Clostridium perfringens toxin types in hooded seals in the Greenland Sea, determined by PCR and ELISA

The Gut Microbial Community Structure of the North American River Otter (Lontra canadensis) in the Alberta Oil Sands Region in Canada: Relationship with Local Environmental Variables and Metal Body Burden

The Alberta Oil Sands Region in Canada is home to one of the largest oil bitumen deposits in the world. The North American river otter (Lontra canadensis) is a top predator with a small home range and is sensitive to disturbances; it has been designated as a sentinel species for the potential impacts of the natural resource exploitation on freshwater ecosystems in the Alberta Oil Sands Region. With an increasing interest in noninvasive biomarkers, recent studies suggest that gut microbiota can be used as a potential biomarker of early biological effects on aquatic wildlife. The goal of the present study was to determine the river otter gut microbial structure related to environmental variables characterizing mining activities and metal body burden. We obtained 18 trapped animals from and surrounding the surface mineable area of the Alberta Oil Sands Region. The gut microbial community structure was characterized using high-throughput sequencing of 16S rRNA gene amplicon analyses. Trace metal concentrations in the liver were measured by inductively coupled plasma-mass spectrometry. Our study revealed that the gut bacteria of river otters in the Alberta Oil Sands Region clustered in 4 groups dominated by Peptostreptococcaceae, Carnobacteriaceae, Enterobacteriaceae, Clostridiaceae, and Nostocaceae. We show that arsenic, barium, rubidium, liver-body weight ratio, and δ¹⁵ N were associated with each cluster. When comparing affected versus less affected sites, we show that river otter gut bacterial community and structure are significantly related to trophic level of the river otter but not to Alberta Oil Sands Region mining activities. Our study reveals that the gut bacterial dynamics can provide insights into the diet and habitat use of river otters but that more work is needed to use it as a pollution biomarker. Environ Toxicol Chem 2020;39:2516-2526. © 2020 SETAC.

Symbiotic microbes and potential pathogens in the intestine of dead southern right whale (Eubalaena australis) calves

Between 2003 and 2017, at least 706 southern right whale (Eubalaena australis) calves died at the Península Valdés calving ground in Argentina. Pathogenic microbes are often suggested to be the cause of stranding events in cetaceans; however, to date there is no evidence supporting bacterial infections as a leading cause of right whale calf deaths in Argentina. We used high-throughput sequencing and culture methods to characterize the bacterial communities and to detect potential pathogens from the intestine of stranded calves. We analyzed small and large intestinal contents from 44 dead calves that stranded at Península Valdés from 2005 to 2010 and found 108 bacterial genera, most identified as Firmicutes or Bacteroidetes, and 9 genera that have been previously implicated in diseases of marine mammals. Only one operational taxonomic unit was present in all samples and identified as Clostridium perfringens type A. PCR results showed that all C. perfringens isolates (n = 38) were positive for alpha, 50% for beta 2 (n = 19) and 47% for enterotoxin (CPE) genes (n = 18). The latter is associated with food-poisoning and gastrointestinal diseases in humans and possibly other animals. The prevalence of the cpe gene found in the Valdés' calves is unusually high compared with other mammals. However, insufficient histologic evidence of gastrointestinal inflammation or necrosis (the latter possibly masked by autolysis) in the gut of stranded calves, and absence of enterotoxin detection precludes conclusions about the role of C. perfringens in calf deaths. Further work is required to determine whether C. perfringens or other pathogens detected in this study are causative agents of calf deaths at Península Valdés.

[Focal meningitis in a California sea lion (Zalophus californianus)--diagnostic procedure and pathology]

A 15-year-old female California sea lion (Zalophus californianus) with progressive lameness of the hindlimbs and a chronic skin lesion was presented for clinical examination. The clinical neurological examination, showing a paraparesis, was completed by magnetic resonance imaging. MR images of the cervical and thoracic spine showed a well-defined muscle infiltrating lesion between the seventh cervical vertebra (C7) and the second thoracic vertebra (T2), which extended through the intervertebral foramina between C7 and T1 into the vertebral canal, causing spinal cord compression and displacement. Pathological examination revealed focal purulent meningitis resulting from widespread fistulas of the chronic skin leasion, which was infected with Escherichia coli var. haemolytica and Clostridium perfringens.

