developed single-analyte sandwich immunoassays for the detection of Salmonella
enterica serovar Typhimurium, with a detection limit of 10
4 CFU/ml; the limit of
detection was improved ten-fold by lengthening the assay protocol to 1 h. S. enterica
serovar Typhimurium was also detected in the following spiked foodstuffs, with
minimal sample preparation: sausage, cantaloupe, whole liquid egg, alfalfa sprouts,
and chicken carcass rinse. To determine its efficacy as a screening tool for the
diagnosis of asymptomatic Salmonella infection of poultry, chicken samples were
tested and the limit of detection of pathogen was 10
3 CFU/g. The most commonly
used immunoassays for the detection of the pathogen are based on the use of whole
cells, or heat killed (Silbernagel et al. 2005), or formalin fixed (Solve et al. 2000),
and then detected by an ELISA. Feldstine et al. (1997) developed an immunoprecipitation method that made use of heat killed L. monocytogenes cells to detect
contamination between 0.003 and 11 cfu/ml of food samples. An enzyme-linked
immunosorbent assay (ELISA) for Clostridium botulinum type A and type B toxins
was assessed for diagnostic accuracy in cases of infant botulism. Botulism is a
serious food-borne neuroparalytic disease, caused by botulinum neurotoxin
(BoNT), produced by the anaerobic bacterium Clostridium botulinum. Stanker
et al. (2013) developed serotype B-specific monoclonal antibodies for sandwich
(capture) ELISA antibodies ranging from 10 to 48 Â 10
À11 M. Assay performance
for all possible combinations of capture–detector antibody pairs was evaluated, and
the antibody pair resulting in the lowest level of detection (L.O.D.) ~20 pg/mL was
determined.
9.2.3 Laser-Induced Breakdown Spectroscopy
Laser-induced breakdown spectroscopy (LIBS) has a flexible and convenient technique for rapidly determining the elemental composition of samples with minimal or
no sample preparation. This technique is used to analyze the spectral emission from
laser-induced plasmas, the plasma emission intensity being proportional to the
abundance of an element in the sample. The relative simplicity and capability of
fast multielemental analyses of solid, liquid, or gaseous samples make LIBS an ideal
tool to study a wide range of samples. Although the use of LIBS has been most
popular in metallurgical and biological samples, in recent years, it has been used to
study environmental and biological samples. Yu et al. (2010) separated a variety of
bacteria by detecting the trace mineral elements contained in five different types of
bacteria that were grown in the same nutrient liquid, among them are four Gramnegative species (Acinetobacter baylyi, Erwinia chrysanthemi, Escherichia coli, and
Shewanella oneidensis) and one Gram-positive bacterium (Bacillus subtilis). In the
next round of this work, they evaluated the performance of LIBS for both sensitive
detection of mineral trace elements in fresh vegetables and highly spatially resolved
measurements of the amounts. Rosalie et al. (2010) described the use of LIBS to
differentiate live pathogens and killed viruses on substrates. They differentiat the
live pathogens B. anthracis Stern strain and F. tularensis live vaccine strain colonies
on agar and demonstrate that it was found possible to differentiate between a
196
S. Purwar and S. Srivastava
enterica serovar Typhimurium, with a detection limit of 10
4 CFU/ml; the limit of
detection was improved ten-fold by lengthening the assay protocol to 1 h. S. enterica
serovar Typhimurium was also detected in the following spiked foodstuffs, with
minimal sample preparation: sausage, cantaloupe, whole liquid egg, alfalfa sprouts,
and chicken carcass rinse. To determine its efficacy as a screening tool for the
diagnosis of asymptomatic Salmonella infection of poultry, chicken samples were
tested and the limit of detection of pathogen was 10
3 CFU/g. The most commonly
used immunoassays for the detection of the pathogen are based on the use of whole
cells, or heat killed (Silbernagel et al. 2005), or formalin fixed (Solve et al. 2000),
and then detected by an ELISA. Feldstine et al. (1997) developed an immunoprecipitation method that made use of heat killed L. monocytogenes cells to detect
contamination between 0.003 and 11 cfu/ml of food samples. An enzyme-linked
immunosorbent assay (ELISA) for Clostridium botulinum type A and type B toxins
was assessed for diagnostic accuracy in cases of infant botulism. Botulism is a
serious food-borne neuroparalytic disease, caused by botulinum neurotoxin
(BoNT), produced by the anaerobic bacterium Clostridium botulinum. Stanker
et al. (2013) developed serotype B-specific monoclonal antibodies for sandwich
(capture) ELISA antibodies ranging from 10 to 48 Â 10
À11 M. Assay performance
for all possible combinations of capture–detector antibody pairs was evaluated, and
the antibody pair resulting in the lowest level of detection (L.O.D.) ~20 pg/mL was
determined.
9.2.3 Laser-Induced Breakdown Spectroscopy
Laser-induced breakdown spectroscopy (LIBS) has a flexible and convenient technique for rapidly determining the elemental composition of samples with minimal or
no sample preparation. This technique is used to analyze the spectral emission from
laser-induced plasmas, the plasma emission intensity being proportional to the
abundance of an element in the sample. The relative simplicity and capability of
fast multielemental analyses of solid, liquid, or gaseous samples make LIBS an ideal
tool to study a wide range of samples. Although the use of LIBS has been most
popular in metallurgical and biological samples, in recent years, it has been used to
study environmental and biological samples. Yu et al. (2010) separated a variety of
bacteria by detecting the trace mineral elements contained in five different types of
bacteria that were grown in the same nutrient liquid, among them are four Gramnegative species (Acinetobacter baylyi, Erwinia chrysanthemi, Escherichia coli, and
Shewanella oneidensis) and one Gram-positive bacterium (Bacillus subtilis). In the
next round of this work, they evaluated the performance of LIBS for both sensitive
detection of mineral trace elements in fresh vegetables and highly spatially resolved
measurements of the amounts. Rosalie et al. (2010) described the use of LIBS to
differentiate live pathogens and killed viruses on substrates. They differentiat the
live pathogens B. anthracis Stern strain and F. tularensis live vaccine strain colonies
on agar and demonstrate that it was found possible to differentiate between a
196
S. Purwar and S. Srivastava