Repositioning of the Antihyperlipidemic Drug Fenofibrate for the Management of Aeromonas Infections.

Fenofibrate is a fibric acid derivative used as an antihyperlipidemic drug in humans. Its active metabolite, fenofibric acid, acts as an agonist to the peroxisome proliferator-activated receptor alpha (PPAR-α), a transcription factor involved in different metabolic pathways. Some studies have reported the potential protective role of this drug in cell lines and in vivo models against bacterial and viral infections. The aim of this study was to assess the in vitro effect of fenofibrate in the macrophage cell line J744A.1 against infections produced by Aeromonas, a pathogen for humans whose resistance to antibiotics has increased in recent decades. Macrophages were infected at MOI 10 with four strains of Aeromonas caviae and Aeromonas hydrophila isolated from human clinical samples and subsequently treated with fenofibrate. It was observed that fenofibrate-treated macrophages showed lower levels of cytotoxicity and intracellular bacteria compared to non-treated macrophages. In addition, the viability of treated macrophages was dependent on the dose of fenofibrate used. Furthermore, transcriptional analysis by RT-qPCR revealed significant differences in the expression of the PPAR-α gene and immune-related genes TNF-α, CCL3, and BAX in fenofibrate-treated macrophages compared to the macrophages without treatment. This study provides evidence that fenofibrate offered some protection in vitro in macrophages against Aeromonas infection. However, further studies are needed with other bacteria to determine its potential antibacterial effect and the route by which this protection is achieved.

Drosophila melanogaster Systemic Infection Model to Study Altered Virulence during Polymicrobial Infection by Aeromonas.

BACKGROUND: Polymicrobial infections are complex infections associated with worse outcomes compared to monomicrobial infections. We need simple, fast, and cost-effective animal models to assess their still poorly known pathogenesis. METHODS: We developed a Drosophila melanogaster polymicrobial infection model for opportunistic pathogens and assessed its capacity to discriminate the effects of bacterial mixtures taken from cases of human polymicrobial infections by Aeromonas strains. A systemic infection was obtained by needle pricking the dorsal thorax of the flies, and the fly survival was monitored over time. Different lineages of the flies were infected by a single strain or paired strains (strain ratio 1:1). RESULTS: Individual strains killed more than 80% of the flies in 20 h. The course of infection could be altered with a microbial mix. The model could distinguish between the diverse effects (synergistic, antagonistic, and no difference) that resulted in a milder, more severe, or similar infection, depending on the paired strain considered. We then investigated the determinants of the effects. The effects were maintained in deficient fly lineages for the main signaling pathways (Toll deficient and IMD deficient), which suggests an active microbe/microbe/host interaction. CONCLUSION: These results indicate that the D. melanogaster systemic infection model is consistent with the study of polymicrobial infection.

Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers.

Legionella pneumophila (Lp) colonizes aquatic environments and is a potential pathogen to humans, causing outbreaks of Legionnaire's disease. It is mainly associated with contaminated cooling towers (CTs). Several regulations, including Spanish legislation (Sl), have introduced the analysis of heterotrophic plate count (HPC) bacteria and Legionella spp. (Lsp) in management plans to prevent and control Legionella outbreaks from CTs. The 2003 Sl for CTs (RD 865/2003) considered that concentrations of HPC bacteria ≤10,000 cfu/mL and of Lsp ≤100 cfu/L are safe; therefore, no action is required, whereas management actions should be implemented above these standards. We have investigated to what extent the proposed standard for HPC bacteria is useful to predict the presence of Lsp in cooling waters. For this, we analyzed Lsp and HPC concentrations, water temperature, and the levels of chlorine in 1376 water samples from 17 CTs. The results showed that in the 1138 water samples negative for Legionella spp. (LN), the HPC geometric mean was significantly lower (83 cfu/mL, p < 0.05) than in the positive Lsp. samples (135 cfu/mL). Of the 238 (17.3%) LP samples, 88.4% (210/238) were associated with values of HPC ≤10,000 cfu/mL and most of them showed HPC concentrations ≤100 (53.7%). In addition, a relatively low percentage of LP (28/238, 11.6%) samples were associated with HPC bacteria concentrations >10,000 cfu/mL, indicating that this standard does not predict the colonization risk for Legionella in the CTs studied. The present study has demonstrated that a threshold concentration ≤100 cfu/mL of HPC bacteria could better predict the higher concentration of Legionella in CTs, which will aid in preventing possible outbreaks.

