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Biomedical subjects

R F Smith

Publications and source records attributed to R F Smith.

At least 217 records · Page 12Linked to original sources
PubMed1974

Evaluation of media for selective isolation of yeasts from oral, rectal, and burn wound specimens.

Six media were evaluated to determine their ability to isolate yeasts and inhibit bacteria. The media included the following: Snyder, Snyder tellurite, Sabouraud tellurite, Littman-gentamicin, molybdate, and Mycosel (BBL). Doses of mixed intestinal gram-negative bacilli and enterococci were most effectively inhibited by Snyder tellurite agar. Klebsiella pneumoniae was the most common bacterial contaminant of the other media. All six media were comparable in isolating yeasts while preventing the growth of the oral bacterial flora. The selection of a basal fungal growth medium for tellurite incorporation to inhibit bacteria but permit growth of yeasts was affected by pH. The bacteriostatic effect of tellurite was decreased with increasing pH of media while fungistatic action was increased. The arbitrary selection of Snyder and Littman agars to isolate yeast from burn wound cultures demonstrated the need to include a selective medium for these specimens. Blood, phenylethyl alcohol blood agar, and Columbia CN blood agar were all inadequate for isolating yeasts from burns. Growth of a variety of filamentous saprophytic and pathogenic dimorphic fungi grew adequately on four of five selective media tested.

Adult↗
PubMed1974

Sewage treatment by controlled eutrophication: bacterial study.

Several groups of bacteria were isolated and identified in an evaluation of the microbiological properties of a sewage treatment system involving the process of controlled eutrophication in a marine setting (J. G. Songer, N. M. Trieff, R. F. Smith, and D. Grajcer, 1974). Fecal coliforms, enterococci, Salmonellae, Shigellae, Vibrio parahaemolyticus, and Vibrio alginolyticus were studied at three stages of the treatment process. Significant reductions in fecal coliforms (P < 0.01) and enterococci (P < 0.01) were noted from raw sewage to effluent. Salmonellae and Shigellae were not detected at any stage, nor was V. parahaemolyticus. V. alginolyticus was isolated from the effluent only, reflecting the halophilic nature of the organism; low concentrations in raw sewage increased in the more saline effluent. Brine shrimp (Artemia salina), the herbivores in this system, were tested and found to have extremely low numbers of the organisms under study associated with them. Findings point further toward the use of this system as a combined mariculture-sewage treatment facility.

Analysis of Variance↗
PubMed1974

Topography of the food-reinforced key peck and the source of 30-millisecond interresponse times.

High-speed photography of key pecking revealed that the arc described by the upper bill as a pigeon closes its beak is capable of operating a Lehigh Valley pigeon key set at 8 to 14 g. Arc-produced switch closure follows initial switch closure in less than 50 msec. When birds were trained on ratio schedules, the probability of interresponse times (IRTs) shorter than 50 msec exceeded 0.30. Interval-trained birds produced a much lower probability of short-IRTs. When the schedules were reversed, there was only weak evidence of a reversal in the probability of short IRTs. A temporal analysis of topographic features observed in the original photographs failed to reveal differences between ratio and interval pecking topography. It appeared that only the point of contact with the key differed between subjects trained on the two schedules. It was concluded that only the locus, but not the topography, of the food-reinforced key peck was modified by the schedule of reinforcement.

Journal Article↗
PubMed1973

Characterization of Staphylococcus aureus in a pediatric burn unit.

A one-year study on an endemic strain of Staphylococcus aureus phage type 84/85 in a children's burn unit is described. The endemic strain rapidly colonized the burns and nares of acute patients after admission but was not isolated from a patient on admission. Nonendemic strains of S. aureus found on some new patients were mostly non-phage typable and did not prevail in burns. The endemic strain was rarely isolated from the nares and skin of reconstructive patients or from the nares of hospital personnel. The endemic strain did colonize the oral cavity, normal skin, and intestinal tract of some acute patients. Endemic and nonendemic strains of S. aureus from the burned children were compared in their biochemical activities and antibiotic sensitivities to two groups of S. aureus from one other local and one Danish burns unit. The latter groups of strains represented different combinations of staphylococcal phage group III strains. Each of the four groups of strains differed in production of hemolysins, Tween 80 hydrolysis, egg yolk reaction, and proteolysis of casein and gelatin. All of the strains were uniformly sensitive to gentamicin, oxacillin, and cephalothin. Only 4 of 162 strains tested were methicillin resistant. The endemic S. aureus strains of phage type 84/85 were uniformly resistant to eight other antibiotics including lincomycin and clindamycin. The endemic strain was not the known cause of a clinically documented infection in a group of 82 acute patients studied. The possible role of S. aureus strains of phage group III in burn grafting problems is discussed.

Adolescent↗
PubMed1973

Rapid detection of gram-negative bacteriuria by use of the Limulus endotoxin assay.

The Limulus in vitro endotoxin assay was evaluated as a possible method for the prompt detection of significant gram-negative bacteriuria in children. This assay is capable of detecting endotoxin associated with intact cell walls of viable gram-negative bacteria as well as free endotoxin. Quantitative results are obtained following a 1-h incubation of Limulus lysate and 10-fold dilutions of otherwise untreated urine. A standard curve of Limulus activity and viable cell counts of Escherichia coli and Klebsiella pneumoniae in urine demonstrated that a positive Limulus reaction at a dilution of 1:100 or 1:1,000 indicated a colony count of at least 100,000 bacteria/ml. A positive Limulus reaction only from undiluted urine or at a dilution of 1:10 indicated less than 100,000 cells/ml. These experimental observations were confirmed by comparing the Limulus test with quantitative plate counts on 209 urine specimens from a mixed pediatric population. These results indicate that the Limulus assay is a simple, accurate method for rapid presumptive detection of gram-negative bacteriuria in patients where an immediate diagnosis is needed. This test would also seem promising for screening large patient populations for bacteriuria or for monitoring the effectiveness of treatment of urinary tract infections.

Adolescent↗
PubMed1973

Preparation, sensitivity, and specificity of Limulus lysate for endotoxin assay.

Limulus amoebocyte lysate was prepared from a total of 180 crabs during 1971 and 1972 by using a slightly modified lysate preparation procedure. Marked variability of lysate potency was noted both years. In addition, lysate quality appeared diminished in 1972 as compared with 1971. Different lysate batches were evaluated for potency by using a variety of endotoxin preparations. Variations in batch potencies were observed, but little variation in reactivity among different endotoxin preparations was noted. Use of potent lysate batches allowed detection of endotoxin concentrations as low as 100 pg/ml. No endotoxinlike activity was observed from 11 different strains of yeast by use of the Limulus assay.

Animals↗