pH-sensitive niosomes for ATRA delivery: A promising approach to inhibit Pin1 in high-grade serous ovarian cancer

The peptidyl-prolyl cis/trans isomerase Pin1 positively regulates numerous cancer-driving pathways, and it is overexpressed in several malignancies, including high-grade serous ovarian cancer (HGSOC). The findings that all-trans retinoic acid (ATRA) induces Pin1 degradation strongly support that ATRA treatment might be a promising approach for HGSOC targeted therapy. Nevertheless, repurposing ATRA into the clinics for the treatment of solid tumors remains an unmet need mainly due to the insurgence of resistance and its ineffective delivery. In the present study, niosomes have been employed for improving ATRA delivery in HGSOC cell lines. Characterization of niosomes including hydrodynamic diameter, ζ-potential, morphology, entrapment efficiency and stability over time and in culture media was performed. Furthermore, pH-sensitiveness and ATRA release profile were investigated to demonstrate the capability of these vesicles to release ATRA in a stimuli-responsive manner. Obtained results documented a nanometric and monodispersed samples with negative ζ-potential. ATRA was efficiently entrapped, and a substantial release was observed in the presence of acidic pH (pH 5.5). Finally, unloaded niosomes showed good biocompatibility while ATRA-loaded niosomes significantly increased ATRA Pin1 inhibitory activity, which was consistent with cell growth inhibition. Taken together, ATRA-loaded niosomes might represent an appealing therapeutic strategy for HGSOC therapy.

Mucoadhesive Rifampicin-Liposomes for the Treatment of Pulmonary Infection by Mycobacterium abscessus: Chitosan or ε-Poly-L-Lysine Decoration

Mycobacterium abscessus (Mabs) is a dangerous non-tubercular mycobacterium responsible for severe pulmonary infections in immunologically vulnerable patients, due to its wide resistance to many different antibiotics which make its therapeutic management extremely difficult. Drug nanocarriers as liposomes may represent a promising delivery strategy against pulmonary Mabs infection, due to the possibility to be aerosolically administrated and to tune their properties in order to increase nebulization resistance and retainment of encapsulated drug. In fact, liposome surface can be modified by decoration with mucoadhesive polymers to enhance its stability, mucus penetration and prolong its residence time in the lung. The aim of this work is to employ Chitosan or ε-poly-L-lysine decoration for improving the properties of a novel liposomes composed by hydrogenated phosphatidyl-choline from soybean (HSPC) and anionic 1,2-Dipalmitoyl-sn-glycero-3-phosphorylglycerol sodium salt (DPPG) able to entrap Rifampicin. A deep physicochemical characterization of polymer-decorated liposomes shows that both polymers improve mucoadhesion without affecting liposome features and Rifampicin entrapment efficiency. Therapeutic activity on Mabs-infected macrophages demonstrates an effective antibacterial effect of ε-poly-L-lysine liposomes with respect to chitosan-decorated ones. Altogether, these results suggest a possible use of ε-PLL liposomes to improve antibiotic delivery in the lung.

Neem Oil or Almond Oil Nanoemulsions for Vitamin E Delivery: From Structural Evaluation to in vivo Assessment of Antioxidant and Anti-Inflammatory Activity

Purpose

Vitamin E (VitE) may be classified in "the first line of defense" against the formation of reactive oxygen species. Its inclusion in nanoemulsions (NEs) is a promising alternative to increase its bioavailability. The aim of this study was to compare O/W NEs including VitE based on Almond or Neem oil, showing themselves antioxidant properties. The potential synergy of the antioxidant activities of oils and vitamin E, co-formulated in NEs, was explored.

Patients and Methods

NEs have been prepared by sonication and deeply characterized evaluating size, ζ-potential, morphology (TEM and SAXS analyses), oil nanodroplet feature, and stability. Antioxidant activity has been evaluated in vitro, in non-tumorigenic HaCaT keratinocytes, and in vivo through fluorescence analysis of C. elegans transgenic strain. Moreover, on healthy human volunteers, skin tolerability and anti-inflammatory activity were evaluated by measuring the reduction of the skin erythema induced by the application of a skin chemical irritant (methyl-nicotinate).

Results

Results confirm that Vitamin E can be formulated in highly stable NEs showing good antioxidant activity on keratinocyte and on C. elegans. Interestingly, only Neem oil NEs showed some anti-inflammatory activity on healthy volunteers.

Conclusion

From the obtained results, Neem over Almond oil is a more appropriate candidate for further studies on this application.

Nanoparticle Impact on the Bacterial Adaptation: Focus on Nano-Titania

Titanium dioxide nanoparticles (nano-titania/TiO₂ NPs) are used in different fields and applications. However, the release of TiO₂ NPs into the environment has raised concerns about their biosafety and biosecurity. In light of the evidence that TiO₂ NPs could be used to counteract antibiotic resistance, they have been investigated for their antibacterial activity. Studies reported so far indicate a good performance of TiO₂ NPs against bacteria, alone or in combination with antibiotics. However, bacteria are able to invoke multiple response mechanisms in an attempt to adapt to TiO₂ NPs. Bacterial adaption arises from global changes in metabolic pathways via the modulation of regulatory networks and can be related to single-cell or multicellular communities. This review describes how the impact of TiO₂ NPs on bacteria leads to several changes in microorganisms, mainly during long-term exposure, that can evolve towards adaptation and/or increased virulence. Strategies employed by bacteria to cope with TiO₂ NPs suggest that their use as an antibacterial agent has still to be extensively investigated from the point of view of the risk of adaptation, to prevent the development of resistance. At the same time, possible effects on increased virulence following bacterial target modifications by TiO₂ NPs on cells or tissues have to be considered.

pH-responsive oleic acid based nanocarriers: Melanoma treatment strategies

Numerous clinical observations indicate that, despite novel therapeutic approaches, a high percentage of melanoma patients is non-responder or suffers of severe drug-related toxicity. To overcome these problems, we considered the option of designing, preparing and characterizing nanoemulsions and niosomes containing oleic acid, a pH-sensitive monounsaturated fatty acid holding per se an antimetastatic and anti-inflammatory role in melanoma. These new nanostructures will allow in vivo administration of oleic acid, otherwise toxic in its free form. For pulmonary route chitosan, a mucoadhesive agent, was enclosed in these nanocarriers to improve residence time at the lung site. A deep physical and chemical characterization was carried out evaluating size, ζ -potential, microviscosity, polarity as well as stability over time and in culture media. Moreover, their pH-sensitivity was evaluated by fluorometric assay. Cytotoxicity and cellular uptake were assessed in cultured normal fibroblasts and human melanoma cell lines. Interestingly, results obtained confirm nanocarrier stability and pH-sensitivity, associated to absence of cell toxicity, efficient cellular uptake and retention. Therefore, these new pH-sensitive oleic acid-based nanostructures could represent, by combining drug delivery in a pH-dependent manner with the antimetastatic potential of this fatty acid, a powerful strategy for more specific medicine against metastatic melanoma.

