Optimization of a Staphylococcus aureus adhesion assay for equine corneocytes

Meticillin-resistant Staphylococcus aureus (MRSA) causes serious skin and soft-tissue infections of humans and animals. Multiple strains of MRSA have been characterized, and one in particular, designated as strain USA 500, causes infections predominantly of horses and the people who work with them. The purpose of this study was to optimize an assay which could subsequently be used to compare the relative avidity of different S. aureus strains for equine corneocytes. Corneocytes were collected from the perineal skin of 10 healthy horses onto adhesive discs. The discs were then incubated at 37°C with an S. aureus field strain at each of three concentrations [10(7), 10(8) and 10(9) colony forming units (CFU)/mL] and for each of three incubation periods (45, 90 and 180 min). After standardized rinsing and staining procedures, discs were examined at ×1,000 magnification and areas containing confluent corneocytes photographed. The percentage of surface area occupied by adherent bacteria was analysed using image processing and analysis software. Significant colour space image processing was required to distinguish bacteria from the ubiquitous melanin granules present within equine corneocytes. Objective and subjective methods were used to determine optimal conditions for specific adherence without introducing confounding factors. A bacterial concentration of 10(8) CFU/mL incubated with corneocytes for 45 min produced maximal bacterial adhesion with the least amount of interbacterial clumping. Future studies should utilize these conditions for optimal assay performance.     

A decision-analytic approach to the optimal allocation of resources for endangered species consultation

The resources available to support conservation work, whether time or money, are limited. Decision makers need methods to help them identify the optimal allocation of limited resources to meet conservation goals, and decision analysis is uniquely suited to assist with the development of such methods. In recent years, a number of case studies have been described that examine optimal conservation decisions under fiscal constraints; here we develop methods to look at other types of constraints, including limited staff and regulatory deadlines. In the US, Section Seven consultation, an important component of protection under the federal Endangered Species Act, requires that federal agencies overseeing projects consult with federal biologists to avoid jeopardizing species. A benefit of consultation is negotiation of project modifications that lessen impacts on species, so staff time allocated to consultation supports conservation. However, some offices have experienced declining staff, potentially reducing the efficacy of consultation. This is true of the US Fish and Wildlife Service’s Washington Fish and Wildlife Office (WFWO) and its consultation work on federally-threatened bull trout (Salvelinus confluentus). To improve effectiveness, WFWO managers needed a tool to help allocate this work to maximize conservation benefits. We used a decision-analytic approach to score projects based on the value of staff time investment, and then identified an optimal decision rule for how scored projects would be allocated across bins, where projects in different bins received different time investments. We found that, given current staff, the optimal decision rule placed 80% of informal consultations (those where expected effects are beneficial, insignificant, or discountable) in a short bin where they would be completed without negotiating changes. The remaining 20% would be placed in a long bin, warranting an investment of seven days, including time for negotiation. For formal consultations (those where expected effects are significant), 82% of projects would be placed in a long bin, with an average time investment of 15 days. The WFWO is using this decision-support tool to help allocate staff time. Because workload allocation decisions are iterative, we describe a monitoring plan designed to increase the tool’s efficacy over time. This work has general application beyond Section Seven consultation, in that it provides a framework for efficient investment of staff time in conservation when such time is limited and when regulatory deadlines prevent an unconstrained approach.     

The Effect of Long Term Storage on Bacterial Soft Rot Resistance in Potato

Bacterial soft rot is a serious disease in potato (Solanum tuberosum L.), causing rapid tuber tissue maceration and, consequently, marketable yield loss. Soft rot bacteria, including Pectobacterium carotovorum subsp. carotovorum (Pbc), are favored by moist conditions, which are prevalent in large potato storage facilities. However, although most potatoes in North America are stored before use, there are no published surveys of soft rot resistance in cultivars exposed to long-term storage conditions. Thus, we tested 65 cultivars and 13 breeding lines for soft rot resistance after 6 months of storage. There was a significant effect of cultivar and production environment on soft rot resistance score. During 6 months of storage, tuber soft rot resistance in resistant clones did not change, while it changed in susceptible clones. The three most resistant cultivars to soft rot were Freedom Russet, Anett, and Alaska Red Eye.     

Comparison of sympatric freshwater turtle populations from an urbanized Sydney catchment

• 1. Australian freshwater turtles are widely distributed throughout the continent, and in each river catchment there are at least two taxa. In south‐eastern Australia Chelodina longicollis and forms of Emydura macquarii co‐habit within a waterway, although they have been shown to partition habitat within the water column in non‐urban bodies of water. Limited comparative data are available for the urban populations.
• 2. Within urban Sydney C. longicollis (eastern long‐necked turtle) and Emydura macquarii dharuk (Sydney short‐necked turtle) share habitat. However, in contrast with non‐urban studies of C. longicollis and other sympatric E. macquarii taxa, it was observed that the population profile of the two species was similar at all sites, and that C. longicollis were present in greater numbers than E. m. dharuk.
• 3. The continued degradation of preferred habitat, low recruitment, and potential competition from introduced turtles place both species in a precarious position.
• 4. The shallow, impounded waterways of the regulated urban bodies of water align more closely with the preferred habitat of C. longicollis than with that of forms of E. macquarii, which prefer deeper flowing waters or large wetlands adjacent to rivers. Emydura m. dharuk may be at greatest risk of extinction in urban areas.
• 5. Across urban Sydney, the low numbers of E. m. dharuk compared with C. longicollis may be due to the lack of mobility of E. m. dharuk such that individuals tend to be stranded in sub‐optimal habitat. In contrast, C. longicollis has a greater propensity for overland movement, and a preference for the ‘new habitat’ resulting from urban impacts on the associated waterways, and thus appears to be able to utilize these modified urban waters more successfully.

