Prevalence of and Relationship between Two Human-Associated DNA Biomarkers for Bacteroidales in an Urban Watershed.

Human-associated fecal biomarkers offer potent tools for the detection and control of human fecal pollution in watersheds. In some cases, the probability of false-negative findings may call for using a less specific biomarker that is present in higher quantities as long as it can be related to the more specific indicator. The objective of this study is to investigate the relationship between two previously published human-associated biomarkers for Bacteroidales bacteria in an urban watershed influenced by human fecal pollution and to determine if the less specific marker may be used to identify the locations of broken or leaking sewer lines. Samples were collected from 19 stream locations on 10 dates. Sample DNA was extracted and qPCR analysis was conducted for the HuBac and qHF183 biomarkers. The HuBac biomarker was detected more frequently than the qHF183 biomarker and in greater quantities when both were detected. A strong linear relationship ( = 0.91) between the two markers was observed in 219 samples taken from both the watershed and inlet sewage. The relationship between the two biomarkers showed less variance at higher concentrations. However, even when the inlet sewage samples were excluded from the dataset, a clear linear relationship remained ( = 0.74). The results indicate that use of a less specific, but more sensitive, biomarker may provide greater utility when the prevention of false negatives is necessary and the primary fecal source is known, as in spatial distribution studies of human fecal pollution in an urban watershed.

Performance characteristics of qPCR assays targeting human- and ruminant-associated bacteroidetes for microbial source tracking across sixteen countries on six continents.

Numerous quantitative PCR assays for microbial fecal source tracking (MST) have been developed and evaluated in recent years. Widespread application has been hindered by a lack of knowledge regarding the geographical stability and hence applicability of such methods beyond the regional level. This study assessed the performance of five previously reported quantitative PCR assays targeting human-, cattle-, or ruminant-associated Bacteroidetes populations on 280 human and animal fecal samples from 16 countries across six continents. The tested cattle-associated markers were shown to be ruminant-associated. The quantitative distributions of marker concentrations in target and nontarget samples proved to be essential for the assessment of assay performance and were used to establish a new metric for quantitative source-specificity. In general, this study demonstrates that stable target populations required for marker-based MST occur around the globe. Ruminant-associated marker concentrations were strongly correlated with total intestinal Bacteroidetes populations and with each other, indicating that the detected ruminant-associated populations seem to be part of the intestinal core microbiome of ruminants worldwide. Consequently tested ruminant-targeted assays appear to be suitable quantitative MST tools beyond the regional level while the targeted human-associated populations seem to be less prevalent and stable, suggesting potential for improvements in human-targeted methods.

Comparison of cell uptake, biodistribution and tumor retention of folate-coated and PEG-coated gadolinium nanoparticles in tumor-bearing mice.

The purpose of these studies was to compare the cell uptake, biodistribution and tumor retention of folate-coated and PEG-coated gadolinium (Gd) nanoparticles. Gd is a potential agent for neutron capture therapy (NCT) of tumors. Gd nanoparticles were engineered from oil-in-water microemulsion templates. To obtain folate-coated nanoparticles, a folate ligand [folic acid chemically linked to distearoylphosphatidylethanolamine (DSPE) via a PEG spacer MW 3350] was included in nanoparticle preparations. Similarly, control nanoparticles were coated with DSPE-PEG-MW 3350 (PEG-coated). Nanoparticles were characterized based on size, size distribution, morphology, biocompatibility and tumor cell uptake. In vivo studies were carried out in KB (human nasopharyngeal carcinoma) tumor-bearing athymic mice. Biodistribution and tumor retention studies were carried out at pre-determined time intervals after injection of nanoparticles (10 mg/kg). Gd nanoparticles did not aggregate platelets or activate neutrophils. The retention of nanoparticles in the blood 8, 16 and 24 h post-injection was 60%, 13% and 11% of the injected dose (ID), respectively. A maximum Gd tumor localization of 33+/-7 microg Gd/g was achieved. Both folate-coated and PEG-coated nanoparticles had comparable tumor accumulation. However, the cell uptake and tumor retention of folate-coated nanoparticles was significantly enhanced over PEG-coated nanoparticles. Thus, the benefits of folate ligand coating were to facilitate tumor cell internalization and retention of Gd-nanoparticles in the tumor tissue. The engineered nanoparticles may have potential in tumor-targeted delivery of Gd thereby enhancing the therapeutic success of NCT.