Resveratrol-Loaded Nanoemulsions: In Vitro Activity on Human T24 Bladder Cancer Cells

The chemopreventive potential of Resveratrol (RV) against bladder cancer and its mechanism of action have been widely demonstrated. The physicochemical properties of RV, particularly its high reactivity and low solubility in aqueous phase, have been limiting factors for its bioavailability and in vivo efficacy. In order to overcome these limitations, its inclusion in drug delivery systems needs to be taken into account. In particular, oil-in-water (O/W) nanoemulsions (NEs) have been considered ideal candidates for RV encapsulation. Since surfactant and oil composition can strongly influence NE features and their application field, a ternary phase diagram was constructed and evaluated to select a suitable surfactant/oil/water ratio. The selected sample was deeply characterized in terms of physical chemical features, stability, release capability and cytotoxic activity. Results showed a significant decrease in cell viability after the incubation of bladder T24 cancer cells with RV-loaded NEs, compared to free RV. The selected NE formulation was able to preserve and improve RV cytotoxic activity by a more rapid drug uptake into the cells. O/W NEs represent an effective approach to improve RV bioavailability.

Hyaluronic Acid Derivative Effect on Niosomal Coating and Interaction with Cellular Mimetic Membranes

Hyaluronic acid (HA) is one of the most used biopolymers in the development of drug delivery systems, due to its biocompatibility, biodegradability, non-immunogenicity and intrinsic-targeting properties. HA specifically binds to CD44; this property combined to the EPR effect could provide an option for reinforced active tumor targeting by nanocarriers, improving drug uptake by the cancer cells via the HA-CD44 receptor-mediated endocytosis pathway. Moreover, HA can be easily chemically modified to tailor its physico-chemical properties in view of specific applications. The derivatization with cholesterol confers to HA an amphiphilic character, and then the ability of anchoring to niosomes. HA-Chol was then used to coat Span^® or Tween^® niosomes providing them with an intrinsic targeting shell. The nanocarrier physico-chemical properties were analyzed in terms of hydrodynamic diameter, ζ-potential, and bilayer structural features to evaluate the difference between naked and HA-coated niosomes. Niosomes stability was evaluated over time and in bovine serum. Moreover, interaction properties of HA-coated nanovesicles with model membranes, namely liposomes, were studied, to obtain insights on their interaction behavior with biological membranes in future experiments. The obtained coated systems showed good chemical physical features and represent a good opportunity to carry out active targeting strategies.

Exposure to TiO2 Nanoparticles Increases Listeria monocytogenes Infection of Intestinal Epithelial Cells

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in a variety of consumer products. Cellular exposure to TiO2 NPs results in complex effects on cell physiology that could impact biological systems. We investigated the behavior of Listeria monocytogenes in intestinal epithelial cells pre-treated with either a low or high (1 and 20 µg/cm2) dose of TiO2 NPs. Our results indicate that the pre-treated cells with a low dose became more permissive to listeria infection; indeed, both adhesion and invasion were significantly increased compared to control. Increased invasion seems to be correlated to cytoskeletal alterations induced by nanoparticles, and higher bacterial survival might be due to the high levels of listeriolysin O that protects L. monocytogenes from reactive oxygen species (ROS). The potential risk of increased susceptibility to L. monocytogenes infection related to long-term intake of nanosized TiO2 at low doses should be considered.

Improving Quality in Nanoparticle-Induced Cytotoxicity Testing by a Tiered Inter-Laboratory Comparison Study

The quality and relevance of nanosafety studies constitute major challenges to ensure their key role as a supporting tool in sustainable innovation, and subsequent competitive economic advantage. However, the number of apparently contradictory and inconclusive research results has increased in the past few years, indicating the need to introduce harmonized protocols and good practices in the nanosafety research community. Therefore, we aimed to evaluate if best-practice training and inter-laboratory comparison (ILC) of performance of the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay for the cytotoxicity assessment of nanomaterials among 15 European laboratories can improve quality in nanosafety testing. We used two well-described model nanoparticles, 40-nm carboxylated polystyrene (PS-COOH) and 50-nm amino-modified polystyrene (PS-NH2). We followed a tiered approach using well-developed standard operating procedures (SOPs) and sharing the same cells, serum and nanoparticles. We started with determination of the cell growth rate (tier 1), followed by a method transfer phase, in which all laboratories performed the first ILC on the MTS assay (tier 2). Based on the outcome of tier 2 and a survey of laboratory practices, specific training was organized, and the MTS assay SOP was refined. This led to largely improved intra- and inter-laboratory reproducibility in tier 3. In addition, we confirmed that PS-COOH and PS-NH2 are suitable negative and positive control nanoparticles, respectively, to evaluate impact of nanomaterials on cell viability using the MTS assay. Overall, we have demonstrated that the tiered process followed here, with the use of SOPs and representative control nanomaterials, is necessary and makes it possible to achieve good inter-laboratory reproducibility, and therefore high-quality nanotoxicological data.

Satureja montana L. Essential Oils: Chemical Profiles/Phytochemical Screening, Antimicrobial Activity and O/W NanoEmulsion Formulations

Chemical fingerprints of four different Satureja montana L. essential oils (SEOs) were assayed by an untargeted metabolomics approach based on Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) coupled with either electrospray ionization or atmospheric pressure chemical ionization ion sources. Analysis and relative quantification of the non-polar volatile fraction were conducted by gas chromatography (GC) coupled to MS. FT-ICR MS confirmed significant differences in the polar metabolite composition, while GC-MS analyses confirmed slight fluctuations in the relative amount of major terpenes and terpenoids, known to play a key role in antimicrobial mechanisms. Oil in eater (O/W) nanoemulsions (NEs) composed by SEOs and Tween 20 or Tween 80 were prepared and analyzed in terms of hydrodynamic diameter, ζ-potential and polydispersity index. The results confirm the formation of stable NEs homogeneous in size. Minimum inhibitory and minimum bactericidal concentrations of SEOs were determined towards Gram-positive (Listeria monocytogenes, Staphylococcus aureus, Staphylococcus haemolyticus) and Gram-negative clinical isolates (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens). Commercial SEO showed strongest antibacterial activity, while SEO 3 was found to be the most active among the lab made extractions. MIC and MBC values ranged from 0.39 to 6.25 mg·mL⁻¹. Furthermore, a SEO structured in NEs formulation was able to preserve and improve antimicrobial activity.