First Record of the Rare Species Aeromonas lusitana from Rainbow Trout (Oncorhynchus mykiss, Walbaum): Comparative Analysis with the Existing Strains.

The species Aeromonas lusitana was first described in 2016 with five strains recovered from untreated water and vegetables from Portugal. Since then, no further records exist of this species. During a surveillance study on the presence of Aeromonas in fish farms in Mexico, a new strain (ESV-351) of the mentioned species isolated from a rainbow trout was recovered. It was identified because it clustered phylogenetically with the type strain of A. lusitana based on the analysis of the rpoD gene sequences. In the present study, phenotypic characteristics, antimicrobial resistance profiles, and the presence of putative virulence genes of this novel strain (ESV-351) were determined in parallel to the five isolates from the original species description. Phenotypic differential characteristics exhibited by A. lusitana ESV-351 depicted an evident similarity to the characteristics exhibited by the other evaluated strains. However, the novel strain was positive for the production of indole using conventional methods, while the rest of the strains, including the type strain, were negative for its production. Furthermore, intermediate resistance to ampicillin, amoxicillin-clavulanic acid and cephalothin was detected in both the novel and the type strain. Five different virulence-related genes were detected in the novel strain and in the previously described strains, with the type strain exhibiting the highest number of virulence-related genes. In addition to this, the genome of the novel strain (ESV-351) was sequenced and compared with the genomes from the type strain (A. lusitana CECT 7828T) and other Aeromonas spp. The genomic analysis defined Aeromonas tecta as the closest species to A. lusitana with a highly similar number of predicted proteins. The genomic size, the number of protein-encoding genes and the number of different tRNAs, among other characteristics, make it possible to propose that the ESV-351 strain could potentially have the capacity to adapt to different environments. Genome comparison of the ESV-351 strain with the type strain revealed that both possess a similar sequence of the citrate synthase gene. In addition to this finding, the chromosomal region containing the citrate synthase locus of the novel strain exhibits some similarity to the chromosomal region in the genome of the A. hydrophila type strain and other known human pathogens, such as Vibrio cholerae. This could suggest a possible virulence role for the citrate synthase gene in A. lusitana (ESV-351).

Potential Pathogenicity of Aeromonas spp. Recovered in River Water, Soil, and Vegetation from a Natural Recreational Area.

The genus Aeromonas is widely distributed in aquatic environments and is recognized as a potential human pathogen. Some Aeromonas species are able to cause a wide spectrum of diseases, mainly gastroenteritis, skin and soft-tissue infections, bacteremia, and sepsis. Currently, untreated river water is used for irrigation and recreational purposes. In this study, the Aeromonas spp. present in a river recreational environment was investigated by quantifying its presence in water, soil, and vegetation using three techniques: qPCR, plate counting in selective ADA medium, and Most Probable Number, in parallel. The presence of clones in the three types of samples was elucidated through genotyping with the ERIC-PCR technique, whereas the identification of the isolated Aeromonas was carried out by sequencing the rpoD gene. Finally, the pathogenic potential of some of the strains was explored by studying the presence and expression of virulence genes characteristic of the genus, their antimicrobial susceptibility profile, as well as the quantification of their cell damage and intracellular survival in an in vitro macrophages infection model. The results showed the presence of Aeromonas in all samples with the three quantification methods, with Aeromonas popoffii being the most prevalent species. The presence of strains with the same genotype (ERIC-PCR) was also confirmed in different samples. Some of the strains showed a high level of cell damage and intracellular bacterial survival, as well as the presence of various virulence factors. Furthermore, these strains showed resistance to some of the antibiotics tested and used therapeutically in both humans and animals. These results indicate that the presence of Aeromonas in this environment may represent a biosanitary risk that could be a public health problem.

