Taxonomy, epidemiology, and clinical relevance of the genus Arcobacter

Polyphenols as resistance modulators in Arcobacter butzleri

Arcobacter butzleri is an emerging human and animal pathogen for which an increased prevalence of resistance to antibiotics has been observed, and so alternative compounds to modulate resistance of A. butzleri are required. This work aims to study the potential use of several polyphenols as efflux pump inhibitors (EPIs) and to evaluate their interaction with antibiotics, in order to enhance antibiotic activity against A. butzleri. The minimum inhibitory concentration (MIC) of (-)-epicatechin, (+)-catechin, rutin, gallic acid, caffeic acid, chlorogenic acid, resveratrol, pterostilbene, and pinosylvin was determined, in absence and presence of four known EPIs. Subsequently, ethidium bromide accumulation in presence of subinhibitory concentrations of polyphenols was evaluated, and the synergistic potential of the compounds with antibiotics was assessed by checkerboard dilution test. Only stilbenes presented activity against A. butzleri, with MIC values ranging between 64 and 512 μg/mL. The MIC determination of the polyphenols in the presence of subinhibitory concentrations of known EPIs showed that efflux pumps play a role in the resistance to these compounds. Stilbenes also induced a higher intracellular accumulation of ethidium bromide, indicating that they may inhibit the activity of efflux pumps. Checkerboard assays showed that several combinations of polyphenol/antibiotic had an additive effect against A. butzleri. Overall, the results indicate that some polyphenols reduce A. butzleri resistance to antibiotics, suggesting the potential of stilbenes as EPIs. The potential of resveratrol and pinosylvin as resistance modulators was evidenced, insofar as these compounds can even revert antibiotic resistance. Therefore, the use of polyphenols as resistance modulators could be an alternative to overcome the decreasing susceptibility of A. butzleri to antibiotics.

A meta-analytic perspective on Arcobacter spp. antibiotic resistance

OBJECTIVES

Over the years, an increased prevalence of resistant strains of Arcobacter has been observed, which may be due to Arcobacter exposure to antibiotics used both in animal production and human medicine. A systematic review was performed with the objective of summarising the results of the rates of antimicrobial resistance of Arcobacter isolates.

METHODS

The systematic review was performed according to PRISMA (Preferred Reported Items for Systematic Reviews and Meta-Analysis) recommendations, followed by meta-analysis.

RESULTS

It was observed that the resistance rate ranged between 69.3-99.2% for penicillins and 30.5-97.4% for cephalosporins. The overall percentage of resistance to fluoroquinolones ranged from 4.3% to 14.0%, with the highest resistance percentage observed for levofloxacin. Resistance rates ranged between 10.7-39.8% for macrolides, 1.8-12.9% for aminoglycosides and 0.8-7.1% for tetracyclines.

CONCLUSIONS

These results show that Arcobacter spp. present resistance to various antibiotics commonly used and advocate further studies of the associated resistance mechanisms.

White spot syndrome virus (WSSV) infection impacts intestinal microbiota composition and function in Litopenaeus vannamei

Intestinal microbiota homeostasis is crucial to the health of host. Pathogen invasion results in dynamics of microbiota composition and structure, disrupting their function in maintaining host health. WSSV is the most prevalent viral pathogen and is able to cause extremely high mortality in Litopenaeus vannamei. However, the changes of intestinal microbiota induced by WSSV are yet to be elucidated. In this study, we analyzed and compared the microbiota of healthy and WSSV-challenged shrimp intestines. Though the richness and diversity of microbiota was barely affected by WSSV, the abundance of predominant phyla like Proteobacteria and Fusobacteria were upregulated significantly, while Bacteroidetes and Tenericutes were significantly decreased in WSSV-infected shrimps. At the genus level, significant increase was observed in Photobacterium, Propionigenium and Arcobacter, as well as significant decrease in Candidatus Bacilloplasma and Flavobacterium in WSSV-infected shrimps. Additionally, metagenomic predictions by PICRUSt suggested that the altered microbiota was mainly related to metabolism, human diseases, genetic information processing, environmental information processing and cellular processes. These results suggested that the invasion of WSSV could impact intestinal microbiota composition and function in L. vannamei.

Antimicrobial Susceptibility and Genomic Structure of Arcobacter skirrowii Isolates

Campylobacter spp. are considered the most common bacterial cause of foodborne gastroenteritis in the world. The family Campylobacteraceae includes the genus Arcobacter with the three species Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii as emergent enteropathogens and potential zoonotic agents. Here, we characterized genome sequences of Arcobacter that were isolated from water poultry on farms in Germany. Isolates were cultured, identified by MALDI-TOF MS and identification was verified with PCR assays. Antibiotic susceptibility testing of isolates was carried out with erythromycin, ciprofloxacin, doxycycline, tetracycline, gentamicin, and streptomycin using the gradient strip method (E-test). We also sequenced whole genomes and predicted antibiotic resistance determinants, virulence factors, performed a phylogenetic analysis to determine the genetic relatedness of these isolates and searched for plasmids.

Complete Genome Sequence of the Arcobacter bivalviorum Type Strain LMG 26154

Arcobacters are routinely recovered from marine environments, and multiple Arcobacter species have been isolated from shellfish. Arcobacter bivalviorum was recovered from mussels collected in the Ebro Delta in northeastern Spain. This report describes the complete whole-genome sequence of the A. bivalviorum type strain LMG 26154 (= F4^T = CECT 7835^T).

Development of a Quantitative PCR Assay for Arcobacter spp. and its Application to Environmental Water Samples

Arcobacter spp. are emerging pathogens associated with gastroenteritis in humans. The objective of this study was to develop a highly sensitive and broadly reactive quantitative PCR (qPCR) assay for Arcobacter spp. and to apply the developed assay to different water sources in the Kathmandu Valley, Nepal. Fifteen samples to be analyzed by next-generation sequencing were collected from 13 shallow dug wells, a deep tube well, and a river in the Kathmandu Valley in August 2015. Among the 86 potential pathogenic bacterial genera identified, Acinetobacter, Pseudomonas, Flavobacterium, and Arcobacter were detected with relatively high abundance in 15, 14, 12, and 8 samples, respectively. A primer pair was designed with maximal nucleotide homologies among Arcobacter spp. by comparing the sequences of 16S rRNA genes. These primers were highly specific to most of the known species of Arcobacter and quantified between 1.0×10¹ and 6.4×10⁶ copies reaction⁻¹ and sometimes detected as few as 3 copies reaction⁻¹. The qPCR assay was used to quantify Arcobacter spp. in bacterial DNA in not only the above 15 water samples, but also in 33 other samples collected from 15 shallow dug wells, 6 shallow tube wells, 5 stone spouts, 4 deep tube wells, and 3 springs. Thirteen (27%) out of 48 samples tested were positive for Arcobacter spp., with concentrations of 5.3–9.1 log copies 100 mL⁻¹. This qPCR assay represents a powerful new tool to assess the prevalence of Arcobacter spp. in environmental water samples.

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.

