Case report: vertical transmission of Plesiomonas shigelloides. Is it time to strengthen information on safety concerns for raw seafood dietary exposure in pregnancy?

The consumption of raw seafood, generally considered to be a healthy food, has greatly increased worldwide. Pathogens of fish can cause foodborne illnesses in humans, especially following the consumption of raw seafood from contaminated water.Foodborne illness in pregnant women is seldom the cause of neonatal infection, but, as in the reported cases, it has been associated with a high degree of morbidity and mortality.We present the case of a newborn with septicemia and meningitis caused by Plesiomonas shigelloides acquired via the transplacental route. There was a maternal history of ingestion of raw seafood 1 week prior to delivery. A few similar cases are described in the existing literature, which reports 7 neonatal deaths.Therefore, the primary objective of this paper is to highlight the fact that the popularity of raw seafood such as sushi, sashimi, and oysters, requires an improvement in dietary advice regarding unsafe choices in pregnancy in order to avoid preventable foodborne diseases, sometimes fatal for the newborn.

Transcriptome Analysis Reveals the Effect of PdhR in Plesiomonas shigelloides

The pyruvate dehydrogenase complex regulator (PdhR) was originally identified as a repressor of the pdhR-aceEF-lpd operon, which encodes the pyruvate dehydrogenase complex (PDHc) and PdhR itself. According to previous reports, PdhR plays a regulatory role in the physiological and metabolic pathways of bacteria. At present, the function of PdhR in Plesiomonas shigelloides is still poorly understood. In this study, RNA sequencing (RNA-Seq) of the wild-type strain and the ΔpdhR mutant strains was performed for comparison to identify the PdhR-controlled pathways, revealing that PdhR regulates ~7.38% of the P. shigelloides transcriptome. We found that the deletion of pdhR resulted in the downregulation of practically all polar and lateral flagella genes in P. shigelloides; meanwhile, motility assay and transmission electron microscopy (TEM) confirmed that the ΔpdhR mutant was non-motile and lacked flagella. Moreover, the results of RNA-seq and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) showed that PdhR positively regulated the expression of the T3SS cluster, and the ΔpdhR mutant significantly reduced the ability of P. shigelloides to infect Caco-2 cells compared with the WT. Consistent with previous research, pyruvate-sensing PdhR directly binds to its promoter and inhibits pdhR-aceEF-lpd operon expression. In addition, we identified two additional downstream genes, metR and nuoA, that are directly negatively regulated by PdhR. Furthermore, we also demonstrated that ArcA was identified as being located upstream of pdhR and lpdA and directly negatively regulating their expression. Overall, we revealed the function and regulatory pathway of PdhR, which will allow for a more in-depth investigation into P. shigelloides pathogenicity as well as the complex regulatory network.

Pathogenicity of Plesiomonas shigelloides causing mass mortalities of largemouth bass (Micropterus salmoides) and its induced host immune response

The outbreak of mass mortality of M. salmoides occurred in an aquaculture farm in Jiangsu province of China, showing signs of skin ulceration and haemorrhages. The bacteria were isolated from diseased largemouth bass, and identified as Plesiomonas shigelloides based on morphological, physiological and biochemical features, as well as 16S rRNA gene sequence analysis. The pathogenicity of P. shigelloides was determined by challenge experiments, and the median lethal dosage (LD₅₀) of the isolate NJS1 for M. salmoides was calculated as 1.6 × 10⁵ CFU/mL at 7 d post-infection. Histopathological analysis revealed that extensive necrosis, vacuolization and inflammation were presented in the kidney, liver and gill of the diseased fish. Detection of virulence-related genes showed that P. shigelloides NJS1 was positive for astA, astB, astD, astE, actP and 6 ahpA. Additionally, the host defensive response of M. salmoides infected by P. shigelloides was analyzed by quantitive real-time PCR (qRT-PCR), and the results showed that the expression levels of Cas3, Hep1, HIF, IgM, IL15 and TGF were significantly up-regulated in head kidney, liver and spleen in different hours post-infection, which revealed varying expression profiles and clear transcriptional activation of immune related genes. The results suggested that P. shigelloides was an etiological element in the mass mortalities of M. salmoides and this study provided deeper insights for the pathogenesis and host defensive system in P. shigelloides invasion.

RpoN is required for the motility and contributes to the killing ability of Plesiomonas shigelloides

BACKGROUND

RpoN, also known as σ⁵⁴, first reported in Escherichia coli, is a subunit of RNA polymerase that strictly controls the expression of different genes by identifying specific promoter elements. RpoN has an important regulatory function in carbon and nitrogen metabolism and participates in the regulation of flagellar synthesis, bacterial motility and virulence. However, little is known about the effect of RpoN in Plesiomonas shigelloides.

RESULTS

To identify pathways controlled by RpoN, RNA sequencing (RNA-Seq) of the WT and the rpoN deletion strain was carried out for comparison. The RNA-seq results showed that RpoN regulates ~ 13.2% of the P. shigelloides transcriptome, involves amino acid transport and metabolism, glycerophospholipid metabolism, pantothenate and CoA biosynthesis, ribosome biosynthesis, flagellar assembly and bacterial secretion system. Furthermore, we verified the results of RNA-seq using quantitative real-time reverse transcription PCR, which indicated that the absence of rpoN caused downregulation of more than half of the polar and lateral flagella genes in P. shigelloides, and the ΔrpoN mutant was also non-motile and lacked flagella. In the present study, the ability of the ΔrpoN mutant to kill E. coli MG1655 was reduced by 54.6% compared with that of the WT, which was consistent with results in RNA-seq, which showed that the type II secretion system (T2SS-2) genes and the type VI secretion system (T6SS) genes were repressed. By contrast, the expression of type III secretion system genes was largely unchanged in the ΔrpoN mutant transcriptome and the ability of the ΔrpoN mutant to infect Caco-2 cells was also not significantly different compared with the WT.

CONCLUSIONS

We showed that RpoN is required for the motility and contributes to the killing ability of P. shigelloides and positively regulates the T6SS and T2SS-2 genes.

