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The human skin microbiota is quantitatively dominated by Gram-positive bacteria, detected by both culture and metagenomics. However, metagenomics revealed a huge variety of Gram-negative taxa generally considered from environmental origin. For species affiliation of bacteria in skin microbiota, clones of 16S rRNA gene and colonies growing on diverse culture media were analyzed. Species-level identification was achieved for 81% of both clones and colonies. Fifty species distributed in 26 genera were identified by culture, mostly belonging to Actinobacteria and Firmicutes, while 45 species-level operational taxonomic units distributed in 30 genera were detected by sequencing, with a high diversity of Proteobacteria. This mixed approach allowed the detection of 100% of the genera forming the known core skin Gram-negative microbiota and 43% of the known diversity of Gram-negative genera in human skin. The orphan genera represented 50% of the current skin pan-microbiota. Improved culture conditions allowed the isolation of Roseomonas mucosa, Aurantimonas altamirensis and Agrobacterium tumefaciens strains from healthy skin. For proteobacterial species previously described in the environment, we proposed the existence of skin-specific ecotypes, which might play a role in the fine-tuning of skin homeostasis and opportunistic infections but also act as a shuttle between environmental and human microbial communities. Therefore, skin-associated proteobacteria deserve to be considered in the One-Health concept connecting human health to the health of animals and the environment.

In the challenging quest for a solution to reduce the risk of implant-associated infections in bone substitution surgery, the use of silver ions is promising regarding its broad spectrum on planktonic, sessile as well as multiresistant bacteria. In view of controlling its delivery in situ at the desired dose, we investigated its encapsulation in carboxymethyl cellulose (CMC) microparticles by spray-drying and included the latter in the formulation of a self-setting calcium phosphate bone cement. We implemented an original step-by-step methodology starting from the in vitro study of the antibacterial properties and cytotoxicity of two silver salts of different solubility in aqueous medium and then in the cement to determine the range of silver loading able to confer anti-biofilm and non-cytotoxic properties to the biomaterial. A dose-dependent efficiency of silver was demonstrated on the main species involved in bone-implant infection (S. aureus and S. epidermidis). Loading silver in microspheres instead of loading it directly inside the cement permitted to avoid undesired silver-cement interactions during setting and led to a faster release of silver, i.e. to a higher dose released within the first days combining anti-biofilm activity and preserved cytocompatibility. In addition, a combined interest of the introduction of about 10% (w/w) silver-loaded CMC microspheres in the cement formulation was demonstrated leading to a fully injectable and highly porous (77%) cement, showing a compressive strength analogous to cancellous bone. This injectable silver-loaded biomimetic composite cement formulation constitutes a versatile bone substitute material with tunable drug delivery properties, able to fight against bone implant associated infection. STATEMENT OF SIGNIFICANCE: This study is based on two innovative scientific aspects regarding the literature: i) Choice of silver ions as antibacterial agent combined with their way of incorporation: Carboxymethylcellulose has never been tested into bone cement to control its drug loading and release properties. ii) Methodology to formulate an antibacterial and injectable bone cement: original and multidisciplinary step-by-step methodology to first define, through (micro)biological tests on two silver salts with different solubilities, the targeted range of silver dose to include in carboxymethylcellulose microspheres and, then optimization of silver-loaded microparticles processing to fulfill requirements (encapsulation efficiency and size). The obtained fully injectable composite controls the early delivery of active dose of silver (from 3 h and over 2 weeks) able to fight against bone implant-associated infections., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The human skin microbiota is quantitatively dominated by Gram-positive bacteria, detected by both culture and metagenomics. However, metagenomics revealed a huge variety of Gram-negative taxa generally considered from environmental origin. For species affiliation of bacteria in skin microbiota, clones of 16S rRNA gene and colonies growing on diverse culture media were analyzed. Species-level identification was achieved for 81% of both clones and colonies. Fifty species distributed in 26 genera were identified by culture, mostly belonging to Actinobacteria and Firmicutes , while 45 species-level operational taxonomic units distributed in 30 genera were detected by sequencing, with a high diversity of Proteobacteria . This mixed approach allowed the detection of 100% of the genera forming the known core skin Gram-negative microbiota and 43% of the known diversity of Gram-negative genera in human skin. The orphan genera represented 50% of the current skin pan-microbiota. Improved culture conditions allowed the isolation of Roseomonas mucosa , Aurantimonas altamirensis and Agrobacterium tumefaciens strains from healthy skin. For proteobacterial species previously described in the environment, we proposed the existence of skin-specific ecotypes, which might play a role in the fine-tuning of skin homeostasis and opportunistic infections but also act as a shuttle between environmental and human microbial communities. Therefore, skin-associated proteobacteria deserve to be considered in the One-Health concept connecting human health to the health of animals and the environment.

An alarming increase in microbial resistance to traditional drugs and classical pharmacophores has spurred the search for new antimicrobial compounds. Indolone-N-oxides (INODs) possess a redox pharmacophore with promising, recently established, antimalarial activities. In this study, the anti-infectious properties of a series of INODs were investigated. The antibacterial activity was evaluated against five bacterial strains Gram-positive (Staphylococcus aureus, Enterococcus hirae), Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and acid-fast (Mycobacterium tuberculosis). The antifungal activity was assessed using two fungal strains (Aspergillus niger, Candida albicans). The antileishmanial activity was tested against two leishmanial strains, axenically-cultured amastigote (Leishmania infantum, Leishmania amazonensis). The pharmacological activities are discussed as a function of structural and lipophilic characteristics. The Gram-positive bacterial strain E. hirae was found to be the most sensitive strain, whereas the Gram-negative E. coli was resistant to this family of compounds. One compound (64) was more potent than nalidixic acid against E. hirae, whereas another one (52) was equipotent as clotrimazole against C. albicans. INODs were microbe -cidal rather than -static. INODs showed good antitubercular activity in the low micromolar range (similar to ciprofloxacin). In addition, INOD-antiprotozoal potencies were confirmed against the leishmania parasite. INODs showed a broad spectrum of antimicrobial activity and offer a promising anti-infectious prototype worthy of being developed.