Winter, S. | bioRxiv Science

bioRxiv2018

In vitro evaluation of the decontamination effect of cold argon plasma on selected bacteria frequently encountered in small animal bite injuries

ObjectiveThe beneficial effects of cold argon plasma (CAP) on wound healing and its capacity for bacterial decontamination has recently been documented. However, despite favourable reports from experimental trials and human applications, the first in vivo studies in small animals did not prove any decontamination effect in canine bite wounds.\n\nThe present study therefore aimed to evaluate the decontamination effect of CAP in different bacteria frequently encountered in canine bite wounds in vitro.\n\nMethodsStandard strains of Escherichia (E.) coli, Staphylococcus (S.) pseudintermedius, S. aureus, Streptococcus (Sc.) canis, Pseudomonas (P.) aeruginosa and Pasteurella multocida were investigated. To evaluate the influence of the bacterial growth phase, each bacterium was incubated in nutrient broth for 3 and 8 hours, respectively, before argon plasma treatment. Three different bacterial concentrations were created per bacterium and growth phase, and each was exposed to cold plasma at a gas flow rate of 5 standard litres/minute of argon for 30 seconds, 1 minute and 2 minutes.\n\nResultsArgon treatment resulted in acceptable decontamination rates (range 98.9-99.9%) in all bacteria species in vitro; however, differences in susceptibility were detected in the different tested bacteria. Treatment time significantly (P<0.05) correlated with the decontamination rate in E. coli, Sc. canis and S. aureus, with an exposure time of 2 minutes being most effective. The initial bacterial concentration significantly (P<0.05) influenced decontamination in Pasteurella multocida and P. aeruginosa, in which treatment time was not as important. The growth phase only influenced decontamination in S. pseudintermedius.\n\nConclusionCAP exerts effective antibacterial activity against the tested bacteria strains in vitro, with species specific effects of treatment time, growth phase and concentration.

microbiology↗

bioRxiv2018

Limited Introgression Supports Division of Giraffe into Four Species

All giraffe (Giraffa) were previously assigned to a single species (G. Camelopardalis) and nine subspecies. However, multi-locus analyses of all subspecies have shown that there are four genetically distinct clades and suggest four giraffe species. This conclusion might not be fully accepted due to limited data and lack of explicit gene flow analyses. Here we present an extended study based on 21 independent nuclear loci from 137 individuals. Explicit gene flow analyses identify less than one migrant per generation, including between the closely related northern and reticulated giraffe. Thus, gene flow analyses and population genetics of the extended dataset confirm four genetically distinct giraffe clades and support four independent giraffe species. The new findings call for a revision of the IUCN classification of giraffe taxonomy. Three of the four species are threatened with extinction, mostly occurring in politically unstable regions, and as such, require the highest conservation support possible.

ecology↗