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Biomedical subjects

R L Walker

Publications and source records attributed to R L Walker.

At least 91 records · Page 5Linked to original sources
PubMed1970

Relationship between atmospheric temperature and survival of airborne bacteria.

Effects of temperatures ranging from -40 to 49 C on the behavior of airborne Serratia marcescens, Escherichia coli, and Bacillus subtilis var. niger were investigated. Aerosol decay rates of B. subtilis spores were not significantly affected by the temperature and remained approximately constant within the temperature range studied. The survival of airborne S. marcescens and E. coli was closely related to the temperature. An increase in temperature from -18 to 49 C resulted in a progressive increase of the biological death rate, and the relationship between the biological death rate and the temperature appeared to be linear. An increase in temperature from 24 to 49 C resulted in significantly reduced aerosol recoveries of the two vegetative organisms. At -40 C, the aerosol recovery of all three agents was consistently lower than at -18 to 24 C.

Aerosols↗
PubMed1970

Effects of atmospheric humidity and temperature on the survival of airborne Flavobacterium.

The survival of airborne Flavobacterium sp. in particle sizes ranging from 1 to 5 mum was significantly influenced by atmospheric temperature. A progressive increase in temperature from -18 to 49 C resulted in increases in death rates of the airborne organism. The lowest death rates were observed in the temperature range of -40 to -18 C, and the highest death rates were observed in the 29 to 49 C range. At 24 C, the survival of airborne Flavobacterium did not appear to be significantly affected by relative humidity ranging from 25 to 99%.

Air Microbiology↗
PubMedDate not supplied

Effects of walking on ventilatory and cardiac function in intact and cardiac-impaired lobsters.

Decapod crustaceans with normal heart function respond to the increased oxygen delivery requirements during walking with a step increase in heart and ventilation rate. In American lobsters, ventilation rate increased by the same amount during exercise at two walking speeds (2.4 and 8 m min(-1)); however, ventilation volume was significantly greater at the fastest walking speed (280 mL min(-1)) compared to animals at rest or walking at the slower speed (180 mL min(-1)). The heart responded in a similar manner to locomotion. Heart rate was elevated to the same level at the two different walking speeds, but cardiac stroke volume was greater, implying increased cardiac output, at the faster walking speed. The communication and compensation between the cardiac and ventilatory systems was revealed when the function of one was impaired. Ventilatory rate was significantly elevated when cardiac output was impaired by sectioning two of the alary ligaments and/or the regulatory nerves to the heart. When cardiac output was more severely impaired, ventilation rate was greater. Despite ventilatory compensation, anaerobic metabolism made a greater contribution to energy production with impaired heart function. Hemolymph lactate concentration was three to five times greater in impaired animals than controls. It is known that the ventilatory and cardiac systems of lobsters are coregulated. These data demonstrate that the performance of one system can respond to compensate for impaired function in the other.

Animals↗
PubMedDate not supplied

Comparison of three skin preparation techniques in the dog. Part 1: Experimental trial.

Premeasured, clipped areas of skin on both sides of 30 adult dogs were prepared with povidone-iodine (PI), chlorhexidine gluconate (CG) with a saline rinse, or 4% CG with a 70% isopropyl alcohol rinse. Skin bacteria were quantified with Replicating Organism Detection and Counting (RODAC) plates and cultured for identification before, immediately after, and 1 hour after skin preparation. The percentages of bacterial reduction immediately and at hour 1 and the percentages of negative cultures, cultures with more than five colony-forming units (CFUs), and skin reactions were analyzed by analysis of variance and chi-square. The percentage of reduction in skin bacteria for all techniques was significant and comparable with that reported in humans. There were no significant differences between PI and CG results except that acute contact dermatitis was observed more frequently after skin preparation with PI. The authors conclude that for similar application times, PI and 4% CG rinsed with saline or 70% isopropyl alcohol are equally effective for up to 1 hour in the preoperative skin preparation of dogs.

1-Propanol↗
PubMedDate not supplied

Comparison of three skin preparation techniques. Part 2: Clinical trial in 100 dogs.

The skin of 100 dogs undergoing clean or clean-contaminated surgical procedures was prepared with povidone-iodine (PI) or 4% chlorhexidine gluconate (CG) with saline or 70% isopropyl alcohol rinse. Skin bacteria at the incision site were quantified with Replication Organism Detection and Counting (RODAC) plates immediately before and after skin preparation in the preparation room, in the operating room, and postoperatively. The percentage of bacterial reduction, negative cultures, cultures with more than five colony-forming units, and skin reactions for each technique were calculated for each sample period and analyzed with the analysis of variance and Fischer tests. The percentage of bacterial reduction for all techniques was significant and comparable with results of a previous experimental study. There were no significant differences in percentages of bacterial reduction between PI and the CG techniques for surgical times up to 8 hours. There were fewer negative cultures and more cultures with high bacterial counts with PI than with CG and saline after the cleansing scrub. There were fewer negative cultures after surgery with CG and alcohol than with the other two techniques. Duration of the surgical procedure did not significantly affect the culture results. Significantly more skin reactions occurred with PI. The authors conclude that PI and 4% CG with a saline rinse are equally effective in antimicrobial efficacy under clinical conditions. However, 4% CG with a 70% isopropyl alcohol rinse may be inferior in residual antimicrobial activity.

