Mercury Isotope Values in Shoreline Spiders Reveal the Transfer of Aquatic Mercury Sources to Terrestrial Food Webs.

The transfer of aquatic contaminants, including mercury (Hg), to terrestrial food webs is an often-overlooked exposure pathway to terrestrial animals. While research has implemented the use of shoreline spiders to assess aquatic to terrestrial Hg transfer, it is unclear whether Hg sources, estimated from isotope ratios, can be successfully resolved to inform site assessments and remedy effectiveness. To examine aquatic to terrestrial Hg transfer, we collected shoreline spiders (Tetragnatha spp.) and aquatic insect larvae (suborder Anisoptera) across a mosaic of aquatic and shoreline habitats in the St. Louis River and Bad River, tributaries to Lake Superior. The fraction of industrial Hg in sediments was reflected in the δ202Hg values of aquatic dragonfly larvae and predatory fish, connecting benthic Hg sources to the aquatic food web. Shoreline spiders mirrored these aquatic Hg source signatures with highly positive correlations in δ202Hg between tetragnathids and dragonfly larvae (r2 = 0.90). Further assessment of different spider taxa (i.e., araneids and pisaurids) revealed that differences in prey consumption and foraging strategies resulted in isotope differences, highlighting the importance of spider taxa selection for Hg monitoring efforts.

Invasive Dreissena Mussel Coastal Transport From an Already Invaded Estuary to a Nearby Archipelago Detected in DNA and Zooplankton Surveys.

Coastal waters of Lake Superior are generally inhospitable to the establishment of invasive Dreissena spp. mussels (both Dreissena polymorpha and Dreissena bugensis). Dreissena have inhabited the Saint Louis River estuary (SLRE; largest commercial port in the Laurentian Great Lakes) for over three decades, but only in the last few years have small colonies been found in the Apostle Islands National Lakeshore (APIS, an archipelago situated 85 km to the east of SLRE) A 2017 survey determined a low abundance Dreissena spatial distribution in APIS, with the largest colonies on the north and west islands which suggested potential veliger transport from the SLRE via longshore currents. Our objective in this study was to determine if Dreissena veligers are transported by currents at low densities along the south shore of Lake Superior from the SLRE to APIS. To do so, we used both eDNA (water and passive substrate samples) and zooplankton collection methods at eight sites evenly spaced between the SLRE and APIS with three sampling times over five weeks. Dreissena veligers were consistently detected along the south shore, although at low abundances (veligers per m3 range = 0-690, median = 8), and for every 1 km increase in distance from the SLRE, both veliger counts and water eDNA copy numbers decreased on average by 5 and 7%, respectively. D. polymorpha (suited to estuary habitats) was detected two times more than D. bugensis (better suited to deep-lake habitats). There was not a trend in the veliger size distribution along the south shore, and temperature and calcium concentrations fluctuated around the threshold for Dreissena veliger and adult development, averaging 11.0°C and 14.8 ppm, respectively. Three zooplankton taxa representative of the estuary community-Daphnia retrocurva, Diaphanosoma birgei, and Mesocyclops copepodites-decreased as the distance from the SLRE increased mirroring Dreissena veliger abundance patterns. Findings represent multiple sources of evidence of a propagule "conveyor belt" for Dreissena along the south shore of Lake Superior. We conclude that veligers are functioning as a propagule, using coastal currents to spread from the point of invasion, thereby traversing coastal habitat previously reported as inhospitable to distant habitats suitable for colonization.

Mass drug administration campaigns for scabies and impetigo: protocol for a systematic review and meta-analysis.