Immune Response of the Monocytic Cell Line THP-1 Against Six Aeromonas spp.

Aeromonas are autochthonous bacteria of aquatic environments that are considered to be emerging pathogens to humans, producing diarrhea, bacteremia, and wound infections. Genetic identification shows that 95.4% of the strains associated with clinical cases correspond to the species Aeromonas caviae (37.26%), Aeromonas dhakensis (23.49%), Aeromonas veronii (21.54%), and Aeromonas hydrophila (13.07%). However, few studies have investigated the human immune response against some Aeromonas spp. such as A. hydrophila, Aeromonas salmonicida, and A. veronii. The present study aimed to increase the knowledge about the innate human immune response against six Aeromonas species, using, for the first time, an in vitro infection model with the monocytic human cell line THP-1, and to evaluate the intracellular survival, the cell damage, and the expression of 11 immune-related genes (TLR4, TNF-α, CCL2, CCL20, JUN, RELA, BAX, TP53, CASP3, NLRP3, and IL-1ß). Transcriptional analysis showed an upregulated expression of a variety of the monocytic immune-related genes, with a variable response depending upon the Aeromonas species. The species that produced the highest cell damage, independently of the strain origin, coincidentally induced a higher expression of immune-related genes and corresponded to the more prevalent clinical species A. dhakensis, A. veronii, and A. caviae. Additionally, monocytic cells showed an overexpression of the apoptotic and pyroptotic genes involved in cell death after A. dhakensis, A. caviae, and Aeromonas media infection. However, the apoptosis route seemed to be the only way of producing cell damage and death in the case of the species Aeromonas piscicola and Aeromonas jandaei, while A. veronii apparently only used the pyroptosis route.

Aliarcobacter vitoriensis sp. nov., isolated from carrot and urban wastewater.

Two isolates, one recovered from a carrot and another one from urban wastewater, were characterized using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences revealed that both isolates clustered together, and were most closely related to Aliarcobacter lanthieri. Multilocus phylogenetic analysis (MLPA) using the concatenated sequences of five housekeeping genes (atpA, gyrA, gyrB, hsp60 and rpoB) suggested that these isolates formed a distinct phylogenetic lineage among the genera derived from the former genus Arcobacter. Whole-genome sequence, in silico DNA-DNA hybridization (isDDH) and the average nucleotide identity (ANI) value between the genome of strain F199T and those of related species confirmed that these isolates represent a novel species. These strains can be differentiated from its phylogenetically closest species A. lanthieri by its inability to growth on 1% glycine and by their enzyme activity of esterase lipase (C8) and acid phosphatase. Our results, by the application of a polyphasic analysis, confirmed that these two isolates represent a novel species of the genus Aliarcobacter, for which the name Aliarcobacter vitoriensis sp. nov. is proposed. The type strain is F199T (=CECT 9230T=LMG 30050T).

A Case of Aeromonas trota in an Immunocompromised Patient with Diarrhea.

According to recent literature, 95.4% of the Aeromonas strains associated with human clinical cases correspond to four species: Aeromonas caviae, Aeromonas dhakensis, Aeromonas veronii and Aeromonas hydrophila. However, other less prevalent species such as Aeromonas trota, are also described from clinical samples. Based on its low incidence, the latter species can be regarded as rare and it is the only Aeromonas species susceptible to ampicillin. From the taxonomic point of view, A. trota is considered a synonym of the species Aeromonas enteropelogenes. The objective of this study is to present a new clinical case associated with A. trota in order to increase the knowledge about this species. The strain was recovered from the feces of a 69-year-old patient with a diarrheal syndrome and peritoneal psammocarcinoma. The preliminary identification as Aeromonas sp. was obtained with the API 20E, but it was characterized as Aeromonas jandei and also as Aeromonas enteropelogenes with different scores with the matrix-assisted laser desorption ionization time of flight (MALDI-TOF). Based on the sequence of the rpoD gene, it was confirmed to be A. trota. The antimicrobial resistance pattern showed that the strain was susceptible to ampicillin, penicillins in combination with beta-lactamase inhibitors, quinolones, carbapenems, aminoglycosides and cephalosporins, except cephalothin. In conclusion, the recognition of an Aeromonas strain susceptible to ampicillin should alert the clinical microbiologist of the possible involvement of this rare species. Furthermore, the MALDI-TOF database should be updated indicating that the species A. enteropelogenes, is a synonym of A. trota.

