Prevalence of virulence- and antibiotic resistance-associated genotypes and phenotypes in Staphylococcus aureus strains from the food sector compared to clinical and cow mastitis isolates

Background

Infections by the pathogen Staphylococcus aureus currently represent one of the most serious threats to human health worldwide, especially due to the production of enterotoxins and the ability to form biofilms. These structures and the acquisition of antibiotic resistance limit the action of antibiotics and disinfectants used to combat this microorganism in the industry and the clinic.

Methods

This work reports a comparative phenotypic and genotypic study of 18 S. aureus strains from different origins: clinical samples, milk from mastitic cows and food industry surfaces, most of which were isolated in Northern Spain.

Results

Genetically, the strains were very diverse but, in most cases, a closer proximity was observed for those from the same source. Notably, the average number of virulence genes was not significantly different in strains from the food sector. Of the 18 strains, 10 coded for at least one enterotoxin, and four of them carried 6 or 7 enterotoxin genes. The latter were all veterinary or clinical isolates. Most strains carried prophages, plasmids and/or pathogenicity islands. Regarding antibiotic resistance, although phenotypically all strains showed resistance to at least one antibiotic, resistance genes were only identified in 44.5% of strains, being mastitis isolates those with the lowest prevalence. Virulence-related phenotypic properties such as haemolytic activity, staphyloxanthin production, biofilm-forming capacity and spreading ability were widely distributed amongst the isolates.

Conclusions

Our results indicate that production of virulence factors, antibiotic resistance and biofilm formation can be found in S. aureus isolates from diverse environments, including the food industry, although some of these traits are more prevalent in strains isolated from infections in cows or humans. This emphasizes on the importance of monitoring the spread of these determinants not only in samples from the clinical environment, but also along the food chain, a strategy that falls under the prism of a one-health approach.

Phage Lytic Protein CHAPSH3b Encapsulated in Niosomes and Gelatine Films

Antimicrobial resistance (AMR) has emerged as a global health challenge, sparking worldwide interest in exploring the antimicrobial potential of natural compounds as an alternative to conventional antibiotics. In recent years, one area of focus has been the utilization of bacteriophages and their derivative proteins. Specifically, phage lytic proteins, or endolysins, are specialized enzymes that induce bacterial cell lysis and can be efficiently produced and purified following overexpression in bacteria. Nonetheless, a significant limitation of these proteins is their vulnerability to certain environmental conditions, which may impair their effectiveness. Encapsulating endolysins in vesicles could mitigate this issue by providing added protection to the proteins, enabling controlled release, and enhancing their stability, particularly at temperatures around 4 °C. In this work, the chimeric lytic protein CHAPSH3b was encapsulated within non-ionic surfactant-based vesicles (niosomes) created using the thin film hydrating method (TFH). These protein-loaded niosomes were then characterized, revealing sizes in the range of 30-80 nm, zeta potentials between 30 and 50 mV, and an encapsulation efficiency (EE) of 50-60%. Additionally, with the objective of exploring their potential application in the food industry, these endolysin-loaded niosomes were incorporated into gelatine films. This was carried out to evaluate their stability and antimicrobial efficacy against Staphylococcus aureus.

NKG2D-CAR memory T cells target pediatric T-cell acute lymphoblastic leukemia in vitro and in vivo but fail to eliminate leukemia initiating cells

Introduction

Refractory/relapsed pediatric acute leukemia are still clinically challenging and new therapeutic strategies are needed. Interactions between Natural Killer Group 2D (NKG2D) receptor, expressed in cytotoxic immune cells, and its ligands (NKG2DL), which are upregulated in leukemic blasts, are important for anti-leukemia immunosurveillance. Nevertheless, leukemia cells may develop immunoescape strategies as NKG2DL shedding and/or downregulation.

Methods

In this report, we analyzed the anti-leukemia activity of NKG2D chimeric antigen receptor (CAR) redirected memory (CD45RA-) T cells in vitro and in a murine model of T-cell acute lymphoblastic leukemia (T-ALL). We also explored in vitro how soluble NKG2DL (sNKG2DL) affected NKG2D-CAR T cells' cytotoxicity and the impact of NKG2D-CAR T cells on Jurkat cells gene expression and in vivo functionality.

Results

In vitro, we found NKG2D-CAR T cells targeted leukemia cells and showed resistance to the immunosuppressive effects exerted by sNKG2DL. In vivo, NKG2D-CAR T cells controlled T cell leukemia burden and increased survival of the treated mice but failed to cure the animals. After CAR T cell treatment, Jurkat cells upregulated genes related to proliferation, survival and stemness, and in vivo, they exhibited functional properties of leukemia initiating cells.

Discussion

The data here presented suggest, that, in combination with other therapeutic approaches, NKG2D-CAR T cells could be a novel treatment for pediatric T-ALL.

Impact of the calcium concentration on the efficacy of phage phiIPLA-RODI, LysRODIΔAmi and nisin for the elimination of Staphylococcus aureus during lab-scale cheese production

Staphylococcus aureus is a Gram-positive human opportunistic pathogen that may also cause food poisoning because of the ability of some strains to produce heat stable enterotoxins that can persist in food even after the pathogen is successfully eliminated. In this context, biopreservation may be a forward-looking strategy to help eliminate staphylococcal contamination in dairy products by using natural compounds. However, these antimicrobials exhibit individual limitations that may be overcome by combining them. This work investigates the combination of a virulent bacteriophage, phiIPLA-RODI, a phage-derived engineered lytic protein, LysRODIΔAmi, and the bacteriocin nisin for the elimination of S. aureus during lab-scale cheese production at two CaCl₂ concentrations (0.2 % and 0.02 %), and subsequent storage at two different temperatures (4 °C and 12 °C). In most of the assayed conditions, our results demonstrate that the combined action of the antimicrobials led to a greater reduction of the pathogen population than the compounds individually, albeit this effect was additive and not synergistic. However, our results did show synergy between the three antimicrobials for reducing the bacterial load after 14 days of storage at 12 °C, temperature at which there is growth of the S. aureus population. Additionally, we tested the impact of the calcium concentration on the activity of the combination treatment and observed that higher CaCl₂ levels led to a notable increase in endolysin activity that allowed the utilization of approximately 10-times less protein to attain the same efficacy. Overall, our data show that the combination of LysRODIΔAmi with nisin and/or phage phiIPLA-RODI, and an increase in the calcium concentration are successful strategies to decrease the amount of protein required for the control of S. aureus contamination in the dairy sector with a low potential for resistance selection, thereby reducing costs.