Introduction: Scabies is recognised as a neglected tropical disease, disproportionately affecting the most vulnerable populations around the world. Impetigo often occurs secondarily to scabies. Several studies have explored mass drug administration (MDA) programmes, with some showing positive outcomes-but a systematic evaluation of such studies is yet to be reported. The main aim of this systematic review is to generate comprehensive evidence on the effect and feasibility of MDA programmes in reducing the burden of scabies and impetigo. Methods and analysis: A systematic review and meta-analysis will be conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis statement. Electronic databases to be searched will include CINAHL EBSCOhost, Medline Ovid, ProQuest, Science Direct, PubMed and SCOPUS. In addition, grey literature will be explored via the Australian Institute of Health and Welfare, Australian Indigenous HealthInfoNet, Informit, OaIster database and WHO. No language restrictions will be applied. All treatment studies following an MDA protocol, including randomised/quasi-controlled trials, and prospective before-after interventional studies, will be considered. The main outcome is the change in prevalence of scabies and impetigo The Cochrane collaboration risk of bias assessment tool will be used for assessing the methodological quality of studies. A random-effect restricted maximum likelihood meta-analysis will be performed to generate pooled effect (OR) using STATA V.16. Appropriate statistical tests will be carried out to quantify heterogeneity between studies and publication bias. Ethics and dissemination: Ethical approval is not required since data will be extracted from published works. The findings will be communicated to the scientific community through a peer-reviewed journal publication. This systematic review will present an evidence on the effect of MDA interventions on scabies and impetigo, which is instrumental to obtain a clear understanding of the treatments widely used in these programmes. PROSPERO registration number: CRD42020169544.

Examining historical mercury sources in the Saint Louis River estuary: How legacy contamination influences biological mercury levels in Great Lakes coastal regions.

Industrial chemical contamination within coastal regions of the Great Lakes can pose serious risks to wetland habitat and offshore fisheries, often resulting in fish consumption advisories that directly affect human and wildlife health. Mercury (Hg) is a contaminant of concern in many of these highly urbanized and industrialized coastal regions, one of which is the Saint Louis River estuary (SLRE), the second largest tributary to Lake Superior. The SLRE has legacy Hg contamination that drives high Hg concentrations within sediments, but it is unclear whether legacy-derived Hg actively cycles within the food web. To understand the relative contributions of legacy versus contemporary Hg sources in coastal zones, Hg, carbon, and nitrogen stable isotope ratios were measured in sediments and food webs of SLRE and the Bad River, an estuarine reference site. Hg stable isotope values revealed that legacy contamination of Hg was widespread and heterogeneously distributed in sediments of SLRE, even in areas lacking industrial Hg sources. Similar isotope values were found in benthic invertebrates, riparian spiders, and prey fish from SLRE, confirming legacy Hg reaches the SLRE food web. Direct comparison of prey fish from SLRE and the Bad River confirmed that Hg isotope differences between the sites were not attributable to fractionation associated with rapid Hg bioaccumulation at estuarine mouths, but due to the presence of industrial Hg within SLRE. The Hg stable isotope values of game fish in both estuaries were dependent on fish migration and diet within the estuaries and extending into Lake Superior. These results indicate that Hg from legacy contamination is actively cycling within the SLRE food web and, through migration, this Hg also extends into Lake Superior via game fish. Understanding sources and the movement of Hg within the estuarine food web better informs restoration strategies for other impaired Great Lakes coastal zones.

Early detection monitoring for non-indigenous fishes; comparison of survey approaches during two species introductions in a Great Lakes port.

Assessing relative performance of different sampling methods used for early detection monitoring (EDM) is a critical step in understanding the likelihood of detecting new non-indigenous species (NIS) in an environment of interest. EDM performance metrics are typically based on the probability of detecting established NIS or rare indigenous species; however, detection probability estimates for these proxies may not accurately reflect survey effectiveness for newly introduced NIS. We used data from three different EDM survey approaches that varied by targeted life-stage (adult-juvenile versus ichthyoplankton), media (physical fish versus environmental DNA), and taxonomic method (morphology-based versus DNA-based taxonomy) to explore relative detection sensitivity for recently introduced white bass (Morone chrysops) and gizzard shad (Dorosoma cepedianum) in the Port of Duluth-Superior, a NIS introduction hot spot within the Laurentian Great Lakes. Detection efficiency, measured by the effort (number of samples) required to achieve 95% probability of detection, differed by EDM approach and species. Also, the relative sensitivity (detection rate) of each survey approach differed by species. For both species, detection in surveys using DNA-based taxonomy was generally as good or better than the adult-juvenile survey using morphology-based taxonomy. While both species appear to have been detected at early stages of invasion, white bass were likely present up to 5 years prior to initial detection, whereas gizzard shad may have been detected in the first year of introduction. We conclude that using complimentary sampling methods can help to balance the strengths and weaknesses of each approach and provide more reliable early detection of new invaders.

