infections: old and new fighting strategies

Interpenetrated Polymer Network Systems (PEG/PNIPAAm) Using Gamma Irradiation: Biological Evaluation for Potential Biomedical Applications

The potential antimicrobial and antibiofouling properties of previously synthesized PEG/NiPAAm interpenetrated polymer networks (IPNs) were investigated against three of the most common bacteria (E. coli, S. aureus, and S. epidermidis). The main goal was to evaluate the material's biocompatibility and determine its potential use as an antifouling component in medical devices. This was intended to provide an alternative option that avoids drug usage as the primary treatment, thus contributing to the fight against antimicrobial resistance (AMR). Additionally, characterization and mechanical testing of the IPN were carried out to determine its resistance to manipulation processes in medical/surgical procedures. IPNs with different NiPAAm ratios exhibited excellent cytocompatibility with BALB/3T3 murine fibroblast cells, with cell viability values of between 90 and 98%. In addition, the results regarding the adsorption of albumin as a model protein showed a nearly constant adsorption percentage of almost zero. Furthermore, the bacterial inhibition tests yielded promising results, demonstrating effective pathogen growth inhibition after 48 h. These findings suggest the material's suitability for use in biomedical applications.

Analysis of the broad-spectrum potential of nitric oxide for antibacterial activity against clinically isolated drug-resistant bacteria

The development of drug-resistant microorganisms is taking a heavy toll on the biomedical world. Clinical infections are costly and becoming increasingly dangerous as bacteria that once responded to standard antibiotic treatment are developing resistance mechanisms that require innovative treatment strategies. Nitric oxide (NO) is a gaseous molecule produced endogenously that has shown potent antibacterial capabilities in numerous research studies. Its multimechanistic antibacterial methods prevent the development of resistance and have shown potential as an alternative to antibiotics. However, there has yet to be a direct comparison study evaluating the antibacterial properties of NO against antibiotic susceptible and antibiotic-resistant clinically isolated bacterial strains. Herein, standardized lab and clinically isolated drug-resistant bacterial strains are compared side-by-side for growth and viability following treatment with NO released from S-nitrosoglutathione (GSNO), an NO donor molecule. Evaluation of growth kinetics revealed complete killing of E. coli lab and clinical strains at 17.5 mM GSNO, though 15 mM displayed >50% killing and significantly reduced metabolic activity, with greater dose dependence for membrane permeability. Clinical P. aeruginosa showed greater susceptibility to GSNO during growth curve studies, but metabolic activity and membrane permeability demonstrated similar effects for 12.5 mM GSNO treatment of lab and clinical strains. MRSA lab and clinical strains exhibited total killing at 17.5 mM treatment, though metabolic activity was decreased, and membrane permeation began at 12.5 mM for both strains. Lastly, both S. epidermidis strains were killed by 15 mM GSNO, with sensitivities in metabolic activity and membrane permeability at 12.5 mM GSNO. The mirrored antibacterial effects seen by the lab and clinical strains of two Gram-negative and two Gram-positive bacteria reveal the translational success of NO as an antibacterial therapy and potential alternative to standard antibiotic treatment.

Evaluation of visible light and natural photosensitizers against Staphylococcus epidermidis and Staphylococcus saprophyticus planktonic cells and biofilm

Antimicrobial photoinactivation (API) has shown some promise in potentially treating different nosocomial bacterial infections, however, its application on staphylococci, especially other than Staphylococcus aureus or methicillin-resistant S. aureus (MRSA) species is still limited. Although S. aureus is a well-known and important nosocomial pathogen, several other species of the genus, particularly coagulase-negative Staphylococcus (CNS) species such as Staphylococcus epidermidis and Staphylococcus saprophyticus, can also cause healthcare-associated infections and foodborne intoxications. CNS are often involved in resilient biofilm formation on medical devices and can cause infections in patients with compromised immune systems or those undergoing invasive procedures. In this study, the effects of chlorophyllin and riboflavin-mediated API on S. epidermidis and S. saprophyticus planktonic cells and biofilm are demonstrated for the first time. Based on the residual growth determination and metabolic reduction ability changes, higher inactivating efficiency of chlorophyllin-mediated API was determined against the planktonic cells of both tested species of bacteria and against S. saprophyticus biofilm. Some insights on whether aqueous solutions of riboflavin and chlorophyllin, when illuminated with optimal exciting wavelength (440 nm and 402 nm, respectively) generate O2-•, are also provided in this work.

Synergistic antimicrobial photodynamic therapy using gated mesoporous silica nanoparticles containing curcumin and polymyxin B

Photodynamic Therapy is a therapy based on combining a non-toxic compound, known as photosensitizer (PS), and irradiation with light of the appropriate wavelength to excite the PS molecule. The photon absorption by the PS leads to reactive oxygen species generation and a subsequent oxidative burst that causes cell damage and death. In this work, we report an antimicrobial nanodevice that uses the activity of curcumin (Cur) as a PS for antimicrobial Photodynamic Therapy (aPDT), based on mesoporous silica nanoparticles in which the action of the classical antibiotic PMB is synergistically combined with the aPDT properties of curcumin to combat bacteria. The synergistic effect of the designed gated device in combination with irradiation with blue LED light (470 nm) is evaluated against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus epidermidis. The results show that the nanodevice exhibits a noteworthy antibacterial activity against these microorganisms, a much more significant effect than free Cur and PMB at equivalent concentrations. Thus, 0.1 µg/mL of MSNs-Cur-PMB eliminates a bacterial concentration of about 105 CFU/mL of E. coli, while 1 µg/mL of MSNs-Cur-PMB is required for P. aeruginosa and S. epidermidis. In addition, antibiofilm activity against the selected bacteria was also tested. We found that 0.1 mg/mL of MSNs-Cur-PMB inhibited 99 % biofilm formation for E. coli, and 1 mg/mL of MSNs-Cur-PMB achieved 90 % and 100 % inhibition of biofilm formation for S. epidermidis and P. aeruginosa, respectively.

Bacterial Contamination of Healthcare Students' Mobile Phones: Impact of Specific Absorption Rate (SAR), Users' Demographics and Device Characteristics on Bacterial Load

We quantitatively and qualitatively evaluated the bacterial contamination of mobile phones (MPs) in relation to users' demographics, habits, and device characteristics by administering questionnaires to 83 healthcare university students and sampling their MPs by following a cross-sectional design. The heterotrophic plate count (HPC) at 22 °C (HPC 22 °C) and 37 °C (HPC 37 °C), Enterococci, Gram-negative bacteria, and Staphylococci were evaluated. Higher bacterial loads were detected for HPC 37 °C and Staphylococci (416 and 442 CFU/dm², respectively), followed by HPC 22 °C, Enterococci, and Gram-negative bacteria; the vast majority of samples were positive for HPC 37 °C, HPC 22 °C, and Staphylococci (98%), while Enterococci (66%) and Gram-negative bacteria (17%) were detected less frequently. A statistically significant positive correlation (r = 0.262, p < 0.02) was found between the European head specific absorption rate (SAR) and both HPC 37 °C and Staphylococci; Enterococci showed a strong, significant correlation with HPC 37 °C, HPC 22 °C, and Gram-negative bacteria (r = 0.633, 0.684, 0.884) and a moderate significant correlation with Staphylococci (r = 0.390). Significant differences were found between HPC 22 °C and the type of internship attendance, with higher loads for Medicine. Students with a daily internship attendance had higher HPC 22 °C levels than those attending <6 days/week. Our study showed that bacteria can survive on surfaces for long periods, depending on the user's habits and the device's characteristics.

