Biomedical subjects

S W Dufour

Publications and source records attributed to S W Dufour.

3 recordsLinked to original sources

PubMed1978

Electrical impedance measurements: rapid method for detecting and monitoring microorganisms.

A conceptually simple and east-to-use technique is described that uses continuous impedance measurements for automated monitoring of microbial growth and metabolism. The method has been applied to a wide range of microorganisms. Optical clarity is not required. The sensitivity and reproducibility of the method are demonstrated. The mechanism whereby microbial growth alters the impedance of the medium is discussed, as well as potential applications of the method to clinical microbiology.

Aspergillus niger↗

PubMed1978

Impedimetric screening for bacteriuria.

A rapid, automated instrumental procedure for distinguishing urine cultures containing greater than 10(5) organism per ml is described. The method is based upon the measurement of changes in impedance that take place as microorganisms alter the chemical composition of the medium. The time required to detect impedance change is inversely related to the initial concentration of microorganisms in the sample. By defining an impedance-positive culture as one that gives detectable impedance change within 2.6 h, 95.8% of 1,133 urine cultures tested were correctly classified as containing more than or fewer than 10(5) organisms per ml. Selection of a longer detection time decreases false negative results at the cost of increased false positive results. Impedance screening is compared with screening data reported in the literature using adenosine-5'-triphosphate detection, microcalorimetry, electrochemical measurements, and optical microscopy.

Bacteriological Techniques↗

PubMed1977

Rapid detection of microbial contamination in frozen vegetables by automated impedance measurements.

Automated impedance measurements can be used to rapidly assess whether a sample of frozen vegetables contains greater or less than 10(5) organisms per g. Microorganisms growing pureed food samples cause a change in the impedance of the medium when the organisms reach a threshold concentration of between 10(6) and 10(7) organisms per ml. Estimates of the concentration of microorganisms initially present in the food sample can be made by recording the time required for the organisms in the sample to replicate to threshold levels. In this study, the detection times for 357 samples of frozen vegetables were compared with standard plate counts for each sample. The agreement between the two methods in distinguishing samples containing more than 10(5) organisms per g was 92.6% for 257 assorted frozen vegetables and somewhat higher (93 to 96%) when separate cutoff times were used for each type of vegetable. The time required for analysis was about 5 h, compared to the 48 to 72 h required for standard plate counts.

Bacteria↗