Survey on the spirilar flora of Lagomorphs

Members of the genera Campylobacter and Helicobacter have been in the spotlight in recent decades because of their status as animals and/or humans pathogens, both confirmed and emerging, and because of their association with food-borne and zoonotic diseases. First observations of spiral shaped bacteria or Campylobacter-like organisms (CLO) date back to the end of the 19th century, however the lack of adequate isolation methods hampered further research. With the introduction of methods such as selective media and a filtration procedure during the 1970s led to a renewed interest in Campylobacter, especially as this enabled elucidation of their role in human hosts. On the other hand the classification and identification of these bacteria was troublesome, mainly because of the biochemical inertness and fastidious growth requirements. In 1991, the taxonomy of Campylobacter and related organisms was thoroughly revised, since this revision several new Campylobacter and Helicobacter species have been described. Moreover, thanks to the introduction of a polyphasic taxonomic practice, the classification of these novel species is well-founded. Indeed, a polyphasic approach was here followed for characterizing eight isolates obtained from rabbits epidemiologically not correlated and as a result a new Campylobacter species was proposed: Campylobacter cuniculorum (Chapter 1). Furthermore, there is a paucity of data regarding the occurrence of spiral shaped enteric flora in leporids. In order to define the prevalence both of this new species and other CLO in leporids (chapter 2), a total of 85 whole intestinal tracts of rabbits reared in 32 farms and 29 capture hares, epidemiologically not correlated, were collected just after evisceration at the slaughterhouse or during necroscopy. Examination and isolation methods were varied in order to increase the sensibility level of detection, and 100% of rabbit farms resulted positive for C. cuniculorum in high concentrations. Moreover, in 3.53% of the total rabbits examined, a Helicobacter species was detected. Nevertheless, all hares resulted negative both for Campylobacter or Helicobacter species. High prevalence of C. cuniculorum were found in rabbits, and in order to understand if this new species could play a pathological role, a study on some virulence determinants of C. cuniculorum was conducted (Chapter 3). Although this new species were able to adhere and invade, exert cytolethal distending toxin-like effects although at a low titre, a cdtB was not detected. There was no clear relationship between source of isolation or disease manifestation and possession of statistically significantly levels of particular virulence-associated factors although, cell adhesion and invasion occurred. Furthermore, antibiotic susceptibility was studied (chapter 4) in Campylobacter and in Escherichia coli strains, isolated from rabbits. It was possible to find acquired resistance of C. cuniculorum to enrofloxacin, ciprofloxacin and erytromycin. C. coli isolate was susceptible to all antimicrobial tested and moreover it is considered as a wild-type strain. Moreover, E. coli was found at low caecal concentration in rabbits and 30 phenotypes of antibiotic resistance were founded as well as the high rate of resistances to at least one antibiotic (98.1%). The majority of resistances were found from strains belonging to intensive farming system. In conclusion, in the course of the present study a new species isolated from rabbits was described, C. cuniculorum, and its high prevalence was established. Nevertheless, in hare samples no Campylobacter and Helicobacter species were detected. Some virulence determinants were further analyzed, however further studied are needed to understand the potential pathogenicity of this new species. On the other hand, antimicrobial susceptibility was monitored both in C. cuniculorum and indicator bacteria and acquired resistance was observed towards some antibiotics, indicating a possible role of rabbitries in the diffusion of antibiotic resistance. Further studies are necessary to describe and evaluate the eventual zoonotic role of Campylobacter cuniculorum.

Transposable elements dynamics in taxa with different reproductive strategies or speciation rate

In recent years the advances in genomics allowed to understand the importance of Transposable Elements (TE) in the evolution of eukaryotic genomes. In this thesis I face two aspects of the TE impact on the in the animal kingdom. The first part is a comparison of the dynamics of the TE dynamics in three species of stick-insects of the Genus Bacillus. I produced three random genomic libraries of 200 Kbps for the three parental species of the taxon: a gonochoric population of Bacillus rossius (facultative parthenogenetic), Bacillus grandii (gonochoric) and Bacillus atticus (obligate parthenogenetic). The unisexual taxon Bacillus atticus does not shows dramatic differences in TE total content and activity with respect to Bacillus grandii and Bacillus rossius. This datum does not confirm the trend observed in other animal models in which unisexual taxa tend to repress the activity of TE to escape the extinction by accumulation of harmful mutations. In the second part I tried to add a contribute to the debate initiated in recent years about the possibility that a high TE content is linked to a high rate of speciation. I designed an evolutionary framework to establish the different rate of speciation among two or more taxa, then I compared TE dynamics considering the different rates of speciation. The species dataset comprises: 29 mammals, four birds, two fish and two insects. On the whole the majority of comparisons confirms the expected trend. In particular the amount of species analyzed in Mammalia allowed me to get a statistical support (p<0,05) of the fact that the TE activity of recently mobilized elements is positively related with the rate of speciation.