Tuning the carrier injection barrier of hybrid metal-organic interfaces on rare earth-gold surface compounds

Magnetic hybrid metal-organic interfaces possess a great potential in areas such as organic spintronics and quantum information processing. However, tuning their carrier injection barriers on-demand is fundamental for the implementation in technological devices. We have prepared hybrid metal-organic interfaces by the adsorption of copper phthalocyanine CuPc on REAu₂ surfaces (RE = Gd, Ho and Yb) and studied their growth, electrostatics and electronic structure. CuPc exhibits a long-range commensurability and a vacuum level pinning of the molecular energy levels. We observe a significant effect of the RE valence of the substrate on the carrier injection barrier of the hybrid metal-organic interface. CuPc adsorbed on trivalent RE-based surfaces (HoAu₂ and GdAu₂) exhibits molecular level energies that may allow injection carriers significantly closer to an ambipolar injection behavior than in the divalent case (YbAu₂).

Self-Standing Bioinspired Polymer Films Doped with Ultrafine Silver Nanoparticles as Innovative Antimicrobial Material

Thin self-standing films with potential antimicrobial synergistic activity have been produced by a simple green chemical synthesis with overnight thermal treatment. Their properties have been studied by scanning electron microscopy, X-ray photoelectron spectroscopy and other techniques to understand their potential range of applications. In this work, the focus was set on the development of a potential novel and effective alternative to conventional antimicrobial materials. By creating an antimicrobial polymer blend, and using it to develop and immobilize fine (~25 nm) silver nanophases, we further aimed to exploit its film-forming properties and create a solid composite material. The resulting polymer matrix showed improved water uptake percentage and better stability in the presence of water. Moreover, the antimicrobial activity of the films, which is due to both organic and inorganic components, has been evaluated by Kirby-Bauer assay against common foodborne pathogens (Staphylococcus aureus and Salmonella enterica) and resulted in a clear inhibition zone of 1.2 cm for the most complex nanocomposition. The excellent performance against bacteria of fresh and 6-month-old samples proves the prospects of this material for the development of smart and biodegradable food packaging applications.

Assessment of humoral immune response to two mRNA SARS-CoV-2 VACCINES (Moderna and Pfizer) in healthcare workers fully vaccinated with and without a history of previous infection

Aims

Presence of anti‐S1 region of SARS‐CoV‐2 spike protein was analysed, at two and eight months, in 477 immunocompetent healthcare workers in Zaragoza, Spain, vaccinated with mRNA‐1273 (Moderna) or BNT162b2 (Pfizer).

Methods and results

Antibody analysis was performed with Alinity i System (Abbott). At 2 months, 100% of vaccinated had anti‐S1 IgG (mean = 13,285 AU ml⁻¹). This value was significantly higher with Moderna (18,192 AU ml⁻¹) than with Pfizer (10,441 AU ml⁻¹). The mean value of anti‐S1 IgG after vaccination was significantly higher in patients with than without previous infection (18,539 vs. 7919 AU ml⁻¹); in both groups was significantly higher with Moderna than with Pfizer (21,881 vs. 15,733 AU ml⁻¹ and 11,949 vs. 6387 AU ml⁻¹), respectively. At 8 months, 100% of patients were IgG positive, with higher levels with Moderna than with Pfizer. Nevertheless, in ensemble of cases, a mean decrease of antibody levels of 11,025 AU ml⁻¹ was observed.

Conclusion

At 2 and 8 months after vaccination, IgG response persists with both vaccines but with important decrease which suggests the need for revaccination.

Significance and impact of study

The study contributes to know the immune status after vaccination with two of more used anti‐SARS‐CoV‐2 vaccines. This knowledge is important for establishing the best vaccination strategy

ASSESSMENT OF OCCUPATIONAL EXPOSURE IN THE MAIN PAEDIATRIC INTERVENTIONAL RADIOLOGY PROCEDURES

The aim of this study is to evaluate the personal dose equivalent Hp(10) in the most frequent (non-cardiac) paediatric interventional radiology (PIR) procedures: central venous catheters (CVC), hepatic/biliary and sclerotherapy interventions. i2 active solid-state dosemeters placed over the lead apron were used to monitor the exposure of three interventional radiologists over 18 months. A database was created to register all procedures performed by each radiologist (including the type of procedure and the kerma-area product, PKA). The mean Hp(10) per procedure for CVC, sclerotherapy and hepatic/biliary interventions was respectively 0.01 ± 0.01 mSv, 0.18 ± 0.13 mSv and 0.12 ± 0.06 mSv (k = 2). A similar value of Hp(10)/PKA was found despite the type of procedure or the patient weight (~10 μSv/Gy·cm2). There was high variability among individual interventions, probably due to the variable level of complexity, which led to uncertainties in the measurements' mean higher than those associated with the dosemeter's angular and energy dependence. i2 therefore proved suitable for monitoring Hp(10) in PIR procedures.

Mind the orthography: Revisiting the contribution of prereading phonological awareness to reading acquisition

Reading acquisition is based on a set of preliteracy skills that lay the foundation for future reading abilities. Phonological awareness-the ability to identify and manipulate the sound units of oral language-has been reported to play a central role in reading acquisition. However, current evidence is mixed with respect to its universal contribution to reading acquisition across orthographies. This longitudinal study examines the development and contribution of phonological awareness to early reading skills in Spanish, a transparent orthography. The results of a comprehensive battery of phonological awareness skills in a large sample of children (Time 1 n = 616, 296 females, mean age 5.6, from middle to high socioeconomic backgrounds; Time 2 n = 397) with no reading experience at study onset suggest that the development of phonological awareness is delayed in Spanish. Furthermore, our results show that phonological awareness does not contribute to the prediction of reading acquisition above and beyond other preliteracy skills. Letter knowledge indexes children's ability to identify phonemes and thus takes a more central role in the prediction of early reading skills. Therefore, we underscore the need to thoughtfully address the distinctive features of the reading acquisition process across orthographies, which should be taken into account in models of reading and learning to read. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Systematic analysis of putative phage-phage interactions on minimum-sized phage cocktails

The application of bacteriophages as antibacterial agents has many benefits in the “post-antibiotic age”. To increase the number of successfully targeted bacterial strains, phage cocktails, instead of a single phage, are commonly formulated. Nevertheless, there is currently no consensus pipeline for phage cocktail development. Thus, although large cocktails increase the spectrum of activity, they could produce side effects such as the mobilization of virulence or antibiotic resistance genes. On the other hand, coinfection (simultaneous infection of one host cell by several phages) might reduce the potential for bacteria to evolve phage resistance, but some antagonistic interactions amongst phages might be detrimental for the outcome of phage cocktail application. With this in mind, we introduce here a new method, which considers the host range and each individual phage-host interaction, to design the phage mixtures that best suppress the target bacteria while minimizing the number of phages to restrict manufacturing costs. Additionally, putative phage-phage interactions in cocktails and phage-bacteria networks are compared as the understanding of the complex interactions amongst bacteriophages could be critical in the development of realistic phage therapy models in the future.