Computational Design of a Chimeric Vaccine against Plesiomonas shigelloides Using Pan-Genome and Reverse Vaccinology

The swift emergence of antibiotic resistance (AR) in bacterial pathogens to make themselves adaptable to changing environments has become an alarming health issue. To prevent AR infection, many ways can be accomplished such as by decreasing the misuse of antibiotics in human and animal medicine. Among these AR bacterial species, Plesiomonas shigelloides is one of the etiological agents of intestinal infection in humans. It is a gram-negative rod-shaped bacterium that is highly resistant to several classes of antibiotics, and no licensed vaccine against the aforementioned pathogen is available. Hence, substantial efforts are required to screen protective antigens from the pathogen whole genome that can be subjected easily to experimental evaluations. Here, we employed a reverse vaccinology (RV) approach to design a multi-antigenic epitopes based vaccine against P. shigelloides. The complete genomes of P. shigelloides were retrieved from the National Center for Biotechnological Information (NCBI) that on average consist of 5226 proteins. The complete proteomes were subjected to different subtractive proteomics filters, and in the results of that analysis, out of total proteins, 2399 were revealed as non-redundant and 2827 as redundant proteins. The non-redundant proteins were further checked for subcellular localization analysis, in which three were localized in the extracellular matrix, eight were outer membrane, and 13 were found in the periplasmic membrane. All surface localized proteins were found to be virulent. Out of a total of 24 virulent proteins, three proteins (flagellar hook protein (FlgE), hypothetical protein, and TonB-dependent hemoglobin/transferrin/lactoferrin family receptor protein) were considered as potential vaccine targets and subjected to epitopes prediction. The predicted epitopes were further examined for antigenicity, toxicity, and solubility. A total of 10 epitopes were selected (GFKESRAEF, VQVPTEAGQ, KINENGVVV, ENKALSQET, QGYASANDE, RLNPTDSRW, TLDYRLNPT, RVTKKQSDK, GEREGKNRP, RDKKTNQPL). The selected epitopes were linked with each other via specific GPGPG linkers in order to design a multi-epitopes vaccine construct, and linked with cholera toxin B subunit adjuvant to make the designed vaccine construct more efficient in terms of antigenicity. The 3D structure of the vaccine construct was modeled ab initio as no appropriate template was available. Furthermore, molecular docking was carried out to check the interaction affinity of the designed vaccine with major histocompatibility complex (MHC-)I (PDB ID: 1L1Y), MHC-II (1KG0), and toll-like receptor 4 ((TLR-4) (PDB: 4G8A). Molecular dynamic simulation was applied to evaluate the dynamic behavior of vaccine-receptor complexes. Lastly, the binding free energies of the vaccine with receptors were estimated by using MMPB/GBSA methods. All of the aforementioned analyses concluded that the designed vaccine molecule as a good candidate to be used in experimental studies to disclose its immune protective efficacy in animal models.

Clinical and microbiological features of intratumor abscess with bloodstream infection caused by Plesiomonas shigelloides, Citrobacter freundii, Streptococcus mitis/oralis, Clostridium perfringens, and Candida albicans in a patient with cholangiocarcinoma: A case report

Plesiomonas shigelloides is a gram-negative facultative anaerobic bacillus, usually found in soil and freshwater, which causes self-limited diarrhea, although reports of bacteremia are rare. Here, we report the first case of an intratumoral abscess with mixed bacteremia caused by P. shigelloides, Citrobacter freundii, Streptococcus mitis/oralis, Clostridium perfringens, and Candida albicans in a patient with recurrent postoperative cholangiocarcinoma. A 77-year-old man with hilar cholangiocarcinoma and hypertension was admitted to our hospital with fever and abdominal pain. He had visited Vietnam for 3 years, 20 years ago. Abdominal computed tomography showed air within the recurrent tumor at the left liver lobectomy resection margin site, which was diagnosed as an intratumor abscess perforating the intestinal tract. P. shigelloides, C. freundii, S. mitis/oralis, C. perfringens, and C. albicans were isolated in blood culture. P. shigelloides was identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and 16S ribosomal RNA (16S rRNA) sequencing. Piperacillin-tazobactam was administered for almost a week, ampicillin-sulbactam and levofloxacin for almost 3 weeks, and antifungal agents for almost 2 weeks, and the patient was discharged thereafter. Although bloodstream infections caused by P. shigelloides in patients with cancer are extremely rare, long-term colonization and the potential for future intra-abdominal infections were implicated.

Distinction between Antimicrobial Resistance and Putative Virulence Genes Characterization in Plesiomonas shigelloides Isolated from Different Sources

Plesiomonas shigelloides are gram-negative, thermotolerant, motile, and pleomorphic microorganisms that are only distantly related to those of the Enterobacteriaceae and Vibrionaceae families. One of the most common sources of P. shigelloides contamination is human stool, but it may also be found in a wide range of other animals, plants, and aquatic habitats. Antimicrobial resistance in P. shigelloides from seawater and shellfish was investigated, and pathogenicity involved genes were characterized as part of this study. Out of 384 samples of shellfish, 5.7% included P. shigelloides. The presence of P. shigelloides was also discovered in 5% of the seawater sampled. The antimicrobial resistance of 23 P. shigelloides isolates derived from those samples was investigated. All isolates were sensitive to nalidixic acid, carbenicillin, cephalothin, erythromycin, kanamycin, tetracycline, and ciprofloxacin in the study. Several strains isolated from diseased shellfish were tested for virulence in shellfish by intraperitoneal injections. The LD₅₀ values ranged from 12 × 10⁸ to 3 × 10¹² cfu/shellfish. When looking for possible virulence factors that may play a significant role in bacterial infection in the current study, we found that all of these genes were present in these strains. These include genes such as elastase, lipase, flagellin, enterotoxin, and DNases. According to these findings, shellfish may serve as a reservoir for multi-resistant P. shigelloides and help spread virulence genes across the environment.

Enhanced Asymptomatic Systemic Infection Caused by Plesiomonas shigelloides in a Captive Gray Wolf (Canis lupus)

A 7-year-old male gray wolf was found dead at a zoo during exhibition. To determine the cause of death, histological and gross necropsy diagnoses and a molecular analysis were performed. The gross necropsy revealed a swollen abdomen, hemorrhagic exudates around the mouth, splenomegaly, a discolored liver, a congested kidney, hemorrhagic ascites, and dark gray-colored membranes and air bubbles in the fundus of the stomach. Rod-shaped bacteria were found in the liver parenchyma and hemorrhagic ascites using Giemsa staining. The nucleotide sequencing of the cultured bacteria identified the causative agent as Plesiomonas shigelloides, which is rarely responsible for systemic infections. This study describes a rare case and the first reported systemic gastrointestinal infection due to P. shigelloides in a zoo animal.

