Characterization of methicillin-resistant staphylococcus aureus in commercial and wild rabbits (oryctolagus cuniculus) and immunological evaluation of a paternal line of commercial rabbits. Study of the pathogen-host interaction

• Autores: Elena Moreno Grua
• Directores de la Tesis: Juan Manuel Corpa Arenas (dir. tes.), Laura Selva Martínez (codir. tes.)
• Lectura: En la Universidad CEU - Cardenal Herrera ( España ) en 2021
• Idioma: inglés
• Tribunal Calificador de la Tesis: Juan José Pascual Amorós (presid.), Juan José Quereda Torres (secret.), Carles Ubeda Morant (voc.), Nuria Quiles Puchalt (voc.), M. Angeles Tormo Mas (voc.)
• Materias:
  • Ciencias de la vida
    • Biología animal (zoología)
      • Genética animal
  • Ciencias agrarias
    • Ciencias veterinarias
      • Inmunología
      • Microbiología
• Enlaces
  • Tesis en acceso abierto en: Repositorio Institucional CEU
• Resumen

  • Staphylococcus aureus is an important pathogen that is well able to develop resistance to antibiotics. One of the most remarkable clones to have spread worldwide and caused pandemic outbreaks is methicillin-resistant Staphylococcus aureus (MRSA), a dangerous strain that is frequently multiresistant to antibiotics. In this work, we studied the pathogen S. aureus by focusing on MRSA strains. We evaluated the presence of S. aureus on rabbit farms and in wild rabbits before carrying out an in-depth study of the isolated clones through their sequencing. Then we studied a frequent host of this pathogen, the rabbit (Oryctolagus cuniculus), to which this bacterium is highly adapted and is, therefore, a very useful model of infections by this pathogen. We evaluated the immune system of commercial rabbits at remarkable time points of the productive cycle and then performed experimental infection to evaluate the immune system when it faces an infectious challenge. First, an unexpected large number of MRSA strains from infrequent lesions were found on rabbit farms. This is the first time that mecC-MRSA strains isolated from rabbit farms are described. The MRSA strains isolated from rabbit farms showed limited genetic diversity, with ST2855 being the most prevalent clone. The majority of the tested MRSA isolates were multidrug-resistant. Second, a high percentage of S. aureus carriers was detected in wild rabbits and hares hunted in high-density areas in east Spain, and the ear was the main ecological niche where S. aureus was isolated. Another finding was the marked presence of ST1945 MRSA of the CC130 lineage containing the mecC gene in these animals. These strains harboured mobile genetic element SCCmec type XI. Therefore, farm rabbits and wild rabbits can act as a reservoir for MRSA strains being transmitted in nature. As a result of sequencing mobile genetic element SCCmec, we describe two new SCCmec cassette types: one containing the mecC gene and another simultaneously containing mecA and mecC genes. Two of these mecA-mecC-MRSA strains had the SCCmec excised from the genome. We also observed that each SCCmec type was associated with certain STs. The phenotypic resistance profile revealed that strains had an antibiotic resistance profile depending on whether they had methicillin-resistance gene mecA or mecC. Nevertheless, simultaneously carrying the two genes offered no more advantages than having only the mecA gene in the resistance profile to the tested antibiotics. Finally, after evaluating the immune system by flow cytometry at main time points of the productive cycle of commercial rabbits the genetic selection by average daily gain did not affect rabbit females’ ability to mount immune response. After evaluating lesions and immune system evolution during an experimental infection by S. aureus in skin, the results evidenced that this breeding programme favoured the immune system’s capability to undergo an infectious challenge with S. aureus. To evaluate vitrification effects, a group of animals obtained from vitrified embryos was compared to another group obtained by routine artificial insemination. A long-term vitrification effect on the immune response to infection with S. aureus was observed insofar as the animals from the restored vitrificated population presented better performance during infection.