New insights into the human risk posed by Arcobacter spp.

Abstract

[EN]Arcobacter is a bacterial genus that is wodely distributed in natura. Bacteria belonging to this genus are frequently found in food and water, making them the main sources of transmission to humans. Within the genus, A. buzleri is the most frequently isolated species from human cases, followed by A. cryaerophilus. However, other species have also been with human cases.The prevalence of Arcobacter infections in humans is on the rise. However, the virulence mechanisms of these bacteria remain unclear. Therefore, the objective of this thesis is to enhance the knowledge of the risk that Arcobacter poses to humans by providing new data on their pathogenic potential and the mechanisms they employ to cause disease.This thesis presents two new cases of A. butzleri infection in patients with different symptoms. It proposes methods to improve the diagnosis of these bacteria and carries out a characterisation based on whole genome sequencing, supported by several phenotypic analyses conducted on both strains.Acrobacter species, not necessarily associated with human infection. The in vitro study on human intestinal cells, carried out with sewage- and food-derives isolates, highlights not only A butzleri but also other less common Arcobacter species for their high virulence, and warns of the potential risk that strins isolated from sewage may pose for human transmission. The design os species-specific primers has improved the detection of cadF, ABU_RS00335, claB and hecA, four common virulence genes associated to cell adhesion and invasion, in Acrobacter species other than A. buztleri. As a result, correlation has been established between the presence of two of those genes (cadF and hecA) and a high ability to adhere to cells. It has also been found that the cadFgene plays an essential role in adgerence to and invasion of human intestinal cells, while the claB and flaAB genes are important factors in both processes.Finally, this thesis also investigates the activation of the innate system by human associated Arcobacter apecies. It shows that the A. butzleri species ir more adept at evading such activation. In addition, several genetic markers that may contribute to TLR5 activation have been identified in the A. slirrowii species.

[EU]Arcobacter bakterio genero bat da, naturan oso zabalduta dagoena. Genero horretako bakterioak maiz egoten dira elikagaietan eta uretan, eta, beraz, gizakiei transmititzeko iturri nagusiak dira. Generoaren barruan, A. butzleri giza kasuetatik gehien isolatzen den espeziea da, eta ondoren A. cryaerophilus. Beste espezie batzuk, ordea, giza kasuekin ere lotu dira. Arcobacter-ek gizakiengan eragiten dituen infekzioen prebalentzia handitzen ari da. Hala ere, bakterio horien birulentzia-mekanismoak ez daude oraindik argi. Beraz, tesi honen helburua Arcobacter-ek gizakientzat duen arriskuaren ezagutza hobetzea da, haren ahalmen patogenikoari eta gaixotasunak eragiteko erabiltzen dituzten mekanismoei buruzko datu berriak emanez.