Background: The genus Arcobacter, belonging to the family Campylobacteraceae, includes polar flagellated, curved or
spiral rod shaped bacteria firstly described as Vibrio/Spirillum organisms and later as aerotolerant Campylobacter-like
microorganisms. Currently, this genus comprises nine validated species and a candidatus. Among Arcobacter species, Arcobacter
butzleri is recognized as a zoonotic agent and the most common species of the genus isolated from environmental water, food
and clinical samples. Recently, this species was considered a serious hazard to human health. However, their pathological
properties, potential virulence factors as well as their clinical significance remain uncertain or not completely defined. The aim
of this study was to establish the ability of 78 A. butzleri strains isolated from different sources to adhere to HEp-2 cells in vitro.
Materials, Methods & Results: All the strains were isolated using first an enrichment medium incubated aerobically at 26ºC
for 48h. After that, 100 μL of the broth were streaked onto Arcobacter selective agar plates and incubated at 26°C for 72h. All
the strains were identified phenotypically using standard assays. Definitive identification was achieved using a multiplex
polymerase chain reaction. Adhesive capacity was determined infecting HEp-2 cells with the strains under study following
Skaletsky et al. protocol, with slight modifications. An adherent Escherichia coli isolate was included as a positive control,
whereas uninoculated cell lines were used as negative controls. Adhesion results were expressed as the percentage of HEp-2
cells showing adhering bacteria and the number of bacteria (± SD) adhered to cells was determined. Strains were considered as
adherent, if at least 20% of HEp-2 cells showed one ore more adhered bacteria. Adherence was also demonstrated by scanning
electronic microscopy. All the strains showed adhesive capacity to HEp-2 cells in vitro. The lowest adhesion percentage (27%)
was observed in a strain isolated from dog feces. In at least one strain per source it was possible to observe 100% adhesion. The
lowest number of adhered bacteria (1.03 ± 1.53) was observed in a strain isolated from river water and the highest number (76.6
± 5.59), in a strain isolated from duck feces.
Discussion: Regardless of their isolation source, the 78 Arcobacter butzleri strains tested in the present study were able to
adhere to HEp-2 cells in vitro. This property was demonstrated in different proportions by other authors in strains isolated from
environmental, meat and human fecal samples. Electronic scanning microscopy shows curved bacilli adhering to HEp-2 cells
forming a microcolony-like arrangement. This may occur in a stepwise mechanism. First, A. butzleri adhere to HEp-2 cells and
then, due to their capacity to form biofilms, interbacterial adherence can be expressed. The capacity of A. butzleri to form
biofilms attaching to stainless steel, copper and glass has been demonstrated in previous studies. Further studies are necessary
to elucidate the molecular and cellular mechanisms accounting for this biological property; and hence, its actual role in the
colonization of human and animal intestinal epithelium by A. butzleri.
