Characterization of Arcobacter suis isolated from water buffalo (Bubalus bubalis) milk

Improved culture enrichment broth for isolation of Arcobacter-like species from the marine environment

Arcobacter-like species are found associated with many matrices, including shellfish in marine environments. The culture media and conditions play a major role in the recovery of new Arcobacter-like species. This study was aimed to develop a culture media for isolation and enhanced growth of Arcobacter-like spp. from marine and shellfish matrices. For this purpose, 14 different Arcobacter-like spp. mostly isolated from shellfish, were grown in 24 different formulations of enrichment broths. The enrichment broths consisted of five main groups based on the organic contents (fresh oyster homogenate, lyophilized oyster either alone or in combination with other standard media), combined with artificial seawater (ASW) or 2.5% NaCl. Optical density (OD_420nm) measurements after every 24 h were compared with the growth in control media (Arcobacter broth) in parallel. The mean and standard deviation were calculated for each species in each broth and statistical differences (p < 0.05) among broths were calculated by ANOVA. The results indicated that shellfish-associated Arcobacter-like species growth was significantly higher in Arcobacter broth + 50% ASW and the same media supplemented with lyophilized oysters. This is the first study to have used fresh or lyophilized oyster flesh in the enrichment broth for isolation of shellfish-associated Arcobacter-like spp.

Complete Genome Sequence of the Arcobacter suis Type Strain LMG 26152

Arcobacter species are prevalent in pigs, and strains have been isolated from pig feces and pork meat; some Arcobacter strains may be porcine abortifacients. Arcobacter suis was recovered from pork meat in Spain. This study describes the whole-genome sequence of the A. suis type strain LMG 26152 (=F41T =CECT 7833T).

Revisiting the Taxonomy of the Genus Arcobacter: Getting Order From the Chaos

Since the description of the genus Arcobacter in 1991, a total of 27 species have been described, although some species have shown 16S rRNA similarities below 95%, which is the cut-off that usually separates species that belong to different genera. The objective of the present study was to reassess the taxonomy of the genus Arcobacter using information derived from the core genome (286 genes), a Multilocus Sequence Analysis (MLSA) with 13 housekeeping genes, as well as different genomic indexes like Average Nucleotide Identity (ANI), in silico DNA–DNA hybridization (isDDH), Average Amino-acid Identity (AAI), Percentage of Conserved Proteins (POCPs), and Relative Synonymous Codon Usage (RSCU). The study included a total of 39 strains that represent all the 27 species included in the genus Arcobacter together with 13 strains that are potentially new species, and the analysis of 57 genomes. The different phylogenetic analyses showed that the Arcobacter species grouped into four clusters. In addition, A. lekithochrous and the candidatus species ‘A. aquaticus’ appeared, as did A. nitrofigilis, the type species of the genus, in separate branches. Furthermore, the genomic indices ANI and isDDH not only confirmed that all the species were well-defined, but also the coherence of the clusters. The AAI and POCP values showed intra-cluster ranges above the respective cut-off values of 60% and 50% described for species belonging to the same genus. Phenotypic analysis showed that certain test combinations could allow the differentiation of the four clusters and the three orphan species established by the phylogenetic and genomic analyses. The origin of the strains showed that each of the clusters embraced species recovered from a common or related environment. The results obtained enable the division of the current genus Arcobacter in at least seven different genera, for which the names Arcobacter, Aliiarcobacter gen. nov., Pseudoarcobacter gen. nov., Haloarcobacter gen. nov., Malacobacter gen. nov., Poseidonibacter gen. nov., and Candidate ‘Arcomarinus’ gen. nov. are proposed.

Enhanced recovery of Arcobacter spp. using NaCl in culture media and re-assessment of the traits of Arcobacter marinus and Arcobacter halophilus isolated from marine water and shellfish

The genus Arcobacter is a relatively poorly known group of bacteria, and the number of new species and sequences from non-culturable strains has increased considerably in recent years. This study investigates whether using media that contain NaCl might help to improve the recovery of Arcobacter spp. from marine environments. To this aim, 62 water and shellfish samples were analysed in parallel, with both a commonly used culture method (enrichment in Arcobacter-CAT broth followed by culture on Blood Agar) and a new one that supplements the Arcobacter-CAT enrichment broth with 2.5% NaCl (w/v) followed by culturing on Marine Agar. The new method yielded ca. 40% more positive samples and provided a higher diversity of known (11 vs. 7) and unknown (7 vs. 2) Arcobacter species. Among the 11 known species recovered, Arcobacter marinus and Arcobacter halophilus were isolated only by this new method. No more strains of these species have been isolated since their original descriptions, both of which were based only on a single strain. In view of that, the phenotypic characteristics of these species are re-evaluated in the present study, using the new strains. Strains of A. halophilus had the same phenotypic profile as the type strain. However, some strains of A. marinus differed from the type strain in that they did not hydrolyse indoxyl-acetate, becoming, therefore, the first Arcobacter species to show a varying ability to hydrolyse indoxyl-acetate. This study shows to what extent a simple variation to the culture media can have a big influence on positive samples and on the community of species recovered.

Isolation and identification of Arcobacter species from environmental and drinking water samples

Water plays an important role in the transmission of Arcobacter spp. to animals and humans. The aim of this study was to isolate and characterize Arcobacter spp. from 115 different water samples (66 sewage, 25 rivers, 16 spring water, and 8 drinking water) in Izmir, Turkey. In total, 41 samples (35.7 %) were found positive for Arcobacter spp. by the genus-specific PCR. Arcobacter butzleri was detected in 39 out of 115 samples (33.9 %) including 24 sewage, 13 rivers, and 2 spring water. The remaining Arcobacter spp. (n = 2) isolates could not be identified by m-PCR and 16S rRNA gene sequencing. Based on the phenotypic characterization, most of the Arcobacter species (87.8 %) indicated weak catalase activity. In addition, there were differences in phenotypic patterns among isolated species during growth at 37 °C under microaerobic and aerobic conditions, in the presence of 2 % (39/41) and 3.5 % (32/41) NaCl and 0.04 % TTC (39/41) and on MacConkey agar (38/41). The results of this study indicated that environmental water samples are common sources for Arcobacter spp. Therefore, effective control measures should be taken to protect human health.