The effect of ArcA on the growth, motility, biofilm formation, and virulence of Plesiomonas shigelloides

BACKGROUND

The anoxic redox control binary system plays an important role in the response to oxygen as a signal in the environment. In particular, phosphorylated ArcA, as a global transcription factor, binds to the promoter regions of its target genes to regulate the expression of aerobic and anaerobic metabolism genes. However, the function of ArcA in Plesiomonas shigelloides is unknown.

RESULTS

In the present study, P. shigelloides was used as the research object. The differences in growth, motility, biofilm formation, and virulence between the WT strain and the ΔarcA isogenic deletion mutant strain were compared. The data showed that the absence of arcA not only caused growth retardation of P. shigelloides in the log phase, but also greatly reduced the glucose utilization in M9 medium before the stationary phase. The motility of the ΔarcA mutant strain was either greatly reduced when grown in swim agar, or basically lost when grown in swarm agar. The electrophoretic mobility shift assay results showed that ArcA bound to the promoter regions of the flaK, rpoN, and cheV genes, indicating that ArcA directly regulates the expression of these three motility-related genes in P. shigelloides. Meanwhile, the ability of the ΔarcA strain to infect Caco-2 cells was reduced by 40%; on the contrary, its biofilm formation was enhanced. Furthermore, the complementation of the WT arcA gene from pBAD33-arcA⁺ was constructed and all of the above features of the pBAD33-arcA⁺ complemented strain were restored to the WT level.

CONCLUSIONS

We showed the effect of ArcA on the growth, motility, biofilm formation, and virulence of Plesiomonas shigelloides, and demonstrated that ArcA functions as a positive regulator controls the motility of P. shigelloides by directly regulating the expression of flaK, rpoN and cheV genes.

Screening of a Plesiomonas shigelloides phage and study of the activity of its lysis system

Plesiomonas shigelloides is an important fish pathogen that causes significant losses in aquaculture. Phage therapy is a new approach to overcome the problem of multidrug-resistant bacteria. Herein, a virulent phage of P. shigelloides was isolated from the intestines of grass carp. This phage belongs to the Siphoviridae family and was designated PSP01. The optimal multiplicity of infection of PSP01 was 1 with a latent period of 30 min and a lytic period of 140 min. Good activity was observed over a wide range of temperatures (-20 °C-50 °C), pH values (3-12), and NaCl concentrations (0.1-3.5%). The phage PSP01 lysis cassette is composed of 3 genes, HolPSP, LysPSP-1 and LysPSP-2. Expression of HolPSP or LysPSP-2 in Escherichia coli resulted in bacterial lysis, and a synergistic effect was observed when the HolPSP and LysPSP-1 proteins were co-expressed. In-frame deletion uncovered an important role of the transmembrane domain (TMD) in HolPSP and the signal peptide (SP) in LysPSP-2 for bacterial lysis function. The protective effects of phage PSP01 were investigated by intraperitoneal injection into grass carp infected with P. shigelloides, showing a 33.3% increase in the survival rate of the infected grass carp. Pathological analysis of the spleens from the infected grass carp revealed alleviation of the pathological symptoms. In conclusion, isolation and bacterial lysis investigations of phage PSP01 provide a new tool for the control of fish pathogens and possesses potential for aquaculture applications.

Plesiomonas shigelloides Septic Shock Following Ingestion of Dojo Nabe (Loach Hotpot)

Plesiomonas shigelloides is a gram-negative bacillus that commonly causes self-limited diarrhea in humans. We present the case of P shigelloides bacteremia in a 49-year-old man with alcoholic cirrhosis who developed septic shock a day after eating Dojo nabe (loach hotpot), a Japanese traditional dish.

Deficiency of interleukin-17 receptor A1 induces microbiota disruption in the intestine of Japanese medaka, Oryzias latipes

The mutual relationship between the intestinal immune system and the gut microbiota has received a great deal of attention. In mammals, interleukin-17A and F (IL-17A/F) are inflammatory cytokines and key regulators of the gut microbiota. However, in teleosts, the function of IL-17A/F in controlling the gut microbiota is poorly understood. We attempted to elucidate the importance of teleost IL-17 signaling in controlling gut microbiota. We previously established a knockout (KO) of IL-17 receptor A (RA) 1, a receptor for IL-17A/F, in the Japanese medaka (Oryzias latipes) using the CRISPR-Cas9 system and performed 16S rRNA-based metagenomic analyses using the anterior and posterior sections of the intestinal tract. The number of observed OTUs in the anterior intestine was significantly decreased in IL-17RA1 KO medaka compared to that in the wild-type (WT). Furthermore, β-diversity analysis (weighted UniFrac) revealed considerably different bacterial composition in the anterior intestine of IL-17RA1 KO compared to WT, with similar findings in α-diversity. Notably, the pathogen Plesiomonas shigelloides was significantly increased in the posterior intestine of IL-17RA1 KO medaka. These findings indicate that signaling via IL-17RA1 is required to maintain a healthy gut microbiota in teleosts and mammals. The involvement of IL-17RA1 in controlling the gut microbiota has been demonstrated, resulting in microbiome dysbiosis in IL-17RA1 KO medaka.

Superimposed Infectious Colitis in Crohn's Disease

The differential diagnosis for an acute Crohn's flare should include enteric infection, a challenging yet critical distinction to make when determining appropriate therapy. Since both present similarly, identification of an enteric infection should be performed with comprehensive stool microbial testing. In the setting of moderate-to-severe disease, patients on biologic therapy may be more prone to infectious complications. We present a patient with chronic Crohn's disease with an unusual, previously undetected enteric infection due to Plesiomonas shigelloides. Once identified, appropriate antibiotic treatment led to resolution of the patient's acute symptomatology. This is the first reported case of P. shigelloides infection in Crohn's disease.