Metagenomic evaluation of the effects of storage conditions on the bacterial microbiota of oysters Crassostrea gasar (Adanson, 1757)

AIMS

To evaluate the influence of storage conditions on the composition of the bacterial microbiota of living oysters Crassostrea gasar.

METHODS AND RESULTS

The oysters used in this study came from marine farms (Guaratuba Bay, Brazil) and were exposed to two conditions that simulated different storage situations: immersion in water (group I) and exposure to air (group II). The animals were subjected to five different temperatures (5-25°C), for 10 days. The 16S rRNA gene from oysters was amplified and sequenced to determine the taxonomic units and bacterial strains present in the samples. Group I showed higher diversity of bacteria (163 genera) rather than group II (104 genera). In all, 59 bacterial genera potentially pathogenic to humans were identified (n = 56 in group I and n = 45 in group II).

CONCLUSIONS

The storage conditions having a direct influence on the oyster microbiota. Live C. gasar should be stored exposed to air at 5-25°C, because it favours a lower prevalence of bacteria potentially pathogenic to humans.

SIGNIFICANCE AND IMPACT OF THE STUDY

During the oyster commercialization process, some conditions of storage, time and temperature must be followed in order to reduce the prevalence of bacteria potentially pathogenic to humans.

Filling the gaps in clinical proteomics: a do-it-yourself guide for the identification of the emerging pathogen Arcobacter by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Arcobacters are considered emerging gastrointestinal pathogens. Rapid, reliable and species-specific identification of these bacteria is important. Biochemical tests commonly yield negative or variable results. Molecular methods prove more reliable but are time consuming and lack specificity. Matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is a fast, cheap and robust technique that has revolutionized genus and species identification in clinical microbiology. The performance of an in vitro diagnostic (RUO) spectral database of MALDI-TOF MS for the identification of human clinically relevant Arcobacter isolates was validated and compared to an in house created Reference Spectral database (RS) containing a representative set of deposited Arcobacter strains of zoonotic interest. A challenge panel of clinical, human and veterinary, unique Campylobacteraceae strains was used to test accuracy. Using direct colony transfer, sensitivity with RS was significantly better than with RUO for A. butzleri and A. cryaerophilus identification (100% and 92% versus 74% and 16%). For A. skirrowii, sensitivity remained low (21% versus 0%). Reanalysis using formic acid overlay (on-target extraction) augmented sensitivity for the latter species to 64%. Specificity of RS database remained excellent without any misidentifications of human clinical strains including Campylobacter fetus and C. jejuni/coli. The use of an enriched database for MALDI-TOF MS identification of Arcobacter spp. of human interest produced high-confidence identifications to species level resulting in a significantly improved sensitivity with conservation of excellent specificity. Misidentifications, which can have therapeutic and public health consequences, were not encountered.

Detection of Arcobacter spp. in food products collected from Sicilia region: A preliminary study

The aim of the study was to evaluate the occurrence of Arcobacter spp. in food samples collected from Sicilia region. A total of 91 food products of animal origin (41 meat, 17 fresh milk, 18 shellfish) and 15 samples of fresh vegetables, were examined by cultural method and confirmed by biochemical analysis and PCR methods. The detection of Arcobacter spp. was performed, after selective enrichment, on two selective agar plates: Arcobacter agar and mCCD (modified charcoal cefoperazone deoxycholate) agar supplemented with CAT (Cefoperazone, Amphotericin B and Teicoplanin). Arcobacter species were isolated using the membrane filtration technique. In 13 (14.3%) out of the 91 tested samples, the presence of Arcobacter spp. was found: the isolates were confirmed by multiplex PCR and identified as belonging to the species A. butzleri and A. cryaerophilus. The highest prevalence rate was observed in chicken meat (8.8%) followed by shellfish (3.3%). Negative results have been obtained for raw milks and vegetables samples. The preliminary study highlights the importance of this emerging pathogen and the need for further studies on its prevalence and distribution in different types of food for human consumption.

Ocean warming alters predicted microbiome functionality in a common sea urchin

The microbiome of sea urchins plays a role in maintaining digestive health and innate immunity. Here, we investigated the effects of long-term (90 day) exposure to elevated seawater temperatures on the microbiome of the common, subtropical sea urchin Lytechinus variegatus The community composition and diversity of microbes varied according to the type of sample collected from the sea urchin (seawater, feed, intestines, coelomic fluid, digested pellet and faeces), with the lowest microbial diversity (predominately the order Campylobacterales) located in the intestinal tissue. Sea urchins exposed to near-future seawater temperatures maintained the community structure and diversity of microbes associated with their tissues. However, marginal, non-significant shifts in microbial community structure with elevated temperature resulted in significant changes in predicted metagenomic functions such as membrane transport and amino acid and carbohydrate metabolism. The predicted changes in key metabolic categories suggest that near-future climate-induced increases in seawater temperature could shift microbial community function and impact sea urchin digestive and immune physiology.

Occurrence of virulence-associated genes in Arcobacter butzleri and Arcobacter cryaerophilus isolates from foodstuff, water, and clinical samples within the Czech Republic

Bacteria of the Arcobacter (A.) genus, originating mainly from food and water, are dreaded germs for humans as well as animals. However, the virulence of these bacteria has not been fully elucidated yet. This study looked at the occurrence of eight virulence-associated factors (ciaB, cj1349, pldA, irgA, hecA, tlyA, mviN, hecB) in a total of 80 isolates of Arcobacter butzleri and 22 isolates of A. cryaerophilus. The isolates were derived from food, water, and clinical samples. A polymerase chain reaction using specific primers was used to detect these virulence-associated genes. The presence of all genes in the isolates of A. butzleri (98.8% ciaB, 95.0% cj1349, 98.8% pldA, 22.5% irgA, 31.3% hecA, 95.0% tlyA, 97.5% mviN, 38.8% hecB) and A. cryaerophilus (95.5% ciaB, 0.0% cj1349, 9.1% pldA, 0.0% irgA, 0.0% hecA, 31.8% tlyA, 90.9% mviN, 0.0% hecB) was monitored. Among the tested isolates, there were 13 isolates (12.7%) of A. butzleri, in which the presence of all eight virulence-associated genes was recorded in the genome. In contrast, in one A. cryaerophilus strain, none of the observed genes were detected. The presence of ciaB and mviN genes was significantly more frequent in A. cryaerophilus isolates than other genes (P < 0.05). In general, more virulence-associated genes have been detected in A. butzleri isolates compared to A. cryaerophilus. The most common gene combination (ciaB, cj1349, pldA, tlyA, mviN) was detected in case of 39 isolates. In 50.0% of A. butzleri isolates derived from clinical samples, all eight virulence-associated genes were significantly more frequently detected (P < 0.05). The tlyA gene occurred significantly more frequent in A. butzleri isolates from meat and water samples and irgA and hecB genes in clinical samples. Therefore, our study provides information about occurrence of virulence-associated genes in genome of Arcobacter isolates. These findings could be hazardous to human health, because the presence of virulence-associated genes is the assumption for potential dangerousness of these bacteria. Our results indicate high incidence of virulence-associated genes in Arcobacter genomes and hence potentially pathogenic properties of the studied strains.