Bovine Lactoferrin Prevents Influenza A Virus Infection by Interfering with the Fusogenic Function of Viral Hemagglutinin

Bovine lactoferrin (bLf) is an iron-binding glycoprotein folded in two symmetric globular lobes (N- and C-lobes) with potent antimicrobial and immunomodulatory activities. Recently, we have shown that bLf, and in particular its C-lobe, interacts with influenza A virus hemagglutinin and prevents infection by different H1 and H3 viral subtypes. Influenza virus hemagglutinin (HA), and in particular its highly conserved fusion peptide involved in the low-pH-mediated fusion process, plays a significant role in the early steps of viral infection and represents an attractive target for the development of anti-influenza drugs. In the present research, we further investigated the influence of low pH on the interactions between bLf and influenza A H1N1 virus by different techniques, such as enzyme-linked immunosorbent assay, electron microscopy, hemolysis inhibition assay, and time course assay. Our results demonstrate that lactoferrin interaction with influenza hemagglutinin at low pH induces alterations that stabilize the conformation of the hemagglutinin, resulting in the inhibition of the fusion peptide activity. Taken together, our data allowed to better characterize the HA-specific inhibiting activity of bLf and to confirm HA as a good target for drug development.

Satureja montana L. essential oil and its antimicrobial activity alone or in combination with gentamicin

Many essential oils (EOs) are screened as potential sources of antimicrobial compounds. EOs from the genus Satureja have recognized biological properties, including analgesic, anti-inflammatory, immunomodulatory, anticancer, and antimicrobial activity. This study aimed to obtain a metabolite profile of commercial essential oil of S. montana L. (SEO) and to evaluate its antimicrobial properties, both alone and combined with gentamicin towards Gram-negative and Gram-positive bacterial strains. Untargeted analyses based on direct infusion Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and on GC-MS have provided a high metabolome coverage, allowing to identify carvacrol, cymene and thymol as the major components of commercial SEO. SEO exerted an antimicrobial activity and induced a synergistic interaction with gentamicin against both reference and clinical bacterial strains. A significant reduction of Escherichia coli, Staphylococcus aureus and Listeria monocytogenes biofilm formation was induced by SEO. As a result of SEO treatment, clear morphological bacterial alterations were visualized by scanning electron microscopy: L. monocytogenes and S. aureus showed malformed cell surface or broken cells with pores formation, whereas E. coli displayed collapsed cell surface. These results encourage further studies about bactericidal and antibiotic synergistic effect of SEO for combined therapy in clinical setting as well as in agricultural systems.

Virulence behavior of uropathogenic Escherichia coli strains in the host model Caenorhabditis elegans

Urinary tract infections (UTIs) are among the most common bacterial infections in humans. Although a number of bacteria can cause UTIs, most cases are due to infection by uropathogenic Escherichia coli (UPEC). UPEC are a genetically heterogeneous group that exhibit several virulence factors associated with colonization and persistence of bacteria in the urinary tract. Caenorhabditis elegans is a tiny, free-living nematode found worldwide. Because many biological pathways are conserved in C. elegans and humans, the nematode has been increasingly used as a model organism to study virulence mechanisms of microbial infections and innate immunity. The virulence of UPEC strains, characterized for antimicrobial resistance, pathogenicity-related genes associated with virulence and phylogenetic group belonging was evaluated by measuring the survival of C. elegans exposed to pure cultures of these strains. Our results showed that urinary strains can kill the nematode and that the clinical isolate ECP110 was able to efficiently colonize the gut and to inhibit the host oxidative response to infection. Our data support that C. elegans, a free-living nematode found worldwide, could serve as an in vivo model to distinguish, among uropathogenic E. coli, different virulence behavior.

Bacterial biofilm associated with a case of capsular contracture

Capsular contracture is one of the most common complications of implant-based breast augmentation. Despite its prevalence, the etiology of capsular contracture remains controversial although the surface texture of the breast implant, the anatomical position of the prosthesis and the presence of bacterial biofilm could be considered trigger factors. In fact, all medical implants are susceptible to bacterial colonization and biofilm formation. The present study demonstrated the presence of microbial biofilm constituted by cocci in a breast implant obtained from a patient with Baker grade II capsular contracture. This suggests that subclinical infection can be present and involved in low grade capsular contracture.

Neem oil nanoemulsions: characterisation and antioxidant activity

The aim of the present work is to develop nanoemulsions (NEs), nanosized emulsions, manufactured for improving the delivery of active pharmaceutical ingredients. In particular, nanoemulsions composed of Neem seed oil, contain rich bioactive components, and Tween 20 as nonionic surfactant were prepared. A mean droplet size ranging from 10 to 100 nm was obtained by modulating the oil/surfactant ratio. Physicochemical characterisation was carried out evaluating size, ζ-potential, microviscosity, polarity and turbidity of the external shell and morphology, along with stability in simulated cerebrospinal fluid (CSF), activity of Neem oil alone and in NEs, HEp-2 cell interaction and cytotoxicity studies. This study confirms the formation of NEs by Tween 20 and Neem oil at different weight ratios with small and homogenous dimensions. The antioxidant activity of Neem oil alone and in NEs was comparable, whereas its cytotoxicity was strongly reduced when loaded in NEs after interaction with HEp-2 cells.

Coriander (Coriandrum sativum) Essential Oil: Effect on Multidrug Resistant Uropathogenic Escherichia coli

Coriander ( Coriandrum sativum L., Apiaceae) is known for its antimicrobial activity and the aim of this study was to investigate the effect of its essential oil (CDO) against multidrug resistant uropathogenic Escherichia coli (UPEC). CDO was able to inhibit the growth of UPEC strains and propidium iodide uptake, and electron microscopy examination suggested that bacterial structural modifications occurred. The presence of CDO reduced the MIC of gentamicin. E.coli adhesion efficiency on cell monolayers and abiotic surfaces was not affected by subMIC oil concentrations; furthermore, CDO showed cytotoxic activity towards the HEp-2 tumor cell line. These findings contribute to the knowledge about essential oils as sources of potential antimicrobial agents against uropathogenic E. coli and encourage further investigations.

Coriander (Coriandrum sativum) Essential Oil: Effect on Multidrug Resistant Uropathogenic Escherichia coli

Coriander (Coriandruim sativum L., Apiaceae) is known for its antimicrobial activity and the aim of this study was to investigate the effect of its essential oil (CDO) against multidrug resistant uropathogenic Escherichia coli (UPEC). CDO was able to inhibit the growth of UPEC strains and propidium iodide uptake, - and electron microscopy examination suggested that bacterial structural modifications occurred. The presence of CDO reduced the MIC of gentamicin. E.coli adhesion efficiency on cell monolayers and abiotic surfaces was not affected by subMIC oil concentrations; furthermore, CDO showed cytotoxic activity towards the HEp-2 tumor cell line. These findings contribute to the knowledge about essential oils as sources of potential antimicrobial agents against uropathogenic E. coli and encourage further investigations.