Genetic Analysis and Serological Detection of Novel O-Antigen Gene Clusters of Plesiomonas shigelloides

Plesiomonas shigelloides, a member of the family Vibrionaceae, is a gram-negative, rod-shaped, facultative anaerobic bacterium with flagella. P. shigelloides has been isolated from such sources as freshwater, surface water, and many wild and domestic animals. P. shigelloides contains 102 Oantigens and 51 H-antigens. The diversity of O-antigen gene clusters is relatively poorly understood. In addition to O1 and O17 reported by other laboratories, and the 12 O serogroups (O2, O10, O12, O23, O25, O26, O32, O33, O34, O66, O75, and O76) reported previously by us, in the present study, nine new P. shigelloides serogroups (O8, O17, O18, O37, O38, O39, O44, O45, and O61) were sequenced and annotated. The genes for the O-antigens of these nine groups are clustered together in the chromosome between rep and aqpZ. Only O38 possesses the wzm and wzt genes for the synthesis and translocation of O-antigens via the ATP-binding cassette (ABC) transporter pathway; the other eight use the Wzx/Wzy pathway. Phylogenetic analysis using wzx and wzy showed that both genes are diversified. Among the nine new P. shigelloides serogroups, eight use wzx/wzy genes as targets. In addition, we developed an O-antigen-specific PCR assay to detect these nine distinct serogroups with no cross reactions among them.

A multiplex PCR assay for the detection of five human pathogenic Vibrio species and Plesiomonas

A multiplex PCR (mPCR) assay was established to detect five pathogenic Vibrio species and Plesiomonas shigelloides. Twelve genes were included: ompW, ctxA, rfbN, and wbfR from V. cholerae; tl, tdh, and trh from V. parahaemolyticus; toxR and vmhA from V. mimicus; toxR from V. fluvialis; vvhA from V. vulnificus; and the 23S rRNA gene from P. shigelloides. The specificity of the mPCR assay was 100% for the detection of 136 strains and the limits of detection (LoD) were 12.5-50 pg/reaction. The assay exhibited higher sensitivity than cultivation methods in the detection of APW cultures of 113 diarrhea samples. In the analysis of 369 suspected Vibrio populations from estuarine water samples, the specificity of the mPCR for V. cholerae and V. parahaemolyticus was 100% for both, while the sensitivities were 100% and 96.1%, respectively. The assay can be applied to screen enrichment cultures and suspected colonies from environmental and clinical samples.

Horizontal Gene Transfer Clarifies Taxonomic Confusion and Promotes the Genetic Diversity and Pathogenicity of Plesiomonas shigelloides

The taxonomic position of P. shigelloides has been the subject of debate for a long time, and until now, the evolutionary dynamics and pathogenesis of P. shigelloides were unclear. In this study, pan-genome analysis indicated extensive genetic diversity and the presence of large and variable gene repertoires. Our results revealed that horizontal gene transfer was the focal driving force for the genetic diversity of the P. shigelloides pan-genome and might have contributed to the emergence of novel properties. Vibrionaceae and Aeromonadaceae were found to be the predominant donor taxa for horizontal genes, which might have caused the taxonomic confusion historically. Comparative genomic analysis revealed the potential of P. shigelloides to cause intestinal and invasive diseases. Our results could advance the understanding of the evolution and pathogenesis of P. shigelloides, particularly in elucidating the role of horizontal gene transfer and investigating virulence-related elements.

Plesiomonas shigelloides is an emerging pathogen that has been shown to be involved in gastrointestinal diseases and extraintestinal infections in humans. However, the taxonomic position, evolutionary dynamics, and pathogenesis of P. shigelloides remain unclear. We reported the draft genome sequences of 12 P. shigelloides strains representing different serogroups. We were able to determine a clear distinction between P. shigelloides and other members of Enterobacterales via core genome phylogeny, Neighbor-Net network, and average genome identity analysis. The pan-genome analysis of P. shigelloides revealed extensive genetic diversity and presented large flexible gene repertoires, while the core genome phylogeny exhibited a low level of clonality. The discordance between the core genome phylogeny and the pan-genome phylogeny indicated that flexible accessory genomes account for an important proportion of the evolution of P. shigelloides, which was subsequently characterized by determinations of hundreds of horizontally transferred genes (horizontal genes), massive gene expansions and contractions, and diverse mobile genetic elements (MGEs). The apparently high levels of horizontal gene transfer (HGT) in P. shigelloides were conferred from bacteria with novel properties from other taxa (mainly Vibrionaceae and Aeromonadaceae), which caused the historical taxonomic confusion and shaped the virulence gene pools. Furthermore, P. shigelloides genomes contain many macromolecular secretion system genes, virulence factor genes, and resistance genes, indicating its potential to cause intestinal and invasive infections. Collectively, our work provides insights into the phylogenetic position, evolutionary dynamic, and pathogenesis of P. shigelloides at the genomic level, which could facilitate the observation and research of this important pathogen.

IMPORTANCE The taxonomic position of P. shigelloides has been the subject of debate for a long time, and until now, the evolutionary dynamics and pathogenesis of P. shigelloides were unclear. In this study, pan-genome analysis indicated extensive genetic diversity and the presence of large and variable gene repertoires. Our results revealed that horizontal gene transfer was the focal driving force for the genetic diversity of the P. shigelloides pan-genome and might have contributed to the emergence of novel properties. Vibrionaceae and Aeromonadaceae were found to be the predominant donor taxa for horizontal genes, which might have caused the taxonomic confusion historically. Comparative genomic analysis revealed the potential of P. shigelloides to cause intestinal and invasive diseases. Our results could advance the understanding of the evolution and pathogenesis of P. shigelloides, particularly in elucidating the role of horizontal gene transfer and investigating virulence-related elements.

Molecular Characterization, Intra-Species Diversity and Abundance of Freshwater Plesiomonas shigelloides Isolates

Molecular signatures of Plesiomonas shigelloides strain specific to pathogenic and nonpathogenic variants are not well established till present. There is a need for intra-species barcoding of P. shigelloides to aid infection control. This study aims at characterizing and assessing intra-species diversity and abundance of P. shigelloides isolated from three freshwaters in the Eastern Cape Province. The study used a Plesiomonas-specific PCR to characterize the isolates. Intra-species (dis)similarities were assessed using ERIC-PCR and (GTG)5-PCR techniques. The DNA fingerprints produced were electrophoresed, digitized, and documented via computer-assisted pattern analysis. The fingerprints were analyzed using neighbor-joining clustering (NJC) based on Euclidean similarity index. Results revealed 80%, 83.64%, and 80% of the water samples from Tyhume, Kat, and Kubusie rivers, respectively, positive for P. shigelloides isolation. The prevalence of P. shigelloides from sites ranged from 13.5% to 88.9%. NJC delineated 48 isolates to 8 clades (ERIC-fingerprints) and 34 isolates into 7 clades ((GTG)5-fingerprints). The relative abundance of unique strains ranged from 6.3% to 22.9% via the two methods. Both fingerprinting approaches have strain-differentiating potential for P. shigelloides, however ERIC-PCR possessed higher resolution (D = 37.46) advantage over (GTG)5-PCR (D = 29.64). In conclusion, the study achieved intra-species diversity and abundance of P. shigelloides from aquatic milieu and provide further opportunity for intra-species-specific barcoding.