Crown-of-Thorns Sea Star Acanthaster cf. solaris Has Tissue-Characteristic Microbiomes with Potential Roles in Health and Reproduction

Outbreaks of coral-eating crown-of-thorns sea stars (CoTS; Acanthaster species complex) cause substantial coral loss; hence, there is considerable interest in developing prevention and control strategies. We characterized the microbiome of captive CoTS and assessed whether dysbiosis was evident in sea stars during a disease event. Most tissue types had a distinct microbiome. The exception was female gonads, in which the microbiomes were highly variable among individuals. Male gonads were dominated (>97% of reads) by a single Mollicutes-related operational taxonomic unit (OTU). Detailed phylogenetic and microscopy analysis demonstrated the presence of a novel Spiroplasma-related bacterium in the spermatogenic layer. Body wall samples had high relative abundance (43 to 64% of reads) of spirochetes, likely corresponding to subcuticular symbionts reported from many echinoderms. Tube feet were characterized by Hyphomonadaceae (24 to 55% of reads). Pyloric cecal microbiomes had high alpha diversity, comprising many taxa commonly found in gastrointestinal systems. The order Oceanospirillales (genera Endozoicomonas and Kistimonas) was detected in all tissues. A microbiome shift occurred in diseased individuals although differences between tissue types were retained. The relative abundance of spirochetes was significantly reduced in diseased individuals. Kistimonas was present in all diseased individuals and significantly associated with diseased tube feet, but its role in disease causation is unknown. While Arcobacter was significantly associated with diseased tissues and Vibrionaceae increased in diversity, no single OTU was detected in all diseased individuals, suggesting opportunistic proliferation of these taxa in this case. This study shows that CoTS have tissue-characteristic bacterial communities and identifies taxa that could play a role in reproduction and host health.

IMPORTANCE Coral-eating crown-of-thorns sea stars (CoTS; Acanthaster species complex) are native to the Indo-Pacific, but during periodic population outbreaks they can reach extreme densities (>1,000 starfish per hectare) and function as a pest species. On the Great Barrier Reef, Australia, CoTS have long been considered one of the major contributors to coral loss. There has been significant investment in a targeted control program using lethal injection, and there is interest in developing additional and complementary technologies that can increase culling efficiencies. The biology of CoTS has been studied extensively, but little is known about their associated microbiome. This cultivation-independent analysis of the CoTS microbiome provides a baseline for future analyses targeting the functional role of symbionts, the identification of pathogens, or the development of reproduction manipulators.

Antimicrobial susceptibility testing of Arcobacter butzleri: development and application of a new protocol for broth microdilution

Objectives

To develop a standard reference broth microdilution method for antimicrobial susceptibility testing (AST) of Arcobacter butzleri. The protocol was subsequently applied to a collection of A. butzleri isolates from different sources.

Methods

Broth microdilution susceptibility testing was performed on eight A. butzleri isolates in three media: non-supplemented CAMHB, CAMHB + 2% FBS and CAMHB + 5% FBS. The MIC values were read after 24 and 48 h of incubation at 35 ± 2 °C in ambient air. A logistic regression model was used to determine the combination of medium and incubation time yielding the most homogeneous results. Subsequently, the protocol was applied to 65 A. butzleri isolates to determine their MICs of 31 antimicrobial agents.

Results

The statistical analysis revealed that the most homogeneous MIC values were obtained with CAMHB + 5% FBS and reading of MIC values after 24 h of incubation. The standardized method was successful for AST of all 65 A. butzleri isolates. MIC values were distributed unimodally for most antimicrobial agents. However, one field isolate showed elevated MIC values of gentamicin, streptomycin, tetracycline and trimethoprim/sulfamethoxazole.

Conclusions

This study presents a new protocol for AST of A. butzleri by broth microdilution and shows the distribution of MIC values of 31 antimicrobial agents for a collection of A. butzleri isolates from different origins.

Do the Escherichia coli European Union shellfish safety standards predict the presence of Arcobacter spp., a potential zoonotic pathogen?

The genus Arcobacter comprises Campylobacter-related species, considered zoonotic emergent pathogens, the presence of which in water has been associated with fecal pollution. Discharges of fecal polluted water into the sea have been considered as one of the main reasons for the presence of Arcobacter in shellfish, and this may represent a risk for public health. In this study, the European Union shellfish food safety criteria based on levels of Escherichia coli were studied in relation to their capacity to predict the presence of Arcobacter species. In addition, the accumulation factor (AF) that measures the concentration ratio between the microbes present in the shellfish and in the water, was also studied for both bacteria. The results show that the presence of E. coli correlated with the presence of the potentially pathogenic species A. butzleri and A. cryaerophilus. However, in 26.1% of the shellfish samples (corresponding to those taken during summer months) E. coli failed to predict the presence of, for instance A. butzleri and A. skirrowii, among other species. In the rest of the samples a significant correlation between the concentration of E. coli and Arcobacter spp. (mussels and oyster; R²=0.744) was found. This study indicates that the presence of E. coli can predict the presence of pathogenic Arcobacter species in shellfish samples harvested from water with temperatures lower than 26.2°C. Consumption of shellfish collected at higher temperatures which may not be permissive to the growth of E. coli but does allow growth of Arcobacter spp., may represent a risk for consumers.

Rearing Water Treatment Induces Microbial Selection Influencing the Microbiota and Pathogen Associated Transcripts of Cod (Gadus morhua) Larvae

We have previously shown that K-selection and microbial stability in the rearing water increases survival and growth of Atlantic cod (Gadus morhua) larvae, and that recirculating aquaculture systems (RAS) are compatible with this. Here, we have assessed how water treatment influenced the larval microbiota and host responses at the gene expression level. Cod larvae were reared with two different rearing water systems: a RAS and a flow-through system (FTS). The water microbiota was examined using a 16S rDNA PCR/DGGE strategy. RNA extracted from larvae at 8, 13, and 17 days post hatching was used for microbiota and microarray gene expression analysis. Bacterial cDNA was synthesized and used for 16S rRNA amplicon 454 pyrosequencing of larval microbiota. Both water and larval microbiota differed significantly between the systems, and the larval microbiota appeared to become more dissimilar between systems with time. In total 4 phyla were identified for all larvae: Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The most profound difference in larval microbiota was a high abundance of Arcobacter (Epsilonproteobacteria) in FTS larvae (34 ± 9% of total reads). Arcobacter includes several species that are known pathogens for humans and animals. Cod larval transcriptome responses were investigated using an oligonucleotide gene expression microarray covering approximately 24,000 genes. Interestingly, FTS larvae transcriptional profiles revealed an overrepresentation of upregulated transcripts associated with responses to pathogens and infections, such as c1ql3-like, pglyrp-2-like and zg16, compared to RAS larvae. In conclusion, distinct water treatment systems induced differences in the larval microbiota. FTS larvae showed up-regulation of transcripts associated with responses to microbial stress. These results are consistent with the hypothesis that RAS promotes K-selection and microbial stability by maintaining a microbial load close to the carrying capacity of the system, and ensuring long retention times for both bacteria and water in the system.