Iron Availability Influences Aggregation, Biofilm, Adhesion and Invasion of Pseudomonas Aeruginosa and Burkholderia Cenocepacia

Pseudomonas aeruginosa and Burkholderia cenocepacia are predominant opportunistic pathogens in cystic fibrosis (CF) patients. In healthy humans the lower respiratory tract as well as all mucosa, contains a very low free iron concentration (10−18 M), while in CF patients' sputum iron concentration is very high, showing a median value of 63×10−6 M. Accumulation of catalytic reactive iron heavily contributes to subsequent clinical complications in the lung disorders by the production of reactive oxygen species and increases bacterial growth and virulence. The data reported in this study indicate that low iron concentration (Fe3+1 μM) induced free-living forms and motility both in P. aeruginosa and B. cenocepacia, while high iron concentrations (Fe3+ 10 and 100 μM) stimulated aggregation and biofilm formation already in the fluid phases, so demonstrating that aggregation and biofilm formation are positively iron-modulated in these bacteria. Moreover, the different morphological forms (free-living, aggregates and biofilm) showed different capabilities of adhering and invading the bronchial cell line A549. P. aeruginosa PAO1 aggregates, and mostly biofilm, exerted the highest adhesion efficiency, while B. cenocepacia PV1 aggregates or biofilm the lowest. A significant reduction in invasion efficiency by P. aeruginosa biofilm and a significant increase in cell internalization by B. cenocepacia biofilm has been reported. Therefore, the iron availability is an important signal to which P. aeruginosa and B. cenocepacia counteract by leaving the motile free-living forms and entering into a new lifestyle, i.e. biofilm. These data could contribute to explain that the iron-overload of the sputum of CF patients, inducing nonmotile forms, aggregates and biofilm, may facilitate penetration of host epithelial barriers contributing to the establishment of infection, colonization, persistence and systemic spread of these opportunistic pathogens.

Amino-functionalized poly(L-lactide) lamellar single crystals as a valuable substrate for delivery of HPV16-E7 tumor antigen in vaccine development

Background

Poly(l-lactide) (PLLA) is a biodegradable polymer currently used in many biomedical applications, including the production of resorbable surgical devices, porous scaffolds for tissue engineering, nanoparticles and microparticles for the controlled release of drugs or antigens. The surfaces of lamellar PLLA single crystals (PLLA_sc) were provided with amino groups by reaction with a multifunctional amine and used to adsorb an Escherichia coli-produced human papillomavirus (HPV)16-E7 protein to evaluate its possible use in antigen delivery for vaccine development.

Methods

PLLA single crystals were made to react with tetraethylenepentamine to obtain amino-functionalized PLLA single crystals (APLLA_sc). Pristine and amino-functionalized PLLA_sc showed a two-dimensional microsized and one-dimensional nanosized lamellar morphology, with a lateral dimension of about 15–20 μm, a thickness of about 12 nm, and a surface specific area of about 130 m²/g. Both particles were characterized and loaded with HPV16-E7 before being administered to C57BL/6 mice for immunogenicity studies. The E7-specific humoral-mediated and cell-mediated immune response as well as tumor protective immunity were analyzed in mice challenged with TC-1 cancer cells.

Results

Pristine and amino-functionalized PLLA_sc adsorbed similar amounts of E7 protein, but in protein-release experiments E7-PLLA_sc released a higher amount of protein than E7-APLLA_sc. When the complexes were dried for observation by scanning electron microscopy, both samples showed a compact layer, but E7-APLLA_sc showed greater roughness than E7-PLLA_sc. Immunization experiments in mice showed that E7-APLLA_sc induced a stronger E7-specific immune response when compared with E7-PLLA_sc. Immunoglobulin G isotyping and interferon gamma analysis suggested a mixed Th1/Th2 immune response in both E7-PLLA_sc-immunized and E7-APLLA_sc-immunized mice. However, only the mice receiving E7-APLLA_sc were fully protected from TC-1 tumor growth after three doses of vaccine.

Conclusion

Our results show that APLLA single crystals improve the immunogenicity of HPV16-E7 and indicate that E7-APLLA_sc could be used for development of an HPV16 therapeutic vaccine against HPV16-related tumors.

Evaluation of transcription levels of inlA, inlB, hly, bsh and prfA genes in Listeria monocytogenes strains using quantitative reverse-transcription PCR and ability of invasion into human CaCo-2 cells

Listeria monocytogenes virulence depends on the activity of well-characterized virulence factors. In this study, transcription levels of inlA, inlB, hly, bsh and prfA genes in L. monocytogenes strains, and the ability of invasion into CaCo-2 cells were investigated. Serotyping, multiplex-PCR for serovar identification and restriction fragment analysis of inlA were performed. Transcription levels and invasiveness were evaluated by quantitative reverse-transcription PCR and by in vitro assays, respectively. The isolates were of serovars 1/2a, 4b, 1/2c, 1/2b and 3a. Full-length inlA profiles were found for nine of ten clinical isolates, while five of seven cultures from foods showed truncated profile. The analysis of transcription levels of virulence factors encoding genes demonstrated a substantial inter-strain heterogeneity, with clinical strains showing higher levels for almost all genes than isolates from food. A correlation between transcription levels of inlA and inlB, as well as between bsh and prfA, was observed. Significant differences between clinical strains and food isolates in the invasion of CaCo-2 cells were found. Analysis of gene transcription and invasiveness of human cells suggests different virulence phenotypes among L. monocytogenes populations, and this characterization could be a useful tool for risk assessment purposes and for the development of public health strategies.

Listeria monocytogenes behaviour in presence of non-UV-irradiated titanium dioxide nanoparticles

Listeria monocytogenes is the agent of listeriosis, a food-borne disease. It represents a serious problem for the food industry because of its environmental persistence mainly due to its ability to form biofilm on a variety of surfaces. Microrganisms attached on the surfaces are a potential source of contamination for environment and animals and humans. Titanium dioxide nanoparticles (TiO₂ NPs) are used in food industry in a variety of products and it was reported that daily exposure to these nanomaterials is very high. Anti-listerial activity of TiO₂ NPs was investigated only with UV-irradiated nanomaterials, based on generation of reactive oxigen species (ROS) with antibacterial effect after UV exposure. Since both Listeria monocytogenes and TiO₂ NPs are veicolated with foods, this study explores the interaction between Listeria monocytogenes and non UV-irradiated TiO₂ NPs, with special focus on biofilm formation and intestinal cell interaction. Scanning electron microscopy and quantitative measurements of biofilm mass indicate that NPs influence both production and structural architecture of listerial biofilm. Moreover, TiO₂ NPs show to interfere with bacterial interaction to intestinal cells. Increased biofilm production due to TiO₂ NPs exposure may favour bacterial survival in environment and its transmission to animal and human hosts.