Severe cellulitis and bacteremia caused by Plesiomonas shigelloides following a traumatic freshwater injury

Plesiomonas shigelloides is a gram-negative bacillus that most commonly causes self-limited diarrhea in humans. Extraintestinal manifestations of P. shigelloides, including skin and soft tissue infections, are extremely uncommon. We present a case of severe cellulitis and bacteremia in an 80-year-old female caused by Plesiomonas shigelloides following a traumatic freshwater injury in Michigan, USA

Antimicrobial resistance in freshwater Plesiomonas shigelloides isolates: Implications for environmental pollution and risk assessment

Antibiotic resistance is known to impact treatment efficiency of Plesiomonas infections negatively with fatal outcomes. This study investigated antibiogram fingerprint of P. shigelloides (n = 182) isolated from three South Africa rivers using the disc diffusion technique. Environmental pollution and analogous health risk (given infections) that could associate with the freshwaters and empirical treatment of Plesiomonas were assessed using Antibiotic Resistance Index (ARI) and Multiple Antibiotic Resistance Indices (MARI), respectively. Thirteen EUCAST recommended (ERAs) and eleven non-recommended antibiotics (NAs) used as first line agents in the treatment of gastroenteritis and extraintestinal infections were tested. Resistance against ERAs decreased from cefoxitin (37.91%), cefuroxime (35.17%), cefepime (31.87%), ceftriaxone (29.67%), ciprofloxacin (18.13%), trimethoprim-sulfamethoxazole (10.44%), piperacillin/tazobactam (8.79%), ertapenem (4.95%), norfloxacin (4.40%), levofloxacin (2.75%), meropenem (1.10%) to imipenem (0.55%). The isolates had higher resistance (≥36.07%) against NAs but were susceptible to amikacin (67.58%), gentamycin (73.08%), and tetracycline (80.77%). MARI of the isolates were significantly different between ERAs and NAs (P-value < 0.05) and had an average of 0.17 ± 0.18 and 0.45 ± 0.13, respectively. About 33.87% and 95.63% of the isolates had MARI value from 0.23 to 0.62 and 0.27-0.82 to ERAs and NAs, respectively. Also, ERAs-based and NAs-based ARI across sampling units showed significantly different (P-value < 0.05) means of 0.18 ± 0.09 and 0.46 ± 0.05, respectively. MARI attributed low risk of empirical treatment to recommended antibiotics but higher risk to non-recommended antibiotics. Model estimated successful and unsuccessful empirical treatment of infections risks due to resistance in the isolates using recommended antibiotics as 65.93% and 34.07%, respectively; 1.65% and 98.35% in the case of non-recommended antibiotics, respectively. ARI based on recommended antibiotics identified potential environmental pollutions in a number of sites. Resistance in freshwater P. shigelloides especially against cephalosporin, quinolones and fluoroquinolones is distressing and might suggests high pollution of the freshwaters in the Eastern Cape Province.

Visual and rapid detection of Plesiomonas shigelloides using loop-mediated isothermal amplification method

Plesiomonas shigelloides is a common pathogen of aquatic animals and can pose a certain hazard to aquaculture. Here, we aimed to develop a loop-mediated isothermal amplification (LAMP) method for the visual detection of P. shigelloides to aid the diagnosis of infections caused by this pathogen in aquatic animals. We used LAMP to amplify P. shigelloides DNA and combined it with calcein or nucleic acid dipstick assay (NADA) to visualize the amplified products. The optimal LAMP amplification temperature was 64°C, and the reaction lasted for 50 min. The limit of detection of recombinant plasmids containing the target gene using the LAMP method was 2·0 × 10² copies per μl, which is ten times higher than that using conventional polymerase chain reaction (PCR). LAMP products could be visualized without agarose gel electrophoresis. We tested 85 fish specimens using the established LAMP method and conventional PCR. The detection rate was 42·4% using the LAMP method and 34·1% using conventional PCR. Based on our results, the LAMP method combined with calcein or NADA is a rapid, specific, sensitive and accurate method for visual detection of fish-derived P. shigelloides and can be used for the laboratory diagnosis of infections caused by it. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of loop-mediated isothermal amplification (LAMP) and calcein and nucleic acid dipstick assay (NADA) provided a rapid, specific and sensitive method for detecting Plesiomonas shigelloides, which is an important pathogen that causes diseases in aquatic animals worldwide. In the present study, the LAMP method showed a higher detection rate than conventional PCR for P. shigelloides using templates from 85 fish specimens. Thus, the LAMP method could be a reliable and convenient tool for diagnosing diseases in aquatic animals in the laboratory.

Modelling the effects of physicochemical variables and anthropogenic activities as ecological drivers of Plesiomonas shigelloides distribution and freshwaters quality

Spatio-temporal distribution of pathogens in freshwater is driven by environmental variables (EVs), natural, and human-induced activities and the spread of infections and disease outbreaks are triggered significantly by these processes. The role of EVs and anthropogenic activities on the distribution of Plesiomonas shigelloides is not well understood; hence this study aimed at modelling the effects of EVs and anthropogenic gradients on the densities of Plesiomonas in freshwaters and freshwater quality. Three freshwaters were sampled from February to December 2017. The EVs and Plesiomonas densities of the freshwaters were determined using standard techniques, while partial least square path modelling and correlation analysis were performed on the data collected. Factors underpinning the quality of the freshwaters were identified through principal component analysis (PCA). Most EVs fell within the bounds of recommended permissible limits except turbidity, TSS, salinity and TDS. Results revealed a significant increase of Plesiomonas densities with an increase in the magnitude of path coefficients and intensities of anthropogenic activities along the freshwaters. The distribution of Plesiomonas correlated with temperature (r = 0.69, p < 0.01), TSS (r = 0.30, p < 0.01), TBS (r = 0.28, p < 0.01), and BOD (r = 0.39, p < 0.01). Similarly, a significant correlation existed between conductivity and TDS (r = 0.97, p < 0.01) and salinity (r = 0.99, p < 0.01). Network analysis of EVs identified three closed networks essential for freshwaters quality and Plesiomonas distribution with nodes of variables under synergistic latent influences. Overall, PCA identified four drivers of the freshwater quality and in part, Plesiomonas density; namely, nutrient loading; thermal and organic pollutions, aesthetic pollution, and pH modulators. Higher component score indicated a greater impact of nutrient loading on the freshwater quality. The study concluded that Plesiomonas distribution is largely shaped by anthropogenic gradients and EVs in rivers, and these may play a major role in its dissemination along freshwater milieus.