Pathogens transmitted in animal feces in low- and middle-income countries

Animals found in close proximity to humans in low-and middle-income countries (LMICs) harbor many pathogens capable of infecting humans, transmissible via their feces. Contact with animal feces poses a currently unquantified-though likely substantial-risk to human health. In LMIC settings, human exposure to animal feces may explain some of the limited success of recent water, sanitation, and hygiene interventions that have focused on limiting exposure to human excreta, with less attention to containing animal feces. We conducted a review to identify pathogens that may substantially contribute to the global burden of disease in humans through their spread in animal feces in the domestic environment in LMICs. Of the 65 potentially pathogenic organisms considered, 15 were deemed relevant, based on burden of disease and potential for zoonotic transmission. Of these, five were considered of highest concern based on a substantial burden of disease for which transmission in animal feces is potentially important: Campylobacter, non-typhoidal Salmonella (NTS), Lassa virus, Cryptosporidium, and Toxoplasma gondii. Most of these have a wide range of animal hosts, except Lassa virus, which is spread through the feces of rats indigenous to sub-Saharan Africa. Combined, these five pathogens cause close to one million deaths annually. More than half of these deaths are attributed to invasive NTS. We do not estimate an overall burden of disease from improperly managed animal feces in LMICs, because it is unknown what proportion of illnesses caused by these pathogens can be attributed to contact with animal feces. Typical water quantity, water quality, and handwashing interventions promoted in public health and development address transmission routes for both human and animal feces; however, sanitation interventions typically focus on containing human waste, often neglecting the residual burden of disease from pathogens transmitted via animal feces. This review compiles evidence on which pathogens may contribute to the burden of disease through transmission in animal feces; these data will help prioritize intervention types and regions that could most benefit from interventions aimed at reducing human contact with animal feces.

A Polyphasic and Taxogenomic Evaluation Uncovers Arcobacter cryaerophilus as a Species Complex That Embraces Four Genomovars

The species Arcobacter cryaerophilus is found in many food products of animal origin and is the dominating species in wastewater. In addition, it is associated with cases of farm animal and human infectious diseases,. The species embraces two subgroups i.e., 1A (LMG 24291^T = LMG 9904^T) and 1B (LMG 10829) that can be differentiated by their 16S rRNA-RFLP pattern. However, some authors, on the basis of the shared intermediate levels of DNA-DNA hybridization, have suggested abandoning the subgroup classification. This contradiction indicates that the taxonomy of this species is not yet resolved. The objective of the present study was to perform a taxonomic evaluation of the diversity of A. cryaerophilus. Genomic information was used along with a Multilocus Phylogenetic Analysis (MLPA) and phenotypic characterization on a group of 52 temporally and geographically dispersed strains, coming from different types of samples and hosts from nine countries. The MLPA analysis showed that those strains formed four clusters (I–IV). Values of Average Nucleotide Identity (ANI) and in silico DNA-DNA Hybridization (isDDH) obtained between 13 genomes representing strains of the four clusters were below the proposed cut-offs of 96 and 70%, respectively, confirming that each of the clusters represented a different genomic species. However, none of the evaluated phenotypic tests enabled their unequivocal differentiation into species. Therefore, the genomic delimited clusters should be considered genomovars of the species A. cryaerophilus. These genomovars could have different clinical importance, since only the cluster I included strains isolated from human specimens. The discovery of at least one stable distinctive phenotypic character would be needed to define each cluster or genomovar as a different species. Until then, we propose naming them “A. cryaerophilus gv. pseudocryaerophilus” (Cluster I = LMG 10229^T), “A. cryaerophilus gv. crypticus” (Cluster II = LMG 9065^T), “A. cryaerophilus gv. cryaerophilus” (Cluster III = LMG 24291^T) and “A. cryaerophilus gv. occultus” (Cluster IV = LMG 29976^T).

Application of MALDI-TOF MS for the subtyping of Arcobacter butzleri strains and comparison with their MLST and PFGE types

For the first time, this study evaluated the use of MALDI-TOF as a typing tool for Arcobacter butzleri. A total of 104 A. butzleri strains isolated from different sources in an artisanal dairy plant in Italy were identified and typed using MALDI-TOF and compared with their multilocus sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) profiles found in previous studies. MALDI-TOF correctly identified all the isolates to species level. No clearly delineated clusters appeared on dendrograms based on either the complete spectra or the significant peaks, but nine clusters were defined using the cophenetic correlation. Interestingly, MALDI-TOF proved able to discriminate A. butzleri strains below species level, confirming its potential use for epidemiological surveys. As expected, the comparative analysis with PFGE and MLST showed that the discriminatory index was lower for MALDI-TOF but roughly comparable to sequence types and pulsotypes. MALDI-TOF appears to be a relatively low cost answer to the urgent need for more rapid, less expensive typing tools suitable for source attribution studies, readily allowing multiple typing methods to be combined. This study provides insights into MALDI-TOF as potential epidemiological tool. Its application in healthcare surveillance systems awaits further exploration to encourage interaction and convergence studies between primary care in humans and animal and food veterinary authorities as part of the One Health concept.

Potential human pathogenic bacteria in five hot springs in Eritrea revealed by next generation sequencing

Human pathogens can survive and grow in hot springs. For water quality assessment, Escherichia coli or Enterococci are the main thermotolerant enteric bacteria commonly used to estimate the load of pathogenic bacteria in water. However, most of the environmental bacteria are unculturable thus culture methods may cause bias in detection of most pathogens. Illumina sequencing can provide a more comprehensive and accurate insight into environmental bacterial pathogens, which can be used to develop better risk assessment methods and promote public health awareness. In this study, high-throughput Illumina sequencing was used to identify bacterial pathogens from five hot springs; Maiwooi, Akwar, Garbanabra, Elegedi and Gelti, in Eritrea. Water samples were collected from the five hot springs. Total community DNA was extracted from samples using the phenol-chloroform method. The 16S rRNA gene variable region (V4—V7) of the extracted DNA was amplified and library construction done according to Illumina sequencing protocol. The sequence reads (length >200 bp) from Illumina sequencing libraries ranged from 22,091 sequences in the wet sediment sample from Garbanabra to 155,789 sequences in the mat sample from Elegedi. Taxonomy was assigned to each OTU using BLASTn against a curated database derived from GreenGenes, RDPII, SILVA SSU Reference 119 and NCBI. The proportion of potential pathogens from the water samples was highest in Maiwooi (17.8%), followed by Gelti (16.7%), Akwar (13.6%) and Garbanabra (10.9%). Although the numbers of DNA sequence reads from Illumina sequencing were very high for the Elegedi (104,328), corresponding proportion of potential pathogens very low (3.6%). Most of the potential pathogenic bacterial sequences identified were from Proteobacteria and Firmicutes. Legionella and Clostridium were the most common detected genera with different species. Most of the potential pathogens were detected from the water samples. However, sequences belonging to Clostridium were observed more abundantly from the mat samples. This study employed high-throughput sequencing technologies to determine the presence of pathogenic bacteria in the five hot springs in Eritrea.

