Food-borne pathogen campylobacteria. Rapid detection methods for virulence-associated genes in campylobacter jejuni, and study of pathogenicity-associated factors in arcobacter spp

Resumen

Campylobacter spp. is associated with reproductive disorders in sheep and cattle, and to a lesser degree, with intestinal infections in animals (Taylor and Al-Mashat, 1985). On the other hand, C. jejuni is an important human pathogen. However, whether all the C. jejuni strains are equally virulent to humans still remains to be elucidated Regarding with Arcobacter spp., their role in causing disease has not been clearly established yet, but there are evidences that indicate an association of Arcobacter species with animal and human disease. Due to their association with human infections via consumption of contaminated water or food, they are classified as emerging pathogens (ICMSF, 2002). Yet, almost nothing is known about their virulence determinants, but the large number of signal transduction systems encoded by the genome of A. butzleri (Miller et al., 2007) supports its capability to adapt to and to survive in a wide range of environments and to cause disease. Remarkably little is known about pathogenicity-associated bacterial factors in Campylobacter spp., and almost nothing in Arcobacter spp. Does the pathogenicity of Campylobacter spp. vary among species? Is a subset of strains present in poultry the one which reaches the consumer and causes human disease? Do Arcobacter spp. have the capability to acquire antimicrobial resistances? As it occurs in other pathogenic bacteria, are the ECF sigma factors implied in the pathogenicity of A. butzleri? The first aim of the work described in this thesis was to determine the prevalence of virulence-associated genes in C. jejuni in order to find possible virulence markers associated to the origin of the strains. In this thesis, two possible virulence markers associated to human C. jejuni isolates in the Basque Country have been identified. As a next step, the antimicrobial susceptibility of Arcobacter spp. from the North of Spain was studied and the nature of the resistances that Arcobacter displays to various agents was discussed. The studies described in this thesis may be supportive for devising alternative drug treatments against possible human Arcobacter infections. Finally, for the first time, Arcobacter mutants on the ECF sigma and anti-sigma factor encoding genes were constructed and the role of six of the seven Arcobacter ECF sigma factors was described and discussed. The A. butzleri ECF sigma factors are not required under standard growth conditions. They regulate a number of genes involved in the binding and transport of different compounds, in the energy metabolism and in sulphur oxidation. Interestingly, as previously observed in Bacillus subtilis (Mascher et al., 2007; Luo and Helmann, 2009), number of these genes are regulated by more than one ECF sigma factor