Poster Presentation The Prato Conference on the Pathogenesis of Bacterial Infections of Animals 2016

Characterization of Moraxella strains from the nasal cavities of piglets (#65)

Sergi Lopez-Serrano 1 , Nuria Galofré-Milà 1 , Ana M Perez de Rozas 1 , Virginia Aragon 1
  1. IRTA CReSA, Bellaterra, BARCELONA, Spain

Upper eukaryotes live in mutualist relationship with microbial communities that colonize the external surfaces of their organisms. These communities are called the microbiota and play a role in protection against infectious diseases. Analysis of the nasal microbiota of weaned piglets have shown that the genus Moraxella is commonly present on this location. Nasal swabs from 3-4 week old piglets were cultured on chocolate agar under aerobic conditions. Isolates were identified as Moraxella by partial sequencing of the 16S rRNA gene. ERIC-PCR was used to differentiate 26 strains from a collection of 51 isolates. Whole 16S rRNA gene allowed the identification of the different strains at species level. Analysis of the 16S sequences showed that the majority of the strains belonged to the species Moraxella pluranimalium, nonetheless Moraxella porci was also detected. In addition, a cluster of 7 strains could not be classified as any described Moraxella species, probably representing a new one.Subsequent phenotypic characterization was performed to explore serum susceptibility, biofilm formation and antimicrobial susceptibility of the different strains. Strains of Moraxella pluranimalium were mainly sensitive to the serum complement, while the cluster classified as a new species was highly resistant. Biofilm formation capacity was also very variable, while adherence to epithelial cell lines was similar among the strains. Antimicrobial tests evidenced that multiresistant strains were mainly found in farms where antibiotic treatment was systematically performed. Additionally, selected strains were tested in phagocytosis assays with porcine alveolar macrophages. Again, high variability was observed in the susceptibility of the Moraxella strains to macrophages.

In summary, phenotypic characterization revealed heterogeneity among Moraxella strains from the nasal cavity of piglets. Strains with pathogenic potential were detected as well as those that may be commensal members of the nasal microbiota. The role of Moraxella in porcine diseases and health should be further evaluated.