Isolation and molecular characterization of Arcobacter butzleri and Arcobacter cryaerophilus from the pork production chain in Brazil

ABSTRACT: Arcobacter is an emerging zoonotic pathogen, and the major transmission routes to humans are the handling or consumption of contaminated raw/undercooked food products of animal origin, water and seafood. The isolation and identification of Arcobacter species are not routine in clinical laboratories; therefore, its true incidence in human infections may be underestimated. The present study aimed to isolate and characterize Arcobacter from carcasses and fecal samples collected at swine slaughterhouses and from meat markets in São Paulo State, Brazil. The isolates were identified using multiplex-PCR to differentiate the species and analyzed by single-enzyme amplified fragment length polymorphism (SE-AFLP). Arcobacter spp. were isolated from 73.0% of swine carcasses, 4% of fecal samples and 10% of pork samples. A. butzleri was the most prevalent species identified, followed by A. cryaerophilus. Interestingly, the carcasses presented higher frequency of A. butzleri isolation, whereas only A. cryaerophilus was isolated from fecal samples. SE-AFLP enabled the characterization of A. butzleri and A. cryaerophilus into 51 and 63 profiles, respectively. The great genetic heterogeneity observed for both species corroborates previous reports. This study confirms the necessity for a standard isolation protocol and the improvement of molecular tools to further elucidate Arcobacter epidemiology.

Arcobacter canalis sp. nov., isolated from a water canal contaminated with urban sewage

Four bacterial strains recovered from shellfish (n=3) and from the water (n=1) of a canal contaminated with urban sewage were recognized as belonging to a novel species of the genus Arcobacter (represented by strain F138-33^T) by using a polyphasic characterization. All the new isolates required 2 % NaCl to grow. Phylogenetic analyses based on 16S rRNA gene sequences indicated that all strains clustered together, with the most closely related species being Arcobacter marinus and Arcobactermolluscorum. However, phylogenetic analyses using the concatenated sequences of housekeeping genes (atpA, gyrB, hsp60, gyrA and rpoB) showed that all the novel strains formed a distinct lineage within the genus Arcobacter. Results of in silico DNA-DNA hybridization and the average nucleotide identity between the genome of strain F138-33^T and those of the closely related species A. marinus and other relatively closely related species such as A. molluscorum and Arcobacterhalophilus were all below 70 and 96 %, respectively. All the above results, together with the 15 physiological and biochemical tests that could distinguish the newly isolated strains from the closely related species, confirmed that these strains represent a novel species for which the name Arcobacter canalis sp. nov. is proposed, with the type strain F138-33^T (=CECT 8984^T=LMG 29148^T).

Arcobacter butzleri Ciprofloxacin Resistance: Point Mutations in DNA Gyrase A and Role on Fitness Cost

Arcobacter butzleri is a widely distributed emerging pathogen resistant to various classes of antimicrobial agents, namely fluoroquinolones. A. butzleri resistance to fluoroquinolones is conferred by point mutations at the antibiotic target. The aim of this study was to evaluate mutations at gyrA associated with ciprofloxacin resistance and evaluate whether acquisition of resistance impacts on fitness and stress tolerance of A. butzleri. A. butzleri ciprofloxacin mutants were generated by laboratory induction. Identification of mutations associated with ciprofloxacin resistance was performed by gyrA sequencing. Growth kinetics, cost of fitness, biofilm formation ability, and stress tolerance were assessed. Two amino acid substitutions in the quinolone resistance-determining region of GyrA were identified in the mutant strains, one previously described (Thr-85-Ile) and a new substitution (Asp-89-Tyr). No differences in growth kinetics were recorded between parental and mutant strains; however, fitness cost was variable, according to the genetic background of the strains, and independently of ciprofloxacin resistance. Overall, the ciprofloxacin resistance development did not significantly affect stress tolerance, motility, or biofilm-forming ability. In conclusion, acquisition of ciprofloxacin resistance in A. butzleri is associated with mutations in gyrA and is likely well compensated, with cost of fitness reflecting the diversity in genetic background of this bacterium.

The Inner Workings of the Outer Surface: Skin and Gill Microbiota as Indicators of Changing Gut Health in Yellowtail Kingfish

The mucosal surfaces and associated microbiota of fish are an important primary barrier and provide the first line of defense against potential pathogens. An understanding of the skin and gill microbial assemblages and the factors which drive their composition may provide useful insights into the broad dynamics of fish host–microbial relationships, and may reveal underlying changes in health status. This is particularly pertinent to cultivated systems whereby various stressors may led to conditions (like enteritis) which impinge on productivity. As an economically important species, we assessed whether the outer-surface bacterial communities reflect a change in gut health status of cultivated Yellowtail Kingfish (Seriola lalandi). Active bacterial assemblages were surveyed from RNA extracts from swabs of the skin and gills by constructing Illumina 16S rRNA gene amplicon libraries. Proteobacteria and Bacteroidetes were predominant in both the skin and gills, with enrichment of key β-proteobacteria in the gills (Nitrosomonadales and Ferrovales). Fish exhibiting early stage chronic lymphocytic enteritis comprised markedly different global bacterial assemblages compared to those deemed healthy and exhibiting late stages of the disease. This corresponded to an overall loss of diversity and enrichment of Proteobacteria and Actinobacteria, particularly in the gills. In contrast, bacterial assemblages of fish with late stage enteritis were generally similar to those of healthy individuals, though with some distinct taxa. In conclusion, gut health status is an important factor which defines the skin and gill bacterial assemblages of fish and likely reflects changes in immune states and barrier systems during the early onset of conditions like enteritis. This study represents the first to investigate the microbiota of the outer mucosal surfaces of fish in response to underlying chronic gut enteritis, revealing potential biomarkers for assessing fish health in commercial aquaculture systems.

Sewers as potential reservoirs of antibiotic resistance

Wastewater transport along sewers favors the colonization of inner pipe surfaces by wastewater-derived microorganisms that grow forming biofilms. These biofilms are composed of rich and diverse microbial communities that are continuously exposed to antibiotic residues and antibiotic resistant bacteria (ARB) from urban wastewater. Sewer biofilms thus appear as an optimal habitat for the dispersal and accumulation of antibiotic resistance genes (ARGs). In this study, the concentration of antibiotics, integron (intI1) and antibiotic resistance genes (qnrS, sul1, sul2, bla_TEM, bla_KPC, ermB, tetM and tetW), and potential bacterial pathogens were analyzed in wastewater and biofilm samples collected at the inlet and outlet sections of a pressurized sewer pipe. The most abundant ARGs detected in both wastewater and biofilm samples were sul1 and sul2 with roughly 1 resistance gene for each 10 copies of 16s RNA gene. Significant differences in the relative abundance of gene intI1 and genes conferring resistance to fluoroquinolones (qnrS), sulfonamides (sul1 and sul2) and betalactams (bla_TEM) were only measured between inlet and outlet biofilm samples. Composition of bacterial communities also showed spatial differences in biofilms and a higher prevalence of Operational Taxonomic Units (OTUs) with high sequence identity (>98%) to well-known human pathogens was observed in biofilms collected at the inlet pipe section. Our study highlights the role of sewer biofilms as source and sink of ARB and ARGs and supports the idea that community composition rather than antibiotic concentration is the main factor driving the diversity of the sewage resistome.