Facing CAR T Cell Challenges on the Deadliest Paediatric Brain Tumours

Central nervous system (CNS) tumours comprise 25% of the paediatric cancer diagnoses and are the leading cause of cancer-related death in children. Current treatments for paediatric CNS tumours are far from optimal and fail for those that relapsed or are refractory to treatment. Besides, long-term sequelae in the developing brain make it mandatory to find new innovative approaches. Chimeric antigen receptor T cell (CAR T) therapy has increased survival in patients with B-cell malignancies, but the intrinsic biological characteristics of CNS tumours hamper their success. The location, heterogeneous antigen expression, limited infiltration of T cells into the tumour, the selective trafficking provided by the blood-brain barrier, and the immunosuppressive tumour microenvironment have emerged as the main hurdles that need to be overcome for the success of CAR T cell therapy. In this review, we will focus mainly on the characteristics of the deadliest high-grade CNS paediatric tumours (medulloblastoma, ependymoma, and high-grade gliomas) and the potential of CAR T cell therapy to increase survival and patients' quality of life.

Design and Selection of Engineered Lytic Proteins With Staphylococcus aureus Decolonizing Activity

Staphylococcus aureus causes various infections in humans and animals, the skin being the principal reservoir of this pathogen. The widespread occurrence of methicillin-resistant S. aureus (MRSA) limits the elimination and treatment of this pathogen. Phage lytic proteins have been proven as efficient antimicrobials against S. aureus. Here, a set of 12 engineered proteins based on endolysins were conceptualized to select the most optimal following a stepwise funnel approach assessing parameters including turbidity reduction, minimum inhibitory concentration (MIC), time-kill curves, and antibiofilm assays, as well as testing their stability in a broad range of storage conditions (pH, temperature, and ionic strength). The engineered phage lysins LysRODIΔAmi and ClyRODI-H5 showed the highest specific lytic activity (5 to 50 times higher than the rest), exhibited a shelf-life up to 6 months and remained stable at temperatures up to 50°C and in a pH range from 3 to 9. LysRODIΔAmi showed the lower MIC values against all staphylococcal strains tested. Both proteins were able to kill 6 log units of the strain S. aureus Sa9 within 5 min and could remove preformed biofilms (76 and 65%, respectively). Moreover, LysRODIΔAmi could prevent biofilm formation at low protein concentrations (0.15–0.6 μM). Due to its enhanced antibiofilm properties, LysRODIΔAmi was selected to effectively remove S. aureus contamination in both intact and disrupted keratinocyte monolayers. Notably, this protein did not demonstrate any toxicity toward human keratinocytes, even at high concentrations (22.1 μM). Finally, a pig skin ex vivo model was used to evaluate treatment of artificially contaminated pig skin using LysRODIΔAmi (16.5 μg/cm²). Following an early reduction of S. aureus, a second dose of protein completely eradicated S. aureus. Overall, our results suggest that LysRODIΔAmi is a suitable candidate as antimicrobial agent to prevent and treat staphylococcal skin infections.

Gram-Positive Pneumonia: Possibilities Offered by Phage Therapy

Pneumonia is an acute pulmonary infection whose high hospitalization and mortality rates can, on occasion, bring healthcare systems to the brink of collapse. Both viral and bacterial pneumonia are uncovering many gaps in our understanding of host–pathogen interactions, and are testing the effectiveness of the currently available antimicrobial strategies. In the case of bacterial pneumonia, the main challenge is antibiotic resistance, which is only expected to increase during the current pandemic due to the widespread use of antibiotics to prevent secondary infections in COVID-19 patients. As a result, alternative therapeutics will be necessary to keep this disease under control. This review evaluates the advantages of phage therapy to treat lung bacterial infections, in particular those caused by the Gram-positive bacteria Streptococcus pneumoniae and Staphylococcus aureus, while also highlighting the regulatory impediments that hamper its clinical use and the difficulties associated with phage research.

NKG2D-CAR-transduced natural killer cells efficiently target multiple myeloma

CAR-T-cell therapy against MM currently shows promising results, but usually with serious toxicities. CAR-NK cells may exert less toxicity when redirected against resistant myeloma cells. CARs can be designed through the use of receptors, such as NKG2D, which recognizes a wide range of ligands to provide broad target specificity. Here, we test this approach by analyzing the antitumor activity of activated and expanded NK cells (NKAE) and CD45RA- T cells from MM patients that were engineered to express an NKG2D-based CAR. NKAE cells were cultured with irradiated Clone9.mbIL21 cells. Then, cells were transduced with an NKG2D-4-1BB-CD3z-CAR. CAR-NKAE cells exhibited no evidence of genetic abnormalities. Although memory T cells were more stably transduced, CAR-NKAE cells exhibited greater in vitro cytotoxicity against MM cells, while showing minimal activity against healthy cells. In vivo, CAR-NKAE cells mediated highly efficient abrogation of MM growth, and 25% of the treated mice remained disease free. Overall, these results demonstrate that it is feasible to modify autologous NKAE cells from MM patients to safely express a NKG2D-CAR. Additionally, autologous CAR-NKAE cells display enhanced antimyeloma activity demonstrating that they could be an effective strategy against MM supporting the development of NKG2D-CAR-NK-cell therapy for MM.

[Palatine tonsil lymphoma: a pediatric case report]

Lymphoma is the most common childhood malignancy in the head and neck. The most common clinical manifestations of lymphoma in palatine tonsil are the tonsils asymmetry, alteration in the appearance of the mucous and cervical lymphadenopathy. The unilateral tonsillar hypertrophy must be differentiated with infectious processes, with chronic processes, other tumors or benign tonsillar hyperplasia. The monitoring of tonsillar hypertrophy is strict, because early diagnosis and treatment are of great importance in the prognosis of tonsillar lymphoma patients. A 14 year-old girl presents unilateral tonsillar enlargement and odynophagia. After 21 days of antibiotic treatment, she has not clinical improvement. The diagnosis is Burkitt's lymphoma. One year after diagnosis, she presents complete remission of the disease.

The relationship between the phageome and human health: are bacteriophages beneficial or harmful microbes?

In the context of the global antibiotic resistance crisis, bacteriophages are increasingly becoming promising antimicrobial agents against multi-resistant bacteria. Indeed, a huge effort is being made to bring phage-derived products to the market, a process that will also require revising the current regulations in order to facilitate their approval. However, despite the evidence supporting the safety of phages for humans, the general public would still be reluctant to use 'viruses' for therapeutic purposes. In this scenario, we consider that it is important to discuss the role of these microorganisms in the equilibrium of the microbiota and how this relates to human health. To do that, this review starts by examining the role of phages as key players in bacterial communities (including those that naturally inhabit the human body), modulating the species composition and contributing to maintain a 'healthy' status quo. Additionally, in specific situations, e.g. an infectious disease, bacteriophages can be used as target-specific antimicrobials against pathogenic bacteria (phage therapy), while being harmless to the desirable microbiota. Apart from that, incipient research shows the potential application of these viruses to treat diseases caused by bacterial dysbiosis. This latter application would be comparable to the use of probiotics or prebiotics, since bacteriophages can indirectly improve the growth of beneficial bacteria in the gastrointestinal tract by removing undesirable competitors. On the other hand, possible adverse effects do not appear to be an impediment to promote phage therapy. Nonetheless, it is important to remember their potentially negative impact, mainly concerning their immunogenicity or their potential spread of virulence and antibiotic resistance genes, especially by temperate phages. Overall, we believe that phages should be largely considered beneficial microbes, although it is paramount not to overlook their potential risks.