Dietary Niche and Growth Rate of the Nonnative Tubenose Goby (Proterorhinus semilunaris) in the Lake Superior Basin.

The tubenose goby (Proterorhinus semilunaris) entered the Great Lakes in the 1990s via ballast water, but remains poorly studied within North America, making it difficult to predict its effects on native ecosystems. Dietary breadth and somatic growth rate have important ramifications for survival, competitiveness, and dispersal ability of a fish species, and thereby its ecological impact. We studied diet and growth of age-0 tubenose goby within the St. Louis River, a tributary to Lake Superior that contains the largest population within the Lake Superior basin. We sampled tubenose gobies from shallow, vegetated habitat during summer and fall. Stomach contents were identified and weighed to measure fullness and dietary breadth between seasons and several locations. We aged fish based on otolith daily increments to model somatic growth. Diet was dominated by isopods and amphipods, and dietary breadth was low and not significantly different between locations and seasons. Tubenose goby diet strongly overlapped with that of tadpole madtom (Noturus gyrinus), a native, demersal species. We tested several candidate growth models; the Gompertz Growth Function was the most parsimonious model among those examined. The model demonstrates that tubenose goby obtains a small maximum size and is short-lived. We conclude that tubenose goby presents a unique risk to the Great Lakes and other freshwater bodies because their life history is typical of invasive species, their diet overlaps with native fish, and because they occupy shallow, vegetated habitat which functions as both nursery and foraging habitat for many native fishes.

Pharmacist-led medication reviews in aged care residents with dementia: A systematic review.

OBJECTIVES: To evaluate outcomes associated with pharmacist-led medication reviews in residential aged care facility (RACF) residents with dementia. METHODS: Six scientific databases were searched. All study designs investigating pharmacist-led medication reviews in RACF residents with dementia were considered. The protocol was registered with PROSPERO (CRD42019121681). RESULTS: One randomised controlled trial (RCT) and five observational studies were identified. Two studies reported reductions in medication usage per resident, and one study reported improved appropriateness of psychotropic use following reviews as part of multi-faceted, collaborative interventions. In three studies, reviews undertaken as an isolated intervention or by a visiting pharmacist with minimal collaboration with physicians were associated with low implementation rates of recommendations to alter therapy. CONCLUSION: Pharmacist-led medication reviews, when conducted collaboratively, may improve the use of medicines in RACF residents with dementia. However, robust conclusions cannot be drawn, largely due to the low quality of evidence available, including only one RCT.

Canaries in the coalmine: Stakeholder perspectives of medication management reviews for residents with dementia.

BACKGROUND: Residential medication management reviews (RMMRs) are the primary strategy enabling collaborative and individualised medication reviews in Australian residential aged care homes (RACHs). Residents with dementia often have complex health needs and care goals, which makes them a useful benchmark of health service efficacy. OBJECTIVE: To analyse perspectives of pharmacists, general practitioners (GPs) and nurses on the suitability and delivery of the current RMMR model for residents with dementia; and to identify scope for improvement in medication review service delivery. METHODS: Electronic surveys were distributed to the included health professions via professional agencies. Descriptive statistics and non-parametric tests were used to summarise quantitative variables. Qualitative data obtained from open-text responses underwent iterative thematic analysis. Two researchers independently conducted the thematic categorisation; data within responses was inductively coded, then codes were linked to identify emergent themes that described the data content. In a triangulated exploratory mixed method approach, the qualitative findings were used to explain the quantitative findings. RESULTS: None of the participants agreed that the current program recommendation of a single RMMR every 24 months was suitable for the residents' needs. Participants were more likely to use written, rather than verbal, means of communication during RMMRs. RMMRs were perceived to have minimal benefit if there was minimal face-to-face interaction between stakeholders. Individualised medicine management in relation to resident goals of care was the key benefit of RMMRs. Insufficient remuneration was the primary barrier to effective face-to-face collaboration and delivery of individualised resident care. CONCLUSIONS: Increasing support for stakeholder participation in face-to-face interactions during medication reviews may enable delivery of a more patient-centred service for residents with dementia and improve health professional satisfaction and engagement.