Putative virulence factors of Plesiomonas shigelloides

Plesiomonas shigelloides is a Gram-negative rod-shaped bacterium which has been isolated from humans, animals and the environment. It has been associated with diarrhoeal disease in humans and various epizootic diseases in animals. In this study P. shigelloides strains were isolated from the faecal material of a captive Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis; YFP) living in semi-natural conditions in China. Plesiomonas shigelloides strain EE2 was subjected to whole genome sequencing. The draft genome was then compared to the genome sequences of ten other P. shigelloides isolates using the Pathosystems Resource Integration Center pipeline. In addition to several virulence factors which have been previously reported, we are proposing new candidate virulence factors such as a repeats-in-toxin protein, lysophospholipase, a twin-arginine translocation system and the type VI secretion effector Phospholipase A1.

Incidence and antimicrobial susceptibility fingerprints of Plesiomonas shigelliodes isolates in water samples collected from some freshwater resources in Southwest Nigeria

Plesiomonas shigelloides, is an emerging and significant enteric pathogen in water having implication in both localised and gastrointestinal infections with characteristic of displaying high resistance against commonly used antibiotics. This study evaluated the prevalence of Plesiomonas shigelloides and their antibiogram fingerprints in water sample collected from four rivers in South-western Nigeria. In all, 148 presumptive Plesiomonas shigelloides isolates was recovered from the rivers out of which 66 (44.6%) were confirmed positive for the organism using polymerase chain reaction techniques. Confirmed isolates were evaluated for their antibiogram profiles against a panel of 20 antimicrobials using the disc diffusion method and further screened for relevant antibiotic resistance genes. Resistance of the isolates against the antimicrobials followed the order: sulphamethoxazole (100%), erythromycin (93%), ampicillin (90%), cephalotin (82%), streptomycin (64%), and chloramphenicol (58%), amoxicillin (53%), cefotaxime (50%), tetracycline (49%), neomycin (38%) and trimethoprim + sulphamethoxazole (38%). Conversely, all the isolates were susceptible against netilmicin, and susceptibility against the other antibiotics follows the order: meropenem (94%), gentamicin (88%), imipenem (79%), amikacin (70%), ciprofloxacin (70%), norfloxacin (59%), trimethoprim (56%) and ceftazidine (56%). The multiple antibiotic resistance indices of the organism were higher than the accepted threshold of 0.2. The incidence of 11 antimicrobial resistance determinants were obtained as follows: [sulphonamides; (sulI (18%), sulII (20%), dfr1 (70%), dfr(18) (5%)), [beta-lactams; (ampC 37%)], [tetracyclines; (tetA (78%), tetE (57%)], [phenicols; (catII (16%), cmlA1 (11%)] and [aminoglycosides; (aphA2 (36%) and strA (67%)]. Pearson chi-square exact test revealed positive associations among tetA, tetE, sullI and catII and tetA genes. To the best of our knowledge, this is the first report on the incidence and antibiogram fingerprint of P. shigelloides in these freshwater resources and we conclude that these rivers are important reservoirs of multiple antimicrobial resistant biotypes of this organism, and consequently a threat to public health.

Emerging agents of gastroenteritis: Aeromonas, Plesiomonas, and the diarrheagenic pathotypes of Escherichia coli

Knowledge of the pathogenic roles of certain bacterial agents in gastroenteritis has been growing over the past few decades. With the increasing use of multiplex molecular-based syndromic stool pathogen panels, the roles of Plesiomonas shigelloides and some of the diarrheagenic pathotypes of Escherichia coli (enterotoxigenic E. coli [ETEC], enteropathogenic E. coli [EPEC], enteroinvasive E. coli [EIEC], and enteroaggregative E. coli [EAEC]) have been better understood. Although not currently targeted on Food and Drug Administration (FDA)-cleared commercial multiplex stool panels, Aeromonas has also emerged as a possible cause of bacterial gastroenteritis. The clinical presentation, pathophysiology, and diagnostic approaches to these pathogens in stool specimens are reviewed. Variability in inclusion of these pathogens on multiplex molecular panels and difficulties in detection by stool culture techniques utilized by clinical microbiology laboratories have contributed to an unclear understanding of the pathogenic role of several of these pathogens. Nonetheless, most evidence points towards a clear pathogenic role for P. shigelloides and ETEC, and possibly EPEC and EIEC. The contribution of Aeromonas spp. and EAEC to bacterial gastroenteritis has not been fully established. Further studies of pathogenicity of these pathogens are needed.

O-Antigen Gene Clusters of Plesiomonas shigelloides Serogroups and Its Application in Development of a Molecular Serotyping Scheme

Plesiomonas shigelloides is a Gram-negative, flagellated, rod-shaped, ubiquitous, and facultative anaerobic bacterium. It has been isolated from various sources, such as freshwater, surface water, and many wild and domestic animals. P. shigelloides is associated with diarrheal diseases of acute secretory gastroenteritis, an invasive shigellosis-like disease, and a cholera-like illness in humans. At present, 102 somatic antigens and 51 flagellar antigens of P. shigelloides have been recognized; however, very little is known about variations of O-antigens among P. shigelloides species. In this study, 12 O-antigen gene clusters of P. shigelloides, O2H1a1c (G5877), O10H41 (G5892), O12H35 (G5890), O23H1a1c (G5263), O25H3 (G5879), O26H1a1c (G5889), O32H37 (G5880), O33H38 (G5881), O34H34 (G5882), O66H3 (G5270), O75H34 (G5885), and O76H39 (G5886), were sequenced and analyzed. The genes that control O-antigen synthesis are present as chromosomal gene clusters that maps between rep and aqpZ, and most of the synthesis and translocation of OPS (O-specific polysaccharide) belongs to Wzx/Wzy pathway with the exception of O12, O25, and O66, which use the ATP-binding cassette (ABC) transporter pathway. Phylogenetic analysis of wzx and wzy show that the wzx and wzy genes are specific to individual O-antigens and can be used as targets in molecular typing. Based on the sequence data, an O-antigen specific suspension array that detects 12 distinct OPS’ has been developed. This is the first report to catalog the genetic features of P. shigelloides O-antigen variations and develop a suspension array for the molecular typing. The method has several advantages over traditional bacteriophage and serum agglutination methods and lays the foundation for easier identification and detection of additional O-antigen in the future.