Recent Approaches for Downplaying Antibiotic Resistance: Molecular Mechanisms

Antimicrobial resistance (AMR) is a ubiquitous public health menace. AMR emergence causes complications in treating infections contributing to an upsurge in the mortality rate. The epidemic of AMR in sync with a high utilization rate of antimicrobial drugs signifies an alarming situation for the fleet recovery of both animals and humans. The emergence of resistant species calls for new treatments and therapeutics. Current records propose that health drug dependency, veterinary medicine, agricultural application, and vaccination reluctance are the primary etymology of AMR gene emergence and spread. Recently, several encouraging avenues have been presented to contest resistance, such as antivirulent therapy, passive immunization, antimicrobial peptides, vaccines, phage therapy, and botanical and liposomal nanoparticles. Most of these therapies are used as cutting-edge methodologies to downplay antibacterial drugs to subdue the resistance pressure, which is a featured motive of discussion in this review article. AMR can fade away through the potential use of current cutting-edge therapeutics, advancement in antimicrobial susceptibility testing, new diagnostic testing, prompt clinical response, and probing of new pharmacodynamic properties of antimicrobials. It also needs to promote future research on contemporary methods to maintain host homeostasis after infections caused by AMR. Referable to the microbial ability to break resistance, there is a great ultimatum for using not only appropriate and advanced antimicrobial drugs but also other neoteric diverse cutting-edge therapeutics.

The nitric oxide synthase gene negatively regulates biofilm formation in Staphylococcus epidermidis

Staphylococcus epidermidis (S. epidermidis) is a clinically important conditioned pathogen that can cause a troublesome chronic implant-related infection once a biofilm is formed. The nitric oxide synthase (NOS) gene, which is responsible for endogenous nitric oxide synthesis, has already been found in the genome of S. epidermidis; however, the specific mechanisms associated with the effects of NOS on S. epidermidis pathogenicity are still unknown. The purpose of the current study was to investigate whether the NOS gene has an impact on biofilm formation in S. epidermidis. Bioinformatics analysis of the NOS gene was performed, and homologous recombination was subsequently employed to delete this gene. The effects of the NOS gene on biofilm formation of S. epidermidis and its underlying mechanisms were analyzed by bacterial growth assays, biofilm semiquantitative determination, Triton X-100-induced autolysis assays, and bacterial biofilm dispersal assays. Additionally, the transcription levels of fbe, aap, icaA, icaR and sigB, which are related to biofilm formation, were further investigated by qRT-PCR following NOS deletion. Phylogenetic analysis revealed that the NOS gene was conserved between bacterial species originating from different genera. The NOS deletion strain of S. epidermidis 1457 and its counterpart were successfully constructed. Disruption of the NOS gene resulted in significantly enhanced biofilm formation, slightly retarded bacterial growth, a markedly decreased autolysis rate, and drastically weakened bacterial biofilm dispersal. Our data showed that the fbe, aap and icaA genes were significantly upregulated, while the icaR and sigB genes were significantly downregulated, compared with the wild strain. Therefore, these data strongly suggested that the NOS gene can negatively regulate biofilm formation in S. epidermidis by affecting biofilm aggregation and dispersal.

Activity of singly and doubly modified derivatives of C20-epi-salinomycin against Staphylococcus strains

Natural polyether ionophore salinomycin (Sal) has been widely used in veterinary medicine as an antibiotic effective in the treatment of coccidian protozoa and Gram-positive bacteria. Moreover, chemical modification of the Sal structure has been found to be a promising strategy to generate semisynthetic analogs with biological activity profiles improved relative to those of the native compound. In this context, we synthesized and thoroughly evaluated the antibacterial potential of a library of C1/C20 singly and doubly modified derivatives of C20-epi-salinomycin, that is, analogs of Sal with inversed stereochemistry at the C20 position. Among the synthesized analog structures, the most promising antibacterial active agents were those obtained via regioselective O-acylation of C20-epi-hydroxyl, particularly esters 7, 9, and 11. Such C20 singly modified compounds showed excellent inhibitory activity against planktonic staphylococci, both standard and clinical strains, and revealed potential in preventing the formation of bacterial biofilms. In combination with their non-genotoxic properties, these Sal derivatives represent attractive candidates for further antimicrobial drug development.

Efficacy of the PlasmaShield®, a Non-Thermal, Plasma-Based Air Purification Device, in Removing Airborne Microorganisms

Airborne microorganisms play a significant role in the transmission of infectious diseases. As such, improving indoor microbial air quality can enhance infection control in numerous settings. This study examined the efficacy of the PlasmaShield® air purification device to remove airborne microorganisms under laboratory conditions. Pure cultures of model microorganisms at varying concentrations were aerosolized using a 1-jet Collison nebulizer through stainless-steel removable piping prior to reaching the PlasmaShield® device. The surviving microorganisms were captured using the Staplex® MBS-6 Six Stage Microbial Air Sampler and enumerated via culture on agar plates. The positive-hole-corrected colony/plaque-forming units were compared with the negative control (microorganisms aerosolized through an empty PlasmaShield® casing). The PlasmaShield® statistically significantly (p < 0.05) reduced airborne Escherichia coli, Staphylococcus epidermidis, Bacteriophage MS2 and Cladosporium sp. compared with the negative control. The maximum removal achieved was estimated to be 4 × log10E. coli (99.99% removal), 4 × log10S. epidermidis (99.97% removal), 7 × log10 MS2 (99.99998% removal) and 5 × log10Cladosporium sp. (99.999% removal). Scanning electron microscope images of the surviving microorganisms showed that the PlasmaShield® damaged the cell membrane of these model microorganisms. This study provides proof-of-concept evidence to support the use of this technology to improve indoor microbial air quality.

Innovative Surface Modification Procedures to Achieve Micro/Nano-Graded Ti-Based Biomedical Alloys and Implants

Due to the growing aging population of the world, and as a result of the increasing need for dental implants and prostheses, the use of titanium and its alloys as implant materials has spread rapidly. Although titanium and its alloys are considered the best metallic materials for biomedical applications, the need for innovative technologies is necessary due to the sensitivity of medical applications and to eliminate any potentially harmful reactions, enhancing the implant-to-bone integration and preventing infection. In this regard, the implant’s surface as the substrate for any reaction is of crucial importance, and it is accurately addressed in this review paper. For constructing this review paper, an internet search was performed on the web of science with these keywords: surface modification techniques, titanium implant, biomedical applications, surface functionalization, etc. Numerous recent papers about titanium and its alloys were selected and reviewed, except for the section on forthcoming modern implants, in which extended research was performed. This review paper aimed to briefly introduce the necessary surface characteristics for biomedical applications and the numerous surface treatment techniques. Specific emphasis was given to micro/nano-structured topographies, biocompatibility, osteogenesis, and bactericidal effects. Additionally, gradient, multi-scale, and hierarchical surfaces with multifunctional properties were discussed. Finally, special attention was paid to modern implants and forthcoming surface modification strategies such as four-dimensional printing, metamaterials, and metasurfaces. This review paper, including traditional and novel surface modification strategies, will pave the way toward designing the next generation of more efficient implants.