Metagenomic analysis of viruses, bacteria and protozoa in irrigation water.

Viruses (e.g., noroviruses and hepatitis A and E virus), bacteria (e.g., Salmonella spp. and pathogenic Escherichia coli) and protozoa (e.g., Cryptosporidium parvum and Giardia intestinalis) are well-known contributors to food-borne illnesses linked to contaminated fresh produce. As agricultural irrigation increases the total amount of water used annually, reclaimed water is a good alternative to reduce dependency on conventional irrigation water sources. European guidelines have established acceptable concentrations of certain pathogens and/or indicators in irrigation water, depending on the irrigation system used and the irrigated crop. However, the incidences of food-borne infections are known to be underestimated and all the different pathogens contributing to these infections are not known. Next-generation sequencing (NGS) enables the determination of the viral, bacterial and protozoan populations present in a water sample, providing an opportunity to detect emerging pathogens and develop improved tools for monitoring the quality of irrigation water. This is a descriptive study of the virome, bacteriome and parasitome present in different irrigation water sources. We applied the same concentration method for all the studied samples and specific metagenomic approaches to characterize both DNA and RNA viruses, bacteria and protozoa. In general, most of the known viral species corresponded to plant viruses and bacteriophages. Viral diversity in river water varied over the year, with higher bacteriophage prevalences during the autumn and winter. Reservoir water contained Enterobacter cloacae, an opportunistic human pathogen and an indicator of fecal contamination, as well as Naegleria australiensis and Naegleria clarki. Hepatitis E virus and Naegleria fowleri, emerging human pathogens, were detected in groundwater. Reclaimed water produced in a constructed wetland system presented a virome and bacteriome that resembled those of freshwater samples (river and reservoir water). Viral, bacterial and protozoan pathogens were occasionally detected in the different irrigation water sources included in this study, justifying the use of improved NGS techniques to get a comprehensive evaluation of microbial species and potential environmental health hazards associated to irrigation water.

An Update on the Genus Aeromonas: Taxonomy, Epidemiology, and Pathogenicity.

The genus Aeromonas belongs to the Aeromonadaceae family and comprises a group of Gram-negative bacteria widely distributed in aquatic environments, with some species able to cause disease in humans, fish, and other aquatic animals. However, bacteria of this genus are isolated from many other habitats, environments, and food products. The taxonomy of this genus is complex when phenotypic identification methods are used because such methods might not correctly identify all the species. On the other hand, molecular methods have proven very reliable, such as using the sequences of concatenated housekeeping genes like gyrB and rpoD or comparing the genomes with the type strains using a genomic index, such as the average nucleotide identity (ANI) or in silico DNA-DNA hybridization (isDDH). So far, 36 species have been described in the genus Aeromonas of which at least 19 are considered emerging pathogens to humans, causing a broad spectrum of infections. Having said that, when classifying 1852 strains that have been reported in various recent clinical cases, 95.4% were identified as only four species: Aeromonas caviae (37.26%), Aeromonas dhakensis (23.49%), Aeromonas veronii (21.54%), and Aeromonas hydrophila (13.07%). Since aeromonads were first associated with human disease, gastroenteritis, bacteremia, and wound infections have dominated. The literature shows that the pathogenic potential of Aeromonas is considered multifactorial and the presence of several virulence factors allows these bacteria to adhere, invade, and destroy the host cells, overcoming the immune host response. Based on current information about the ecology, epidemiology, and pathogenicity of the genus Aeromonas, we should assume that the infections these bacteria produce will remain a great health problem in the future. The ubiquitous distribution of these bacteria and the increasing elderly population, to whom these bacteria are an opportunistic pathogen, will facilitate this problem. In addition, using data from outbreak studies, it has been recognized that in cases of diarrhea, the infective dose of Aeromonas is relatively low. These poorly known bacteria should therefore be considered similarly as enteropathogens like Salmonella and Campylobacter.