Regional differences in access to acute ischaemic stroke care and patient outcomes.

BACKGROUND: Advances in stroke management such as acute stroke units and thrombolysis are not uniformly distributed throughout our population, with rural areas being relatively disadvantaged. It remains unclear, however, whether such disparities have led to corresponding differences in patient outcomes. AIMS: To describe the regional differences in acute ischaemic stroke care and outcomes within the Australian state of Tasmania. METHODS: A retrospective case note audit was used to assess the care and outcomes of 395 acute ischaemic stroke patients admitted to Tasmania's four major public hospitals. Sixteen care processes were recorded, which covered time-critical treatment, allied health interventions and secondary prevention. Outcome measures were assessed using 30-day mortality and discharge destination, both of which were analysed for differences between urban and rural hospitals using logistic regression. RESULTS: No patients in rural hospitals were administered thrombolysis; these hospitals also did not have acute stroke units. With few exceptions, patients' access to the remaining care indicators was comparable between regions. After adjusting for confounders, there were no significant differences between regions in terms of 30-day mortality (odds ratio (OR) = 0.99, 95% confidence interval (CI) 0.46-2.18) or discharge destination (OR = 1.24, 95% CI 0.81-1.91). CONCLUSIONS: With the exception of acute stroke unit care and thrombolysis, acute ischaemic stroke care within Tasmania's urban and rural hospitals was broadly similar. No significant differences were found between regions in terms of patient outcomes. Future studies are encouraged to employ larger data sets, which capture a broader range of urban and rural sites and record patient outcomes at extended interval.

Urban-rural differences in the care and outcomes of acute stroke patients: Systematic review.

OBJECTIVE: To describe literature pertaining to urban-rural differences in both the quality of care and outcomes of acute stroke patients. METHODS: We systematically searched CINAHL, PubMed, ProQuest Dissertations & Theses, and Scopus for published and unpublished literature until 9th December 2017. Studies were included if they compared the acute care provided to, or outcomes of, patients hospitalised for stroke in urban versus rural settings. Abstract, full-text review, and data extraction were conducted in duplicate. Findings are presented in the form of narrative syntheses. RESULTS: A total of 28 studies were included in the review (16 on care, 12 on outcomes). With few exceptions, studies addressing the provision of care suggested that rural patients have less access to most aspects of acute stroke care. Studies reporting urban-rural differences in patient outcomes were inconsistent in their findings, however, few of these studies were primarily focused on the issue of urban-rural disparities. Overall, study findings did not appear to differ in line with study quality ratings, stroke subtypes included, or how inter-facility patient transfers were accounted for. CONCLUSIONS: There is convincing, albeit not unanimous, evidence to suggest that stroke patients in rural areas receive less acute care than their urban counterparts. Despite this, the available data and methodology have largely not been used to study urban-rural differences in patient outcomes. PROSPERO registration information: URL: https://www.crd.york.ac.uk/prospero. Unique identifier: CRD42017073262.

Effects of a community-based care management model for super-utilizers.