Vancomycin-Loaded Collagen/Hydroxyapatite Layers Electrospun on 3D Printed Titanium Implants Prevent Bone Destruction Associated with S. epidermidis Infection and Enhance Osseointegration

The aim of the study was to develop an orthopedic implant coating in the form of vancomycin-loaded collagen/hydroxyapatite layers (COLHA+V) that combine the ability to prevent bone infection with the ability to promote enhanced osseointegration. The ability to prevent bone infection was investigated employing a rat model that simulated the clinically relevant implant-related introduction of bacterial contamination to the bone during a surgical procedure using a clinical isolate of Staphylococcus epidermidis. The ability to enhance osseointegration was investigated employing a model of a minipig with terminated growth. Six weeks following implantation, the infected rat femurs treated with the implants without vancomycin (COLHA+S. epidermidis) exhibited the obvious destruction of cortical bone as evinced via a cortical bone porosity of up to 20% greater than that of the infected rat femurs treated with the implants containing vancomycin (COLHA+V+S. epidermidis) (3%) and the non-infected rat femurs (COLHA+V) (2%). The alteration of the bone structure of the infected COLHA+S. epidermidis group was further demonstrated by a 3% decrease in the average Ca/P molar ratio of the bone mineral. Finally, the determination of the concentration of vancomycin released into the blood stream indicated a negligible systemic load. Six months following implantation in the pigs, the quantified ratio of new bone indicated an improvement in osseointegration, with a two-fold bone ingrowth on the COLHA (47%) and COLHA+V (52%) compared to the control implants without a COLHA layer (27%). Therefore, it can be concluded that COLHA+V layers are able to significantly prevent the destruction of bone structure related to bacterial infection with a minimal systemic load and, simultaneously, enhance the rate of osseointegration.

Additive manufacturing of Ti6Al4V alloy via electron beam melting for the development of implants for the biomedical industry

Additive Manufacturing (AM) or rapid prototyping technologies are presented as one of the best options to produce customized prostheses and implants with high-level requirements in terms of complex geometries, mechanical properties, and short production times. The AM method that has been more investigated to obtain metallic implants for medical and biomedical use is Electron Beam Melting (EBM), which is based on the powder bed fusion technique. One of the most common metals employed to manufacture medical implants is titanium. Although discovered in 1790, titanium and its alloys only started to be used as engineering materials for biomedical prostheses after the 1950s. In the biomedical field, these materials have been mainly employed to facilitate bone adhesion and fixation, as well as for joint replacement surgeries, thanks to their good chemical, mechanical, and biocompatibility properties. Therefore, this study aims to collect relevant and up-to-date information from an exhaustive literature review on EBM and its applications in the medical and biomedical fields. This AM method has become increasingly popular in the manufacturing sector due to its great versatility and geometry control.

Immobilization of alkyl-pterin photosensitizer on silicon surfaces through in situ SN2 reaction as suitable approach for photodynamic inactivation of Staphylococcus aureus

The tuning of surface properties through functionalization is an important field of research with a broad spectrum of applications. Self-assembled monolayers (SAMs) allow the surface tailoring through the adsorption of molecular layers having the appropriate functional group or precursor group enabling in situ chemical reactions and thus to the incorporation of new functionalities. The latter approach is particularly advantageous when the incorporation of huge groups is needed. In this study, we report the immobilization of pterin moieties on 11-bromoundecyltrichlorosilane-modified silicon substrates based on the in situ replacement of the bromine groups by pterin (Ptr), the parent derivative of pterins, by means of a nucleophilic substitution reaction. The modified surface was structurally characterized through a multi-technique approach, including high-resolution XPS analysis, contact angle measurements, and AFM. The designed synthesis method leads to the functionalization of the silicon surface with two compounds, O-undecyl-Ptr and N-undecyl-Ptr, with a higher proportion of the N-derivative (1:8 ratio). The alkyl-pterins immobilized via the proposed strategy, retain their photochemical properties, being able to inhibit Staphylococcus aureus growth under irradiation (84.3 ± 15.6 % reduction in viable cells). Our results open the possibility for the modification of several materials, such as glass and metal, through the formation of SAMs having the proper head group, thus allowing the design of photosensitive surfaces with potential microbiological self-cleaning properties.

Taking Screenshots of the Invisible: A Study on Bacterial Contamination of Mobile Phones from University Students of Healthcare Professions in Rome, Italy

Mobile phones (MPs) are commonly used both in the personal and professional life. We assessed microbiological contamination of MPs from 108 students in healthcare professions (HPs), in relation to their demographic characteristics and MPs handling habits, collected by means of a questionnaire. Cultural and biochemical tests were performed, and statistical analyses were carried out. Staphylococci were present in 85% of MPs, Enterococci in 37%, Coliforms in 6.5%; E. coli was never detected. Staphylococcus epidermidis was the most frequently isolated staphylococcal species (72% of MPs), followed by S. capitis (14%), S. saprophyticus, S. warneri, S. xylosus (6%), and by S. aureus (4%). Heterotrophic Plate Counts (HPC) at 37 °C, ranged from 0 to 1.2 × 10⁴ CFU/dm² (mean = 362 CFU/dm²). In univariate analysis, the male gender only was significantly associated with higher HPCs and enterococcal contamination. Multiple linear regression models explained only 17% and 16% of the HPC 37 °C and staphylococcal load variability, respectively. Developing specific guidelines for a hygienic use of MPs in clinical settings, for preventing cross-infection risks, is advisable, as well as introducing specific training programs to HP students. MPs decontamination procedures could also be implemented in the community.

Oxytropis glabra DC. Inhibits Biofilm Formation of Staphylococcus epidermidis by Down-Regulating ica Operon Expression

Staphylococcus epidermidis is one of the main causes of medical device-related infections and bovine mastitis owing to its biofilm-forming abilities. Oxytropis glabra DC. is one of the most widespread Fabaceae species and used as a Chinese herbal formulation in Western China. Our research investigated the effects of O. glabra on the biofilm formation of S. epidermidis and the possible inhibiting mechanism. The biofilm-forming reference strain, S. epidermidis SE-1 (ATCC 35,984), was employed as a model and semi-quantitative biofilm assay was performed to evaluate the antibiofilm activity of O. glabra. The exopolysaccharides (EPS) production and expression of ica operon were studied to explore the possible antibiofilm mechanism using thin-layer chromatography and quantitative real-time PCR assay, respectively. The results obtained indicated that O. glabra decoction at 7.5 mg mL-1 significantly inhibited biofilm formation by about 95% without affecting cell growth of S. epidermidis. Two hydrolysis productions of EPS were significantly decreased by 64% and 54% with the addition of 7.5 mg mL-1O. glabra and the expression of icaR was significantly up-regulated 2.2-times, whereas icaB was significantly down-regulated more than 50% by 7.5 mg mL-1O. glabra. These findings suggest a potential application for O. glabra as a promising candidate for the exploration of new drugs against S. epidermidis biofilm-associated infections.

Common Plant-Derived Terpenoids Present Increased Anti-Biofilm Potential against Staphylococcus Bacteria Compared to a Quaternary Ammonium Biocide

The antimicrobial actions of three common plant-derived terpenoids (i.e., carvacrol, thymol and eugenol) were compared to those of a typical quaternary ammonium biocide (i.e., benzalkonium chloride; BAC), against both planktonic and biofilm cells of two widespread Staphylococcus species (i.e., S. aureus and S. epidermidis). The minimum inhibitory and bactericidal concentrations (MICs, MBCs) of each compound against the planktonic cells of each species were initially determined, together with their minimum biofilm eradication concentrations (MBECs). Various concentrations of each compound were subsequently applied, for 6 min, against each type of cell, and survivors were enumerated by agar plating to calculate log reductions and determine the resistance coefficients (Rc) for each compound, as anti-biofilm effectiveness indicators. Sessile communities were always more resistant than planktonic ones, depending on the biocide and species. Although lower BAC concentrations were always needed to kill a specified population of either cell type compared to the terpenoids, for the latter, the required increases in their concentrations, to be equally effective against the biofilm cells with respect to the planktonic ones, were not as intense as those observed in the case of BAC, presenting thus significantly lower Rc. This indicates their significant anti-biofilm potential and advocate for their further promising use as anti-biofilm agents.