Natural killer cells efficiently target multiple myeloma clonogenic tumor cells

The multiple myeloma (MM) landscape has changed in the last few years, but most patients eventually relapse because current treatment modalities do not target clonogenic stem cells, which are drug-resistant and can self-renew. We hypothesized that side population (SP) cells represent myeloma clonogenic stem cells and, searching for new treatment strategies, analyzed the anti-myeloma activity of natural killer (NK) cells against clonogenic cells. Activated and expanded NK cells (NKAE) products were obtained by co-culturing NK cells from MM patients with K562-mb15-41BBL cell line and characterized by flow cytometry. Functional experiments against MM cells were performed by Eu-TDA release assays and methylcellulose clonogenic assays. Side population was detected by Dye Cycle Violet labeling and then characterized by flow cytometry and RNA-Seq. Self-renewal capacity was tested by clonogenic assays. Sorting of both kind of cells was performed for time-lapse microscopy experiments. SP cells exhibited self-renewal potential and overexpressed genes involved in stem cell metabolism. NK cells from MM patients exhibited dysregulation and had lower anti-tumor potential against clonogenic cells than healthy donors’ NK cells. Patients’ NK cells were activated and expanded. These cells recovered cytotoxic activity and could specifically destroy clonogenic myeloma cells. They also had a highly cytotoxic phenotype expressing NKG2D receptor. Blocking NKG2D receptor decreased NK cell activity against clonogenic myeloma cells, and activated NK cells were able to destroy SP cells, which expressed NKG2D ligands. SP cells could represent the stem cell compartment in MM. This is the first report describing NK cell activity against myeloma clonogenic cells.

Optimizing the Procedure to Manufacture Clinical-Grade NK Cells for Adoptive Immunotherapy

Simple Summary

Natural Killer cells have shown promise to treat different malignancies. Several methods have been described to obtain fully activated NK cells for clinical use. Here, we use different cell culture media and different artificial antigen presenting cells to optimize a GMP compliant manufacturing method to obtain activated and expanded NK cells suitable for clinical use.

Abstract

Natural killer (NK) cells represent promising tools for cancer immunotherapy. We report the optimization of an NK cell activation–expansion process and its validation on clinical-scale. Methods: RPMI-1640, stem cell growth medium (SCGM), NK MACS and TexMACS were used as culture mediums. Activated and expanded NK cells (NKAE) were obtained by coculturing total peripheral blood mononuclear cells (PBMC) or CD45RA⁺ cells with irradiated K562mbIL15-41BBL or K562mbIL21-41BBL. Fold increase, NK cell purity, activation status, cytotoxicity and transcriptome profile were analyzed. Clinical-grade NKAE cells were manufactured in CliniMACS Prodigy. Results: NK MACS and TexMACs achieved the highest NK cell purity and lowest T cell contamination. Obtaining NKAE cells from CD45RA⁺ cells was feasible although PBMC yielded higher total cell numbers and NK cell purity than CD45RA⁺ cells. The highest fold expansion and NK purity were achieved by using PBMC and K562mbIL21-41BBL cells. However, no differences in activation and cytotoxicity were found when using either NK cell source or activating cell line. Transcriptome profile showed to be different between basal NK cells and NKAE cells expanded with K562mbIL21-41BBL or K562mbIL15-41BBL. Clinical-grade manufactured NKAE cells complied with the specifications from the Spanish Regulatory Agency. Conclusions: GMP-grade NK cells for clinical use can be obtained by using different starting cells and aAPC.

Staphylococcal Biofilms: Challenges and Novel Therapeutic Perspectives

Staphylococci, like Staphylococcus aureus and S. epidermidis, are common colonizers of the human microbiota. While being harmless in many cases, many virulence factors result in them being opportunistic pathogens and one of the major causes of hospital-acquired infections worldwide. One of these virulence factors is the ability to form biofilms-three-dimensional communities of microorganisms embedded in an extracellular polymeric matrix (EPS). The EPS is composed of polysaccharides, proteins and extracellular DNA, and is finely regulated in response to environmental conditions. This structured environment protects the embedded bacteria from the human immune system and decreases their susceptibility to antimicrobials, making infections caused by staphylococci particularly difficult to treat. With the rise of antibiotic-resistant staphylococci, together with difficulty in removing biofilms, there is a great need for new treatment strategies. The purpose of this review is to provide an overview of our current knowledge of the stages of biofilm development and what difficulties may arise when trying to eradicate staphylococcal biofilms. Furthermore, we look into promising targets and therapeutic methods, including bacteriocins and phage-derived antibiofilm approaches.

Iron oxide-mediated photo-Fenton catalysis in the inactivation of enteric bacteria present in wastewater effluents at neutral pH

The pressure on natural water resources associated with increasing water scarcity highlights the value of using reclaimed water through the development of efficient and environmentally friendly treatment technologies. In this work, the use of magnetic nanoparticles in photo-Fenton catalysis for water disinfection was considered to inactivate natural enteric bacteria present in municipal wastewater effluents under white light and neutral pH. The most recommended ranges were evaluated in key variables such as the loading and composition of nanoparticles (NPs), hydrogen peroxide (H₂O₂) concentration, the light source (UV and visible) and treatment time were evaluated in wastewater disinfection expressed in terms of total coliforms and Escherichia coli colony forming units (CFU). The magnetic separation of NPs allowed the disinfection process to be carried out in different cycles, facilitating the recovery of the nanocatalyst and avoiding its discharge with the treated effluent.

VIP conditions human endometrial receptivity by privileging endoplasmic reticulum stress through ATF6α pathway

Endometrial stromal cells undergo endoplasmic reticulum (ER) stress and unfolded protein response (UPR) during the decidualization linked with the inflammation and angiogenesis processes. Considering VIP (vasoactive intestinal peptide) induces the decidualization program, we studied whether modulates the ER/UPR pathways to condition both processes for embryo implantation. When Human Endometrial Stromal Cell line (HESC) were decidualized by VIP we observed an increased expression of ATF6α, an ER stress-sensor, and UPR markers, associated with an increase in IL-1β production. Moreover, AEBSF (ATF6α -inhibitor pathway) prevented this effect and decreased the expansion index in the in vitro model of implantation. VIP-decidualized cells also favor angiogenesis accompanied by a strong downregulation in thrombospondin-1. Finally, ATF6α, VIP and VPAC2-receptor expression were reduced in endometrial biopsies from women with recurrent implantation failures in comparison with fertile. In conclusion, VIP privileged ATF6α-pathway associated with a sterile inflammatory response and angiogenesis that might condition endometrial receptivity.