Clostridium perfringens septicemia in a long-beaked common dolphin Delphinus capensis: an etiology of gas bubble accumulation in cetaceans

An adult female long-beaked common dolphin Delphinus capensis live-stranded in La Jolla, California, USA, on July 30, 2012 and subsequently died on the beach. Computed tomography and magnetic resonance imaging revealed gas bubble accumulation in the vasculature, organ parenchyma, mandibular fat pads, and subdermal sheath as well as a gas-filled cavity within the liver, mild caudal abdominal effusion, and fluid in the uterus. Gross examination confirmed these findings and also identified mild ulcerations on the palate, ventral skin, and flukes, uterine necrosis, and multifocal parenchymal cavitations in the brain. Histological review demonstrated necrosis and round clear spaces interpreted as gas bubbles with associated bacterial rods within the brain, liver, spleen, and lymph nodes. Anaerobic cultures of the lung, spleen, liver, bone marrow, and abdominal fluid yielded Clostridium perfringens, which was further identified as type A via a multiplex PCR assay. The gas composition of sampled bubbles was typical of putrefaction gases, which is consistent with the by-products of C. perfringens, a gas-producing bacterium. Gas bubble formation in marine mammals due to barotrauma, and peri- or postmortem off-gassing of supersaturated tissues and blood has been previously described. This case study concluded that a systemic infection of C. perfringens likely resulted in production of gas and toxins, causing tissue necrosis.

Enteric bacterial pathogen detection in southern sea otters (Enhydra lutris nereis) is associated with coastal urbanization and freshwater runoff

Although protected for nearly a century, California's sea otters have been slow to recover, in part due to exposure to fecally-associated protozoal pathogens like Toxoplasma gondii and Sarcocystis neurona. However, potential impacts from exposure to fecal bacteria have not been systematically explored. Using selective media, we examined feces from live and dead sea otters from California for specific enteric bacterial pathogens (Campylobacter, Salmonella, Clostridium perfringens, C. difficile and Escherichia coli O157:H7), and pathogens endemic to the marine environment (Vibrio cholerae, V. parahaemolyticus and Plesiomonas shigelloides). We evaluated statistical associations between detection of these pathogens in otter feces and demographic or environmental risk factors for otter exposure, and found that dead otters were more likely to test positive for C. perfringens, Campylobacter and V. parahaemolyticus than were live otters. Otters from more urbanized coastlines and areas with high freshwater runoff (near outflows of rivers or streams) were more likely to test positive for one or more of these bacterial pathogens. Other risk factors for bacterial detection in otters included male gender and fecal samples collected during the rainy season when surface runoff is maximal. Similar risk factors were reported in prior studies of pathogen exposure for California otters and their invertebrate prey, suggesting that land-sea transfer and/or facilitation of pathogen survival in degraded coastal marine habitat may be impacting sea otter recovery. Because otters and humans share many of the same foods, our findings may also have implications for human health.

Effects of climate change on Arctic marine mammal health

The lack of integrated long-term data on health, diseases, and toxicant effects in Arctic marine mammals severely limits our ability to predict the effects of climate change on marine mammal health. The overall health of an individual animal is the result of complex interactions among immune status, body condition, pathogens and their pathogenicity, toxicant exposure, and the various environmental conditions that interact with these factors. Climate change could affect these interactions in several ways. There may be direct effects of loss of the sea ice habitat, elevations of water and air temperature, and increased occurrence of severe weather. Some of the indirect effects of climate change on animal health will likely include alterations in pathogen transmission due to a variety of factors, effects on body condition due to shifts in the prey base/food web, changes in toxicant exposures, and factors associated with increased human habitation in the Arctic (e.g., chemical and pathogen pollution in the runoff due to human and domestic-animal wastes and chemicals and increased ship traffic with the attendant increased risks of ship strike, oil spills, ballast pollution, and possibly acoustic injury). The extent to which climate change will impact marine mammal health will also vary among species, with some species more sensitive to these factors than others. Baseline data on marine mammal health parameters along with matched data on the population and climate change trends are needed to document these changes.

Occurrence of microbial indicators and Clostridium perfringens in wastewater, water column samples, sediments, drinking water, and Weddell seal feces collected at McMurdo Station, Antarctica

McMurdo Station, Antarctica, has discharged untreated sewage into McMurdo Sound for decades. Previous studies delineated the impacted area, which included the drinking water intake, by using total coliform and Clostridium perfringens concentrations. The estimation of risk to humans in contact with the impacted and potable waters may be greater than presumed, as these microbial indicators may not be the most appropriate for this environment. To address these concerns, concentrations of these and additional indicators (fecal coliforms, Escherichia coli, enterococci, coliphage, and enteroviruses) in the untreated wastewater, water column, and sediments of the impacted area and drinking water treatment facility and distribution system at McMurdo Station were determined. Fecal samples from Weddell seals in this area were also collected and analyzed for indicators. All drinking water samples were negative for indicators except for a single total coliform-positive sample. Total coliforms were present in water column samples at higher concentrations than other indicators. Fecal coliform and enterococcus concentrations were similar to each other and greater than those of other indicators in sediment samples closer to the discharge site. C. perfringens concentrations were higher in sediments at greater distances from the discharge site. Seal fecal samples contained concentrations of fecal coliforms, E. coli, enterococci, and C. perfringens similar to those found in untreated sewage. All samples were negative for enteroviruses. A wastewater treatment facility at McMurdo Station has started operation, and these data provide a baseline data set for monitoring the recovery of the impacted area. The contribution of seal feces to indicator concentrations in this area should be considered.

Significance of beta 2-toxigenic clostridium perfringens infections in animals and their predisposing factors--a review

The novel beta 2-toxin of Clostridium perfringens has recently been described as the cause of enteric diseases in animals. The biological activity of beta 2-toxin is similar to that of the beta1-toxin with a possibly weaker cytotoxic activity. However, the production of beta 2-toxin in vitro is not seen in all beta 2-toxin-gene (cpb2)-positive C. perfringens strains, and to deduce a clinical importance solely from the detection of cpb2 is difficult. Detection of cpb2-positive C. perfringens from various animal species with and without enteric diseases demonstrates the wide distribution of cpb2 in nature, and the presence of cpb2 gene is therefore not considered a risk by itself. Predisposing factors like low trypsin activity in the intestinal tract, antibiotic and/or antiphlogistic treatment or changes in diet can result in the selection of beta 2-toxigenic C. perfringens which may lead to enteritis or enterotoxaemia.

Clostridium perfringens toxin types from wild-caught Atlantic cod (Gadus morhua L.), determined by PCR and ELISA

Ninety-five fecal samples from Atlantic cod (Gadus morhua L.), caught along the northern Norwegian coast, were examined bacteriologically for occurrence of C. perfringens. Isolates were examined by polymerase chain reaction (PCR) for genes encoding the four lethal toxins (alpha, beta, epsilon, and iota) for classification into toxin types and for genes encoding enterotoxin and the novel beta2 toxin for further subclassification. In addition, a commercial enzyme-linked immunosorbent assay (ELISA) kit for detection of C. perfringens alpha, beta, and epsilon toxin was used. Clostridium perfringens could be isolated in 37 fecal samples (38.9%) from cod. All isolates were C. perfringens toxin type A (alpha toxin positive) as determined by PCR and also ELISA. In addition, in isolates from two cod (2.1%) the gene encoding for beta2 toxin was found (A, beta2) by PCR. Genes encoding for beta, epsilon, and iota toxins and enterotoxin were not found. This is the first detection of C. perfringens alpha and beta2 toxin in cod and of beta2 toxin in fish in general. The origin of this bacterium in cod is discussed.