Microbiological contamination of conventional and reclaimed irrigation water: Evaluation and management measures.

The wide diversity of irrigation water sources (i.e., drinking water, groundwater, reservoir water, river water) includes reclaimed water as a requested measure for increasing water availability, but it is also a challenge as pathogen exposure may increase. This study evaluates the level of microbial contamination in different irrigation waters to improve the knowledge and analyses management measures for safety irrigation. Over a one-year period, the occurrence of a set of viruses, bacteria and protozoa, was quantified and the performance of a wetland system, producing reclaimed water intended for irrigation, was characterized. Human fecal pollution (HAdV) was found in most of the irrigation water types analysed. Hepatitis E virus (HEV), an emerging zoonotic pathogen, was present in groundwater where porcine contamination was identified (PAdV). The skin-carcinoma associated Merkel cell polyomavirus (MCPyV), was found occasionally in river water. Noroviruses were detected, as expected, in winter, in river water and reclaimed water. Groundwater, river water and reservoir water also harboured potential bacterial pathogens, like Helicobacter pylori, Legionella spp. and Aeromonas spp. that could be internalized and viable inside amoebas like Acanthamoeba castellanii, which was also detected. Neither Giardia cysts, nor any Cryptosporidium oocysts were detected. The wetland system removed 3 Log10 of viruses and 5 Log10 of bacteria, which resembled the river water quality. Irrigation waters were prone to variable contamination levels and according to the European guidance documents, the E. coli (EC) levels were not always acceptable. Sporadic detection of viral pathogens as NoV GII and HAdV was identified in water samples presenting lower EC than the established limit (100MNP/100 mL). When dealing with reclaimed water as a source of irrigation the analysis of some viral parameters, like HAdV during the peak irrigation period (summer and spring) or NoV during the coldest months, could complement existing water management tools based on bacterial indicators.

T6SS and ExoA of flesh-eating Aeromonas hydrophila in peritonitis and necrotizing fasciitis during mono- and polymicrobial infections.

An earlier report described a human case of necrotizing fasciitis (NF) caused by mixed infection with 4 Aeromonas hydrophila strains (NF1-NF4). While the NF2, NF3, and NF4 strains were clonal and possessed exotoxin A (ExoA), the NF1 strain was determined to be phylogenetically distinct, harboring a unique type 6 secretion system (T6SS) effector (TseC). During NF1 and NF2 mixed infection, only NF1 disseminated, while NF2 was rapidly killed by a contact-dependent mechanism and macrophage phagocytosis, as was demonstrated by using in vitro models. To confirm these findings, we developed 2 NF1 mutants (NF1ΔtseC and NF1ΔvasK); vasK encodes an essential T6SS structural component. NF1 VasK and TseC were proven to be involved in contact-dependent killing of NF2 in vitro, as well as in its elimination at the intramuscular injection site in vivo during mixed infection, with overall reduced mouse mortality. ExoA was shown to have an important role in NF by both NF1-exoA (with cis exoA) and NF2 during monomicrobial infection. However, the contribution of ExoA was more important for NF2 than NF1 in the murine peritonitis model. The NF2∆exoA mutant did not significantly alter animal mortality or NF1 dissemination during mixed infection in the NF model, suggesting that the ExoA activity was significant at the injection site. Immunization of mice to ExoA protected animals from NF2 monomicrobial challenge, but not from polymicrobial infection because of NF2 clearance. This study clarified the roles of T6SS and ExoA in pathogenesis caused by A. hydrophila NF strains in both mouse peritonitis and NF models in monomicrobial and polymicrobial infections.

The Metallochaperone Encoding Gene hypA Is Widely Distributed among Pathogenic Aeromonas spp. and Its Expression Is Increased under Acidic pH and within Macrophages.