Environmental pH is a key modulator of Staphylococcus aureus biofilm development under predation by the virulent phage phiIPLA-RODI

Previous work had shown that, in some Staphylococcus aureus strains, low concentrations of the virulent phage vB_SauM_phiIPLA-RODI (phiIPLA-RODI) promoted the formation of DNA-rich biofilms, whose cells exhibited significant transcriptional differences compared to an uninfected control. This study aimed to dissect the sequence of events leading to these changes. Analysis of phage propagation throughout biofilm development revealed that the number of phage particles increased steadily up to a certain point and then declined. This partial phage inactivation seemed to be a consequence of medium acidification due to glucose fermentation by the bacterium. Computer simulation of phage-host dynamics during biofilm development showed how even small differences in pH evolution can affect the outcome of phage infection. An acidic pH, together with successful phage propagation, was also necessary to observe the phage-associated changes in biofilm architecture and in the transcriptional profile of the bacterial population. Altogether, this study shows how the dynamics between phage and host can be tightly coordinated through an environmental cue, even in the context of a complex biofilm population.

Encapsulation of the Antistaphylococcal Endolysin LysRODI in pH-Sensitive Liposomes

Phage lysins are promising new therapeutics against multidrug-resistant bacteria. These so-called enzybiotics offer, amongst their most notable advantages, high target specificity and low resistance development. Moreover, there are numerous recent and ongoing studies aimed at demonstrating the efficacy and safety of endolysins in animal models or even in clinical trials. Nonetheless, as is the case for other antimicrobials, it is important to assess potential strategies that may broaden their potential applications or improve their stability. Encapsulation, for instance, has given very good results for some antibiotics. This study sought to evaluate the feasibility of encapsulating an endolysin against the opportunistic human pathogen Staphylococcus aureus, one of the most problematic bacteria in the context of the current antibiotic resistance crisis. Endolysin LysRODI has antimicrobial activity against many S. aureus strains from different sources, including methicillin-resistant S. aureus (MRSA) isolates. Here, this protein was encapsulated in pH-sensitive liposomes with an efficacy of approximately 47%, retaining its activity after being released from the nanocapsules. Additionally, the encapsulated endolysin effectively reduced S. aureus cell counts by > 2log units in both planktonic cultures and biofilms upon incubation at pH 5. These results demonstrate the viability of LysRODI encapsulation in liposomes for its targeted delivery under mild acidic conditions.

Haemophilus influenzae type b invasive infections in children hospitalized between 2000 and 2017 in a Pediatric Reference Hospital (PRH)

Background

Uruguay incorporated the conjugate vaccine against Haemophilus influenzae b (Hib) in 1994. In 2008, the vaccine was changed from one with natural conjugated capsular polysaccharide to one with a synthetic polysaccharide component. We describe the frequency and characteristics of invasive Hib infections in children hospitalized in a Pediatric Reference Hospital (PRH) between January 1st, 2000 and December 31st, 2017.

Methods

Sterile site Hib isolations from hospitalized children were included. Clinical and microbiological characteristics were analyzed. Favorable conditions for the infection were considered: incomplete immunization, immunodeficiencies and associated pathologies. Two periods are described: 1, prior to vaccine change (1/1 st/2000- 12/31/08) and 2, post-change (1/1 st/09- 12/31st/17).

Results

45 children were hospitalized: 5 in the first period and 40 in the second. The hospitalization rate per 10,000 discharges was 0.41 (95% CI 0.05–0.77) and 4.2/10,000 (95% CI 2.89–5.48), respectively (p < 0.01). The diagnoses at discharge were: meningitis/ventriculitis (20), pneumonia (16), bacteremia (3), epiglottitis (1), arthritis (1), cellulitis (3) and obstruction of the upper airway (1). Four children presented comorbidities. Twenty seven received less than 3 doses of anti-Hib vaccination and 18 were properly vaccinated (2 were immunodeficient). The median hospitalization was 14 days, 18 children required intensive therapy.

Conclusions

Observed change may be due to: incomplete primary series, inhomogeneous vaccine coverage and immunogenicity of the synthetic polysaccharide. To reduce this public health problem, epidemiological surveillance.

Local diagnostic reference levels for paediatric non-cardiac interventional radiology procedures

PURPOSE

To establish local diagnostic reference levels (DRLs) for non-cardiac interventional procedures in paediatrics.

METHODS

The type of procedure, the patient's weight and age and dose-related data from 279 interventions was recorded in a database completed by interventional radiologists, radiographers and technicians of the Medical Physics department. These procedures were classified into 14 categories and 6 weight ranges. Local DRLs were proposed for those ranges in which a sample of at least 15 patients could be gathered and were calculated as the third quartile (Q3) of the air kerma-area product (P_KA) values. The Q3 of the fluoroscopy time (FT) and number of digital subtraction angiography (DSA) images were also obtained. Finally, the correlation between P_KA and weight was analysed.

RESULTS

Local DRLs are proposed for three types of procedures: hepatic/biliary interventions (5-15 kg, 1304 cGy·cm²; 15-30 kg, 2121 cGy·cm²), sclerotherapy procedures (15-30 kg, 704 cGy·cm²; 30-50 kg, 4049 cGy·cm²; 50-80 kg, 3734 cGy·cm²) and central venous catheter (CVC) procedures (5-15 kg, 84 cGy·cm²). Hepatic/biliary interventions showed a moderate correlation (r = 0.61), while sclerotherapy procedures presented a poor correlation (r = 0.34) between P_KA and weight, possibly due to the P_KA dependence on the complexity level. Regarding CVC procedures, a clearly higher correlation was found when the fluoroscopy P_KA value was normalised to the FT (r = 0.85 vs r = 0.35).

CONCLUSIONS

The results support the feasibility of establishing DRLs for the most common procedures (sclerotherapy, hepatic/biliary and CVC interventions) despite the small number of paediatric interventions.