A novel comprehensive efficacy test for textiles intended for use in the healthcare setting

Soft surfaces, including textiles are found throughout healthcare settings. Pathogens can survive for long periods of time on textiles, and can be transferred to and from the skin. Antimicrobial fabrics are used as an engineering control to prevent infection. Efficacy testing standards have limitations, including single microorganism challenges, multiple fabric plies tested, and lengthy contact times. We developed a novel method that better models in-use conditions through testing standardized mixtures of pathogens and normal skin microorganisms, artificial soils, and a 15-min contact time. Reproducible growth of all microorganisms from frozen stocks was achieved using this method. A novel rechargeable, monitorable N-halamine cotton cellulose fabric, containing 5885 ± 98 ppm of active chlorine, was evaluated with the new method using PBS, artificial sweat, and artificial sweat plus 5% serum as soil. Pathogens tested included Acinetobacter baumannii, Candida albicans, Escherichia coli, vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, methicillin-susceptible Staphylococcus aureus, and Pseudomonas aeruginosa. Each was tested singly and in the presence of a representative normal skin flora mixture, including: Acinetobacter lwoffii, Corynebacterium striatum, Micrococcus luteus, and Staphylococcus epidermidis. When tested singly, all microorganisms were reduced by 3.00 log₁₀ or greater, regardless of artificial soil. In mixture, 4.00 log₁₀ or greater reductions were achieved for all microorganisms. These results suggest that the novel testing method can be used to provide more comprehensive and realistic efficacy information for antimicrobial textiles intended for use in healthcare. Furthermore, the N-halamine fabric demonstrated efficacy against multiple pathogens, singly and in mixtures, regardless of the presence of artificial soils.

Characterization of Serine Hydrolases Across Clinical Isolates of Commensal Skin Bacteria Staphylococcus epidermidis Using Activity-Based Protein Profiling

The bacterial genus Staphylococcus comprises diverse species that colonize the skin as commensals but can also cause infection. Previous work identified a family of serine hydrolases termed fluorophoshonate-binding hydrolases (Fphs) in the pathogenic bacteria Staphylococcus aureus, one of which, FphB, functions as a virulence factor. Using a combination of bioinformatics and activity-based protein profiling (ABPP), we identify homologues of these enzymes in the related commensal bacteria Staphylococcus epidermidis. Two of the S. aureus Fph enzymes were not identified in S. epidermidis. Using ABPP, we identified several candidate hydrolases that were not previously identified in S. aureus that may be functionally related to the Fphs. Interestingly, the activity of the Fphs vary across clinical isolates of S. epidermidis. Biochemical characterization of the FphB homologue in S. epidermidis (SeFphB) suggests it is a functional homologue of FphB in S. aureus, but our preliminary studies suggest it may not have a role in colonization in vivo. This potential difference in biological function between the Fphs of closely related staphylococcal species may provide mechanisms for specific inhibition of S. aureus infection without perturbing commensal communities of related bacteria.

2-Hydroxy-4-methoxybenzaldehyde from Hemidesmus indicus is antagonistic to Staphylococcus epidermidis biofilm formation

Staphylococcus epidermidis (SE) is an opportunistic nosocomial pathogen that accounts for recalcitrant device-related infections worldwide. Owing to the growing interest in plants and their secondary metabolites targeting bacterial adhesion, this study was intended to uncover the anti-biofilm potential of Hemidesmus indicus and its major constituent 2-hydroxy-4-methoxybenzaldehyde (HMB) against SE. The minimum biofilm inhibitory concentration (MBIC) of H. indicus root extract and HMB were found to be 500 and 250 µg ml^-1, respectively. The results of time-dependent biofilm inhibition and mature biofilm disruption assays confirmed that HMB targets initial cell adhesion. Furthermore, interference by HMB in the expression of adhesin genes (icaA, aap and bhp) and biofilm components was associated with an increased susceptibility of SE to oxidative stress and antibiotics. To conclude, this study reports for the first time HMB as a potential drug against SE biofilms.

Study on the Effects of Estradiol in Staphylococcus epidermidis Device-Related Capsule Formation

BACKGROUND

Capsular contracture, mainly caused by Staphylococcus epidermidis (S. epidermidis) biofilm formation, is a complex problem for breast cancer patients who undergo surgical prosthetic breast reconstruction. Estradiol has been reported to be involved in the formation of bacterial biofilms. Thus, the underlying mechanism of estradiol in capsular contracture needs to be investigated.

METHODS

Biofilm-related gene expressions were measured by qRT-PCR after sterilizing the silicone with bacterial suspension and E2 treatment in vitro. Rat models were established with bilateral ovariectomy operations and estradiol subcutaneous injections. The effects of estradiol on capsular contracture were detected by monitoring serum estradiol levels, bacterial infection rate in organs, biofilm formation and capsular contracture in vivo; inflammatory factors in vivo were examined as well. Biofilm on the silicone implants was observed under a scanning electron microscope.

RESULTS

Both positive regulatory genes and negative regulatory genes were increased by the high concentration of estradiol, suggesting that estradiol can promote the formation of biofilm by not only positive but also negative regulations. High estradiol levels increased bacterial infection rate in organs, biofilm formation and capsular contracture. Further, high estradiol caused a large number of inflammatory cells to infiltrate and caused serious inflammatory reactions that aggravate the immune imbalances of the host.

CONCLUSION

High estradiol levels contribute to increasing capsular contracture caused by S. epidermidis biofilm formation.

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Underrated Staphylococcus species and their role in antimicrobial resistance spreading

The increasing threat of antimicrobial resistance has shed light on the interconnection between humans, animals, the environment, and their roles in the exchange and spreading of resistance genes. In this review, we present evidences that show that Staphylococcus species, usually referred to as harmless or opportunistic pathogens, represent a threat to human and animal health for acting as reservoirs of antimicrobial resistance genes. The capacity of genetic exchange between isolates of different sources and species of the Staphylococcus genus is discussed with emphasis on mobile genetic elements, the contribution of biofilm formation, and evidences obtained either experimentally or through genome analyses. We also discuss the involvement of CRISPR-Cas systems in the limitation of horizontal gene transfer and its suitability as a molecular clock to describe the history of genetic exchange between staphylococci.

Antibacterial, Antibiofilm, and Antiadhesive Properties of Different Quaternized Chitosan Derivatives

In the era of antimicrobial resistance, the identification of new antimicrobials is a research priority at the global level. In this regard, the attention towards functional antimicrobial polymers, with biomedical/pharmaceutical grade, and exerting anti-infective properties has recently grown. The aim of this study was to evaluate the antibacterial, antibiofilm, and antiadhesive properties of a number of quaternized chitosan derivatives that have displayed significant muco-adhesive properties and wound healing promotion features in previous studies. Low (QAL) and high (QAH) molecular weight quaternized chitosan derivatives were synthetized and further modified with thiol moieties or pendant cyclodextrin, and their antibacterial activity evaluated as minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC). The ability of the derivatives to prevent biofilm formation was assessed by crystal violet staining. Both QAL and QAH derivatives exerted a bactericidal and/or inhibitory activity on the growth of P. aeruginosa and S. epidermidis. The same compounds also showed marked dose-dependent anti-biofilm activity. Furthermore, the high molecular weight derivative (QAH) was used to functionalize titanium plates. The successful functionalization, demonstrated by electron microscopy, was able to partially inhibit the adhesion of S. epidermidis at 6 h of incubation. The shown ability of the chitosan derivatives tested to both inhibit bacterial growth and/or biofilm formation of clinically relevant bacterial species reveals their potential as multifunctional molecules against bacterial infections.

