In vitro biofilms and antifungal susceptibility of dermatophyte and non-dermatophyte moulds involved in foot mycosis

Tinea pedis and onychomycosis are among the commonest fungal diseases in the world. Dermatophytes and, less frequently, non-dermatophyte moulds are aetiological agents of foot mycosis and are capable of forming biofilms. Fungal biofilm has demonstrated increasing drug resistance. This work aims to evaluate, in vitro, the ability to form biofilm and the susceptibility to antifungal drugs of sessile dermatophytes and non-dermatophyte moulds involved in foot mycosis. Thirty-six dermatophytes and non-dermatophyte moulds isolated from Tunisian patients with foot mycoses, and identified with MALDI-TOF have been tested. MICs of fluconazole, econazole, itraconazole, terbinafine and griseofulvin were carried out using CLSI broth microdilution method. The ability to form biofilm and antifungal activities of drugs against fungal biofilm formation has been quantified by Crystal Violet and Safranin Red staining. Biomass quantification revealed that all species studied were able to form biofilms in vitro after 72 hours. Fluconazole, econazole, itraconazole and terbinafine inhibited fungal growth with MIC values ranging from 0.031 to >64 μg mL(-1) . The best antifungal activity has been obtained with terbinafine against Fusarium solani. Econazole showed the highest activity against fungal biofilm formation. These findings can help clinicians to develop the appropriate therapy of foot mycosis

Identification of Disalicyloyl Curcumin as a Potential DNA Polymerase Inhibitor for Marek’s Disease Herpesvirus: A Computational Study Using Virtual Screening and Molecular Dynamics Simulations

Marek’s disease virus (MDV) is a highly contagious and persistent virus that causes T-lymphoma in chickens, posing a significant threat to the poultry industry despite the availability of vaccines. The emergence of new virulent strains has further intensified the challenge of designing effective antiviral drugs for MDV. In this study, our main objective was to identify novel antiviral phytochemicals through in silico analysis. We employed Alphafold to construct a three-dimensional (3D) structure of the MDV DNA polymerase, a crucial enzyme involved in viral replication. To ensure the accuracy of the structural model, we validated it using tools available at the SAVES server. Subsequently, a diverse dataset containing thousands of compounds, primarily derived from plant sources, was subjected to molecular docking with the MDV DNA polymerase model, utilizing AutoDock software V 4.2. Through comprehensive analysis of the docking results, we identified Disalicyloyl curcumin as a promising drug candidate that exhibited remarkable binding affinity, with a minimum energy of −12.66 Kcal/mol, specifically targeting the DNA polymerase enzyme. To further assess its potential, we performed molecular dynamics simulations, which confirmed the stability of Disalicyloyl curcumin within the MDV system. Experimental validation of its inhibitory activity in vitro can provide substantial support for its effectiveness. The outcomes of our study hold significant implications for the poultry industry, as the discovery of efficient antiviral phytochemicals against MDV could substantially mitigate the economic losses associated with this devastating disease.Funder: King Saud University, Riyadh, Saudi Arabia; Grant(s): RSPD2023R74

Production and partial characterization of chitinase from a halotolerant Planococcus rifitoensis strain M2-26

peer reviewedThis paper is the first to investigate the production and partial characterization of the chitinase enzyme from a moderately halophilic bacterium Planococcus rifitoensis strain M2-26, earlier isolated from a shallow salt lake in Tunisia. The impact of salt, salinity concentration, pH, carbon and nitrogen sources on chitinase production and activity have been determined. This is the first report on a high salt-tolerant chitinase from P. rifitoensis, since it was active at high salinity (from 5 to 30% NaCl) as well as in the absence of salt. This enzyme showed optimal activity at 70 C and retained up to 82 and 66% of its original activity at 80 or 90 C, respectively. The activity of the enzyme was also shown over a wide pH range (from 5 to 11). For characterization of the enzyme activity, the chitinase secreted in the culture supernatant was partially purified. The preliminary study of the concentrated dialysed supernatant on native PAGE showed at least three chitinases produced by strain M2-26, with highest activity approximately at 65 kDa. Thus, the thermo-tolerant and high salt-tolerant chitinases produced by P. rifitoensis strain M2-26 could be useful for application in diverse areas such as biotechnology and agro-industry

Antioxidant and Antimicrobial Potentials of Seed Oil from Carthamus tinctorius L. in the Management of Skin Injuries

Infection of skin injuries by pathogenic microbial strains is generally associated if not treated with a lasting wound bed oxidative stress status, a delay in healing process, and even wound chronicity with several human health complications. The aim of the current study was to explore the antioxidant and antimicrobial potentialities of safflower (Carthamus tinctorius L.) extracted oil from seeds by cold pressing which would be beneficial in the management of skin wounds. Antioxidant capacity of the oil was evaluated (scavenging ability against 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric reducing antioxidant power (FRAP)). Total phenolic, total flavonoid, total carotenoid, and total chlorophyll contents were determined. Antimicrobial activities of safflower oil were tested against 10 skin pathogenic microorganisms: 4 bacterial strains (Escherichia coli, Enterobacter cloacae, Staphylococcus aureus, and Streptococcus agalactiae), 3 yeast species strains (Candida albicans, Candida parapsilosis, and Candida sake), and 3 fungi species (Aspergillus niger, Penicillium digitatum, and Fusarium oxysporum). A notable antioxidant capacity was demonstrated for the tested oil that exhibited moreover high antibacterial effects by both bacteriostatic and bactericidal pathways including lysozyme activity. An antifungal effect was further observed on the spore’s germination. Safflower oil could be considered as a good natural alternative remedy in the management of skin wounds and their possible microbial infections