Phage Lytic Protein LysRODI Prevents Staphylococcal Mastitis in Mice

Phage lytic proteins are promising antimicrobials that could complement conventional antibiotics and help to combat multi-drug resistant bacteria that cause important human and animal infections. Here, we report the characterization of endolysin LysRODI (encoded by staphylophage phiIPLA-RODI) and its application as a prophylactic mastitis treatment. The main properties of LysRODI were compared with those of endolysin LysA72 (encoded by staphylophage phiIPLA35) and the chimeric protein CHAPSH3b (derived from the virion-associated peptidoglycan hydrolase HydH5 and lysostaphin). Time-kill experiments performed with Staphylococcus aureus and Staphylococcus epidermidis demonstrated that the killing rate of LysRODI and CHAPSH3b is higher than that of LysA72 (0.1 μM protein removed 10⁷ CFU/ml of S. aureus in 30 min). Of note, all proteins failed to select resistant mutants as bacterial exposure to sub-lethal concentrations of the proteins did not alter the MIC values. Additionally, LysRODI and CHAPSH3b were non-toxic in a zebrafish embryo model at concentrations near the MIC (0.5 and 0.7 μM, respectively). Moreover, these two proteins significantly reduced mortality in a zebrafish model of systemic infection. In contrast to LysRODI, the efficacy of CHAPSH3b was dose-dependent in zebrafish, requiring higher-dose treatments to achieve the maximum survival rate. For this reason, LysRODI was selected for further analysis in mice, demonstrating great efficacy to prevent mammary infections by S. aureus and S. epidermidis. Our findings strongly support the use of phage lytic proteins as a new strategy to prevent staphylococcal mastitis.

[Identification of ICF categories representative of functioning problems in adult cancer patients at hospital discharge: National expert consensus]

INTRODUCTION

The International Classification of Functioning, Disability and Health (ICF) provides a standardised language and conceptual framework for health and health-related conditions, aiming to unify communication between different disciplines.

OBJECTIVE

To describe the process of selecting (through national expert consensus) ICF categories representative of functioning problems in cancer patients at hospital discharge.

METHOD

We conducted a descriptive qualitative and quantitative study that used the expert consensus method to design a clinical instrument. The study included 21 experts, consisting of 2 patients and 19 health professionals from different disciplines. A total of 208 ICF categories obtained in a previous stage through a systematic review and linking process were evaluated in 3 rounds. Participants evaluated each code and classified it as: highly relevant, relevant, slightly relevant, and not relevant at all. Only those codes assessed as «highly relevant» by more than 50% of the experts were included (cut off). In addition, another 143 ICF categories were evaluated in the second round.

RESULTS

In all, 24 ICF categories were obtained: 10 corresponded to the body function component, 11 to activities and participation, and 3 to environmental factors.

CONCLUSIONS

Consensus using the common language of the ICF resulted in the selection of 24 representative categories of the main health problems related to functioning at hospital discharge in adults treated for cancer.

[Secondary glomerulonephritis in neurofibromatosis type 1. Two case reports]

Neurofibromatosis type 1 (NF-1) is an autosomal dominant neurocutaneous disorder with systemic clinical manifestations. There are few publications about the renal effects of this disease, with renal vascular disease and adrenal tumors being the most frequent forms of renal involvement, while cases describing glomerular effects are exceptional. Despite the lack of published information, common molecular mechanisms in both NF-1 and nephrotic syndrome, involving the mTOR pathway, were suggested to explain a possible association between both pathologies. We present two cases of renal involvement in the form of nephrotic syndrome in patients diagnosed with NF1. A 41-year-old female was diagnosed of NF-1 in the context of a nephrotic syndrome with resistance to steroid treatment; the renal biopsy revealed a diagnosis of minimal changes disease. The second case is other 71-year-old woman with a history of NF-1, who presented a nephrotic syndrome and secondary renal amyloidosis.

[Recurrent orbital complication by rhinosinusitis. A case report]

Orbital infection is the most frequent complication of ethmoiditis. Recurrent periorbital cellulitis is a very rare complication of rhinosinusitis with only three reports in the literature describing this pathological process. This complication can be favored by an anatomical abnormality of the uncinate process or mucocele obstructing the normal drainage pathway, in addition to ethmoidal sinusitis. Computed tomography and magnetic resonance guide the diagnosis. The treatment is based on antibiotics, corticosteroids and local decongestants. Surgical treatment is indicated in the absence of response to treatment established after 48 hours or decrease in visual acuity or recurrent orbital complications without underlying tumor pathology. In this report, we present a case of orbital complication of rhinosinusitis in a 4 year-old-child with six episodes of unilateral periorbital cellulitis and one episode of subperiosteal orbital abscess since the age of 3 months. There was a complete resolution with no recurrence after the surgical intervention.

GMP-Compliant Manufacturing of NKG2D CAR Memory T Cells Using CliniMACS Prodigy

Natural killer group 2D (NKG2D) is a natural killer (NK) cell-activating receptor that recognizes different stress-induced ligands that are overexpressed in a variety of childhood and adult tumors. NKG2D chimeric antigen receptor (CAR) T cells have shown potent anticancer effects against different cancer types. A second-generation NKG2D CAR was generated by fusing full-length human NKG2D to 4-1BB costimulatory molecule and CD3ζ signaling domain. Patient-derived CAR T cells show limitations including inability to manufacture CAR T cells from the patients' own T cells, disease progression, and death prior to return of engineered cells. The use of allogeneic T cells for CAR therapy could be an attractive alternative, although undesirable graft vs. host reactions may occur. To avoid such adverse effects, we used CD45RA⁻ memory T cells, a T-cell subset with less alloreactivity, as effector cells to express NKG2D CAR. In this study, we developed a protocol to obtain large-scale NKG2D CAR memory T cells for clinical use by using CliniMACS Prodigy, an automated closed system compliant with Good Manufacturing Practice (GMP) guidelines. CD45RA⁺ fraction was depleted from healthy donors' non-mobilized apheresis using CliniMACS CD45RA Reagent and CliniMACS Plus device. A total of 10⁸ CD45RA⁻ cells were cultured in TexMACS media supplemented with 100 IU/mL IL-2 and activated at day 0 with T Cell TransAct. Then, we used NKG2D-CD8TM-4-1BB-CD3ζ lentiviral vector for cell transduction (MOI = 2). NKG2D CAR T cells expanded between 10 and 13 days. Final cell products were analyzed to comply with the specifications derived from the quality and complementary controls carried out in accordance with the instructions of the Spanish Regulatory Agency of Medicines and Medical Devices (AEMPS) for the manufacture of investigational advanced therapy medicinal products (ATMPs). We performed four validations. The manufacturing protocol here described achieved large numbers of viable NKG2D CAR memory T cells with elevated levels of NKG2D CAR expression and highly cytotoxic against Jurkat and 531MII tumor target cells. CAR T cell final products met release criteria, except for one showing myc overexpression and another with viral copy number higher than five. Manufacturing of clinical-grade NKG2D CAR memory T cells using CliniMACS Prodigy is feasible and reproducible, widening clinical application of CAR T cell therapies.