From Antihistamine to Anti-infective: Loratadine Inhibition of Regulatory PASTA Kinases in Staphylococci Reduces Biofilm Formation and Potentiates β-Lactam Antibiotics and Vancomycin in Resistant Strains of Staphylococcus aureus

Staphylococcus epidermidis and Staphylococcus aureus are important human pathogens responsible for two-thirds of all postsurgical infections of indwelling medical devices. Staphylococci form robust biofilms that provide a reservoir for chronic infection, and antibiotic-resistant isolates are increasingly common in both healthcare and community settings. Novel treatments that can simultaneously inhibit biofilm formation and antibiotic-resistance pathways are urgently needed to combat the increasing rates of antibiotic-resistant infections. Herein we report that loratadine, an FDA-approved antihistamine, significantly inhibits biofilm formation in both S. aureus and S. epidermidis. Furthermore, loratadine potentiates β-lactam antibiotics in methicillin-resistant strains of S. aureus and potentiates both β-lactam antibiotics and vancomycin in vancomycin-resistant strains of S. aureus. Additionally, we elucidate loratadine's mechanism of action as a novel inhibitor of the regulatory PASTA kinases Stk and Stk1 in S. epidermidis and S. aureus, respectively. Finally, we describe how Stk1 inhibition affects the expression of genes involved in both biofilm formation and antibiotic resistance in S. epidermidis and S. aureus.

Enzyme responsive copolymer micelles enhance the anti-biofilm efficacy of the antiseptic chlorhexidine

Staphylococcal biofilms cause many infectious diseases and are highly tolerant to the effects of antimicrobials; this is partly due to the biofilm matrix, which acts as a physical barrier retarding the penetration and reducing susceptibility to antimicrobials, thereby decreasing successful treatment outcomes. In this study, both single and mixed micellar systems based on poly vinyl caprolactam (PCL)-polyethylene glycol (PEG) copolymers were optimised for delivery of chlorhexidine (CHX) to S. aureus, MRSA and S. epidermidis biofilms and evaluated for their toxicity using Caenorhabditis elegans. The respective polyethylene glycol (PEG) and poly vinyl caprolactam (PCL) structural components promoted stealth properties and enzymatic responsive release of CHX inside biofilms, leading to significantly enhanced penetration (56%) compared with free CHX and improving the efficacy against Staphylococcus aureus biofilms grown on an artificial dermis (2.4 log reduction of CFU). Mixing Soluplus-based micelles with Solutol further enhanced the CHX penetration (71%) and promoted maximum reduction in biofilm biomass (>60%). Nematodes-based toxicity assay showed micelles with no lethal effects as indicated by their high survival rate (100%) after 72 h exposure. This study thus demonstrated that bio-responsive carriers can be designed to deliver a poorly water-soluble antimicrobial agent and advance the control of biofilm associated infections.

Tannin profile, antioxidant properties, and antimicrobial activity of extracts from two Mediterranean species of parasitic plant Cytinus

BACKGROUND

Cytinus is small genus of endophytic parasitic plants distributed in South Africa, Madagascar, and in the Mediterranean region. In the latter area, two species occur, Cytinus hypocistis and C. ruber, distinguished by both morphological characters and ecological traits. We characterized the ethanolic and aqueous extracts obtained from the inflorescences of C. hypocistis and C. ruber collected in Sardinia, Italy, and explored their tannin content, antioxidant properties and antimicrobial activities.

METHODS

Total phenolic contents were determined by Folin-Ciocalteu spectrophotometric method. Tannin content was determined by HPLC. Antioxidant activity of the extracts was tested with both electron transfer-based (FRAP, TEAC, DPPH) and spectrophotometric HAT methods (ORAC-PYR). The antimicrobial activities of extracts/compounds were evaluated using the broth microdilution method. The bactericidal activity was evaluated using the time-kill method. Biofilm formation was evaluated by crystal violet (CV) staining assay.

RESULTS

Characterization of the tannin profile of C. hypocistis and C. ruber revealed a significant amount of gallotannins, in particular 1-O-galloyl-β-D-glucose. In addition, pentagalloyl-O-β-D-glucose was present in all extracts, reaching the concentration of 0.117 g/kg in the ethanolic extract of C. hypocistis. C. hypocistis extracts displayed a strongest antioxidant activity than C. ruber extracts. Three Gram-positive bacterial species tested (Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecium) resulted sensitive to both Cytinus extracts, with MICs ranging from 125 to 500 μg/ml for aqueous extracts and from 31.25 to 250 μg/ml for ethanolic extracts; on the contrary, Gram-negative strains (Pseudomonas aeruginosa and Klebsiella pneumoniae) were not affected by Cytinus extracts. Intriguingly, we observed the suppressive activity of ethanolic extracts of C. hypocistis and C. ruber on biofilm formation of S. epidermidis. Experiments performed with synthetic compounds indicated that pentagalloyl-O-β-D-glucose is likely to be one of the active antimicrobial components of Cytinus extracts.

CONCLUSIONS

These findings show that Cytinus extracts have antimicrobial and antioxidant activities, suggesting a possible application of Cytinus as sources of natural antimicrobials and antioxidants.

Deciphering the Antibacterial Mode of Action of Alpha-Mangostin on Staphylococcus epidermidis RP62A Through an Integrated Transcriptomic and Proteomic Approach

Background: Alpha-mangostin (α-MG) is a natural xanthone reported to exhibit rapid bactericidal activity against Gram-positive bacteria, and may therefore have potential clinical application in healthcare sectors. This study sought to identify the impact of α-MG on Staphylococcus epidermidis RP62A through integrated advanced omic technologies. Methods: S. epidermidis was challenged with sub-MIC (0.875 μg/ml) of α-MG at various time points and the differential expression pattern of genes/proteins were analyzed in the absence and presence of α-MG using RNA sequencing and LC-MS/MS experiments. Bioinformatic tools were used to categorize the biological processes, molecular functions and KEGG pathways of differentially expressed genes/proteins. qRT-PCR was employed to validate the results obtained from these analyses. Results: Transcriptomic and proteomic profiling of α-MG treated cells indicated that genes/proteins affected by α-MG treatment were associated with diverse cellular functions. The greatest reduction in expression was observed in transcription of genes conferring cytoplasmic membrane integrity (yidC2, secA and mscL), cell division (ftsY and divlB), teichoic acid biosynthesis (tagG and dltA), fatty-acid biosynthesis (accB, accC, fabD, fabH, fabI, and fabZ), biofilm formation (icaA) and DNA replication and repair machinery (polA, polC, dnaE, and uvrA). Those with increased expression were involved in oxidative (katA and sodA) and cellular stress response (clpB, clpC, groEL, and asp23). The qRT-PCR analysis substantiated the results obtained from transcriptomic and proteomic profiling studies. Conclusion: Combining transcriptomic and proteomic methods provided comprehensive information about the antibacterial mode of action of α-MG. The obtained results suggest that α-MG targets S. epidermidis through multifarious mechanisms, and especially prompts that loss of cytoplasmic membrane integrity leads to rapid onset of bactericidal activity.