Exosomes released in vitro from Epstein-Barr virus (EBV)-infected cells contain EBV-encoded latent phase mRNAs

EBV is a human herpesvirus associated with a number of malignancies. Both lymphoblastoid cell lines (LCLs), and EBV-infected nasopharyngeal carcinoma (NPC) cells have been demonstrated to release exosomes containing the EBV-encoded latent membrane protein 1 (LMP1), and mature micro-RNAs (EBV-miRNAs). Here we analyze the EBV protein and nucleic acid content of exosomes from different EBV-infected cells (LCL, 721 and Daudi) and we show for the first time that exosomes released from LCLs and 721 also contain EBV-encoded latent phase mRNAs. This confirms and strengthens exosomes pathogenetic potential, and might provide insights for development of novel diagnostic and therapeutic strategies.

Bovine lactoferrin-derived peptides as novel broad-spectrum inhibitors of influenza virus

Bovine lactoferrin (bLf) is a multifunctional glycoprotein that plays an important role in innate immunity against infections, including influenza. Here we have dissected bLf into its C- and N-lobes and show that inhibition of influenza virus hemagglutination and cell infection is entirely attributable to the C-lobe and that all major virus subtypes, including H1N1 and H3N2, are inhibited. By far-western blotting and sequencing studies, we demonstrate that bLf C-lobe strongly binds to the HA(2) region of viral hemagglutinin, precisely the highly conserved region containing the fusion peptide. By molecular docking studies, three C-lobe fragments were identified which inhibited virus hemagglutination and infection at fentomolar concentration range. Besides contributing to explain the broad anti-influenza activity of bLf, our findings lay the foundations for exploiting bLf fragments as source of potential anti-influenza therapeutics.

Bovine lactoferrin: involvement of metal saturation and carbohydrates in the inhibition of influenza virus infection

Influenza is a highly contagious, acute respiratory illness, which represents one of the main plagues worldwide. Even though some antiviral drugs are available, the alarming increase of virus strains resistant to them highlights the need to find new antiviral compounds. As we have recently demonstrated that bovine lactoferrin (bLf) prevents influenza virus-induced apoptosis, in the present wor,k we have attempted to investigate in depth the mechanism of the anti-influenza virus effect of this protein. To this aim, experiments have been carried out whereby different forms of bLf were added to the cells during different phases of viral infection. Results obtained showed that bLf was able to prevent influenza virus cytopathic effects when incubated with the cells after the adsorption step, independently from ion saturation or carbohydrate content. Moreover, the influence of iron saturations or sialic acid/carbohydrates removal on bLf activity on the early phases of infection has been observed. Our results provide further insights on the antiviral activity of bLf and suggest novel strategies for treatment of influenza virus infection.

Bovine lactoferrin inhibits influenza A virus induced programmed cell death in vitro

Influenza is one of the main plagues worldwide. The statistical likelihood of a new pandemic outbreak, together with the alarming emergence of influenza virus strains that are resistant to available antiviral medications, highlights the need for new antiviral drugs. Lactoferrin, a 80 kDa bi-globular iron-binding glycoprotein, is a pleiotropic factor with potent antimicrobial and immunomodulatory activities. Although the antiviral effect of lactoferrin is one of its major biological functions, the mechanism of action is still under debate. In this research, we have analyzed the effect of bovine lactoferrin (bLf) on Influenza A virus infection in vitro. Our results showed that (i) Influenza virus infected cells died as a result of apoptosis, (ii) bLf treatment inhibited programmed cell death by interfering with function of caspase 3, a major virus-induced apoptosis effector, and (iii) bLf efficiently blocked nuclear export of viral ribonucleoproteins so preventing viral assembly. These results provide further insights on the antiviral activity of bLf and suggest novel strategies for treatment of Influenza virus infection.

Necrotic cell death in human amniotic cells infected by Listeria monocytogenes

Listeria monocytogenes can cause a placental-foetal infection that results in spontaneous abortion, premature labour, stillbirth, or neonatal sepsis and meningitis. Bacteria cross the maternofoetal barrier at the villous syncytiotrophoblast level and subsequently spread from the placenta to the fetus. L. monocytogenes is able to induce different kinds of death in a variety of cells. Murine hepatocytes, murine T and human B lymphocytes, and murine dendritic cells die by apoptosis, whereas bacterial infection of murine and human macrophages leads mainly to necrotic cell death. As we previously described the efficient infection and growth of L. monocytogenes in a human amniotic cell line, we investigated the fate of these cells in order to analyse the mode of cell death. Our results provide biochemical and morphological evidence of necrotic death induced by L. monocytogenes infection.

Primary effusion lymphoma cells undergoing human herpesvirus type 8 productive infection produce C-type retroviral particles

Primary effusion lymphomas (PELs) are invariably infected by the human herpesvirus 8 (HHV8)that is present in most PEL cells as latent virus but replicates in a subset of permissive cells to produce infectious progeny. Here we show that productively infected PEL cells release C-type retrovirus-like particles encoding an Mn++-dependent RT activity, which is typical of endogenous retroviruses. Strikingly, C-type particles are produced only in cells showing advanced HHV8 morphogenesis. Phorbol esters, which induce productive HHV8 replication and morphogenesis in PEL cells, increase RLP production. Phosphonoacetic acid, a blocker of HHV8 late gene expression, inhibits the production of C-type particles, whereas neutralizing anti-alphaIFN antibodies, which are known to increase HHV8 assembly, increases C-type particle production. These data suggest that factors expressed in advanced stages of HHV8 reactivation support endogenous C-type particle morphogenesis in PEL cells.

New advances in anti-HSV chemotherapy

Treatment of human herpes simplex virus (HSV) diseases represents an important goal, as herpetic infections are not controlled by vaccination. Many therapeutic agents have been developed and used for HSV infections and several alternative natural compounds are under investigation. Most of the drugs clinically employed against HSV types 1 and 2 are represented by guanosine nucleoside analogues, such as aciclovir and aciclovir-like drugs. The emergence of aciclovir-resistant virus strains provided a stimulus for increased search of new effective agents. Alternative drugs are other nucleoside analogues, such as the vidarabine, brivudin, and cidofovir, or pyrophosphate analogues such as foscarnet, that showed efficacy for HSV infections refractory to aciclovir. However, the risk of adverse effects reported for available anti-herpetic compounds and the frequent development of drug-resistant strains of HSV following therapeutic treatment generate the need for new antiviral agents. In the last years, several studies have been carried out on the anti-HSV activity of different components of innate host defences such as cationic antimicrobial peptides. The antiviral activity of these peptides often appears to be related to the viral adsorption and entry process or is a result of a direct effect on the viral envelope. Other natural compounds, extracts from medicinal plants employed in ethnomedicine and displaying marked anti-herpetic activity, are at present under investigation to determine the scientific evidence and rationale for their clinical use. This review discusses the anti-HSV activity of compounds licensed for clinical use and promising natural molecules.

Glycosaminoglycans are not indispensable for the anti-herpes simplex virus type 2 activity of lactoferrin

Lactoferrin has been recognized as a potent inhibitor of human herpetic viruses, such as herpes simplex type 1 (HSV-1) and 2 (HSV-2). In particular, bovine lactoferrin (bLf) has been found to prevent viral infection by binding to heparan sulphate (HS) glycosaminoglycans (GAGs) that in turn can act as cell receptors for human herpetic viruses. In this study we further investigate the mechanism of inhibiting activity of both human lactoferrin (hLf) and bLf against HSV-2. The antiviral effect of these proteins towards HSV-2 strain 333 and its glycoprotein C (gC)-truncated derivative HSV-2 gC-neg1 has been tested in monkey kidney cells. Our results indicate that the antiviral activity of bLf does not involve gC-HS interaction as there was no difference in its effectiveness towards wild type and mutant virus. As regards hLf, the mutant virus HSV-2 gC-neg1 was more sensitive compared to the wild type, suggesting that the human protein might interact with some viral structures that in wild-type viruses are masked by gC. When the modulation of HSV-2 infection by bLf and hLf was investigated under different experimental conditions, the bovine protein proved more effective than the human protein. Moreover, we found that, differently from what observed with HSV-1, bLf inhibited HSV-2 plaque-forming activity also in cells devoid of GAG expression. These results suggest that bLf may block a virus receptor of non-GAG nature and add new information on the anti-herpes virus activity of this protein, confirming it as an outstanding candidate for the treatment of herpetic infections.

Bovine lactoferrin prevents the entry and intercellular spread of herpes simplex virus type 1 in Green Monkey Kidney cells

Lactoferrin (Lf) is a multifunctional glycoprotein that plays an important role in immune regulation and defence mechanisms against bacteria, fungi and viruses. Bovine lactoferrin (bLf) has been recognized as a potent inhibitor of human herpetic viruses, such as cytomegalovirus and herpes simplex virus type 1 and 2. BLf has been found to prevent viral infection by binding to heparan sulphate containing proteoglycans that also act as cell receptors for herpetic viruses. In this study we further investigated the inhibiting activity of bLf against herpes simplex virus type 1 (HSV-1) in Green Monkey Kidney (GMK) cells and found that, in addition to the viral adsorption step, bLf also targets the HSV-1 entry process and cell-to-cell viral spread. Our study showed that the inhibition of HSV-1 infectivity by bLf is dependent on its interaction with specific structural viral proteins. Apart from the prevention of early phases of viral infection, cell-to-cell spread inhibition activity of HSV-1 by bLf confirmed that this protein is an outstanding candidate for the treatment of herpetic infections since it would offer the advantage to prevent also viral infections caused by cell-associated virus.

Invasive pathway of Listeria ivanovii in human amnion-derived WISH cells

Among Listeria genus, only two species, Listeria ivanovii and Listeria monocytogenes, are pathogenic. L. ivanovii is almost only associated with infections in animals, mainly sheep and cattle, and has rarely been associated with human infections, whereas L. monocytogenes causes severe illnesses in both humans and animals. To further investigate the pathogenetic features of L. ivanovii in humans, we undertook a study in which the intracellular behaviour of this pathogen was analysed in WISH cells, a cell line derived from human amniotic tissue, and compared to that of L. monocytogenes. Using microbiological, biochemical, and ultrastructural approaches, we demonstrate that L. ivanovii can adhere to and invade human amniotic cells, lyse the phagosomal membrane, polymerize host cell actin, and spread from cell to cell more efficiently than L. monocytogenes. However, although L. ivanovii is capable of specifically infecting and replicating in human amnion cells, its survival in cytoplasm is limited compared to that of L. monocytogenes.

Molecular characterization of virulence determinants of Stenotrophomonas maltophilia strains isolated from patients affected by cystic fibrosis

Stenotrophomonas maltophilia is an emerging nosocomial bacterial pathogen which is currently isolated with increasing frequency from the airways of cystic fibrosis (CF) patients. In this study 13 S. maltophilia strains (11 isolated from the airways of independent CF patients, and two non-CF respiratory reference strains) have been characterized for the expression of several virulence-associated factors. In particular, the ability to form biofilm on abiotic surfaces has been determined and correlated with different features, such as motility, adherence and the ability to invade A549 respiratory epithelial cells. Moreover, the presence of a flagellum-associated gene as well as that of the StmPr1 gene, which encodes an extracellular protease, have been determined by Southern blot hybridization. Our data indicate that the different degree of biofilm formation exhibited by the 11 CF isolates does not correlate with motility, ability to adhere to and invade A549 cells, or with the presence of flagella. On the other hand, among the CF isolates the StmPr1 gene was found only in two strains, both able to establish chronic lung infections in CF patients. Moreover, only four of the strains analyzed show a temperature-independent antibiotic-resistance profile, suggesting either a different origin of these strains or an intervening adaptation to host tissues.

Acid adaptation and survival of Listeria monocytogenes in Italian-style soft cheeses

AIMS

The ability of Listeria monocytogenes to survive and grow at high salt concentrations and low pH makes it a potential hazard after the consumption of milk and dairy products, often implicated in severe outbreaks of listeriosis. This study was designed to evaluate the behaviour of L. monocytogenes in traditional acid and salted Italian-style soft cheeses and to investigate whether Listeria occurrence and growth in these environments may represent a potential increase of hazard.

METHODS AND RESULTS

A first approach was addressed to in vitro evaluate survival, acid tolerance response, ability to produce biofilm, and capability to invade intestinal-like cells of a L. monocytogenes strain grown under experimental conditions mimicking environmental features that this pathogen encounters in soft cheeses (such as acid pH and high NaCl content). A second set of experiments was performed to monitor, during the storage at 4 degrees C, the survival of acid-adapted and nonadapted Listeriae in artificially contaminated soft cheeses. Both acid tolerance response and invasion efficiency of acid-adapted bacteria resulted in an increase, even when bacteria were simultaneously pre-exposed to increasing salt stress. The contamination of cheeses with acid-adapted and nonadapted bacteria evidenced in all products a good survival. A significant increased survival, the recovery of bacterial cells highly resistant to lethal pH exposure, and the prevalence of filamentous structures were observed in crescenza cheese during the storage.

CONCLUSIONS

The Listeria survival and acid pH tolerance observed during refrigerated storage are probably related to the intrinsic acid and saline features of soft cheeses analysed.

SIGNIFICANCE AND IMPACT OF THE STUDY

Italian soft cheeses tested may represent a potential hazard for the recovery of acid-adapted L. monocytogenes cells with enhanced ability to adhere to inert surfaces and/or to penetrate host cells.

