Biomedical subjects

David L Johnson

Publications and source records attributed to David L Johnson.

22 records · Page 2Linked to original sources

PubMed2002

Efficacy of extended pirlimycin hydrochloride therapy for treatment of environmental Streptococcus spp and Staphylococcus aureus intramammary infections in lactating dairy cows.

Fifty-one chronically infected lactating dairy cows were used to evaluate the efficacy of extended pirlimycin therapy regimens for treatment of intramammary infections by environmental Streptococcus spp and Staphylococcus aureus. Cows (n = 47) with one or more infected mammary quarters were blocked by parity and randomly allocated to one of three groups for treatment with pirlimycin (50 mg/mammary quarter) as follows: one treatment per day for 2 days (n = 36 infected mammary quarters); one treatment per day for 5 days (n = 36 infected mammary quarters); and one treatment per day for 8 days (n = 20 infected mammary quarters). Four cows with nine infected mammary quarters were included as untreated controls. Milk samples from each mammary quarter were collected 7 days before treatment, immediately before treatment, and weekly for 4 weeks after the final treatment for microbiological evaluation. A bacteriologic cure was defined as a treated, infected quarter that was bacteriologically negative for the presence of previously identified bacteria at weekly intervals after treatment. Efficacy of pirlimycin therapy against intramammary infections caused by environmental Streptococcus spp and S. aureus was 44.4%, 61.1%, and 95.0% for the 2-, 5-, and 8-day treatment regimens, respectively. None of the infections in the untreated control quarters was cured. Significant differences in efficacy were detected between all pirlimycin groups and the untreated control group, between the 8- and 2-day treatment regimens, and between the 8-day and 5-day treatment regimens (P < or = .05). Results of this study indicate that extended pirlimycin therapy was effective in eliminating intramammary infections caused by environmental streptococci and S. aureus in lactating dairy cows.

Animals↗

PubMedDate not supplied

Replication of human tracheobronchial hollow airway models using a selective laser sintering rapid prototyping technique.

Exposures to toxic or pathogenic aerosols are known to produce adverse health effects. The nature and severity of these effects often are governed in large part by the location and amount of aerosol deposition within the respiratory tract. Morphologically detailed replica hollow lung airway casts are widely used in aerosol deposition research; however, techniques are not currently available that allow replicate deposition studies in identical morphologically detailed casts produced from a common reference anatomy. This project developed a technique for the precision manufacture of morphologically detailed human tracheobronchial airway models based on high-resolution anatomical imaging data. Detailed physical models were produced using the selective laser sintering (SLS) rapid prototyping process. Input to the SLS process was a three-dimensional computer model developed by boundary-based two-dimension to three-dimension conversion of anatomical images from the original National Institutes of Health/National Library of Medicine Visible Human male data set. The SLS process produced identical replicate models that corresponded exactly to the anatomical section images, within the limits of the measurement. At least five airway generations were achievable, corresponding to airways less than 2 mm in diameter. It is anticipated that rapid prototyping manufacture of respiratory tract structures based on reference anatomies such as the Visible Male and Visible Female may provide "gold standard" models for inhaled aerosol deposition studies. Adaptations of the models to represent various disease states may be readily achieved, thereby promoting exploration of pharmaceutical research on targeted drug delivery via inhaled aerosols.

Aerosols↗

PubMedDate not supplied

UV disinfection of soluble oil metalworking fluids.

The efficacy of a new high-intensity germicidal ultraviolet (UV) lamp for disinfection of opaque metalworking fluids (MWF) was investigated under laboratory conditions. Three dilutions of "soluble oil" MWF and water controls in a circulating system were inoculated with suspensions of Pseudomonas fluorescens to an initial concentration of about 10(7) colony forming units (CFU) per milliliter and irradiated with a submerged nonglass UV lamp. Aliquots of the circulating fluid were withdrawn before irradiation and at 10-sec intervals in the water control and 10-min intervals in the MWF. The samples were diluted with sterile water, plated, and counted after 18-24 hours' incubation. The UV-C radiation output of the lamp was estimated by irradiance measurements using a research radiometer. The concentration of CFU decreased by at least 2 logs (>99% reduction in culturability) in 30 sec in irradiated water. In all three dilutions of MWF, a 2-log decrease was obtained within 60 min. The UV-C output of the lamp was estimated at about 6 W. The disinfection appeared to follow a first order rate law both in MWF and in water. The CFU concentration was stable over time in unirradiated controls. These results demonstrate that UV disinfection is feasible in MWF opaque to both visible and UV wavelengths of light.

Aerosols↗

PubMedDate not supplied

Self-assessment in the measurement of public health workforce preparedness for bioterrorism or other public health disasters.

OBJECTIVE: The purpose of this study was to examine effective ways to evaluate public health workers' competence for preparedness. METHODS: The Public Health Ready project, developed by the National Association of County and City Public Health Officials and the Centers for Disease Control and Prevention, is a pilot program designed to prepare local public health agencies to respond to emergency events. Workers at a Public Health Ready site (N=265) rated their need for training and their competence in meeting generic emergency response goals. Cluster analysis of cases was conducted on the self-assessed need for training. RESULTS: Three groups of workers emerged, differing in their overall ratings of need for training. A given worker tended to report similar needs for training across all training goals. CONCLUSIONS: In this study, workers' ratings of need for training may reflect an overall interest in training rather than need for training in a particular area. Caution should be exercised in interpretation when generic goals and self-assessment are used to measure need for training. Future assessments of training needs may be more effective if they use objective measures of specific local plans.

Attitude of Health Personnel↗