Arcobacter: an emerging food-borne zoonotic pathogen, its public health concerns and advances in diagnosis and control - a comprehensive review

Arcobacter has emerged as an important food-borne zoonotic pathogen, causing sometimes serious infections in humans and animals. Newer species of Arcobacter are being incessantly emerging (presently 25 species have been identified) with novel information on the evolutionary mechanisms and genetic diversity among different Arcobacter species. These have been reported from chickens, domestic animals (cattle, pigs, sheep, horses, dogs), reptiles (lizards, snakes and chelonians), meat (poultry, pork, goat, lamb, beef, rabbit), vegetables and from humans in different countries. Arcobacters are implicated as causative agents of diarrhea, mastitis and abortion in animals, while causing bacteremia, endocarditis, peritonitis, gastroenteritis and diarrhea in humans. Three species including A. butzleri, A. cryaerophilus and A. skirrowii are predominantly associated with clinical conditions. Arcobacters are primarily transmitted through contaminated food and water sources. Identification of Arcobacter by biochemical tests is difficult and isolation remains the gold standard method. Current diagnostic advances have provided various molecular methods for efficient detection and differentiation of the Arcobacters at genus and species level. To overcome the emerging antibiotic resistance problem there is an essential need to explore the potential of novel and alternative therapies. Strengthening of the diagnostic aspects is also suggested as in most cases Arcobacters goes unnoticed and hence the exact epidemiological status remains uncertain. This review updates the current knowledge and many aspects of this important food-borne pathogen, namely etiology, evolution and emergence, genetic diversity, epidemiology, the disease in animals and humans, public health concerns, and advances in its diagnosis, prevention and control.

Antimicrobial susceptibility, virulence potential and sequence types associated with Arcobacter strains recovered from human faeces

PURPOSE

The genus Arcobacter includes bacteria that are considered emergent pathogens because they can produce infections in humans and animals. The most common symptoms are bloody and non-bloody persistent diarrhea but cases with abdominal cramps without diarrhea or asymptomatic cases have also been described as well as cases with bacteremia. The objective was to characterize Arcobacter clinical strains isolated from the faeces of patients from three Spanish hospitals.

METHODOLOGY

We have characterized 28 clinical strains (27 of A. butzleri and one of A. cryaerophilus) isolated from faeces, analysing their epidemiological relationship using the multilocus sequence typing (MLST) approach and screening them for their antibiotic susceptibility and for the presence of virulence genes.Results/Key findings. Typing results showed that only one of the 28 identified sequence types (i.e. ST 2) was already present in the MLST database. The other 27 STs constituted new records because they included new alleles for five of the seven genes or new combinations of known alleles of the seven genes. All strains were positive for the ciaB virulence gene and sensitive to tetracycline. However, 7.4 % of the A. butzleri and A. cryaerophilus strains showed resistance to ciprofloxacin.

CONCLUSION

The fact that epidemiological unrelated strains show the same ST indicates that other techniques with higher resolution should be developed to effectively recognize the infection source. Resistance to ciprofloxacin, one of the antibiotics recommended for the treatment of Arcobacter intestinal infections, demonstrated in 10.7 % of the strains, indicates the importance of selecting the most appropriate effective treatment.

Enhanced Single-tube Multiplex PCR Assay for Detection and Identification of Six Arcobacter Species

AIM

A single-tube multiplex PCR (mPCR) assay was developed for rapid, sensitive and simultaneous detection and identification of six Arcobacter species including two new species, A. lanthieri and A. faecis, along with A. butzleri, A. cibarius, A. cryaerophilus and A. skirrowii on the basis of differences in the lengths of their PCR products. Previously designed monoplex, mPCR and RFLP assays do not detect or differentiate A. faecis and A. lanthieri from other closely related known Arcobacter spp.

METHODS AND RESULTS

Primer pairs for each target species (except A. skirrowii) and mPCR protocol were newly designed and optimized using variable regions of housekeeping including cpn60, gyrA, gyrB and rpoB genes. The accuracy and specificity of the mPCR assay was assessed using DNA templates from six targets and 11 other Arcobacter spp. as well as 50 other bacterial reference species and strains. Tests on the DNA templates of target Arcobacter spp. were appropriately identified, whereas all 61 other DNA templates from other bacterial species and strains were not amplified. Sensitivity and specificity of the mPCR assay was 10 pg μl^-1 of DNA concentration per target species. The optimized assay was further evaluated, validated and compared with other mPCR assays by testing Arcobacter cultures isolated from various faecal and water sources.

CONCLUSIONS

Study results confirm that the newly developed mPCR assay is rapid, accurate, reliable, simple, and valuable for the simultaneous detection and routine diagnosis of six human- and animal-associated Arcobacter spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

The new mPCR assay is useful not only for pure but also mixed cultures. Moreover, it has the ability to rapidly detect six species which enhances the value of this technology for aetiological and epidemiological studies.

First isolation report of Arcobacter cryaerophilus from a human diarrhea sample in Costa Rica

Arcobacter cryaerophilus is an emerging enteropathogen and potential zoonotic agent transmitted by food and water. In Costa Rica, this bacterium has not been associated with cases of human gastroenteritis, even though it has been isolated from farm animals, especially poultry. This paper reports the first isolation of A. cryaerophilus from a human case of bloody watery diarrhea and the virulence genes associated with this isolate.

Changes in the gut microbiome of the Chinese mitten crab (Eriocheir sinensis) in response to White spot syndrome virus (WSSV) infection

Intestinal microorganisms play important roles in maintaining host health, but their functions in aquatic animal hosts have yet to be fully elucidated. The Chinese mitten crab, Eriocheir sinensis, is one such example. We attempted to identify the shift of gut microbiota that occurred in response to infection of white spot syndrome virus (WSSV), an emerging viral pathogen in the crab aquaculture industry. The microbiota may exert some control over aspects of the viral pathogenesis. We investigated the changes in composition and structure of the crab gut microbiome during various WSSV infection stages of 6 h post-infection (hpi) and 48 hpi, using a 16S rRNA approach on the MiSeq Illumina sequencing platform. Four phyla (Firmicutes, Proteobacteria, Tenericutes and Bacteroidetes) were most dominant in the gut of E. sinensis regardless of the WSSV infection stages. However, further analysis revealed that over 12 bacterial phyla, 44 orders and 68 families were significantly different in abundance at various states of WSSV infection. Several intriguing aspects of E. sinensis gut bacteria that had not been previously reported were also uncovered, such as class Mollicutes was dominant here, but absent in crabs from Yangtze River estuary and Chongming Islands. Overall, this study provided the first evidence that changes in gut microbiome were closely associated with the severity of WSSV infection and that indicator taxa could be used to evaluate the crab health status.