1-Propanol↗
PubMedDate not supplied

Comparison of an antimicrobial adhesive drape and povidone-iodine preoperative skin preparation in dogs.

The antimicrobial efficacy of an adhesive drape applied after a 1-minute alcohol scrub was compared to a povidone-iodine (PI) skin preparation technique in dogs. Each technique was applied to both sides of 15 adult anesthetized dogs on premeasured, clipped areas of skin. Skin bacteria were quantified before, immediately after, and 1 hour after skin preparation. Predominant skin bacteria were isolated by swabbing the skin. The percentages of bacterial reduction immediately after and 1 hour after skin preparation, percentages of negative culture results, cultures with more than five colony-forming units, and the frequency of skin reactions were calculated and analyzed statistically. Drape adhesion was assessed subjectively. The percentage reduction in skin bacteria was significant for both techniques and comparable to that reported in humans. The adhesive drape was significantly less effective in both the immediate and 1-hour periods. Lift occurred in 66% of drape applications but was not associated with high bacterial counts. Acute contact dermatitis was more frequent after skin preparation with PI. There was no difference between the techniques in recovery of potential skin pathogens. The authors conclude that application of this antimicrobial adhesive drape after a 1-minute alcohol scrub is not as effective in the reduction of skin bacteria in dogs as is PI preparation of the skin.

Adhesives↗
PubMedDate not supplied

Selecting a physician executive.

Selecting a physician executive can be a complex task. The process is complicated by the explosive demand for qualified physician executives. Although the number of physician managers has grown since 1979, the demand still outstrips the supply of physicians with track records. Also, many organizations have never had a full-time person serving in the capacity of Medical Director or Vice President of Medical Affairs, so the process of recruiting this person is new to them.

Personnel Management↗
PubMedDate not supplied

An atypical strain of Pasteurella gallinarum: pathogenic, phenotypic, and genotypic characteristics.

The pathogenicity of a strain of Pasteurella gallinarum isolated in Fresno County, Calif., was compared with the American Type Culture Collection (ATCC) strain. Broiler chickens were inoculated intranasally with 10(7) colony-forming units (CFU) and intramuscularly with 10(5) CFU of each strain. The only notable lesions were in chickens inoculated intramuscularly with 10(5) CFU of the Fresno strain, which developed severe myositis at the inoculation site, pericarditis, perihepatitis, airsacculitis, and synovitis. P. gallinarum was reisolated from these lesions. Phenotypic characteristics of the two strains were identical except in reactions in ONPG broth and fermentation of xylose. Protein-banding patterns for the two strains were identical except for a single band difference in the 35-kilodalton region. Restriction endonuclease analysis confirmed that the Fresno strain was a distinct one. Plasmid analysis revealed that the ATCC strain had two plasmids and the Fresno strain had none.

Animals↗
PubMedDate not supplied

Severe mortality in broiler chickens associated with Mycoplasma synoviae and Pasteurella gallinarum.

Severe economic loss due to high mortality and condemnation rates occurred on two commercial broiler facilities. Chickens had moderate-to-severe airsacculitis, pericarditis, perihepatitis, tracheitis, and synovitis. Pasteurella gallinarum was isolated from 16 of 18 pericardia, four of 14 livers, 11 of 16 air sacs, six of seven joints and one of 28 tracheas in pure culture. In addition, Mycoplasma synoviae was isolated from trachea and air sac. Lesions were suggestive of an Escherichia coli septicemia, but E. coli was isolated from only four of 28 tracheas and one of 14 livers in pure culture. A coronavirus was isolated from trachea and lung. Whether this coronavirus represented a vaccine or field strain of infectious bronchitis was not determined. These findings suggested that the severe lesions were due to a concomitant infection with an atypical strain of P. gallinarum.

Animals↗
PubMedDate not supplied

Favus in a backyard flock of game chickens.

Favus, or avian ringworm, was diagnosed in a backyard flock of game chickens from which Microsporum gallinae was isolated. Infected birds had white crusts on the comb and on the skin of the head and neck. Histopathological lesions included hyperkeratosis of the skin epithelium with invasion of the stratum corneum by fungal mycelia, acanthosis, acantholysis, and hydropic degeneration of cells in the stratum spinosum. The underlying dermis was infiltrated by mononuclear cells and contained lymphoid foci. Daily topical treatment with miconazole was applied in the field and in the laboratory, with apparent success.

Administration, Topical↗
PubMedDate not supplied

Diagnosis of favus (avian dermatophytosis) in Oriental breed chickens.

Chickens of various Oriental breeds (Shamo and Aseel) and crossbreeds in California's Central Valley were observed to have an unusual skin condition and feather loss. The appearance of white plaques on the comb, face, and/or ear lobes was followed by feather loss starting at the caudal base of the comb and progressing down the neck. Although the cocks were affected first, the condition spread to the hens paired with those cocks. The birds showed no other signs of illness. The affected areas were scraped and biopsied. The samples were examined histologically and by culturing on Sabouraud's dextrose agar and dermatophyte test medium. Microsporum gallinae, the causative agent of favus (avian dermatophytosis), was identified by the histological and mycological tests.

Animals↗