Metallochaperones are essential proteins that insert metal ions or metal cofactors into specific enzymes, that after maturation will become metalloenzymes. One of the most studied metallochaperones is the nickel-binding protein HypA, involved in the maturation of nickel-dependent hydrogenases and ureases. HypA was previously described in the human pathogens Escherichia coli and Helicobacter pylori and was considered a key virulence factor in the latter. However, nothing is known about this metallochaperone in the species of the emerging pathogen genus Aeromonas. These bacteria are native inhabitants of aquatic environments, often associated with cases of diarrhea and wound infections. In this study, we performed an in silico study of the hypA gene on 36 Aeromonas species genomes, which showed the presence of the gene in 69.4% (25/36) of the Aeromonas genomes. The similarity of Aeromonas HypA proteins with the H. pylori orthologous protein ranged from 21-23%, while with that of E. coli it was 41-45%. However, despite this low percentage, Aeromonas HypA displays the conserved characteristic metal-binding domains found in the other pathogens. The transcriptional analysis enabled the determination of hypA expression levels under acidic and alkaline conditions and after macrophage phagocytosis. The transcriptional regulation of hypA was found to be pH-dependent, showing upregulation at acidic pH. A higher upregulation occurred after macrophage infection. This is the first study that provided evidence that the HypA metallochaperone in Aeromonas might play a role in acid tolerance and in the defense against macrophages.

The Use of a DNA-Intercalating Dye for Quantitative Detection of Viable Arcobacter spp. Cells (v-qPCR) in Shellfish.

The genus Arcobacter (Vandamme et al., 1991), comprised of Campylobacter-related species, are considered zoonotic emergent pathogens. The presence of Arcobacter in food products like shellfish, has an elevated incidence worldwide. In this study, we developed a specific viable quantitative PCR (v-qPCR), using the dye propidium monoazide (PMA), for quantification of the viable Arcobacter spp. cells in raw oysters and mussels. The high selectivity of primers was demonstrated by using purified DNA from 38 different species, 20 of them from the genus Arcobacter. The optimization of PMA concentration showed that 20 µM was considered as an optimal concentration that inhibits the signal from dead cells at different concentrations (OD550 from 0.2 to 0.8) and at different ratios of live: dead cells (50:50 and 90:10). The v-qPCR results from shellfish samples were compared with those obtained in parallel using several culture isolation approaches (i.e., direct plating on marine and blood agar and by post-enrichment culturing in both media). The enrichment was performed in parallel in Arcobacter-CAT broth with and without adding NaCl. Additionally, the v-qPCR results were compared to those obtained with traditional quantitative (qPCR). The v-qPCR and the qPCR resulted in c.a. 94% of positive detection of Arcobacter vs. 41% obtained by culture approaches. When examining the reduction effect resulting from the use of v-qPCR, samples pre-enriched in Arcobacter-CAT broth supplemented with 2.5% NaCl showed a higher reduction (3.27 log copies) than that of samples obtained directly and those pre-enriched in Arcobacter-CAT broth isolation (1.05 and 1.04). When the v-qPCR was applied to detect arcobacter from real shellfish samples, 15/17 samples tested positive for viable Arcobacter with 3.41 to 8.70 log copies 1g-1. This study offers a new tool for Arcobacter surveillance in seafood.

Arcobacter lacus sp. nov. and Arcobacter caeni sp. nov., two novel species isolated from reclaimed water.

Two strains (RW43-9T and RW17-10T) recovered from secondary treated wastewater from the Wastewater Treatment Plant (WWTP) in Reus (Spain) were characterized by a polyphasic taxonomic study, showing evidence that they represented two novel Arcobacter species. Based on the 16S rRNA gene for strain RW43-9T, the closest relative was Arcobacter butzleri LMG 10828T (99.9 % similarity), while for strain RW17-10T it was Arcobacter venerupis CECT 7836T (99.4 %). Additionally, multilocus phylogenetic analysis of five concatenated housekeeping genes (atpA, gyrA, gyrB, hsp60 and rpoB) showed that the two strains formed separate branches that are different from known Arcobacter species. Whole genome sequences of the two strains (RW43-9T and RW17-10T) were obtained and they were compared with those of the type strains of their nearest species. Using average nucleotide identity and in silico DNA-DNA hybridization gave values that were below 96 and 70 %, respectively. These results clearly confirm that they represent novel species. Additionally, the phenotypic characterization of the strains allowed their differentiation from other species. Therefore, the strains are proposed as representing two novel species with the names Arcobacter lacus sp. nov. (type strain RW43-9T=CECT 8994T=LMG 29062T) and Arcobacter caeni sp. nov. (type strain RW17-10T=CECT 9140T=LMG 29151T).

