Endemic Chromoblastomycosis Caused Predominantly by Fonsecaea nubica, Madagascar1.

Chromoblastomycosis is an implantation fungal infection. Twenty years ago, Madagascar was recognized as the leading focus of this disease. We recruited patients in Madagascar who had chronic subcutaneous lesions suggestive of dermatomycosis during March 2013-June 2017. Chromoblastomycosis was diagnosed in 50 (33.8%) of 148 patients. The highest prevalence was in northeastern (1.47 cases/100,000 persons) and southern (0.8 cases/100,000 persons) Madagascar. Patients with chromoblastomycosis were older (47.9 years) than those without (37.5 years) (p = 0.0005). Chromoblastomycosis was 3 times more likely to consist of leg lesions (p = 0.003). Molecular analysis identified Fonsecaea nubica in 23 cases and Cladophialophora carrionii in 7 cases. Of 27 patients who underwent follow-up testing, none were completely cured. We highlight the persistence of a high level of chromoblastomycosis endemicity, which was even greater at some locations than 20 years ago. We used molecular tools to identify the Fonsecaea sp. strains isolated from patients as F. nubica.

Sporotrichosis in the Highlands of Madagascar, 2013-20171.

Sporotrichosis is a saprozoonotic fungal infection found mostly in tropical and subtropical areas. Few case reports in Madagascar have been published. To document sporotrichosis epidemiology in Madagascar, we conducted a cross-sectional study. During March 2013-June 2017, we recruited from select hospitals in Madagascar patients with chronic cutaneous lesions suggestive of dermatomycosis. Sporotrichosis was diagnosed for 63 (42.5%) of 148 patients. All but 1 patient came from the central highlands, where the prevalence was 0.21 cases/100,000 inhabitants. Frequency was high (64.7%) among patients <18 years of age. Sporotrichosis was diagnosed for 73.8% of patients with arm lesions, 32.3% with leg lesions, and 15.4% with lesions at other sites. Molecular identification identified 53 Sporothrix schenckii isolates. Among the 32 patients who were followed up, response to itraconazole was complete or major for 15 and minor for 17. Overall, endemicity of sporotrichosis in Madagascar was high, concentrated in the highlands.

Pseudomonas aeruginosa Biofilm Formation and Persistence, along with the Production of Quorum Sensing-Dependent Virulence Factors, Are Disrupted by a Triterpenoid Coumarate Ester Isolated from Dalbergia trichocarpa, a Tropical Legume.

Recently, extracts of Dalbergia trichocarpa bark have been shown to disrupt P. aeruginosa PAO1 quorum sensing (QS) mechanisms, which are key regulators of virulence factor expression and implicated in biofilm formation. One of the active compounds has been isolated and identified as oleanolic aldehyde coumarate (OALC), a novel bioactive compound that inhibits the formation of P. aeruginosa PAO1 biofilm and its maintenance as well as the expression of the las and rhl QS systems. Consequently, the production of QS-controlled virulence factors including, rhamnolipids, pyocyanin, elastase and extracellular polysaccharides as well as twitching and swarming motilities is reduced. Native acylhomoserine lactones (AHLs) production is inhibited by OALC but exogenous supply of AHLs does not restore the production of virulence factors by OALC-treated cultures, indicating that OALC exerts its effect beyond AHLs synthesis in the QS pathways. Further experiments provided a significant inhibition of the global virulence factor activator gacA by OALC. OALC disorganizes established biofilm structure and improves the bactericidal activity of tobramycin against biofilm-encapsulated PAO1 cells. Finally, a significant reduction of Caenorhabditis elegans paralysis was recorded when the worms were infected with OALC-pre-treated P. aeruginosa. Taken together, these results show that triterpenoid coumarate esters are suitable chemical backbones to target P. aeruginosa virulence mechanisms.

Endemic malagasy Dalbergia species inhibit quorum sensing in Pseudomonas aeruginosa PAO1.

Various species of the plant genus Dalbergia are traditionally used as medicine for sundry ailments and some of them have been shown recently to quench the virulence of Gram-positive and Gram-negative bacteria. Cell-to-cell communication mechanisms, quorum sensing (QS) in particular, are key regulators of virulence in many pathogenic bacteria. Screening n-hexane extracts of leaves, roots and bark of endemic Malagasy Dalbergia species for their capacity to antagonize QS mechanisms in Pseudomonas aeruginosa PAO1 showed that many reduced the expression of the QS-regulated genes lasB and rhlA. However, only the extract of Dalbergia trichocarpa bark (DTB) showed a significant reduction of QS gene expression without any effect on the aceA gene encoding a QS-independent isocitrate lyase. Further characterization of DTB impact on QS revealed that the QS systems las and rhl are inhibited and that swarming, twitching, biofilm formation and the production of pyocyanin, elastase and proteases are also hampered in the presence of the DTB extract. Importantly, compared with the known QS inhibitor naringenin, the DTB extract showed a stronger negative effect on twitching, biofilm formation and tobramycin resistance. Preliminary structural characterization of these potent biofilm disrupters suggests that they belong to the phytosterols. The strong inhibition of motility and biofilm formation suggests that the DTB extract contains agents disrupting biofilm architecture, which is an important observation in the context of the design of new drugs targeting biofilm-encapsulated pathogens.

Newcastle disease virus in Madagascar: identification of an original genotype possibly deriving from a died out ancestor of genotype IV.

In Madagascar, Newcastle disease (ND) has become enzootic after the first documented epizootics in 1946, with recurrent annual outbreaks causing mortality up to 40%. Four ND viruses recently isolated in Madagascar were genotypically and pathotypically characterised. By phylogenetic inference based on the F and HN genes, and also full-genome sequence analyses, the NDV Malagasy isolates form a cluster distant enough to constitute a new genotype hereby proposed as genotype XI. This new genotype is presumably deriving from an ancestor close to genotype IV introduced in the island probably more than 50 years ago. Our data show also that all the previously described neutralising epitopes are conserved between Malagasy and vaccine strains. However, the potential implication in vaccination failures of specific amino acid substitutions predominantly found on surface-exposed epitopes of F and HN proteins is discussed.