Dianella Savoia

Plant-derived antimicrobial compounds: alternatives to antibiotics

The increasing incidence of drug-resistant pathogens has drawn the attention of the pharmaceutical and scientific communities towards studies on the potential antimicrobial activity of plant-derived substances, an untapped source of antimicrobial chemotypes, which are used in traditional medicine in different countries. The aim of this review is to provide recent insights regarding the possibilities of the most important natural antimicrobial compounds derived from plant sources containing a wide variety of secondary metabolites, which are useful as alternative strategies to control infectious diseases. This review will focus on natural plant products as a useful source of antimicrobial molecules, active in particular, on bacteria and fungi. When considering that many of these compounds, which have been used for centuries, are a source of new drugs and that there are ever-increasing technical breakthroughs, it can be envisaged that in the next years some different molecules discovered by ingenious screening programs and obtained from different plant oils and extracts will become useful therapeutic tools.

Recent updates and perspectives on leishmaniasis

Leishmaniasis is a neglected vector-borne tropical infection considered to be a disease of the poor. Concentrated in poverty-stricken countries within Southeast Asia, East Africa, and Latin America, it is also endemic in several Mediterranean countries. The management of the heterogeneous syndromes determined by parasites belonging to the genus Leishmania is particularly difficult in developed, non-endemic countries owing to the unfamiliarity of physicians with clinical symptoms, diagnostic possibilities, and available treatment options. Therefore, travelers and other people who may be exposed to sand flies in endemic areas should receive counseling regarding leishmaniasis and appropriate protective measures. Serological diagnosis is rarely used for cutaneous and mucocutaneous diseases, but it is the most commonly used technique for visceral leishmaniasis. The drugs used to treat this last disease are expensive and sometimes have toxic side effects. This review highlights the diagnostic, chemotherapeutic, and immunizing strategies to control leishmaniasis, though no human vaccine is commercially available currently owing to the complexity of the cellular immune response to this parasite.

Interaction of Bartonella henselae with the Murine Macrophage Cell Line J774: Infection and Proinflammatory Response

ABSTRACT Bartonella henselae is the causative agent of cat scratch disease (CSD), a self-limiting condition characterized by a subacute regional lymphadenopathy that may develop into disseminated bartonellosis in immunocompromised subjects. Mice experimentally infected with B. henselaedisplay typical liver and spleen granulomas rich in T cells and macrophages. So far there are no data on the interaction between bartonellae and macrophages. In order to clarify this topic, we investigated the interaction of B. henselae with J774, a mouse macrophage cell line. Analysis of bacterial uptake by functional assays and transmission electron microscopy indicates that bartonellae can enter and survive inside J774. Entry occurred within 30 min postinfection and reached a plateau at 160 min. Infection of J774 was followed by a dose-dependent release of the proinflammatory cytokines tumor necrosis factor alpha, interleukin 1β (IL-1β), and IL-6. Bartonellae persisted intracellularly without loss of viability for at least 8 h, and their number slightly decreased 24 h postinfection. Gamma interferon (IFN-γ) treatment of J774 significantly decreased the number of recoverable bacteria at 8 and 24 h. This enhancement of macrophage bactericidal activity was associated with nitric oxide (NO) release and was prevented by the addition of the competitive inhibitor of NO synthesis NG-monomethyll-arginine. These findings suggest that IFN-γ-mediated activation of macrophages may be important for the clearing ofB. henselae infection and that anti-B. henselae microbicidal activity of IFN-γ-activated macrophages is mediated to a large extent by NO production.

Novel approaches for the design and discovery of quorum-sensing inhibitors

Introduction: The spread of antibiotic resistance, together with the lack of antibiotics based on novel molecular scaffolds, marks the so-called ‘post-antibiotic era’. Interference with bacterial virulence has emerged as an attractive approach among the current potential strategies for developing new anti-infective drugs. Furthermore, the discovery that virulence gene expression is mostly regulated by quorum sensing (QS) has raised a lot of interest and prompted a lot of research aimed at finding inhibitors of this mechanism. Areas covered: This paper deals with the most recent strategies aimed at discovering new inhibitors able to disrupt the different steps of the QS system, targeting signal production, signal molecules and signal receptors. The authors provide an overview of the literature, including research papers, mostly dealing with inhibitors of the Staphylococcus aureus and Pseudomonas aeruginosa QS systems, and reviews dealing with the application of the newest technologies in the field. They also highlight the fields latest prospects and emerging concerns regarding their possible clinical applications. Expert opinion: QS inhibition is a promising strategy against infections. However, despite the discovery of a huge number of QS inhibitors, with about 40 patents, the potential of QS inhibition is still to be fully assessed. The current validation methods of QS inhibitors must be optimized, and the discovery that QS disruption may favor or select more virulent strains must be investigated in depth. Given the current market-dependent situation, it should be possible to develop hits into licensed drugs through joint ventures between private companies, academia and public institutions.

Streptococcus agalactiae in pregnant women: Phenotypic and genotypic characters

OBJECTIVE Streptococcus agalactiae (GBS) is considered a leading cause of neonatal sepsis. We evaluated the phenotypic and genotypic characters of 73 S. agalactiae strains isolated from different women at the 35-37 weeks of pregnancy. METHODS Isolates were characterized by serotyping (direct agglutination) and by pulsed-field-gel-electrophoresis (PFGE). Resistance to antimicrobials (penicillin, macrolides, lincosamides, quinolones and tetracyclines) was assessed. RESULTS All isolates were serologically typeable and ascribable to one of the six tested serotypes (Ia, Ib, II, III, IV, and V) and many strains of the same serotype were genetically heterogeneous. Strains belonging to serotypes III, V and Ia were the most prevalent and the most resistant to macrolides. CONCLUSIONS This work reports GBS colonization rate (about 18%) and the prevalent capsular serotypes among pregnant women in Turin (Italy). Penicillin and erythromycin can be still considered the first and second choice drugs for prophylaxis and treatment of early-onset GBS infections in our district. The relevance of phenotypic and genotypic characterization of strains to monitor and control Streptococcus agalactiae infections is briefly discussed.

Transmission of Burkholderia cepacia Complex: Evidence for New Epidemic Clones Infecting Cystic Fibrosis Patients in Italy

ABSTRACT To analyze national prevalence, genomovar distribution, and epidemiology of the Burkholderia cepacia complex in Italy, 225 putative B. cepacia complex isolates were obtained from 225 cystic fibrosis (CF) patients attending 18 CF centers. The genomovar status of these isolates was determined by a polyphasic approach, which included whole-cell protein electrophoresis and recA restriction fragment length polymorphism (RFLP) analysis. Two approaches were used to genotype B. cepacia complex isolates: BOX-PCR fingerprinting and pulsed-field gel electrophoresis (PFGE) of genomic macrorestriction fragments. A total of 208 (92%) of 225 isolates belonged to the B. cepacia complex, with Burkholderia cenocepacia as the most prevalent species (61.1%). Clones delineated by PFGE were predominantly linked to a single center; in contrast, BOX-PCR clones were composed of isolates collected either from the same center or from different CF centers and comprised multiple PFGE clusters. Three BOX-PCR clones appeared of special interest. One clone was composed of 17 B. cenocepacia isolates belonging to recA RFLP type H. These isolates were collected from six centers and represented three PFGE clusters. The presence of insertion sequence IS1363 in all isolates and the comparison with PHDC reference isolates identified this clone as PHDC, an epidemic clone prominent in North American CF patients. The second clone included 22 isolates from eight centers and belonged to recA RFLP type AT. The genomovar status of strains with the latter RFLP type is not known. Most of these isolates belonged to four different PFGE clusters. Finally, a third clone comprised nine B. pyrrocinia isolates belonging to recA RFLP type Se13. They represented three PFGE clusters and were collected in three CF centers.