In vivo protective effect of geraniol on colonization of Staphylococcus epidermidis in rat jugular vein catheter model

Staphylococcal infections associated with indwelling medical devices are difficult to eradicate owing to its recalcitrant nature of biofilms to conventional antibiotics. In our earlier study, we reported the efficacy of geraniol (GE) in inhibiting the in vitro biofilm formation of Staphylococcus epidermidis and adaptive resistant development. To examine the in vivo potential of GE in eradicating the in vivo colonization of S. epidermidis, an implanted rat jugular vein catheter model was developed. Oral supplementation of GE (GE at 200 mg/kg bw for three days) in rats infected with S. epidermidis exhibited a significant reduction of the bacterial burden in catheter, blood, heart and kidney, when compared to the untreated infection control. In addition, GE supplemented animals showed significantly reduced level of inflammatory markers such as nitric oxide and malondialdehyde in heart and kidney tissues. Furthermore, in contrast to the infection control, histopathology analysis of the heart and kidney tissues of the GE-treated group showed a normal histoarchitecture similar to animal control. Thus, the outcome of the present study exhibits the potential of GE as antibiofilm and anti-inflammatory agent against S. epidermidis infections. Furthermore, elucidating the molecular mechanism of GE is important to exploit the therapeutic efficacy of GE.

Review of titanium surface modification techniques and coatings for antibacterial applications

Implanted biomaterials play a key role in the current success of orthopedic and dental procedures. Pure titanium and its alloys are the most commonly used materials for permanent implants in contact with bone. However, implant-related infections remain among the leading reasons for failure. The most critical pathogenic event in the development of infection on biomaterials is biofilm formation, which starts immediately after bacterial adhesion. In the last decade, numerous studies reported the ability of titanium surface modifications and coatings to minimize bacterial adhesion, inhibit biofilm formation and provide effective bacterial killing to protect implanted biomaterials. In the present review, the different strategies to prevent infection onto titanium surfaces are reported: surface modification and coatings by antibiotics, antimicrobial peptides, inorganic antibacterial metal elements and antibacterial polymers. STATEMENT OF SIGNIFICANCE: Implanted biomaterials play a key role in the current success of orthopedic and dental procedures. Pure titanium and its alloys are the most commonly used materials for permanent implants in contact with bone. Microbial infection is one of the main causes of implant failure. Currently, the global infection risk is 2-5% in orthopedic surgery. Numerous solutions exist to render titanium surfaces antibacterial. The LBPS team is an expert on the functionalization of titanium surfaces by using bioactive polymers to improve the biologiocal response. In this review, the different strategies to prevent infection are reported onto titanium and titanium alloy surfaces such as surface modification by antibiotics, antimicrobial peptides, inorganic antibacterial metal elements and antibacterial polymers.

Profiling of headspace volatiles from Escherichia coli cultures using silicone-based sorptive media and thermal desorption GC-MS

Headspace sorptive extraction technique using silicone based sorptive media coated stir bars is used for the first time here to extract, identify, and quantify heavy volatile organic compounds present in Escherichia coli culture headspace. Detection of infection presence is largely accomplished in laboratories through physical sampling and subsequent growth of cultures for biochemical testing. The use of volatile biomarkers released from pathogens as indicators for pathogenic presence can vastly reduce the time needed whilst improving the success rates for infection detection. To validate this, by using a contactless headspace sorptive extraction technique, the volatile compounds released from E. coli, grown in vitro, have been extracted and identified. Two different sorptive media for extracting these headspace volatiles were compared in this study and the identified volatiles were quantified. The large phase volume and wider retention of this sorptive technique compared to traditional sampling approach enabled preconcentration and collection of wider range of volatiles towards developing an extensive database of such heavy volatiles associated with E. coli. This supplements the existing data of potential bacterial markers and use of internal standards in these tests allows semi-quantitative estimation of these compounds towards the development and optimization of novel pathogen sensing devices.

Fighting biofilms with lantibiotics and other groups of bacteriocins

Biofilms are sessile communities of bacteria typically embedded in an extracellular polymeric matrix. Bacterial cells embedded in biofilms are inherently recalcitrant to antimicrobials, compared to cells existing in a planktonic state, and are notoriously difficult to eradicate once formed. Avenues to tackle biofilms thus far have largely focussed on attempting to disrupt the initial stages of biofilm formation, including adhesion and maturation of the biofilm. Such an approach is advantageous as the concentrations required to inhibit formation of biofilms are generally much lower than removing a fully established biofilm. The crisis of antibiotic resistance in clinical settings worldwide has been further exacerbated by the ability of certain pathogenic bacteria to form biofilms. Perhaps the most notorious biofilm formers described from a clinical viewpoint have been methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa, Gardnerella vaginalis and Streptococcus mutans, the latter of which is found in oral biofilms. Due to the dearth of novel antibiotics in recent decades, compounded by the increasing rate of emergence of resistance amongst pathogens with a propensity for biofilm formation, solutions are urgently required to mitigate these crises. Bacteriocins are a class of antimicrobial peptides, which are ribosomally synthesised and often are more potent than their antibiotic counterparts. Here, we review a selection of studies conducted with bacteriocins with the ultimate objective of inhibiting biofilms. Overall, a deeper understanding of the precise means by which a biofilm forms on a substrate as well as insights into the mechanisms by which bacteriocins inhibit biofilms is warranted.

Archaeal tetraether lipid coatings-A strategy for the development of membrane analog spacer systems for the site-specific functionalization of medical surfaces

The primary goal of our investigation was the development of a versatile immobilization matrix based on archaeal tetraether lipids that meets the most important prerequisites to render an implant surface bioactive by binding specific functional groups or functional polymers with the necessary flexibility and an optimal spatial arrangement to be bioavailable. From this point of view, it appears obvious that numerous efforts made recently to avoid initial bacterial adhesion on catheter surfaces as an important prerequisite of material associated infection episodes have shown only a limited efficiency since the bioactive entities could not be presented in an optimal conformation and a stable density. A significant improvement of this situation can be achieved by highly specific biomimetic modifications of the catheter surfaces. The term "biomimetic" originates from the fact that specific archaeal tetraether lipids were introduced to form a membrane analog monomolecular spacer system, which (1) can be immobilized on nearly all solid surfaces and (2) chemically modified to present a tailor-made functionality in contact with aqueous media either to avoid or inhibit surface fouling or to equip any implant surface with the necessary chemical functionality to enable cell adhesion and tissue integration. Ultrathin films based on tetraether lipids isolated from archaea Thermoplasma acidophilum were used as a special biomimetic immobilization matrix on the surface of commercial medical silicon elastomers. A complete performance control of the membrane analog coatings was realized in addition to biofunctionality tests, including the proof of cytotoxicity and hemocompatibility according to DIN EN ISO 10993. In order to make sure that the developed immobilization matrix including the grafted functional groups are biocompatible under in vivo-conditions, specific animal tests were carried out to examine the in vivo-performance. It can be concluded that the tetraether lipid based coating systems on silicone have shown no signs of cytotoxicity and a good hemocompatibility. Moreover, no mutagenic effects, no irritation effects, and no sensitization effects could be demonstrated. After an implantation period of 28 days, no irregularities were found.