Plesiomonas shigelloides sipD mutant, generated by an efficient gene transfer system, is less invasive

Plesiomonas shigelloides is widely associated with human diarrheal disease. Research on this pathogen has been hampered by the absence of an effective genetic manipulation system. In the present study, an efficient and precise conjugation transfer procedure, mediated by suicide vector pRE112 was used to overcome this limitation. The efficiency of generating double recombinants was average 74.3%, and the conjugation protocol may be applied to other P. shigelloides strains. We also identified that the SipD protein of P. shigelloides G5884 (serotype O45) is 65% similar to the SipD in Salmonella pathogenicity island 1 (SPI-1), which is a key element of the type III secretion system related to Salmonella invasion. A P. shigelloides sipD null mutant was generated via the conjugation system, using the suicide vector pRE112. The isogenic mutant strain lacking sipD showed a 50% reduction in its capacity to invade Caco-2 cells.

Pathogenomics of Virulence Traits of Plesiomonas shigelloides That Were Deemed Inconclusive by Traditional Experimental Approaches

One of the major challenges of modern medicine includes the failure of conventional protocols to characterize the pathogenicity of emerging pathogens. This is particularly apparent in the case of Plesiomonas shigelloides. Although a number of infections have been linked to this microorganism, experimental evidence of its virulence factors (VFs), obtained by traditional approaches, is somewhat inconclusive. Hence, it remains unclear whether P. shigelloides is a true or opportunistic one. In the current study, four publicly available whole-genome sequences of P. shigelloides (GN7, NCTC10360, 302-73, and LS1) were profiled using bioinformatics platforms to determine the putative candidate VFs to characterize the bacterial pathogenicity. Overall, 134 unique open reading frames (ORFs) were identified that were homologous or orthologous to virulence genes identified in other pathogens. Of these, 52.24% (70/134) were jointly shared by the strains. The numbers of strain-specific virulence traits were 4 in LS1; 7 in NCTC10360; 10 in 302-73; and 15 in GN7. The pathogenicity islands (PAIs) common to all the strains accounted for 24.07% ORFs. The numbers of PAIs exclusive to each strain were 8 in 302-73; 11 in NCTC10360; 14 in GN7; and 18 in LS1. A PAI encoding Vibrio cholerae ToxR-activated gene d protein was specific to 302-73, GN7, and NCTC10360 strains. Out of 33 antibiotic multi-resistance genes identified, 16 (48.48%) genes were intrinsic to all strains. Further, 17 (22.08%) of 77 antibiotic resistance islands were found in all the strains. Out of 23 identified distinct insertion sequences, 13 were only harbored by strain LS1. The number of intact prophages identified in the strains was 1 in GN7; 2 in 302-73; and 2 in NCTC10360. Further, 1 CRISPR element was identified in LS1; 2 in NCTC10360; and 8 in 302-73. Fifteen (78.95%) of 19 secretion systems and secretion effector variants were identified in all the strains. In conclusion, certain P. shigelloides strains might possess VFs associated with gastroenteritis and extraintestinal infections. However, the role of host factors in the onset of infections should not be undermined.

Structural Masquerade of Plesiomonas shigelloides Strain CNCTC 78/89 O-Antigen-High-Resolution Magic Angle Spinning NMR Reveals the Modified d-galactan I of Klebsiella pneumoniae

The high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR) analysis of Plesiomonas shigelloides 78/89 lipopolysaccharide directly on bacteria revealed the characteristic structural features of the O-acetylated polysaccharide in the NMR spectra. The O-antigen profiles were unique, yet the pattern of signals in the, spectra along with their ¹H,¹³C chemical shift values, resembled these of d-galactan I of Klebsiella pneumoniae. The isolated O-specific polysaccharide (O-PS) of P. shigelloides strain CNCTC 78/89 was investigated by ¹H and ¹³C NMR spectroscopy, mass spectrometry and chemical methods. The analyses demonstrated that the P. shigelloides 78/89 O-PS is composed of →3)-α-d-Galp-(1→3)-β-d-Galf2OAc-(1→ disaccharide repeating units. The O-acetylation was incomplete and resulted in a microheterogeneity of the O-antigen. This O-acetylation generates additional antigenic determinants within the O-antigen, forms a new chemotype, and contributes to the epitopes recognized by the O-serotype specific antibodies. The serological cross-reactivities further confirmed the inter-specific structural similarity of these O-antigens.

Multisite Evaluation of the BD Max Extended Enteric Bacterial Panel for Detection of Yersinia enterocolitica, Enterotoxigenic Escherichia coli, Vibrio, and Plesiomonas shigelloides from Stool Specimens

The purpose of this study was to perform a multisite evaluation to establish the performance characteristics of the BD Max extended enteric bacterial panel (xEBP) assay directly from unpreserved or Cary-Blair-preserved stool specimens for the detection of Yersinia enterocolitica, enterotoxigenic Escherichia coli (ETEC), Vibrio, and Plesiomonas shigelloides The study included prospective, retrospective, and prepared contrived specimens from 6 clinical sites. BD Max xEBP results were compared to the reference method, which included standard culture techniques coupled with alternate PCR and sequencing, except for ETEC, for which the reference method was two alternate PCRs and sequencing. Alternate PCR was also used to confirm the historical results for the retrospective specimens and for discrepant result analysis. A total of 2,410 unformed, deidentified stool specimens were collected. The prevalence in the prospective samples as defined by the reference method was 1.2% ETEC, 0.1% Vibrio, 0% Y. enterocolitica, and 0% P. shigelloides Compared to the reference method, the positive percent agreement (PPA) (95% confidence interval [CI]), negative percent agreement (NPA) (95% CI), and kappa coefficient (95% CI) for the BD Max xEBP assay for all specimens combined were as follows: ETEC, 97.6% (87.4 to 99.6), 99.8% (99.5 to 99.9), and 0.93 (0.87 to 0.99); Vibrio, 100% (96.4 to 100), 99.7% (99.4 to 99.8), and 0.96 (0.93 to 0.99); Y. enterocolitica, 99.0% (94.8 to 99.8), 99.9% (99.8 to 99.9), and 0.99 (0.98 to 1); P. shigelloides, 100% (96.4 to 100), 99.8% (99.5 to 99.9), and 0.98 (0.95 to 1), respectively. In this multicenter study, the BD Max xEBP showed a high correlation (kappa, 0.97; 95% CI, 0.95 to 0.98) with the conventional methods for the detection of ETEC, Vibrio, Y. enterocolitica, and P. shigelloides in stool specimens from patients suspected of acute gastroenteritis, enteritis, or colitis.

