Trace elements in subantarctic false killer whale (Pseudorca crassidens) tissues, including the skin as an offshore bioindicator.

On a global scale, cetaceans are recognized well indicators of marine ecosystem health. Trace elements accumulate in their bodies and potentially constitute a toxicological threat. Here, the concentrations of essential Se; unknown physiological elements Br, Rb, Cs, Ni, and Sr; and pollutants arsenic, Cd, Hg, and Ag were assessed in the skin of false killer whales (Pseudorca crassidens) stranded at Estrecho de Magallanes, South America, and next, tissue comparisons and relationships between elemental concentrations in the skin and internal tissues (liver, kidney, spleen, lung, skeletal muscle, and testis) were assessed. Results showed elemental concentration variations among tissues. Selenium concentration was found to be higher in the liver 398 (75) µg g-1 dry weight (DW) (standard deviation in parenthesis), followed by skin. Rubidium and Br concentrations were higher in testis 7.92 (0.42) and 99.1 (5.4) µg g-1 DW, respectively, and Cs in muscle 0.36 (0.12) µg g-1 DW, while Ni concentrations range (<0.05-0.91 µg g-1 DW) did not show differences among tissues. Cadmium and arsenic were found to be higher in kidneys, 71.2 (17.6) and 2.54 (1.77) µg g-1 DW, respectively, while Hg was highest in the liver 1068 (234) µg g-1 DW. Concerning inter-tissue relationships, a positive skin-to-kidney and skin-to-muscle correlations were observed for Cs concentrations, and also Hg showed positive skin-to-spleen, skin-to-kidney, and skin-to-testis correlations, which support its use as potential offshore marine biomonitor.

Stranded false killer whales, Pseudorca crassidens, in Southern South America reveal potentially dangerous silver concentrations.

Silver (Ag) is a non-essential metal known to bioaccumulate in aquatic organisms. We determined Ag concentrations in five false killer whales stranded in South America. Silver concentrations (in dry weight basis) range as 6.62-10.78 µg g-1 in liver, 0.008-7.41 µg g-1 in spleen, 0.004-5.71 µg g-1 in testis, 0.757-1.69 µg g-1 in kidney, 0.011-0.078 µg g-1 in lung and < 0.01-0.038 µg g-1 in muscle, whereas in the single samples of uterus and ovary were 0.051 and 0.023 µg g-1; respectively. Overall, Ag concentration in liver and kidney exceeded the cetacean toxic thresholds, proposed as "unhealthy concentrations" and "critically dangerous" in liver and kidney. These results warrant further eco-toxicological studies, to examine biological effects of elevated silver levels for individuals and to assess the species' conservation status with respect to marine pollution.

High status of mercury and selenium in false killer whales (Pseudorca crassidens, Owen 1846) stranded on Southern South America: A possible toxicological concern?

The study was carried out to determine Hg and Se concentrations in false killer whales stranded on the Estrecho de Magallanes, Chile, South America. Tissue samples of five mature specimens were analyzed (two females and three males). Mean Hg concentration in liver 1068 (234) µg g-1 dry weight (DW) (standard deviation in parenthesis) was markedly higher than those in kidney 272 (152) µg g-1 DW, lung 423 (325) µg g-1 DW, spleen 725 (696) µg g-1 DW, muscle 118 (94) µg g-1 DW and testicle 18.0 (2.8) µg g-1 DW. Mean Se concentration in liver, 398 (75) µg g-1 DW, was higher than those in kidney 162 (69) µg g-1 DW, lung 128 (84) µg g-1 DW, spleen 268 (245) µg g-1 DW, muscle 47 (38) µg g-1 DW and testicle 25.4 (2.1) µg g-1 DW. Positive correlations were found between Hg and Se molar concentrations in muscle, lung, spleen and kidney. Molar ratio of Se/Hg in liver, lung and muscle were <1, but those in kidney and testicle were markedly >1 suggesting a Se protection against Hg toxicity. In all the examined specimens Hg values exceeded the toxic thresholds defined for hepatic damage in marine mammals, with Se/Hg molar ratios below 1 implying limited protective action of Se. Generally, our results showed that individuals are carrying a significant burden, reflecting a high exposure to this toxic metal. This constitutes the first report on Hg and Se levels for a large subantarctic odontocete in South America region, providing insights into their contamination status and with information to the understanding of possible impacts on wild populations.

Genetic and phenotypic evidence of the Salmonella enterica serotype Enteritidis human-animal interface in Chile.

Salmonella enterica serotype Enteritidis is a worldwide zoonotic agent that has been recognized as a very important food-borne bacterial pathogen, mainly associated with consumption of poultry products. The aim of this work was to determine genotypic and phenotypic evidence of S. Enteritidis transmission among seabirds, poultry and humans in Chile. Genotyping was performed using PCR-based virulotyping, pulse-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Pathogenicity-associated phenotypes were determined with survival to free radicals, acidic pH, starvation, antimicrobial resistance, and survival within human dendritic cells. As result of PCR and PFGE assays, some isolates from the three hosts showed identical genotypic patterns, and through MLST it was determined that all of them belong to sequence type 11. Phenotypic assays show diversity of bacterial responses among isolates. When results were analyzed according to bacterial host, statistical differences were identified in starvation and dendritic cells survival assays. In addition, isolates from seabirds showed the highest rates of resistance to gentamycin, tetracycline, and ampicillin. Overall, the very close genetic and phenotypic traits shown by isolates from humans, poultry, and seabirds suggest the inter-species transmission of S. Enteritidis bacteria between hosts, likely through anthropogenic environmental contamination that determines infection of seabirds with bacteria that are potentially pathogenic for other susceptible organism, including humans.

Serotype-associated polymorphisms in a partial rpoB gene sequence of Salmonella enterica.

Salmonella enterica is a zoonotic bacterium with more than 2500 serotypes, which affect a wide range of hosts and produce diverse clinical outcomes. Strain identification usually involves costly and time-demanding procedures. This paper describes the sequencing of a rpoB hypervariable gene segment (847 bp) that allows identification of serotypes in S. enterica strains isolated from several hosts. The nucleotide similarity values among S. enterica serotypes ranged from 98.23% to 99.88%, with potential usefulness for devising a simple one-step sequencing as a first approach for identification of S. enterica strains. In conclusion, the analysis of polymorphisms in the partial rpoB sequence can discriminate S. enterica strains at the subspecies level.