Bovine lactoferrin inhibits echovirus endocytic pathway by interacting with viral structural polypeptides

Lactoferrin, an 80 kDa bi-globular iron-binding glycoprotein belonging to the transferrin family, is a pleiotropic factor with potent antimicrobial and immunomodulatory activities, present in breast milk, in mucosal secretions, and in the secondary granules of neutrophils. Recently, we have shown that bovine lactoferrin prevents the early phases of echovirus infection and also acts as a survival factor inhibiting viral-induced apoptosis. In the present research we investigated the mechanism of bovine lactoferrin anti-echoviral effect demonstrating that echovirus enters susceptible cells by an endocytic pathway and that lactoferrin treatment is able to prevent viral genome delivery into the cytoplasm. It is likely that lactoferrin interaction with echovirus capsid proteins induces alterations that stabilize the conformation of the virion making it resistant to uncoating. Taken together, the results of our study show that the inhibition of echovirus 6 infectivity by lactoferrin is dependent on its interaction not only with cell surface glycosaminoglycan chains but also with viral structural proteins demonstrating that this glycoprotein targets the virus entry process.

Bovine lactoferrin peptidic fragments involved in inhibition of Echovirus 6 in vitro infection

Bovine lactoferrin is a multifunctional glycoprotein folded in two symmetric globular lobes (N- and C-lobes), each being able to bind one ferric ion. We have previously demonstrated that this protein is able to prevent echovirus-induced apoptosis. In the present study, we have investigated both the role of tryptic fragments of bovine lactoferrin and the mechanism of lactoferrin effect on echovirus infection. Results obtained showed that bovine lactoferrin inhibits echovirus-induced cytopathic effect and antigen synthesis in a dose-dependent manner and that this protein is able to prevent viral replication when added not only during the entire cycle of infection but also before, during or after the viral adsorption step. The N-terminal cationic peptide was sufficient to prevent viral binding. Our data suggest that lactoferrin inhibition of echovirus attachment to cell receptors could be mediated by the cluster of positive charges at its N-terminus (lactoferricin).

Inhibitory activity of bovine lactoferrin against echovirus induced programmed cell death in vitro

Lactoferrin is a glycoprotein and plays an important role in defence against pathogens. Although the antiviral activity of lactoferrin is one of the major biological functions of such protein, the mechanism of action is still under debate. The effect of lactoferrin on echovirus 6 infection in vitro was analysed and results showed that (i) cells infected with echovirus 6, died as a result of apoptosis and that (ii) programmed cell death was inhibited by lactoferrin treatment. In this report, we demonstrate that lactoferrin can exert its anti-enteroviral activity by preventing viral-induced apoptosis.

Glycosaminoglycans Mediate Invasion and Survival ofEnterococcus faecalisinto Macrophages

Enterococcus faecalis is responsible for a large variety of nosocomial infections. The intestinal barrier is thought to be one of the preferential portals of entry of enterococci, and the ability of E. faecalis to survive within peritoneal macrophages may contribute to spreading to distant sites. We examined the ability of a polysaccharide-expressing (biofilm-positive) E. faecalis strain and an isogenic biofilm-negative mutant to enter and survive within professional and nonprofessional phagocytes. Biofilm-positive bacteria survived longer in all cell systems than did biofilm-negative bacteria, through a process of receptor-mediated endocytosis that is dependent on functional reorganization of microtubules and polymerization of microfilament and on activation of protein kinases but not ATPases or protein phosphatases. We suggest that glycosaminoglycans--specifically heparin, heparan sulfate, and chondroitin sulfate A--are the host receptors for enterococci on professional and, possibly, nonprofessional phagocytes, allowing entry of enterococci into cell compartments where killing mechanisms are inhibited.

A Sphingomonas bacterium interacting with epithelial cells

Bacteria of the genus Sphingomonas are environmental organisms that have recently been implicated in a variety of community-acquired and nosocomial infections. During studies on bacteria-cell interactions, we incurred a microorganism contaminating our HeLa cell culture, possibly from water utilized for reagent preparation; this bacterium appeared to tightly adhere to cell monolayers and to survive, with only limited growth rate, which did not seem to alter cells as far as shape, growth rate or survival were concerned. The contaminating organism was isolated and partially characterized by morphological, genetic, and biochemical assays. Mechanisms of cell interaction and entry into epithelial cells were investigated by electron microscopy, immunofluorescence, and biochemical inhibitors. Morphological and biochemical features indicated that the microorganism belonged to the genus Sphingomonas. Electron microscopy showed that contact between the Sphingomonas bacterium and epithelial cells leads to a dramatic alteration of the cell surface, with formation of numerous microvillar extensions plus membrane ruffling. Confocal microscopy and the use of inhibitors showed that actin microfilaments were involved during attachment and entry into HeLa cells. Macropinosome formation and an inhibitory effect by amiloride indicate that internalization occurs in part via a macropinocytosis mechanism. Moreover, cholesterol distribution at the site of bacterial binding suggests that Sphingomonas bacteria could use the lipid rafts as initial binding sites.

Receptor-mediated endocytosis of biofilm-forming Enterococcus faecalis by rat peritoneal macrophages

BACKGROUND & OBJECTIVES

Enterococci are important nosocomial pathogens that are increasingly difficult to treat due to intrinsic and acquired resistance to antibiotics. Studies were taken up to identify virulence factors and to characterise pathogenic mechanisms of such infections to evaluate potential targets for treatments alternative to antibiotic therapy. This study was carried out to evaluate the contribution of extracellular polysaccharide expressed by Enterococcus faecalis to resistance to phagocytosis and survival within rat peritoneal macrophages.

METHODS

Six E. faecalis clinical isolates were tested for their ability to survive within rat peritoneal macrophages. Cytochalasin D, colchicine and monodansylcadaverine were used to investigate the route of enterococcal entry inside macrophages.

RESULTS

Four of the isolates were able to produce extracellular polysaccharide and form biofilm after growth in glucose-supplemented medium, while no production could be detected in glucose deficient medium. Two isolates were polysaccharide-negative in both conditions. Isolates expressing extracellular polysaccharide were able to survive for more than 24 h compared to polysaccharide-negative bacterial cells of the same strain grown in glucose-deficient medium, which were readily cleared. Cytochalasin D virtually abolished the number of viable intracellular bacteria, after growth in either trypticase soy broth (TSB) or TSB supplemented with glucose; colchicine and monodansylcadaverine strongly affected survival of polysaccharide-positive bacteria, significantly more than that of polysaccharide-negative ones.

INTERPRETATION & CONCLUSION

Biofilm-forming E. faecalis survived within rat peritoneal macrophages significantly better than polysaccharide-negative isolates. Perturbators of cytoskeleton and of surface receptors turnover, indicated receptors-mediated endocytosis as the most likely route for enterococcal entry into macrophages.

Invasion of HeLa cells by Enterococcus faecalis clinical isolates

We examined the in vitro ability of Enterococcus faecalis clinical isolates to adhere to and to invade HeLa cells, suggested to be a valuable model system to study bacteria-directed endocytosis. Using a variety of compounds that act on eukaryotic cell structures, both microtubules and microfilaments were found to be involved in enterococcal entry into cells. Two distinct modes of interaction were observed: in one, a close proximity of bacteria with the cell membrane was observed, possibly leading to direct engulfment of the bacterial cell. In the other mode, cellular pseudopodal formation seemed to be stimulated by vicinity of bacterial cells; in some cases, such associations involved formation of clathrin-coated-like vesicles before internalizing enterococci. The above-mentioned experimental data together with the use of monodansylcadaverine, amiloride and NH4Cl, all involved in cytosol acidification and inhibition of receptor-mediated endocytosis (RME), led us to conclude that E. faecalis is internalized within HeLa cells by more than one invasion pathway. One, sensitive to amiloride, is most likely a macropinocytic, actin-dependent uptake mechanism, which determines the production of large smooth-membrane vacuoles engulfing enterococci. The other is RME, in which entry is dependent on both microfilament and microtubule structural integrity.

Enterococcus spp. produces slime and survives in rat peritoneal macrophages

Enterococcal clinical isolates were investigated for the ability to form biofilm on inert surfaces, as a measure of slime production, in an attempt to find new possible virulence factors for these microorganisms. This property was commonly found among Enterococcus faecalis. Also E. faecium isolates were able to form biofilm, although to a lesser extent; for this species, however, biofilm formation seemed more frequently associated with isolates from infection rather than with environmental strains or isolates from healthy individuals. Biofilm formation was strongly affected by the presence of an additional carbohydrate source in the medium, or by iron deprivation, indicating a role of slime for survival in stressful conditions. Slime-producing E. faecalis were able to survive inside peritoneal macrophages for extended periods compared to slime-negative strains or to slime-positive bacteria grown in conditions depressing slime production. In particular, slime-producing and slime-negative cells showed a decrease of 1 and 2 log units, respectively, at 1 h after infection; slime-negative cells were then rapidly killed, with clearance of bacterial cells at 24 h. Slime-producing bacteria persisted up to 48 h, which was the last time point examined, as after that time viability of both infected and non-infected macrophages started to decline. Scanning electron microscopy observations showed the presence of abundant amorphous extracellular material, of possible polysaccharide nature, embedding bacterial cells to form a multilayered biofilm. Even in conditions not supporting biofilm formation, bacterial cells appeared capsulated, suggesting that capsule and slime might represent different structures. Genes belonging to the epa locus or to a putative icaA homolog did not seem to be involved in synthesis and export of slime.

Effect of iron limitation on slime production by Staphylococcus aureus

The aim of this study was to examine the effect of growth conditions on slime production by Staphylococcus aureus clinical isolates. The addition of glucose to the medium enhanced slime production in the majority of Staphylococcus aureus isolates cultured from infections associated with orthopaedic prostheses. Iron limitation also stimulated this ability even in the absence of the additional carbohydrate source. Staphylococcus aureus isolates were classified as Group 1 [strains producing slime only in trypticase soy broth supplemented with 1% glucose (TSBG) or in iron-limited trypticase soy broth (TSB/Fe-)]; Group 2 (slime + only in TSB/Fe-); or Group 3 (slime+ only in TSBG). Seven repeatedly slime-negative strains were stimulated to produce slime by subpassaging in iron-limited medium. Low iron levels, usually found in vivo, could stimulate slime production by Staphylococcus aureus and support chronic infections associated with orthopaedic prostheses.

Virulence and drug susceptibility of Mycobacterium celatum

The virulence and drug susceptibility of a clinical isolate of Mycobacterium celatum which showed smooth transparent (ST) and smooth opaque (SO) colonies were studied. While ST cells multiplied intracellularly and maintained their coccobacillary form in a human macrophage model of infection, SO cells formed long filaments and completely destroyed the phagocytes. In BALB/c mice, the ST variant, but not the SO variant, grew efficiently in the spleen, liver and lung. The ST variant was usually more resistant in vitro than the SO variant to drugs, with MIC values for clarithromycin (CLA), azithromycin (AZI), ciprofloxacin, sparfloxacin, amikacin, clofazimine, ethambutol and isoniazid being higher than those of the SO variant. In beige mice infected with the more highly virulent variant ST, CLA and AZI were the most active drugs in terms of viable count reduction in organs and mutant selection. Together, these observations indicate that the ST variant of M. celatum is a virulent form that can be efficiently inhibited in vivo by CLA and AZI.

Infection of human enterocyte-like cells with rotavirus enhances invasiveness of Yersinia enterocolitica and Y. pseudotuberculosis

Mixed infection with rotavirus and either Yersinia enterocolitica or Y. pseudotuberculosis was analysed in Caco-2 cells, an enterocyte-like cell line highly susceptible to these pathogens. Results showed an increase of bacterial adhesion and internalisation in rotavirus-infected cells. Increased internalisation was also seen with Escherichia coli strain HB101 (pRI203), harbouring the inv gene from Y. pseudotuberculosis, which is involved in the invasion process of host cells. In contrast, the superinfection with bacteria of Caco-2 cells pre-infected with rotavirus resulted in decreased viral antigen synthesis. Transmission electron microscopy confirmed the dual infection of enterocytes. These data suggest that rotavirus infection enhances the early interaction between host cell surfaces and enteroinvasive Yersinia spp.

Acid tolerance in Listeria monocytogenes influences invasiveness of enterocyte-like cells and macrophage-like cells

Clinical and food Listeria monocytogenes isolates, pre-exposed to mild acidic conditions, were able to readily develop acid tolerance, irrespective of their origin. We attempted to investigate the influence of acid tolerance mechanisms, either constitutive or induced, on the invasive behaviour of this facultative food-borne pathogen. Entry efficiency and intracellular growth of acid-tolerant strains were evaluated in in vitro cell models capable to mimic in vivo target cells, such as enterocytes and macrophages. An acid-adapted L. monocytogenes wild-type strain and a constitutively acid-tolerant mutant were able to enter enterocyte-like (Caco-2) cells as well as to survive and proliferate intracellularly in lipopolysaccharide-treated macrophage-like (J774.A1) cells, at a significant increased extent by respect of the non acid-adapted wild-type strain. These findings add new information about the influence of the acid tolerance response on L. monocytogenes virulence, suggesting that in acid-adapted bacteria the early events of pathogenesis which allow the colonization and the spread of bacteria in the host may be highly promoted.

Lytic growth of human herpesvirus 8: morphological aspects

The human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, is a gamma herpesvirus associated with AIDS-related body cavity-based lymphomas (BCBL), also called primary effusion lymphomas (PEL). These are a rare form of non-Hodgkin lymphomas in which HHV-8 is present, often associated with Epstein-Barr virus (EBV) infection. HHV-8 is also present in a latent state or in a state of low-level persistence in different primary effusion lymphoma-derived cell lines, such BCBL-1 cells, that lack EBV infection. This cell line was induced to produce mature virions by treatment with 12-O-tetradecanoyl phorbol-13-acetate (TPA) and the characteristic ultrastructural features of HHV-8 lytic replication were identified and compared to those of the other members of Herpesviridae family.