Plesiomonas shigelloides exports a lethal cytotoxic-enterotoxin (LCE) by membrane vesicles

Plesiomonas shigelloides isolated from water in Brazil was previously described as a hemorrhagic heat-labile cytotoxic-enterotoxin producer. We purified this toxin from culture supernatants using ion metallic affinity chromatography (IMAC) followed by molecular exclusion chromatography. The pure toxin presented molecular mass of 50 kDa and isoelectric point (pI) around 6.9 by 2D electrophoresis. When injected intravenously, the purified cytotoxic-enterotoxin induced also severe spasms followed by sudden death of mice. Hence, we entitled it as lethal cytotoxic-enterotoxin (LCE). The presence of membrane vesicles (MVs) on cell surfaces of P. shigelloides was observed by scan electron microscopy (SEM). From these MVs the LCE toxin was extracted and confirmed by biological and serological assays. These data suggest that P. shigelloides also exports this cytotoxic-enterotoxin by membrane vesicles, a different mechanism of delivering extra cellular virulence factors, so far not described in this bacterium.

The O-antigen of Plesiomonas shigelloides serotype O36 containing pseudaminic acid

The structure of the repeating unit of O-antigen of Plesiomonas shigelloides serotype O36 has been investigated by ¹H and ¹³C NMR spectroscopy, matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry and chemical methods. The new structure of trisaccharide has been established: [Formula: see text] These trisaccharide O-antigen units substitute the core undecasaccharide at C-4 of the β-D-GlcpNAc residue. The core oligosaccharide and lipid A are identical with these of the serotype O17 (PCM 2231) (Maciejewska, A., Lukasiewicz, J., Kaszowska, M., Jachymek, W., Man-Kupisinska, A.; Lugowski, C. Mar. Drugs.2013, 11 (2), 440-454; Lukasiewicz, J., Dzieciatkowska, M., Niedziela, T., Jachymek, W., Augustyniuk, A., Kenne, L., Lugowski, C. Biochemistry, 2006, 45, 10434-10447).

The polar and lateral flagella from Plesiomonas shigelloides are glycosylated with legionaminic acid

Plesiomonas shigelloides is the unique member of the Enterobacteriaceae family able to produce polar flagella when grow in liquid medium and lateral flagella when grown in solid or semisolid media. In this study on P. shigelloides 302-73 strain, we found two different gene clusters, one exclusively for the lateral flagella biosynthesis and the other one containing the biosynthetic polar flagella genes with additional putative glycosylation genes. P. shigelloides is the first Enterobacteriaceae were a complete lateral flagella cluster leading to a lateral flagella production is described. We also show that both flagella in P. shigelloides 302-73 strain are glycosylated by a derivative of legionaminic acid (Leg), which explains the presence of Leg pathway genes between the two polar flagella regions in their biosynthetic gene cluster. It is the first bacterium reported with O-glycosylated Leg in both polar and lateral flagella. The flagella O-glycosylation is essential for bacterial flagella formation, either polar or lateral, because gene mutants on the biosynthesis of Leg are non-flagellated. Furthermore, the presence of the lateral flagella cluster and Leg O-flagella glycosylation genes are widely spread features among the P. shigelloides strains tested.

The novel structure of the core oligosaccharide backbone of the lipopolysaccharide from the Plesiomonas shigelloides strain CNCTC 80/89 (serotype O13)

The new structure of the core oligosaccharide of Plesiomonas shigelloides CNCTC 80/89 (serotype O13) lipopolysaccharide has been investigated by chemical methods, (1)H and (13)C NMR spectroscopy and matrix-assisted laser-desorption/ionization time of flight (MALDI-TOF). It was concluded that the core oligosaccharide of P. shigelloides CNCTC 80/89 is a nonasaccharide with the following structure: The position of glycine was determined by MALDI-TOF MS/MS analyses.

Plesiomonas shigelloides septicemia and meningitis in a neonate

A newborn infant is described who presented with septicemia and meningoencephalitis caused by Plesiomonas shigelloides, a Gram-negative rod belonging to the family Vibrionaceae. This appears to be the first documented case in a neonate in Canada. Despite prompt treatment with appropriate antibiotics, he developed endophthalmitis and lytic brain lesions.

Plesiomonas shigelloides and Aeromonadaceae family pathogens isolated from marine mammals of Southern and Southeastern Brazilian coast

The aquatic environment is the habitat of many microorganisms, including Plesiomonas shigelloides and Aeromonas species which are pathogenic to human and animals. In the present investigation, we evaluated the occurrence of these pathogens from marine mammals beached or accidentally captured by fishing net in southeastern (RJ) and southern (RS) coastal Brazilian regions. A total of 198 swabs from 27 specimens of marine mammals, including 11 different species, were collected by DEENSP and GEMARS-CECLIMAR/ UFRGS Institutes and sent to LRNCEB/IOC/FIOCRUZ. The samples were enriched in Alkaline Peptone Water (APW) added with 1% of sodium chloride (NaCl), APW plus 3% NaCl and incubated at 37°C for 18–24 hours. Following, samples were streaked onto Pseudomonas-Aeromonas Selective Agar Base (GSP Agar) and suspected colonies were biochemically characterized. The results revealed 114 strains, including ten Aeromonas species and P. shigelloides. The main pathogens isolated were A. veronii biogroup veronii (19.3%), A. caviae (12.3%), A. hydrophila (9.6%) and P. shigelloides (7%). The pathogens were isolated in both coastal and offshore marine mammals. These data point the importance of epidemiological surveillance and microbiological monitoring and reinforce the need to implement environmental protection programs, especially related to endangered cetacean species.