Investigation of the virulence and genomics of Aeromonas salmonicida strains isolated from human patients.

The bacterium Aeromonas salmonicida is known since long time as a major fish pathogen unable to grow at 37 °C. However, some cases of human infection by putative mesophilic A. salmonicida have been reported. The goal of the present study is to examine two clinical cases of human infection by A. salmonicida in Spain and to investigate the pathogenicity in mammals of selected mesophilic A. salmonicida strains. An evaluation of the pathogenicity in a mouse model of clinical and environmental A. salmonicida strains was performed. The genomes of the strains were sequenced and analyzed in order to find the virulence determinants of these strains. The experimental infection in mice showed a gradient in the virulence of these strains and that some of them can cause necrotizing fasciitis and tissue damage in the liver. In addition to demonstrating significant genomic diversity among the strains studied, bioinformatics analyses permitted also to shed light on crucial elements for the virulence of the strains, like the presence of a type III secretion system in the one that caused the highest mortality in the experimental infection. Clinicians and microbiologists should consider these results for the inclusion of A. salmonicida in diagnosis tests since it is now clear that some mesophilic strains are also pathogens for humans.

Genome-driven evaluation and redesign of PCR tools for improving the detection of virulence-associated genes in aeromonads.

Many virulence factors have been described for opportunistic pathogens within the genus Aeromonas. Polymerase Chain Reactions (PCRs) are commonly used in population studies of aeromonads to detect virulence-associated genes in order to better understand the epidemiology and emergence of Aeromonas from the environment to host, but their performances have never been thoroughly evaluated. We aimed to determine diagnostic sensitivity and specificity of PCR assays for the detection of virulence-associated genes in a collection of Aeromonas isolates representative for the genetic diversity in the genus. Thirty-nine Aeromonas strains belonging to 27 recognized species were screened by published PCR assays for virulence-associated genes (act, aerA, aexT, alt, ascFG, ascV, ast, lafA, lip, ser, stx1, stx2A). In parallel, homologues of the 12 putative virulence genes were searched from the genomes of the 39 strains. Of the 12 published PCR assays for virulence factors, the comparison of PCR results and genome analysis estimated diagnostic sensitivities ranging from 34% to 100% and diagnostic specificities ranged from 71% to 100% depending upon the gene. To improve the detection of virulence-associated genes in aeromonads, we have designed new primer pairs for aerA/act, ser, lafA, ascFG and ascV, which showed excellent diagnostic sensitivity and specificity. Altogether, the analysis of high quality genomic data, which are more and more easy to obtain, provides significant improvements in the genetic detection of virulence factors in bacterial strains.

Arcobacter haliotis Tanaka et al. 2017 is a later heterotypic synonym of Arcobacter lekithochrous Diéguez et al. 2017.

The draft whole-genome sequence of Arcobacter haliotis strain LMG 28652T was obtained and compared against the type strain of Arcobacter lekithochrous LFT 1.7T. High similarity was found between the two strains, showing average nucleotide identity and in silico DNA-DNA hybridization values of 98.40 and 86.10 %, respectively. These values indicated that both genomes belonged to the same species, confirming the evidences derived from the phylogenetic analysis performed with the 16S rRNA gene and the concatenated sequences of five housekeeping genes. In addition, the metabolic, physiological and chemotaxonomic features of A. haliotis LMG 28652T were shown to be congruent with those of A. lekithochrous. We conclude that Arcobacter haliotis Tanaka et al. 2017 is a later heterotypic synonym of Arcobacter lekithochrousDiéguez et al. 2017.

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 F138-33T) 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 F138-33T 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 F138-33T (=CECT 8984T=LMG 29148T).

Corrigendum: Revisiting the Taxonomy of the Genus Arcobacter: Getting Order From the Caos.

[This corrects the article DOI: 10.3389/fmicb.2018.02077.].