Exploring the Correlation of Dynamic Surface Tension with Antimicrobial Activities of Quaternary Ammonium-Based Disinfectants.

Quaternary ammonium compound (QAC) disinfectants represent one of our first lines of defense against pathogens. Their inhibitory and bactericidal activities are usually tested through minimum inhibitory concentration (MIC) and time-kill assays, but these assays can become cumbersome when screening many compounds. We investigated how the dynamic surface tension (DST) measurements of QACs correlate with these antimicrobial activities by testing a panel of potent and structurally varied QACs against the gram-positive Staphylococcus aureus and the gram-negative Pseudomonas aeruginosa. We found that DST values correlated well with bactericidal activity in real-world disinfection conditions but not with MIC values. Moreover, no correlation between these two antimicrobial activities of QACs (bactericidal and inhibition) was observed. In addition, we observed that the bactericidal activity of our QAC panel against the gram-negative P. aeruginosa was severely affected in the presence of hard water. Interestingly, we found that the counterion of the QAC affects the killing of bacteria in these conditions, a phenomenon not observed in most MIC assessments. Moreover, some of our best-in-class QACs show enhanced bactericidal activity when combined with a commercially available QAC. In conclusion, we determined that an intrinsic physical property of QACs (DST) can be used as a technique to screen for bactericidal activity of QACs in conditions that mimic real-world disinfection conditions.

Economic returns and the perceived obstacles to adopting active management in the forest-grassland transition ecoregion in south-central USA.

Forest-grassland ecotones are a mosaic of grassland, savanna, and upland forest. As such, landowners may have opportunities to choose to manage their lands for multiple objectives. We estimated the economic returns from managing forest and rangeland in southeastern Oklahoma, USA to produce different combinations of timber, cattle forage, and white-tailed deer (Odocoileus virginianus Zimmermann) browse for a 40-year period. We further conducted a survey to understand landowner perceptions of obstacles to adopting active management that involve timber harvest and prescribed fire. The highest net return was obtained from the treatment with harvested timber that was burned every four years (uneven-aged woodland/forest) because it had the greatest gross return from a combination of timber (46%), cattle forage (42%), and deer browse (11%). The return from this treatment was greater than that for managed for timber only (closed-canopy forest) or prioritizing cattle and deer (savanna). Survey results suggested that landowners were aware of the benefits of active management but that the majority (66%) considered cost a major obstacle in the management of their forest or rangeland. In particular, women forestland owners and older landowners considered cost an obstacle. Our findings advocate integrated timber, cattle, and deer management as the best economic strategy within the forest-grassland ecotone and for targeted outreach and landowner education related to the benefits of active management.

Development of a grassland integrity index based on breeding bird assemblages.

We utilized landscape and breeding bird assemblage data from three Breeding Bird Survey (BBS) routes sampled from 1965-1995 to develop and test a grassland integrity index (GII) in a mixed-grass prairie area of Oklahoma. The overall study region is extensively fragmented from long-term agricultural activity, and native habitat remnants have been degraded by recent encroachment of woody vegetation, namely eastern red cedar (Juniperus virginiana L.). The 50 individual bird survey points along the BBS routes, known as stops, were used as sample sites. Our process first focused on developing a grassland disturbance index (GDI) as a measure of cumulative landscape disturbances for these sites. The GDI was based on five key landscape variables identified in an earlier species-level study of long-term avian community dynamics: total tree, shrub, and herbaceous vegetation cover indices, overall mean landscape patch size, and grassland patch core size. The GII was then developed based on breeding bird assemblage data. Assemblages were based on commonly used response guilds reflective of five avian life history parameters: foraging mode/location, nesting location, habitat specificity, migratory pattern, and dietary guild. We tested the response of 78 candidate assemblage metrics to the GDI, and eliminated those with no or poor response or with high correlations (redundant), resulting in 13 metrics for use in the final index. Individual metric scores were scaled to fall between 0 and 10, and the cumulative index to range from 0 to 100. Although broader application and refinement are possible, the avian-based GII has an advantage over labor-intensive, habitat-based monitoring in that the GII is derived from readily available long-term BBS data. Therefore, the GII shows promise as an inexpensive tool that could easily be applied over other areas to monitor changes in regional grassland conditions.

Immune function and hematology of male cotton rats (Sigmodon hispidus) in response to food supplementation and methionine.

We examined effects of supplementation of food quantity and quality (=enhanced methionine) on hematologic and immunologic parameters of wild, but enclosed, adult male cotton rats (Sigmodon hispidus) in north-central Oklahoma. Sheet metal enclosures were stocked with a high density of wild-caught cotton rats (160 animals/ha) and randomly assigned a treatment of no supplementation, mixed-ration supplementation or methionine-enhanced supplementation. Aside from small increases in counts of red blood cells and hematocrit levels, most indices of erythrocytic characteristics were not affected by supplementation with the mixed-ration or enhanced methionine. In contrast, platelet counts were highest in mixed-ration and methionine treatments and counts of total white blood cells were highest with methionine supplementation, albeit relative proportions of different leukocytes did not differ among treatments. Immunologically, neither delayed-type hypersensitivity response nor hemolytic-complement activity differed among treatments. Supplementation of food quantity and quality did not broadly affect hematologic parameters and immune function of male cotton rats, but enhanced platelet and leukocyte counts may confer advantages to overall health. Clarification of the role of such effects on population limitation or regulation requires additional research.