The environmental and host-associated bacterial microbiota of Arctic seawater-farmed Atlantic salmon with ulcerative disorders

The Norwegian aquaculture of Atlantic salmon (Salmo salar L.) is hampered by ulcerative disorders associated with bacterial infections. Chronic ulceration may provide microenvironments that disturb the normal microbial biodiversity of external surfaces. Studying the composition of microbial communities in skin ulcers will enhance our understanding of ulcer aetiology. To achieve this, we tested marine farmed Atlantic salmon and sampled the base and edge of ulcers at the end of winter (April) and end of summer (September), in addition to skin mucus of healthy individuals. In order to assess microbiota associated with the host and obtain insight into the environmental ecology, we also sampled sea water, the sediment layer underneath the farm facility and the distal intestine of Atlantic salmon. The skin microbiota of Atlantic salmon was different from that of the surrounding water. Residential Tenacibaculum and Arcobacter species persistently dominated the cutaneous skin and ulcer mucus surfaces of Atlantic salmon during both winter and summer periods. The intestinal microbiota was dominated by Mycoplasma with an increase in Aliivibrio and Alcaligenes abundance in the intestine of fish with ulcerative disorder at the end of winter. These findings suggest the presence of resilient microbes in the mucus surfaces of Atlantic salmon.

Limited influence of primary treated sewage waters on bacterial abundance, production and community composition in coastal seawaters

The response of bacteria in terms of abundance, production and community structure to changes induced by the discharge of primary treated sewage waters was investigated combining microbiological, chemical and molecular tools. The primary treatment did not affect substantially the bacterial community structure in wastewaters and did not reduce the concentrations of fecal indicators. The spatial distribution of the sewage plume was governed by vertical stratification and currents. Bacterial abundance and production in the sea receiving waste waters depended predominantly on environmental conditions. In the waters with the highest concentration of fecal pollution indicators the bacterial community was characterized by allochthonous bacteria belonging to Epsilonproteobacteria, Firmicutes, Gammaproteobacteria and Bacteroidetes. The latter two taxa were also present in unpolluted waters but had a different structure, typical for oligotrophic environments. Although the impact of primary treated sewage waters was limited, a sanitary risk persisted due to the relevant presence of potentially pathogenic bacteria.

Prevalence of Putative Virulence Genes in Campylobacter and Arcobacter Species Isolated from Poultry and Poultry By-Products in Tunisia

Campylobacter and Arcobacter spp. are common causes of gastroenteritis in humans; these infections are commonly due to undercooked poultry. However, their virulence mechanism is still poorly understood. The aim of this study was to evaluate the presence of genotypic virulence markers in Campylobacter and Arcobacter species using PCR. The prevalence of virulence and cytolethal distending toxin (CDT) genes was estimated in 71 Campylobacteraceae isolates. PCR was used to detect the presence of virulence genes (iam, cadF, virB1, flaA, cdtA, cdtB, and cdtC) using specific primers for a total of 45 Campylobacter isolates, including 37 C. jejuni and 8 C. coli. All the Campylobacter isolates were positive for the cadF gene. The plasmid gene virB11 was not detected in any strain. The invasion associated marker was not detected in C. jejuni. Lower detection rates were observed for flaA, cdtA, cdtB, and cdtC. The presence of nine putative Arcobacter virulence genes (cadF, ciaB, cj1349, mviN, pldA, tlyA, irgA, hecA, and hecB) was checked in a set of 22 Arcobacter butzleri and 4 Arcobacter cryaerophilus isolates. The pldA and mviN genes were predominant (88.64%). Lower detection rates were observed for tlyA (84.76%), ciaB (84.61%), cadF and cj1349 (76.92%), IrgA and hecA (61.53%), and hecB (57.69%). The findings revealed that a majority of the Campylobacteraceae strains have these putative virulence genes that may lead to pathogenic effects in humans.

Occurrence, genetic diversity and antibiotic resistance of Arcobacter sp. in a dairy plant

AIMS

The aim of this study was to evaluate the occurrence, diversity and resistance to antibiotics of Arcobacter sp. in a dairy plant samples.

METHODS AND RESULTS

A total of 75 samples from dairy plant surfaces and materials and several food products collected in different steps of the cheese production process were analysed by culture, under aerobic and microaerobic atmospheric conditions, and by enrichment molecular detection. Isolates were identified and genotyped by ERIC-PCR, and their susceptibility to nine antibiotics was evaluated by agar dilution. Global prevalence of Arcobacter sp. was 42·7%, where 20 of the 42 food samples analysed were positive for A. butzleri by both culture and molecular detection, one for A. marinus by culture and one for A. cryaerophilus by molecular detection only; 10 of the 30 analysed materials and plant surfaces were positive for A. butzleri. All A. butzleri isolates were resistant to nalidixic acid and showed high resistance rates to ampicillin (56·2%) and cefotaxime (97·9%), being all strains susceptible to gentamicin and erythromycin.

CONCLUSIONS

Contamination of dairy plant environment with A. butzleri and its progression along cheese production process were observed, however, the cheese ripening process may have a relevant role in the reduction of the contamination.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study showed the presence of Arcobacter sp. in a dairy plant, displaying its high prevalence and genetic diversity and highlighting its high resistance rates. The data obtained could contribute to further acknowledge the Arcobacter food contamination as a potential health hazard.

Isolation, molecular identification and quinolone-susceptibility testing of Arcobacter spp. isolated from fresh vegetables in Spain

Some species of the Arcobacter genus are considered emerging foodborne and waterborne enteropathogens. However, the presence of Arcobacter spp. in vegetables very little is known, because most studies have focused on foods of animal origin. On the other hand, quinolones are considered as first-line drugs for the treatment of infection by campylobacteria in human patients, but few data are currently available about the resistance levels to these antibiotics among Arcobacter species. Therefore, the aim of this study was to investigate the presence and diversity of arcobacters isolated from fresh vegetables such as lettuces, spinaches, chards and cabbages. Resistance to quinolones of the isolates was also investigated. One hundred fresh vegetables samples purchased from seven local retail markets in Valencia (Spain) during eight months were analysed. The study included 41 lettuces, 21 spinaches, 34 chards and 4 cabbages. Samples were analysed by culture and by molecular methods before and after enrichment. By culture, 17 out of 100 analysed samples were Arcobacter positive and twenty-five isolates were obtained from them. Direct detection by PCR was low, with only 4% Arcobacter spp. positive samples. This percentage increased considerably, up 20%, after 48 h enrichment. By polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), 17 out of the 25 isolates were identified as A. butzleri and 8 as A. cryaerophilus. Only two A. butzleri isolates showed resistance to levofloxacin and ciprofloxacin. The sequencing of a fragment of the QRDR region of the gyrA gene from the quinolones-resistant isolates revealed the presence of a mutation in position 254 of this gene (C-T transition). This study is the first report about the presence of pathogenic species of Arcobacter spp. in chards and cabbages and confirms that fresh vegetables can act as transmission vehicle to humans. Moreover, the presence of A. butzleri quinolone resistant in vegetables could pose a potential public health risk.