Use of physiological information based on grayscale images to improve mass spectrometry imaging data analysis from biological tissues

The characterization of cancer tissues by matrix-assisted laser desorption ionization-mass spectrometry images (MALDI-MSI) is of great interest because of the power of MALDI-MS to understand the composition of biological samples and the imaging side that allows for setting spatial boundaries among tissues of different nature based on their compositional differences. In tissue-based cancer research, information on the spatial location of necrotic/tumoral cell populations can be approximately known from grayscale images of the scanned tissue slices. This study proposes as a major novelty the introduction of this physiologically-based information to help in the performance of unmixing methods, oriented to extract the MS signatures and distribution maps of the different tissues present in biological samples. Specifically, the information gathered from grayscale images will be used as a local rank constraint in Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) for the analysis of MALDI-MSI of cancer tissues. The use of this constraint, setting absence of certain kind of tissues only in clear zones of the image, will help to improve the performance of MCR-ALS and to provide a more reliable definition of the chemical MS fingerprint and location of the tissues of interest. The general strategy to address the analysis of MALDI-MSI of cancer tissues will involve the study of the MCR-ALS results and the posterior use of MCR-ALS scores as dimensionality reduction for image segmentation based on K-means clustering. The resolution method will provide the MS signatures and their distribution maps for each tissue in the sample. Then, the resolved distribution maps for each biological component (MCR scores) will be submitted as initial information to K-means clustering for image segmentation to obtain information on the boundaries of the different tissular regions in the samples studied. MCR-ALS prior to K-means not only provides the desired dimensionality reduction, but additionally resolved non-biological signal contributions are not used and the weight given to the different biological components in the segmentation process can be modulated by suitable preprocessing methods.

The Perfect Bacteriophage for Therapeutic Applications-A Quick Guide

The alarming spread of multiresistant infections has kick-started the quest for alternative antimicrobials. In a way, given the steady increase in untreatable infectious diseases, success in this endeavor has become a matter of life and death. Perhaps we should stop searching for an antibacterial panacea and explore a multifaceted strategy in which a wide range of compounds are available on demand depending on the specific situation. In the context of this novel tailor-made approach to combating bacterial pathogens, the once forgotten phage therapy is undergoing a revival. Indeed, the compassionate use of bacteriophages against seemingly incurable infections has been attracting a lot of media attention lately. However, in order to take full advantage of this strategy, bacteria's natural predators must be taken from their environment and then carefully selected to suit our needs. In this review, we have explored the vast literature regarding phage isolation and characterization for therapeutic purposes, paying special attention to the most recent studies, in search of findings that hint at the most efficient strategies to identify suitable candidates. From this information, we will list and discuss the traits that, at the moment, are considered particularly valuable in phages destined for antimicrobial therapy applications. Due to the growing importance given to biofilms in the context of bacterial infections, we will dedicate a specific section to those characteristics that indicate the suitability of a bacteriophage as an antibiofilm agent. Overall, the objective is not just to have a large collection of phages, but to have the best possible candidates to guarantee elimination of the target pathogens.

Anti-CXCR4 Antibody Combined With Activated and Expanded Natural Killer Cells for Sarcoma Immunotherapy

Sarcoma is one of the most severe forms of pediatric cancer and current therapies -chemotherapy and surgery- fail to eradicate the disease in half of patients. Preclinical studies combining new therapeutic approaches can be useful to design better therapies. On one hand, it is known that CXCR4 expression is implicated in rhabdomyosarcoma progression, so we analyzed relapses and chemotherapy-resistant rhabdomyosarcoma tumors from pediatric patients and found that they had particularly high levels of CXCR4 expression. Moreover, in assays in vitro, anti-CXCR4 blocking antibody (MDX1338) efficiently reduced migration and invasion of alveolar rhabdomyosarcoma RH30 cells. On the other hand, activated and expanded natural killer (NKAE) cell therapy showed high cytotoxicity against sarcoma cells in vitro and completely inhibited RH30 tumor implantation in vivo. Only the combination of MDX1338 and NKAE treatments completely suppressed metastasis in mice. In this study, we propose a novel therapeutic approach based on anti-CXCR4 blocking antibody in combination with NKAE cell therapy to prevent rhabdomyosarcoma tumor implantation and lung metastasis. These results provide the first evidence for the efficacy of this combined immunotherapy for preventing sarcoma disease dissemination.

Preliminary Assessment of Visible, Near-Infrared, and Short-Wavelength-Infrared Spectroscopy with a Portable Instrument for the Detection of Staphylococcus aureus Biofilms on Surfaces

Bacterial biofilms constitute a major source of sanitary problems and economic losses in the food industry. Indeed, biofilm removal may require intense mechanical cleaning procedures or very high concentrations of disinfectants or both, which can be damaging to the environment and human health. This study assessed the efficacy of a technique based on spectroscopy in the visible, near-infrared, and short-wavelength infrared range for the quick detection of biofilms formed on polystyrene by the pathogenic bacterium Staphylococcus aureus. To do that, biofilms corresponding to three S. aureus strains, which differed in biofilm-forming ability and composition of the extracellular matrix, were allowed to develop for 5 or 24 h, representing an active formation stage and mature biofilms, respectively. Spectral analysis of the samples, corresponding to three biological replicates of each condition, was then performed by using a portable device. The results of these experiments showed that partial least-squares discriminant analysis of the spectral profile could discriminate between surfaces containing attached bacterial biomass and noninoculated ones. In this model, the two first principal components accounted for 39 and 19% of the variance and the estimated error rate stabilized after four components. Cross-validation accuracy of this assessment was 100%. This work lays the foundation for subsequent development of a spectroscopy-based protocol that allows biofilm detection on food industrial surfaces.

Insight into antibiotics removal: Exploring the photocatalytic performance of a Fe3O4/ZnO nanocomposite in a novel magnetic sequential batch reactor

The purpose of this research was the preparation and photocatalytic evaluation of a novel nanocomposite (NC) based on Fe₃O₄/ZnO, to eliminate four persistent antibiotics in surface waters: sulfamethoxazole, trimethoprim, erythromycin and roxithromycin. Prior to the operation of the photocatalytic reactor, the influence of pH (3-9), catalyst concentration (50-800 mg L^-1), oxidant dose (0-100 mg L^-1) and concentration of different targets (10-100 μg L^-1) on the catalytic efficiency was evaluated. The analysis of reaction kinetics showed that degradation processes of the four antibiotics followed a pseudo-first-order kinetic model. Antibiotics adsorption onto the nanocomposite surface depended on their electrostatic nature and played an important role when decreasing the initial concentration of antibiotics. In this context, kinetic rates were higher at lower initial levels of organic pollutants, which is a favourable effect from a practical application perspective. On the other hand, a synergistic effect of the available Fe in the nanocomposite was found, contributing to the oxidation of antibiotics by photo-Fenton as a secondary reaction. Then, a magnetic photocatalytic reactor was operated under optimal conditions. The enhanced photonic efficiency of Fe₃O₄/ZnO in the system, as well as the ease of the magnetic separation and catalyst reusability, indicate the viability of this reactor configuration.