Tolerance towards gentamicin is a function of nutrient concentration in biofilms of patient-isolated Staphylococcus epidermidis

Staphylococcus epidermidis is a biofilm-forming bacterial strain that can cause major problems as an agent of nosocomial infections. Bacteria in biofilms are shielded from the environment and can survive high doses of antibiotics. We here test the antibiotic susceptibility of Staphylococcus epidermidis to rising gentamicin concentrations in optimal growth conditions as used in routine bacteriology laboratories with low nutrient situations as suggested to be found in clinical situations. We found that gentamicin-resistant Staphylococcus epidermidis biofilms survived in the absence of external nutrient supply in PBS. While addition of gentamicin sulfate significantly reduced the pH value of all used media and solutions, this acidification did not alter survival of bacteria in the biofilm. We found a statistically significant and dose-dependent reduction of survival in low nutrient situations using gentamicin sulfate in three out of four patient isolates of Staphylococcus epidermidis which have been tested to be gentamicin-resistant under optimal growth conditions. Supporting the original profiling, survival in full media under the same antibiotic dosages was not significantly reduced. Our data here show that antibiotic resistance is a function of the provided nutrient concentration. Antibiotic resistance profiling should consider variations in nutrient availability.

Fast corroding, thin magnesium coating displays antibacterial effects and low cytotoxicity

Bacterial colonisation and biofilm formation are characteristics of implant-associated infections. In search of candidates for improved prosthetic materials, fast corroding Mg-based coatings on titanium surfaces were examined for their cytotoxic and antimicrobial properties. Human osteoblasts and Staphylococcus epidermidis were each cultured on cylindrical Ti samples coated with a thin layer of Mg/Mg₄₅Zn₅Ca, applied via magnetron sputtering. Uncoated titanium samples served as controls. S. epidermidis was quantified by counting colony forming units. The biofilm-bound fraction was isolated via ultrasonic treatment, and the planktonic fraction via centrifugation. Biofilm-bound S. epidermidis was significantly decreased by approximately four to five orders of magnitude in both Mg- and Mg₄₅Zn₅Ca-coated samples after seven days compared to the control. The osteoblast viability was within the tolerance threshold of 70% stated in DIN EN ISO 10993-5:2009-10 for Mg (~80%) but not for Mg₄₅Zn₅Ca (~25%). Accordingly, Mg-coated titanium was identified as a promising candidate for an implant material with antibacterial properties and low cytotoxicity levels. The approach of exploiting fast corrosion contrasts with existing methods, which have generally focused on reducing corrosion.

Skin-bacteria communication: Involvement of the neurohormone Calcitonin Gene Related Peptide (CGRP) in the regulation of Staphylococcus epidermidis virulence

Staphylococci can sense Substance P (SP) in skin, but this molecule is generally released by nerve terminals along with another neuropeptide, Calcitonin Gene Related Peptide (CGRP). In this study, we investigated the effects of αCGRP on Staphylococci. CGRP induced a strong stimulation of Staphylococcus epidermidis virulence with a low threshold (<10⁻¹²M) whereas Staphylococcus aureus was insensitive to CGRP. We observed that CGRP-treated S. epidermidis induced interleukin 8 release by keratinocytes. This effect was associated with an increase in cathelicidin LL37 secretion. S. epidermidis displayed no change in virulence factors secretion but showed marked differences in surface properties. After exposure to CGRP, the adherence of S. epidermidis to keratinocytes increased, whereas its internalization and biofilm formation activity were reduced. These effects were correlated with an increase in surface hydrophobicity. The DnaK chaperone was identified as the S. epidermidis CGRP-binding protein. We further showed that the effects of CGRP were blocked by gadolinium chloride (GdCl₃), an inhibitor of MscL mechanosensitive channels. In addition, GdCl₃ inhibited the membrane translocation of EfTu, the Substance P sensor. This work reveals that through interaction with specific sensors S. epidermidis integrates different skin signals and consequently adapts its virulence.

Anti-biofilm properties of the antimicrobial peptide temporin 1Tb and its ability, in combination with EDTA, to eradicate Staphylococcus epidermidis biofilms on silicone catheters

In search of new antimicrobials with anti-biofilm potential, in the present study activity of the frog-skin derived antimicrobial peptide temporin 1Tb (TB) against Staphylococcus epidermidis biofilms was investigated. A striking ability of TB to kill both forming and mature S. epidermidis biofilms was observed, especially when the peptide was combined with cysteine or EDTA, respectively. Kinetics studies demonstrated that the combination TB/EDTA was active against mature biofilms already after 2-4-h exposure. A double 4-h exposure of biofilms to TB/EDTA further increased the therapeutic potential of the same combination. Of note, TB/EDTA was able to eradicate S. epidermidis biofilms formed in vitro on silicone catheters. At eradicating concentrations, TB/EDTA did not cause hemolysis of human erythrocytes. The results shed light on the anti-biofilm properties of TB and suggest a possible application of the peptide in the lock therapy of catheters infected with S. epidermidis.

Staphylococcus epidermidis as a cause of bacteremia

Staphylococcus epidermidis is a biofilm-producing commensal organism found ubiquitously on human skin and mucous membranes, as well as on animals and in the environment. Biofilm formation enables this organism to evade the host immune system. Colonization of percutaneous devices or implanted medical devices allows bacteria access to the bloodstream. Isolation of this organism from blood cultures may represent either contamination during the blood collection procedure or true bacteremia. S. epidermidis bloodstream infections may be indolent compared with other bacteria. Isolation of S. epidermidis from a blood culture may present a management quandary for clinicians. Over-treatment may lead to patient harm and increases in healthcare costs. There are numerous reports indicating the difficulty of predicting clinical infection in patients with positive blood cultures with this organism. No reliable phenotypic or genotypic algorithms currently exist to predict the pathogenicity of a S. epidermidis bloodstream infection. This review will discuss the latest advances in identification methods, global population structure, pathogenicity, biofilm formation, antimicrobial resistance and clinical significance of the detection of S. epidermidis in blood cultures. Previous studies that have attempted to discriminate between invasive and contaminating strains of S. epidermidis in blood cultures will be analyzed.

Antimicrobial peptides and their interaction with biofilms of medically relevant bacteria

Biofilm-associated infections represent one of the major threats of modern medicine. Biofilm-forming bacteria are encased in a complex mixture of extracellular polymeric substances (EPS) and acquire properties that render them highly tolerant to conventional antibiotics and host immune response. Therefore, there is a pressing demand of new drugs active against microbial biofilms. In this regard, antimicrobial peptides (AMPs) represent an option taken increasingly in consideration. After dissecting the peculiar biofilm features that may greatly affect the development of new antibiofilm drugs, the present article provides a general overview of the rationale behind the use of AMPs against biofilms of medically relevant bacteria and on the possible mechanisms of AMP-antibiofilm activity. An analysis of the interactions of AMPs with biofilm components, especially those constituting the EPS, and the obstacles and/or opportunities that may arise from such interactions in the development of new AMP-based antibiofilm strategies is also presented and discussed. This article is part of a Special Issue entitled: Antimicrobial Peptides edited by Karl Lohner and Kai Hilpert.

