The structure and diversity of microbial communities in Paederus fuscipes (Coleoptera: Staphylinidae): from ecological paradigm to pathobiome

Characterization of bacteria expectorated during forced salivation of the Phlebotomus papatasi: A neglected component of sand fly infectious inoculums

The infectious inoculum of a sand fly, apart from its metacyclic promastigotes, is composed of factors derived from both the parasite and the vector. Vector-derived factors, including salivary proteins and the gut microbiota, are essential for the establishment and enhancement of infection. However, the type and the number of bacteria egested during salivation is unclear. In the present study, sand flies of Phlebotomus papatasi were gathered from three locations in hyperendemic focus of zoonotic cutaneous leishmaniasis (ZCL) in Isfahan Province, Iran. By using the forced salivation assay and targeting the 16S rRNA barcode gene, egested bacteria were characterized in 99 (44%) out of 224 sand flies. Culture-dependent and culture-independent methods identified the members of Enterobacter cloacae and Spiroplasma species as dominant taxa, respectively. Ten top genera of Spiroplasma, Ralstonia, Acinetobacter, Reyranella, Undibacterium, Bryobacter, Corynebacterium, Cutibacterium, Psychrobacter, and Wolbachia constituted >80% of the saliva microbiome. Phylogenetic analysis displayed the presence of only one bacterial species for the Spiroplasma, Ralstonia, Reyranella, Bryobacter and Wolbachia, two distinct species for Cutibacterium, three for Undibacterium and Psychrobacter, 16 for Acinetobacter, and 27 for Corynebacterium, in the saliva. The abundance of microbes in P. papatasi saliva was determined by incorporating the data on the read counts and the copy number of 16S rRNA gene, about 9,000 bacterial cells, per sand fly. Both microbiological and metagenomic data indicate that bacteria are constant companions of Leishmania, from the intestine of the vector to the vertebrate host. This is the first forced salivation experiment in a sand fly, addressing key questions on infectious bite and competent vectors.

The pederin-producing bacteria density dynamics in Paederus fuscipes at different developmental stages

Pederin, a defensive toxin in Paederus fuscipes, is produced by an uncultured Gram-negative symbiont, which establishes a stable symbiotic relationship with a female host before completion of metamorphosis. However, the transmission process of pederin-producing bacteria (PPB) in P. fuscipes at different life stages remains unknown. Herein, the PPB population dynamics and transcriptome atlas for P. fuscipes development (egg, first-instar larva, second-instar larva, pupa, and newly emerged female and male) were characterised. We found that a microbial layer containing PPB covered the eggshell, which could be sterilised by smearing the eggshell with streptomycin. Maternal secretions over the eggshell are likely the main PPB acquisition route for P. fuscipes offspring. The PPB density in eggs was significantly higher than that in other life stages (p < 0.05), which demonstrated that the beetle mothers gave more PPB than the larvae acquired. Physiological changes (hatching and eclosion) led to a decreased PPB density in P. fuscipes. Pattern recognition receptors related to Gram-negative bacteria recognition were identified from P. fuscipes transcriptomes across various life stages, which might be used to screen genes involved in PPB regulation. These results will help advance future efforts to determine the molecular mechanisms of PPB colonisation of P. fuscipes.

Rapid response of midgut bacteria in Bactrocera tau (Walker) (Diptera: Tephritidae) to lambda-cyhalothrin- and spinosad-induced stress

In recent decades, the increasingly widespread application of chemical pesticides has exacerbated the emergence of insecticide resistance among insect pests. In this study, we examined the rapid response of bacteria in the midgut of the fruit fly Bactrocera tau (Walker) (Diptera: Tephritidae) to stress induced by the insecticides lambda-cyhalothrin and spinosad by analyzing the bacterial community structure and diversity in the midguts of 4-day-old B. tau. The results revealed that 4-day-old B. tau females were more resistant to lambda-cyhalothrin and spinosad than their 4-day-old male counterparts. Alpha- and beta-diversity analyses revealed no significant differences between male and female B. tau with respect to the diversity and richness of gut bacteria in response to the same treatments. In response to treatment with lambda-cyhalothrin and spinosad at lethal concentration 50 (LC50), we detected significant changes in the structure and diversity of the bacterial community in the midguts of both male and female B. tau. Particularly among the dominant bacterial genera, there were decreases in the relative abundances of Citrobacter, Enterobacter, Klebsiella, and Pectobacterium. Increases were observed in the relative abundances of Dysgonomonas, Erwinia, and Providencia. Our findings provide a theoretical basis for gaining a better understanding of the relationships between midgut bacteria and the insecticide resistance of B. tau.

Molecular Characterization of Paederus Spp (Coleoptera: Staphylinidae, Paederinae) the Agent of Human Linear Dermatitis in the Caspian Sea Coast, North of Iran

Background

A combined morphological and molecular survey was performed to determine the agent of human linear dermatitis Paederus Fabricius, 1775 (Coleoptera: Staphylinidae, Paederinae) species composition in Mazandaran Province in the Caspian Sea coast in northern Iran, where most of linear dermatitis cases of the country occurred.

Methods

Altogether, 397 Paederus specimens were collected from May to August 2021 and classified using morphological characters and ITS2-rDNA sequence analysis.

Results

Morphological investigation revealed that all the specimens were Paederus fuscipes. ITS2 polymerase chain reaction (PCR) direct-sequences and the profiles of restriction fragment length polymorphism (RFLP) derived from digestion of PCR products by HinfI, HpaII, and SalI enzymes were identical confirming the morphological results, implying that all specimens belonged to a single taxon.

Conclusion

Paederus fuscipes (Fabricius, 1775) is considered the dominant taxon and responsible for linear dermatitis in Mazandaran Province. To our knowledge, we have provided the first molecular typing of Paederus beetles at the species level, suggesting that ITS2-rDNA characterization is an alternative tool for species discrimination of Paederus spp.

Potassium permanganate use in the management of a wound induced by contact with Paederus: A case report

Pederin is a vesicant toxic amide, found in the hemolymph of the beetle genus, Paederus. Physical contact with these insects produces a type of irritant dermatitis with variable clinical symptoms. It has been identified that Pederin (a vesicant toxic amide responsible for the ulcerative lesion) is produced by Gram-negative endosymbiotic bacteria of the Pseudomonas genus. The present study describes the case of a patient who had come into contact with the insect Paederus sp. and developed an ulcerative lesion. He was first treated with topical steroids, as part of the conventional management, and following no response to treatment, he was treated locally with a 5% potassium permanganate solution, in conjunction with systemic antibiotic therapy, obtaining a good response in the healing process. On the whole, the present study demonstrates that potassium permanganate solutions, in conjunction with antibiotics and anti-inflammatories, may be beneficial in the treatment of dermatitis or ulcerative lesions caused by insects of the Paederus genus. However, further research is required to fully determine the complete benefits and any side-effects.