Achromobacter xylosoxidans respiratory tract infections in cystic fibrosis patients

Achromobacter xylosoxidans is a ubiquitous Gram‐negative non‐fermenting rod, recently characterized as an emerging pathogen in cystic fibrosis (CF) patients. Its pathogenic potential and prevalent transmission routes are still unclear. This study investigated the PFGE genetic pattern and antimicrobial resistance profile of 42 A. xylosoxidans isolates obtained over 4 years from the respiratory tract of 22 CF patients. By genotypic analysis, 31 isolates were attributed to 8 distinct PFGE patterns (A–H), whereas 11 isolates were not typable because their DNA was not restricted by XbaI and DraI restriction enzymes. The majority of the isolates showed multidrug resistance; imipenem and piperacillin were the most active drugs. During the course of A. xylosoxidans chronic infection forced expiratory volume and body mass index values were not significantly lowered. The demonstration of widespread antibiotic resistance underscores the importance of antibiogram‐directed therapy. Our data suggest that in some cases the infection may have been acquired from other patients or from a common contaminated source. Further epidemiological studies may be important for the design and implementation of prophylactic measures in CF centers.

Antimicrobial Activity of Euplotin C, the Sesquiterpene Taxonomic Marker from the Marine Ciliate Euplotes crassus

ABSTRACT Strains of the marine ciliate protist Euplotes crassus produce exclusive terpenoids called euplotins that play an ecological role. Among these derivatives, euplotin C is the main of four secondary metabolites isolated from cultures of this protozoon and represents the sesquiterpene taxonomic marker from E. crassus. Because different terpenoid metabolites of plant origin showed a certain antimicrobial activity, we assessed the compound euplotin C, purified by high-pressure liquid chromatography and solubilized in two solubility enhancers, against the protozoa Leishmania major and Leishmani infantum, the fungus Candida albicans, and nine strains of gram-positive and gram-negative microorganisms. An activity of euplotin C against Leishmania promastigotes was demonstrated (50% lethal doses were 4.6 or 8.1 μg/ml depending on the agent used to solubilize the compound), while the effect was less evident on Candida and nearly absent on bacteria. A nonsignificant cytotoxicity (50% lethal dose, >200 μg/ml) against the J774 cell line was observed. A leishmanicidal activity was also shown by the living, euplotin-producing cells of E. crassus cultured together with promastigotes; this activity increased with time from 10 min to 6 h of incubation. This study provides an initial rationale for the evaluation of euplotin C and other similar natural products as alternative or possibly synergistic compounds for current antiprotozoon chemotherapeutics.

In Vitro Leishmanicidal Activity of a Monoclonal Antibody mimicking a Yeast Killer Toxin

Abstract The microbicidal effect of a monoclonal antiidiotypic antibody, mimicking the activity of a yeast killer toxin, characterized by a wide antimicrobial spectrum, has been evaluated in vitro against two relevant species of protozoan parasites, Leishmania major and Leishmania infantum. The antiidiotypic antibody exerted a significant and dose-dependent antileishmanial activity against parasite promastigotes in comparison to an irrelevant isotype-matched monoclonal antibody. This is the first demonstration that an antibody, which had been already shown to be fungicidal and bactericidal, may also exert a direct microbicidal activity against protozoa.

Current Developments in the Therapy of Protozoan Infections

Protozoan parasites cause serious human and zoonotic infections, including life-threatening diseases such as malaria, African and American trypanosomiasis, and leishmaniasis. These diseases are no more common in the developed world, but together they still threaten about 40% of the world population (WHO estimates). Mortality and morbidity are high in developing countries, and the lack of vaccines makes chemotherapy the only suitable option. However, available antiparasitic drugs are hampered by more or less marked toxic side effects and by the emergence of drug resistance. As the main prevalence of parasitic diseases occurs in the poorest areas of the world, the interest of the pharmaceutical companies in the development of new drugs has been traditionally scarce. The establishment of public-private partnerships focused on tropical diseases is changing this situation, allowing the exploitation of the technological advances that took place during the past decade related to genomics, proteomics, and in silico drug discovery approaches. These techniques allowed the identification of new molecular targets that in some cases are shared by different parasites. In this review we outline the recent developments in the fields of protease and topoisomerase inhibitors, antimicrobial and cell-penetrating peptides, and RNA interference. We also report on the rapidly developing field of new vectors (micro and nano particles, mesoporous materials) that in some cases can cross host or parasite natural barriers and, by selectively delivering new or already in use drugs to the target site, minimize dosage and side effects.