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R Smither

Publications and source records attributed to R Smither.

7 recordsLinked to original sources
PubMed1980

Antibiotic residues in meat in the United Kingdom; an assessment of specific tests to detect and identify antibiotic residues.

Investigations were conducted between 1977 and 1979 to assess the performance of microbiological tests for detecting and identifying residues of therapeutic-type antibacterial substances in meat and offal. Of the 5442 home-produced meat samples examined, 34 (0.63%) showed inhibitory activity in the screening test, which used Bacillus subtilis BGA and Micrococcus luteus as indicator organisms. Identification by electrophoretic and thin-layer chromatography/bio-autography techniques confirmed that only two of the 34 screen failures were due to true antibacterial residues: a pig sample contained a trace of penicillin and a horse sample contained a trace of an incompletely identified substance resembling a tetracycline. Twelve of the other 32 failures in the screen test were due to naturally produced inhibition and were, thus, falsely positive, whilst the remainder were shown to be negative. All of the 85 (8.7%) screen test failures from the 972 imported meat and offal samples tested were falsely positive. Additional samples from certain animals known to have been given antibiotic treatment were tested concurrently to give a more searching indication of screen and identification test efficacy.

Animals↗
PubMed1977

Rapid screening for significant bacteriuria using a Coulter Counter.

A Coulter Counter was evaluated for detecting significant bacteriuria. Simple urinary particle counts showed agreement in 883 of the 956 (92.4%) urine specimens examined compared to a standard culture procedure. They also provided a semiquantitative estimate of bacterial numbers in specimens diagnosed as infected by culture. Sample preparation before counting was minimal, and results were obtained within two to four minutes.

Bacteriological Techniques↗
PubMedDate not supplied

Antibiotic identification by high voltage electrophoresis bioautography.

The high voltage electrophoresis bioautography method is applicable to meat, milk, and animal feeds. Meat is freeze-dried, powdered, and extracted with acetonitrile-water (9 + 1), and the extract is concentrated by evaporation at room temperature. Milk is examined directly or following acetonitrile-water extraction. Feed is extracted with acetonitrile-water. Samples or extracts are applied to preliminary assay plates of antibiotic medium No. 1 at pH 6 and 8, seeded with Micrococcus luteus (ATCC 9341), M. luteus DHSR (ATCC 9341A), Bacillus cereus (ATCC 11778), or B. cereus K250 TR (NCIB 11183), and nutrient agar at pH 7 seeded with B. subtilis BGA. Inactivation of penicillinase indicates beta-lactam antibiotics. Addition of trimethoprim increases sensitivity to sulfonamides. After 18-24 h incubation at 30 degrees C, plates yielding clear inhibition zones guide selection of conditions for subsequent electrophoresis bioautography. Extracts are applied (5-100 microL) to 10 mm diameter wells on electrophoresis plates 60 cm long and 40 cm wide, with a gel depth of 1.6 mm. The support medium is 1% agar and 1% agarose in Tris/succinic acid buffers pH 6 and pH 8. A potential of 1500 V is applied for 1.5 h at 15 degrees C. Following electrophoresis, the migrated antibiotics are visualized by over-layering with antibiotic medium No. 1, pH 6 or 8, seeded with M. luteus or B. cereus spore suspension; plates are incubated for 18-24 h at 30 degrees C. Identification is based on results of preliminary screening together with electrophoretic migration distances and inhibition zone appearances compared with standards.

Animal Feed↗