Copyright © 2008 John Wiley & Sons, Ltd.     

Chondrules with peculiar REE patterns: implications for solar nebular condensation at high C/O

Rare earth element (REE) data from two ordinary chondrite chondrules show distinct negative chondrite-normalized concentration anomalies of samarium, europium, and ytterbium. The peculiar patterns may be the result of REE gas/solid fractionation at an oxygen fugacity lower than has been assumed for the canonical solar nebula. We suggest that the two ordinary chondrite chondrules acquired the fractionated REE patterns by incorporation of highly reduced, ultrarefractory condensates in their precursors. This interpretation implies that high-temperature condensation processes occurred in nebular environments with a strong deficit in oxygen, such as regions with an enhanced carbon/oxygen ratio.     

A real-time PCR assay to detect the Panton Valentine Leukocidin toxin in staphylococci: screening Staphylococcus schleiferi subspecies coagulans strains from companion animals

Recent reports suggest that methicillin-resistant strains of Staphylococcus schleiferi subspecies coagulans are now commonly isolated from dogs. Given the association of a potentially mobile SCCmec type IV element with lysogenic phage-encoded Panton Valentine Leukocidin (PVL) toxin genes in community-acquired methicillin-resistant Staphylococcus aureus strains we hypothesized that methicillin-resistant S. schleiferi ssp. coagulans strains may also encode PVL toxin genes. Forty S. schleiferi ssp. coagulans strains isolated from companion animals were studied. Susceptibility to oxacillin was determined by broth microdilution and all isolates were screened by PCR for the presence of the mecA gene. SCCmec typing was performed on 14 isolates. A real-time PCR assay was developed for the detection of the PVL genes using a SmartCycler. Pulsed-field gel electrophoresis (PFGE) was performed to determine whether S. schleiferi ssp. coagulans strains were homogeneous. Twenty-eight of the 40 isolates (70%) were resistant to oxacillin and 26/28 possessed the mecA gene by PCR. SCCmec IV was identified in seven strains; the other seven isolates were not typable by this technique. All 40 strains were negative for the PVL toxin gene. PFGE showed a heterogeneous population and 13 different profiles were determined. In conclusion, this study showed that PVL toxin genes were not detected in a heterogeneous population of methicillin-resistant S. schleiferi ssp. coagulans strains isolated from companion animals.     

Relationships among milk urea-nitrogen, dietary parameters, and fecal nitrogen in commercial dairy herds

Our study objective was to determine the ability of milk urea-nitrogen concentrations ([MUN]) to predict fecal nitrogen concentrations ([Fecal N]) in commercial dairy herds. A total of 83 dairy herds were each visited 3 times within 48 h after a monthly herd milk test. For each farm visit, forages were sampled for nutrient analyses, which were entered into a computerized ration evaluator, and fecal samples were taken per rectum from each of 6 cows (2 early-, 2 mid-, and 2 late-lactation). Fecal samples were pooled, mixed, and analyzed for nitrogen content. Fecal nitrogen concentrations were compared with the routinely measured nutritional parameters from the ration evaluation, and the herd average [MUN] for the previous milk test date using mixed linear regression analyses. Total protein supplied in the ration was significantly positively associated with [Fecal N], but herd average [MUN] was not associated (P > 0.10) with [Fecal N].     

Considerations for selecting disease resistant wild germplasm (<Emphasis Type="Italic">Solanum</Emphasis> spp.): lessons from a case study of resistance to bacterial soft rot and Colorado potato beetle

Predictions of distributions of resistance phenotypes have been attempted for major diseases in wild potato germplasm. Interestingly, no consistent taxonomic or biogeographic predictors have been identified. However, an important lesson learned was that there are interactions among host plants, environmental factors, and characters of the pathogens. A logical extension of the predictivity project is to examine the dynamics of resistances when multiple biotic stresses are involved. In this study, we found that populations susceptible to a foliar feeding pest [Colorado potato beetle, Leptinotarsa decemlineata (Say)] are resistant to a bacterial pathogen [Pectobacterium carotovorum subsp. carotovorum (Jones, 1901; Hauben et al. 1999)]. We propose that wounds caused by the insect pest allow the bacterial pathogen to gain entry and cause disease. This would lead to strong selection pressure for resistance to the bacterial pathogen. Consequently, when searching for traits of interest in germplasm collections, it is important to consider the complex biotic and abiotic environments in which the source populations evolved.     

Putative transmission of Mycobacterium tuberculosis infection from a human to a dog

A 3.5-year-old Yorkshire Terrier was evaluated for anorexia and vomiting; infection with Mycobacterium tuberculosis was diagnosed by use of histology, bacteriologic culture, and polymerase chain reaction (PCR) assay on various tissues. The dog was living with a human with an established M. tuberculosis infection. Findings were unique in that diagnosis of M. tuberculosis infection was obtained via PCR techniques, and isolates from the owner and dog were matched via restriction fragment length polymorphism fingerprinting. Dogs infected with M. tuberculosis from humans are most commonly infected via the respiratory tract. Clinical signs in dogs are variable and depend on the integrity of the immune system and the degree of dissemination. Diagnosis can often be obtained through histopathology and bacteriologic culture; additional diagnostic techniques are also available. Treatment of a dog with confirmed M. tuberculosis infection is controversial, and at least 6 months of multidrug treatment is required.