OBJECTIVES: Medicare, Medicaid, and commercial plans have all explored ways to improve outcomes for patients with high costs and complex medical and social needs. The purpose of this study was to test the effectiveness of a high-intensity care management program that the Rutgers University Center for State Health Policy (CSHP) implemented as an adaptation of a promising model developed by the Camden Coalition of Healthcare Providers. STUDY DESIGN: We estimated the impact of the program on 6 utilization and spending outcomes for a subgroup of beneficiaries enrolled in Medicare fee-for-service (n = 149) and a matched comparison group (n = 1130). METHODS: We used Medicare claims for all analyses. We used propensity score matching to construct a comparison group of beneficiaries with baseline characteristics similar to those of program participants. We employed regression models to test the relationship between program enrollment and outcomes over a 12-month period while controlling for baseline characteristics. RESULTS: A test of joint significance across all outcomes showed that the CSHP program reduced service use and spending in aggregate (P = .012), although estimates for most of the individual measures were not statistically significant. Participants had 37% fewer unplanned readmissions (P = .086) than did comparison beneficiaries. Although we did not find statistically significant results for the other 5 outcomes, the CIs for these outcomes spanned substantively large effects. CONCLUSIONS: Although these findings are mixed, they suggest that adaptations of the Camden model hold promise for reducing short-term service use and spending for Medicare super-utilizers.

Identification of Ruffe larvae (Gymnocephalus cernua) in the St. Louis River, Lake Superior: Clarification and guidance regarding morphological descriptions.

Non-native ruffe (Gymnocephalus cernua; family Percidae) were first detected in the Laurentian Great Lakes in 1986, and are not included in regional larval fish keys which were published several years prior to their discovery. In addition, subsequent scientific literature has inconsistently described ruffe larvae. As a result, identification of larval ruffe remains challenging. We used traditional morphology paired with DNA technology to develop diagnostics for ruffe larvae collected in the lower St. Louis River, and compared them to similar species. We found that ruffe < 6 mm total length phenotypically resemble centrarchids, like black crappie, bluegill, and pumpkinseed, but have myomere counts that are intermediate between values for both common percid and centrarchid species. We suggest that developmental and pigment patterns as well as morphometrics can be used to distinguish ruffe from similar species at this size. At larger sizes, ruffe increasingly resemble other percids such as yellow perch, but can be distinguished using myomere counts and morphological features. The findings presented here clarify conflicting descriptions in the scientific literature, and provide additional data to support more confident morphological identification of larval ruffe.

Assessing the uptake and effectiveness of a quick reference guide to antibiotic prescribing in Australian general practice.

Prescribing guidelines are an essential component of antimicrobial stewardship programs in Australian hospitals. Nonetheless, the majority of antibiotic prescribing occurs in the community and the effectiveness of guidelines developed specifically to meet the needs of Australian general practice is unknown. This study aims to assess the uptake and effectiveness of a quick reference guide to antibiotic prescribing among primary care prescribers. A quick reference guide to antibiotic prescribing was developed and prescribers in five Tasmanian practices were surveyed regarding use of this guide. Thirty-three surveys were returned and, of those answering specific sections, 75% were aware of the guide and 71% had used it within the last month. The guide affected the antibiotic prescribing practice of 74% of responding prescribers; most often on choice of antibiotic; but also on duration of treatment, dose and dosing frequency. A quick reference guide to antibiotic prescribing was well received by prescribers and may usefully support efforts to improve antimicrobial stewardship in the community.

Therapeutic Potential of Tea Tree Oil for Scabies.

Globally, scabies affects more than 130 million people at any time. In the developed world, outbreaks in health institutions and vulnerable communities result in a significant economic burden. A review of the literature demonstrates the emergence of resistance toward classical scabicidal treatments and the lack of effectiveness of currently available scabicides in reducing the inflammatory skin reactions and pyodermal progression that occurs in predisposed patient cohorts. Tea tree oil (TTO) has demonstrated promising acaricidal effects against scabies mites in vitro and has also been successfully used as an adjuvant topical medication for the treatment of crusted scabies, including cases that did not respond to standard treatments. Emerging acaricide resistance threatens the future usefulness of currently used gold standard treatments (oral ivermectin and topical permethrin) for scabies. The imminent development of new chemical entities is doubtful. The cumulative acaricidal, antibacterial, antipruritic, anti-inflammatory, and wound healing effects of TTO may have the potential to successfully reduce the burden of scabies infection and the associated bacterial complications. This review summarizes current knowledge on the use of TTO for the treatment of scabies. On the strength of existing data for TTO, larger scale, randomized controlled clinical trials are warranted.