Characterization of the emerging zoonotic pathogen Arcobacter thereius by whole genome sequencing and comparative genomics

Four Arcobacter species have been associated with human disease, and based on current knowledge, these Gram negative bacteria are considered as potential food and waterborne zoonotic pathogens. At present, only the genome of the species Arcobacter butzleri has been analysed, and still little is known about their physiology and genetics. The species Arcobacter thereius has first been isolated from tissue of aborted piglets, duck and pig faeces, and recently from stool of human patients with enteritis. In the present study, the complete genome and analysis of the A. thereius type strain LMG24486T, as well as the comparative genome analysis with 8 other A. thereius strains are presented. Genome analysis revealed metabolic pathways for the utilization of amino acids, which represent the main source of energy, together with the presence of genes encoding for respiration-associated and chemotaxis proteins. Comparative genome analysis with the A. butzleri type strain RM4018 revealed a large correlation, though also unique features. Furthermore, in silico DDH and ANI based analysis of the nine A. thereius strains disclosed clustering into two closely related genotypes. No discriminatory differences in genome content nor phenotypic behaviour were detected, though recently the species Arcobacter porcinus was proposed to encompass part of the formerly identified Arcobacter thereius strains. The report of the presence of virulence associated genes in A. thereius, the presence of antibiotic resistance genes, verified by in vitro susceptibility testing, as well as other pathogenic related relevant features, support the classification of A. thereius as an emerging pathogen.

Virulence gene profiles of Arcobacter species isolated from animals, foods of animal origin, and humans in Andhra Pradesh, India

Aim::

This study aimed to detect putative virulence genes in Arcobacter species of animal and human origin.

Materials and Methods::

A total of 41 Arcobacter isolates (16 Arcobacter butzleri, 13 Arcobacter cryaerophilus, and 12 Arcobacter skirrowii) isolated from diverse sources such as fecal swabs of livestock (21), raw foods of animal origin (13), and human stool samples (7) were subjected to a set of six uniplex polymerase chain reaction assays targeting Arcobacter putative virulence genes (ciaB, pldA, tlyA, mviN, cadF, and cj1349).

Results::

All the six virulence genes were detected among all the 16 A. butzleri isolates. Among the 13 A. cryaerophilus isolates, cadF, ciaB, cj1349, mviN, pldA, and tlyA genes were detected in 61.5, 84.6, 76.9, 76.9, 61.5, and 61.5% of isolates, respectively. Among the 12 A. skirrowii isolates, cadF, ciaB, cj1349, mviN, pldA, and tlyA genes were detected in 50.0, 91.6, 83.3, 66.6, 50, and 50% of isolates, respectively.

Conclusion::

Putative virulence genes were detected in majority of the Arcobacter isolates examined. The results signify the potential of Arcobacter species as an emerging foodborne pathogen.

Comparative isolation and genetic diversity of Arcobacter sp. from fish and the coastal environment

Arcobacter species are emerging food-borne and water-borne human pathogens associated mostly with food animals and their environment. The present study was aimed to isolate Arcobacter species from fish, shellfish and coastal water samples using two methods and to determine their genetic diversity. Of 201 samples of fish, shellfish and water samples analysed, 66 (32·8%) samples showed the presence of Arcobacter DNA from both Arcobacter enrichment broth and Bolton broth. Arcobacters were isolated from 58 (87·8%) and 38 (57·5%) of Arcobacter DNA-positive samples using Arcobacter blood agar and Preston blood agar, respectively. Arcobacter sp. identified by biochemical tests were further analysed by a genus-specific PCR, followed by a multiplex-PCR and 16S rRNA-RFLP. From both the methods, four different Arcobacter species namely Arcobacter butzleri, Arcobacter skirrowii, Arcobacter mytili and Arcobacter defluvii were isolated, of which A. butzleri was the predominant species. Enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprint analysis revealed that the arcobacters isolated in this study were genetically very diverse and no specific genotype was found associated with a specific source (seafood or water). Since pathogenic arcobacters are not known to be natural inhabitants of coastal marine environment, identifying the sources of contamination will be crucial for effective management of this problem.

SIGNIFICANCE AND IMPACT OF THE STUDY

Arcobacter sp. are emerging food- and water-borne human pathogens. In this study, comparison of two selective media suggested Arcobacter blood agar to be more efficient in yielding Arcobacter sp. from seafood. Furthermore, the isolation of Arcobacter sp. such as Arcobacter butzleri, A. skirrowii, A. mytili and A. defluvii from seafood suggests diverse sources of contamination of seafood by Arcobacter sp. Analysis of enterobacterial repetitive intergenic consensus sequence-PCR patterns of A. butzleri showed high genetic diversity and lack of clonality among the isolates. Arcobacter contamination of seafood is an emerging issue both from seafood safety and seafood trade point of view.

Arcobacter lekithochrous sp. nov., isolated from a molluscan hatchery

Four bacterial strains, LFT 1.7T, LT2C 2.5, LT4C 2.8 and TM 4.6, were isolated from great scallop (Pecten maximus) larvae and tank seawater in a Norwegian hatchery and characterized by a polyphasic approach including determination of phenotypic, chemotaxonomic and genomic traits. All were Gram-stain-negative, motile rods, oxidase- and catalase-positive and required sea salts for growth. Major fatty acids present were summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), summed feature 8 (C18 : 1ω7c or C18 : 1ω6c), C16 : 0, C14 : 0, summed feature 2 (C14 : 0 3-OH/iso-C16 : 1 I), C12 : 0 3-OH and C12 : 0. Strain LFT 1.7T contained menaquinone MK-6 as the sole respiratory quinone. Phylogenetic analysis based on 16S rRNA gene sequences indicated that all strains formed a distinct lineage within the genus Arcobacter with a low similarity to known species (94.77-95.32 %). The DNA G+C content was 28.7 mol%. Results of in silico DNA-DNA hybridization and average nucleotide identity confirmed that the isolates constitute a novel species of Arcobacter, for which the name Arcobacter lekithochrous sp. nov. is proposed. The type strain is LFT 1.7T (=CECT 8942T=DSM 100870T).

Study of Biofilm Formation Ability of Foodborne Arcobacter butzleri under Different Conditions

The transmission of Arcobacter butzleri, an emerging food- and waterborne pathogen, is possibly favored by its ability to adhere to abiotic surfaces. In this study, we assessed the biofilm formation ability of 42 A. butzleri isolates recovered from different food products. Overall, nine isolates (21.4%) were able to adhere to polystyrene. Among them, a chicken-derived isolate was classified as strongly adherent. Based on the chi-square test, no relation was found between the adhesive abilities of the isolates and their source (P > 0.05). An aerobic atmosphere enhanced the adhesion ability of the majority of the adherent isolates (66.7%), because when tested in microaerobic conditions, a t test indicated that only three isolates increased their biofilm formation ability significantly (P < 0.05). In addition, seven (77.8%) of these nine isolates were able to adhere to glass surfaces, and viable cells were recovered from all the stainless steel coupons tested. Therefore, our results confirm the biofilm formation ability of A. butzleri, which may be influenced by the incubation atmosphere and the abiotic surface.