Thermal stability and interlayer exchange processes in heterolayers of TiOPc and PTCDA on Ag(1 1 1)

Organic-organic interfaces, in particular donor-acceptor type heterointerfaces, represent central elements of organic electronic devices. Understanding and controlling their physical properties is key to improve and modify their performance. For this purpose we have investigated the structural properties and thermal evolution of molecular heterointerface model systems. Specifically, various stacked titanyl-phthalocyanine (TiOPc)-3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) heterolayers grown on Ag(1 1 1) have been examined using Fourier transform infrared absorption spectroscopy and spot-profile analysis low-energy electron diffraction. An accurate description of the thermal evolution and prevalence of the various phases of TiOPc and PTCDA is derived from the spectral signatures of the two molecular species explored in previous studies. Exceptionally high thermal stability is found for stacked heterolayers comprising TiOPc double layers with characteristic up-down arrangement of its axial Ti-O unit and single layers of PTCDA. Thereby, interlayer exchange is negligible in a wide temperature range ([Formula: see text] K). This is ascribed to attractive intermolecular interaction (dipole-dipole interaction, hydrogen bonding) among the TiOPc molecules oriented face-to-face within the TiOPc bilayer sheet. Stacked layers of comprising single layers of TiOPc and of PTCDA turn out to be thermally much less stable and more heterogeneous. In the course of their thermal evolution, a number of processes such as interlayer exchange, TiOPc double-layer formation and dewetting are encountered.

Role of Bacteriophages in the Implementation of a Sustainable Dairy Chain

The growing human population is currently facing an unprecedented challenge regarding global food sustainability. Thus, it is of paramount to maintain food production and quality while avoiding a negative impact on climate change and the environment at large. Along the food chain, several practices could compromise future food safety and human health. One example is the widespread use of antibiotics and disinfectants in dairy production, which has contributed to the current antibiotic resistance crisis. Moreover, the uncontrolled release of antimicrobials to the environment poses a significant threat to natural ecosystems. For these reasons, research has recently focused on exploiting natural antimicrobials with the goal of achieving a safer and more sustainable dairy production chain. In this context, bacteriophages, viruses that infect bacteria, may become good allies to prevent and treat diseases in cattle, or be used as disinfectants in dairy facilities and as preservatives in dairy products. This review provides an overview of the current research regarding the use of phages as a global approach to reduce economic losses and food waste, while increasing food safety and reducing the environmental impact of food production. Our current understanding of progress, solutions, and future challenges in dairy production, processing, safety, waste processing, and quality assurance is also discussed.

Comparative analysis of different preservation techniques for the storage of Staphylococcus phages aimed for the industrial development of phage-based antimicrobial products

Bacteriophages have been proven as effective antimicrobial agents in the treatment of infectious diseases and in other biocontrol applications including food preservation and disinfection. The extensive use of bacteriophages requires improved methodologies for medium- and long-term storage as well as for easy shipping. To this aim, we have determined the stability of four Staphylococcus phages (phiIPLA88, phiIPLA35, phiIPLA-RODI and phiIPLA-C1C) with antimicrobial potential at different temperatures (20°C/25°C, 4°C, -20°C, -80°C, -196°C) and during lyophilization (freeze drying) using several stabilizing additives (disaccharides, glycerol, sorbitol and skim milk). Differences between phages were observed at different temperatures (20°C/25°C, 4°C and -20°C), where phages were less stable. At lower temperatures (-80°C and -196°C), all phages showed good viability after 24 months regardless of the stabilizer. Differences between phages were also observed after lyophilization although the addition of skim milk yielded a dry powder with a stable titer after 24 months. As an alternative to facilitate storage and transportation, phage encapsulation has been also explored. Phage phiIPLA-RODI encapsulated in alginate capsules retained high viability when stored at 4°C for 6 months and at 20°C for 1 month. Moreover, the spray-dryer technique allowed obtaining dry powders containing viable encapsulated phages (phiIPLA-RODI and phiIPLA88) in both skim milk and trehalose for 12 months at 4°C. Storage of phages at 20°C was less effective; in fact, phiIPLA88 was stable for at least 12 months in trehalose but not in skim milk, while phiIPLA-RODI was stable only for 6 months in either stabilizer. These results suggest that encapsulated phages might be a suitable way for shipping phages.

Analysis of Different Parameters Affecting Diffusion, Propagation and Survival of Staphylophages in Bacterial Biofilms

The elimination of bacterial biofilms remains a major challenge due to their recalcitrant nature. Bacteriophages, viruses that infect bacteria, have been gaining increasing attention as biofilm control agents. However, the development of a successful phage-based strategy requires in-depth analysis of different parameters. It is particularly important to determine the ability of a given phage to diffuse, propagate and remain viable within the complex biofilm structure. Here, we examine some of these properties for two staphylophages, vB_SauM_phiIPLA-RODI and vB_SepM_phiIPLA-C1C. Both Staphylococcus aureus and Staphylococcus epidermidis are important opportunistic pathogens that readily form biofilms on a wide array of biotic and abiotic surfaces. Our results confirmed that both phages could penetrate through biofilms formed by several bacterial strains with varying degrees of susceptibility to the viruses and biofilm-forming abilities. However, phage penetration differed depending on the specific bacterium or combination of bacteria. The data presented here suggest that the factors determining the diffusion rate of phages in biofilms include the amount of attached biomass, susceptibility of the strain, initial phage titer, phage entrapment in the extracellular matrix, and phage inactivation. This information will help to further characterize phage-bacteria interactions within biofilm communities and will be valuable for the development of antistaphylococcal products based on these phages.

Strategies to Encapsulate the Staphylococcus aureus Bacteriophage phiIPLA-RODI

The antimicrobial properties of bacteriophages make them suitable food biopreservatives. However, such applications require the development of strategies that ensure stability of the phage particles during food processing. In this study, we assess the protective effect of encapsulation of the Staphylococcus aureus bacteriophage phiIPLA-RODI in three kinds of nanovesicles (niosomes, liposomes, and transfersomes). All these systems allowed the successful encapsulation of phage phiIPLA-RODI with an efficiency ranged between 62% and 98%, regardless of the concentration of components (like phospholipids and surfactants) used for vesicle formation. Only niosomes containing 30 mg/mL of surfactants exhibited a slightly lower percentage of encapsulation. Regarding particle size distribution, the values determined for niosomes, liposomes, and transfersomes were 0.82 ± 0.09 µm, 1.66 ± 0.21 µm, and 0.55 ± 0.06 µm, respectively. Importantly, bacteriophage infectivity was maintained during storage for 6 months at 4 °C for all three types of nanovesicles, with the exception of liposomes containing a low concentration of components. In addition, we observed that niosomes partially protected the phage particles from low pH. Thus, while free phiIPLA-RODI was not detectable after 60 min of incubation at pH 4.5, titer of phage encapsulated in niosomes decreased only 2 log units. Overall, our results show that encapsulation represents an appropriate procedure to improve stability and, consequently, antimicrobial efficacy of phages for application in the food processing industry.