Scabies: an ancient global disease with a need for new therapies.

BACKGROUND: Scabies is an ancient disease (documented as far back as 2500 years ago). It affects about 300 million people annually worldwide, and the prevalence is as high as about 60% in Indigenous and Torres Strait Islander children in Australia. This is more than six times the rate seen in the rest of the developed world. Scabies is frequently complicated by bacterial infection leading to the development of skin sores and other more serious consequences such as septicaemia and chronic heart and kidney diseases. This causes a substantial social and economic burden especially in resource poor communities around the world. DISCUSSION: Very few treatment options are currently available for the management of scabies infection. In this manuscript we briefly discuss the clinical consequences of scabies and the problems found (studies conducted in Australia) with the currently used topical and oral treatments. Current scabies treatment options are fairly ineffective in preventing treatment relapse, inflammatory skin reactions and associated bacterial skin infections. None have ovicidal, antibacterial, anti-inflammatory and/or anti-pruritic properties. Treatments which are currently available for scabies can be problematic with adverse effects and perhaps of greater concern the risk of treatment failure. The development of new chemical entities is doubtful in the near future. Though there may be potential for immunological control, the development of a vaccine or other immunotherapy modalities may be decades away. The emergence of resistance among scabies mites to classical scabicides and ineffectiveness of current treatments (in reducing inflammatory skin reactions and secondary bacterial infections associated with scabies), raise serious concerns regarding current therapy. Treatment adherence difficulties, and safety and efficacy uncertainties in the young and elderly, all signal the need to identify new treatments for scabies.

Outer membrane proteins of Fusobacterium necrophorum subsp. necrophorum and subsp. funduliforme.

Fusobacterium necrophorum, classified into subsp. necrophorum (Fnn) and subsp. funduliforme (Fnf), is frequently associated with necrotic infections of animals and humans. The outer membrane proteins (OMP) of many Gram negative bacteria play an important role in bacterial adhesion and establishment of infection. The OMP profile of F. necrophorum has not been well characterized. We analyzed OMP of bovine strains of Fnn and Fnf and human strains of F. necrophorum. Electrophoretic separations of extracted OMP of Fnn and Fnf strains of cattle showed a total of 19 and 20 protein bands, respectively. The most prominent protein band was 40 kDa in Fnn and 37.5 kDa in Fnf. The four human clinical strains examined had more heterogeneous banding patterns and had different profiles than those of bovine Fnf strains. A total of 11 protein bands in Fnn and 13 protein bands in Fnf were recognized by sera from cattle with liver abscesses. The intensities of many of the bands in Fnn were higher than that of Fnf. We conclude that the two subspecies of F. necrophorum differ in their OMP profiles and the difference may account for differences in their virulence and involvement in the pathogenesis of necrotic infections.

Six features of Medicare coordinated care demonstration programs that cut hospital admissions of high-risk patients.

As policy makers seek to slow the growth in Medicare spending, they have appropriately focused attention on beneficiaries with multiple chronic conditions. Many care coordination and disease management programs designed to improve beneficiaries' care and reduce their need for hospitalizations have been tested, but few have been successful. This study, however, found that four of eleven programs that were part of the Medicare Coordinated Care Demonstration reduced hospitalizations by 8-33 percent among enrollees who had a high risk of near-term hospitalization. The six approaches practiced by care coordinators in at least three of the four programs were as follows: supplementing telephone calls to patients with frequent in-person meetings; occasionally meeting in person with providers; acting as a communications hub for providers; delivering evidence-based education to patients; providing strong medication management; and providing timely and comprehensive transitional care after hospitalizations. When care management fees were included, the programs were essentially cost-neutral, but none of these programs generated net savings to Medicare. Our results suggest that incorporating these approaches into medical homes, accountable care organizations, and other policy initiatives could reduce hospitalizations and improve patients' lives. However, the approaches would save money only if care coordination fees were modest and organizations found cost-effective ways to deliver the interventions.

How changes in Washington University's Medicare coordinated care demonstration pilot ultimately achieved savings.

As one of the initial fifteen participants in the Medicare Coordinated Care Demonstration, the Washington University School of Medicine in St. Louis was not able to demonstrate any reduction in hospitalizations or Medicare spending for the patients it served. In fact, the Washington University program increased total Medicare spending by 12 percent. But after a redesign, the results changed. The program stopped conducting care management of most of its patients via telephone from a remote site in California and, instead, served all patients through frequent phone and occasional in-person contact from local care managers in St. Louis. Care management efforts were focused especially on patients deemed at greatest risk of hospitalization, and stronger hospital transition planning and medication reconciliation were provided, among other changes. After that point, the program reduced hospitalizations by 12 percent and monthly Medicare spending by $217 per enrollee-more than offsetting the program's monthly $151 care management fee. The results underscore findings from the overall Medicare Coordinated Care Demonstration that suggest that programs with more in-person contacts were more likely than others to build trusting relationships with patients and providers, improve patient adherence to care plans, and address additional needs and barriers that entirely telephonic contacts had been unable to identify. The results also indicate that programs can be more effective by focusing on the highest-risk patients, for whom the largest savings resulted.

Microarray assessment of virulence, antibiotic, and heavy metal resistance in an agricultural watershed creek.

Potential risks associated with impaired surface water quality have commonly been evaluated by indirect description of potential sources using various fecal microbial indicators and derived source-tracking methods. These approaches are valuable for assessing and monitoring the impacts of land-use changes and changes in management practices at the source of contamination. A more detailed evaluation of putative etiologically significant genetic determinants can add value to these assessments. We evaluated the utility of using a microarray that integrates virulence genes with antibiotic and heavy metal resistance genes to describe and discriminate among spatially and seasonally distinct water samples from an agricultural watershed creek in Eastern Ontario. Because microarray signals may be analyzed as binomial distributions, the significance of ambiguous signals can be easily evaluated by using available off-the-shelf software. The FAMD software was used to evaluate uncertainties in the signal data. Analysis of multilocus fingerprinting data sets containing missing data has shown that, for the tested system, any variability in microarray signals had a marginal effect on data interpretation. For the tested watershed, results suggest that in general the wet fall season increased the downstream detection of virulence and resistance genes. Thus, the tested microarray technique has the potential to rapidly describe the quality of surface waters and thus to provide a qualitative tool to augment quantitative microbial risk assessments.

Effects of two simulated oxytetracycline dosing regimens on horizontal transfer of antimicrobial resistance plasmids in an in vitro pharmacodynamic model.

OBJECTIVE: To evaluate the impact of oxytetracycline exposure on horizontal transfer of an antimicrobial resistance plasmid. SAMPLE: Populations of Salmonella enterica subsp enterica serovar Typhimurium and Escherichia coli. PROCEDURES: Mixed populations of plasmid donor (Salmonella Typhimurium) and recipient (E coli) bacteria were assigned to 1 of 2 simulated oxytetracycline dosing regimens (high peak concentration-short elimination half-life [HC-SHL] or low peak concentration-long elimination half-life [LC-LHL]) or served as untreated control replicates. Donor, recipient, and transconjugant (E coli that acquired the plasmid) bacteria populations were quantified at 12, 24, and 36 hours after oxytetracycline administration by use of culture on selective bacterial growth media. RESULTS: The ratio of transconjugant to donor bacteria was significantly reduced in the oxytetracycline-exposed replicates, compared with the ratio for the control replicates, at 12 hours. At 24 and 36 hours, results for the HC-SHL regimens were not significantly different from results for the respective control replicates, and results for the LC-LHL regimens also were not significantly different from results for the respective control replicates. The oxytetracycline concentration at these time points (12 hours in the HC-SHL regimen and all 3 time points in the LC-LHL regimen) were in excess of the minimum inhibitory concentration of the recipient bacteria. CONCLUSIONS AND CLINICAL RELEVANCE: Transfer of antimicrobial resistance plasmids may be suppressed in vitro by oxytetracycline exposure at concentrations greater than the minimum inhibitory concentration of the recipient bacteria.