Copolymers of acrylonitrile with quaternizable thiazole and triazole side-chain methacrylates as potent antimicrobial and hemocompatible systems

A series of six copolymeric families, P(AN-co-MTAs) with various molar fractions of acrylonitrile (fAN) and methacrylates (fMTA) based on 1,3-thiazole and 1,2,3-triazole pendant groups with several spacers of different length and nature (alkyl or succinic), have been synthesized by conventional radical polymerization. The molar fraction of acrylonitrile in the copolymers (FAN) was determined by CHNS elemental analysis. The copolymers were also characterized by ATR-FTIR and molecular weights were determined by size exclusion chromatography (SEC). Due to the nucleophilic nature of the azole heterocycles the copolymers have been easily modified by N-alkylation reaction with butyl iodide leading to polyelectrolytes of diverse amphiphilic balance, P(AN-co-MTAs-BuI). The degree of quaternization (DQ) was quantitative in all instances and was determined by (1)H NMR spectroscopy. Dynamic light scattering (DLS) measurements were performed in order to determine the particle size and the charge density of the systems. The antimicrobial activity of the copolymers was studied in terms of minimal inhibitory concentration (MIC) against the Gram-positive bacteria Staphylococcus aureus, the Gram-negative Pseudomonas aeruginosa and the yeast Candida parapsilosis, as well as the cytotoxic activity toward human red blood cells (RBCs). These types of amphiphilic copolycations presented high selectivity (>300) maintaining moderate to good antimicrobial activity (MIC=4-64 μg/mL) and being non-hemolytic even at high molar fractions of AN in the copolymers compared to PMTAs-BuI homopolymers. Moreover, two examples of acrylonitrile-enriched copolymers (FAN=0.6) presented an excellent time-killing efficiency against microorganisms with 99.9% of killing ranging from 5 to 30 min. Besides, important changes in the morphology of the cell envelop of the microorganisms after treatment with P(AN-co-MTAs) were observed by Field Emission Scanning Electron Microscopy (FE-SEM) compared to untreated samples. These results indicate that these quaternized copolymers (QUATs) behave like the corresponding PMTAs-BuI homopolymers, being microbiostatic and also highly effective microbiocidal agents.

Chitosan nanoparticles loaded with the antimicrobial peptide temporin B exert a long-term antibacterial activity in vitro against clinical isolates of Staphylococcus epidermidis

Nowadays, the alarming rise in multidrug-resistant microorganisms urgently demands for suitable alternatives to current antibiotics. In this regard, antimicrobial peptides (AMPs) have received growing interest due to their broad spectrum of activities, potent antimicrobial properties, unique mechanisms of action, and low tendency to induce resistance. However, their pharmaceutical development is hampered by potential toxicity, relatively low stability and manufacturing costs. In the present study, we tested the hypothesis that the encapsulation of the frog-skin derived AMP temporin B (TB) into chitosan nanoparticles (CS-NPs) could increase peptide's antibacterial activity, while reducing its toxic potential. TB-loaded CS-NPs with good dimensional features were prepared, based on the ionotropic gelation between CS and sodium tripolyphosphate. The encapsulation efficiency of TB in the formulation was up to 75%. Release kinetic studies highlighted a linear release of the peptide from the nanocarrier, in the adopted experimental conditions. Interestingly, the encapsulation of TB in CS-NPs demonstrated to reduce significantly the peptide's cytotoxicity against mammalian cells. Additionally, the nanocarrier evidenced a sustained antibacterial action against various strains of Staphylococcus epidermidis for at least 4 days, with up to 4-log reduction in the number of viable bacteria compared to plain CS-NPs at the end of the observational period. Of note, the antimicrobial evaluation tests demonstrated that while the intrinsic antimicrobial activity of CS ensured a "burst" effect, the gradual release of TB further reduced the viable bacterial count, preventing the regrowth of the residual cells and ensuring a long-lasting antibacterial effect. The developed nanocarrier is eligible for the administration of several AMPs of therapeutic interest with physical-chemical characteristics analog to those of TB.

A molecular description of cellulose biosynthesis

Cellulose is the most abundant biopolymer on Earth, and certain organisms from bacteria to plants and animals synthesize cellulose as an extracellular polymer for various biological functions. Humans have used cellulose for millennia as a material and an energy source, and the advent of a lignocellulosic fuel industry will elevate it to the primary carbon source for the burgeoning renewable energy sector. Despite the biological and societal importance of cellulose, the molecular mechanism by which it is synthesized is now only beginning to emerge. On the basis of recent advances in structural and molecular biology on bacterial cellulose synthases, we review emerging concepts of how the enzymes polymerize glucose molecules, how the nascent polymer is transported across the plasma membrane, and how bacterial cellulose biosynthesis is regulated during biofilm formation. Additionally, we review evolutionary commonalities and differences between cellulose synthases that modulate the nature of the cellulose product formed.

Photodynamic inactivation induced by carboxypterin: a novel non-toxic bactericidal strategy against planktonic cells and biofilms of Staphylococcus aureus

Microbial related contamination is of major concern and can cause substantial economic losses. Photodynamic inactivation (PDI) has emerged as a suitable approach to inhibit microorganism proliferation. In this work, PDI induced by 6-carboxypterin (Cap), a biocompatible photosensitizer (PS), was analyzed. The growth inhibition of Staphylococcus aureus exposed to artificial UV-A radiation and sunlight in the presence of Cap was investigated. After UV-A irradiation, 50 μM Cap was able to decrease by three orders (with respect to the initial value) the number of S. aureus cells in early biofilms. However, this concentration was 500 times higher than that needed for eradicating planktonic cells. Importantly, under solar exposure, 100 μM Cap was able to suppress sessile bacterial growth. Thus, this strategy is able to exert a bactericidal effect on sessile bacteria and to eradicate planktonic cells by exposing the Cap-containing sample to sunlight.

Microbial composition and antibiotic resistance of biofilms recovered from endotracheal tubes of mechanically ventilated patients

In critically ill patients, breathing is impaired and mechanical ventilation, using an endotracheal tube (ET) connected to a ventilator, is necessary. Although mechanical ventilation is a life-saving procedure, it is not without risk. Because of several reasons, a biofilm often forms at the distal end of the ET and this biofilm is a persistent source of bacteria which can infect the lungs, causing ventilator-associated pneumonia (VAP). There is a link between the microbial flora of ET biofilms and the microorganisms involved in the onset of VAP. Culture dependent and independent techniques were already used to identify the microbial flora of ET biofilms and also, the antibiotic resistance of microorganisms obtained from ET biofilms was determined. The ESKAPE pathogens play a dominant role in the onset of VAP and these organisms were frequently identified in ET biofilms. Also, antibiotic resistant microorganisms were frequently present in ET biofilms. Members of the normal oral flora were also identified in ET biofilms but it is thought that these organisms initiate ET biofilm formation and are not directly involved in the development of VAP.

Antimicrobial polymethacrylates based on quaternized 1,3-thiazole and 1,2,3-triazole side-chain groups

Increasing antimicrobial and non-hemotoxic characteristics of polymers bearing thiazole and triazole groups by the appropriate selection of spacer and quaternization groups.

Discovery of quinoline small molecules with potent dispersal activity against methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis biofilms using a scaffold hopping strategy

Staphylococcus aureus and Staphylococcus epidermidis are recognized as the most frequent cause of biofilm-associated nosocomial and indwelling medical device infections. Biofilm-associated infections are known to be highly resistant to our current arsenal of clinically used antibiotics and antibacterial agents. To exacerbate this problem, no therapeutic option exists that targets biofilm-dependent machinery critical to Staphylococcal biofilm formation and maintenance. Here, we describe the discovery of a series of quinoline small molecules that demonstrate potent biofilm dispersal activity against methicillin-resistant S. aureus and S. epidermidis using a scaffold hopping strategy. This interesting class of quinolines also has select synthetic analogues that demonstrate potent antibacterial activity and biofilm inhibition against S. aureus and S. epidermidis.