Diversity of pathogenic Pseudomonas isolated from citrus in Tunisia

The damages observed in Tunisian citrus orchards have prompted studies on the Pseudomonas spp. responsible for blast and black pit. Prospective orchards between 2015 and 2017 showed that the diseases rapidly spread geographically and to new cultivars. A screening of Pseudomonas spp. isolated from symptomatic trees revealed their wide diversity according to phylogenetic analysis of their housekeeping rpoD and cts genes. The majority of strains were affiliated to Pseudomonas syringae pv. syringae (Phylogroup PG02b), previously described in Tunisia. However, they exhibited various BOX-PCR fingerprints and were not clonal. This work demonstrated, for the first time in Tunisia, the involvement of Pseudomonas cerasi (PG02a) and Pseudomonas congelans (PG02c). The latter did not show significant pathogenicity on citrus, but was pathogenic on cantaloupe and active for ice nucleation that could play a role in the disease. A comparative phylogenetic study of citrus pathogens from Iran, Montenegro and Tunisia revealed that P. syringae (PG02b) strains are closely related but again not clonal. Interestingly P. cerasi (PG02a) was isolated in two countries and seems to outspread. However, its role in the diseases is not fully understood and it should be monitored in future studies. The diversity of pathogenic Pseudomonas spp. and the extension of the diseases highlight that they have become complex and synergistic. It opens questions about which factors favor diseases and how to fight against them efficiently and with sustainable means.This study was funded by the Spanish MINECO (CGL2015-70925), co-founded by the European Regional Development Fund/European Social Fund “Investing in your future” (FEDER). This work was also supported by funds from the PRF Project (PRF14CTABIOTEC02) and by the Ministry of Higher Education and Scientific Research of Tunisia (LR16ES05)

Biological control of Botrytis cinerea on stem wounds with moderately halophilic bacteria

International audienceInfection of tomato stem wounds by Botrytis cinerea is an important problem which can cause severe economic losses in greenhouse tomato crops. Three moderately halophilic bacteria were tested for their ability to protect pruning wounds from attacks by B. cinerea under growth chamber conditions. The severity of the disease estimated by the length of the rotted stem was used to calculate the area under the disease progress curves (AUDPC). Bacterial antagonists (B1, B2 and B3) were very effective in controlling Botrytis-infection on the tomato stems during the first 6 days and later by the end of the experiment. Plants treated with Bacillus subtilis (B1) had the lowest AUDPC (0). It was followed by B. subtilis (B3) and Halomonas sp. (B2) with AUDPC of 9.8 and 17.02, respectively. While the B1 strain best inhibited grey mold development when applied as young culture (24 h), the B3 strain performed better as an older culture (48 h). In contrast to the results obtained with Bacillus species, the efficacy of the bacterial treatment B2 seems to be independent of the growth phase. The co-cultures with fungal spores and either B. subtilis (B1) or Halomonas sp. (B2) applied as a 24 h bacterial culture completely inhibited the germination of B. cinerea after 24 h at 21_

Prevalence, Etiology, and Risk Factors of Tinea Pedis and Tinea Unguium in Tunisia

Background. Foot mycoses are a frequent disease that represents a public health problem worldwide. Objectives. This study aims to evaluate the epidemiology of foot mycoses among Tunisian patients, in order to determine the fungal etiological agents and to identify possible risk factors. Patients and Methods. A prospective study of three hundred and ninety-two patients was undertaken during one year (2013-2014). All subjects were asked to collect demographic data related to the risk factors of foot mycoses. A complete mycological diagnosis was carried out on all patients. Results. A total of 485 samples were collected; tinea pedis and tinea unguium were confirmed in 88.2% of cases. Dermatophytes were isolated in 70.5% and the most frequent pathogen was Trichophyton rubrum (98.1%), followed by yeasts (17.7%) commonly Candida parapsilosis. Non-dermatophyte molds (NDMs) were observed in 8.02% cases and Fusarium sp. was the frequent genus (29.1%). The main predisposing factors of fungal foot infections were practicing ritual washing (56.6%) and frequentation of communal showers (50.5%). Conclusion. This is a recent survey of foot mycoses in Tunisia. Epidemiological studies can be useful to eradicate these infections and to provide further measures of hygiene and education

Biological control of grey mould in strawberry fruits by halophilic bacteria

Aims: Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti- Botrytis metabolites and volatiles. Methods and Results: Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea. Thirty strains (20Æ2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20 C, from 50% to 91Æ66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui, B. subtilis, B. pumilus, B. licheniformis, Terribacillus halophilus, Halomonas elongata, Planococcus rifietoensis, Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites. Conclusions: Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries. Significance and Impact of the study: The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions