Biomedical Engineering Reference
In-Depth Information
Salmonella
and
Shigella
by integrating several of these above-mentioned technologies like,
MEMS [114
-
116], SAMS [113], DNA hybridization, and enzyme amplification. They have
succeeded in detecting
Salmonella
and
Shigella
concentration of 1000 cells/ml. But the great-
est disadvantage of this method is that the combination of several technologies makes it a
multistep, rigorous analysis. The preparation of the MEMS detector array has to be done in
specially equipped laboratory and by skilled personnel. Even though the analysis time is 40
min, the preparation time required for the MEMS and SAMS is time-consuming. The
analyte cannot be used for direct detection. Only samples from the culture media of the
analyte can be used, thus reducing the chances for the developed prototype to be used for
field-testing. The developed prototype can only detect
Salmonella
and
Shigella
concentration
of 1000 cells/ml. Lower concentrations of
Salmonella
and
Shigella
cannot be detected.
21.2.10.1 Potential Markets for Biosensors
Clinical or Medical
: Metabolite analysis (glucose, cholesterol, enzymes, and triglyceride);
drug analysis (salicylate, digoxin, paracetamol, and theophyline); hormone, bacterial, and
viral analysis.
Industrial
: Food and drug processing, quality control, cosmetics testing, and fermentation
.
Security or Defense:
Detection of harmful chemical and biological agents including explo-
sives, nerve gases, pathogenic bacteria, and virus.
Bioterrorism:
A review [117-119] considered the role of biosensors toward the detection
of pathogenic bacteria. There is a recent heightened interest in developing rapid and reli-
able methods of detection especially where bioterrorism is concerned. In addition, biosen-
sors can be used in food poisoning and clinical problems such as antibiotic resistance.
Several different types of transduction modes can be used in high-frequency (surface
acoustic wave) and optical detection. There are three systems that may make a great
impact in the next few years: integrated (lab-on-a-chip) systems, molecular beacons, and
aptamers [117-121]
.
Rapid detection could be achieved if the bacteria are purified before detection. When
purified from the sample matrix, specific advantages of bacterial concentration may
include facilitating the detection of different bacterial strains; removal of any inhibitor in
the matrix; and insurance of adequately reduced sample size to represent food-sample
sizes and small media volumes. Lower levels of pathogenic detection can be obtained
through concentration and elimination of cultural enrichment prior to detection. Of all
concentration methods that have been reported, including centrifugation, filtration, and
immunomagnetic separation, none is ideal for one food system. Sample enrichment and
separation of bacterial cells from food samples during sampling is a major problem in the
advancement of molecular methods for the detection of foodborne pathogens.
A detailed understanding is provided in the review of the possibilities and limitations
of separating and concentrating bacterial cells from the food matrix in an effort to advance
the ability to harness molecular methods for the rapid detection of foodborne pathogens
[117-121]
.
Agriculture and Veterinary:
Diagnosis of plant and animal diseases and chemical mon-
itoring.
Environmental:
Detection of hazardous chemical in air, water, and soil and detection of
personal contamination [122,123].
Obtaining results from traditional methods for detection and enumeration of bacteria in
water samples (or any media) requires several days. Several new techniques that reduce
the time of analysis have been developed. This chapter describes ways to test a rapid
detection and enumeration of total viable bacteria using direct fluorescent labeling and
detection by laser scanning. This method (TVC or total viable count) was compared to a
