Handheld sensor detects
pathogens within 10
minutes
By Ahmed ElAmin
Source of Article: http://www.
foodproductiondaily.com/news/ng.
asp?n=65558-sensor-pathogen-e-coli

02/02/2006 - A handheld sensor
could help food companies quickly
detect within 10 minutes whether their
products are laden with Escherichia
coli or listeria -- before they are
shipped out of the plant.

Increasing regulatory emphasis on
food safety in plants and the cost of
recalls has spurred food companies
to seek faster ways of detecting
pathogens.

Raj Mutharasan, an engineer at
Drexel University in Philadelphia,
Pennsylvania, has developed what
he says is a cheap, quick and simple
detector that just about anyone can
use.

“It will be as easy to use as a
thermometer, giving a result in 10
minutes,” Mutharasan stated in New
Scientist yesterday.

Detecting the bug in plants is a slow
process that involves removing whole
batches of foodstuffs from production
lines while cultures are grown or DNA
amplified. Normal laboratory tests can
take 24 hours or more

The device works by detecting how
the mass of a few E coli cells
changes the vibration of a miniature
glass beam. Mutharasan's prototype
sensor is made up of a sliver of glass
five millimetres long and one
millimetre wide.

The glass is fixed at one end and has
a layer of piezoelectric ceramic called
lead zirconate titanate (PZT) glued to
the other. The glass sliver is coated
with antibodies to E. coli 0157:H7, the
strain that causes food borne illness.

An alternating voltage applied to the
piezoelectric layer makes it expand
and contract, causing the tiny sliver
to vibrate. The vibration is greatest at
the sliver's resonant frequency, and
this can be detected by measuring
the voltage across the PZT
generated by the reverse
piezoelectric effect, as it peaks at the
resonant frequency.

Changes in the resonant frequency
as E. coli cells bind to the antibodies
provide a measure of the
concentration of the pathogen.
more information
Single Tube Screen for Enteric
Pathogens






The Hardy Diagnostics EnteroScreen 4™ is
recommended for use as a single tube screen
on stool specimens for enteric pathogens.
It is specifically designed to rule out normal
enteric flora and to aid in the detection and the
differentiation of Salmonella and Shigella
species.
EnteroScreen 4™ eliminates the need to
inoculate the “classical” 3 to 4 separate tubes.
The EnteroScreen 4™ system, consists of four
layers in a single tube; 3 agar layers and a
petrolatum layer.
The tube contains, in order from bottom to top,
Urea Agar, Petrolatum Plug, Modified Lysine
Iron Agar, and Lysine Iron Agar. With this
method, urease activity, lysine decarboxylase,
lysine deaminase, gas, and hydrogen sulfide
production reactions can be simultaneously
evaluated. Urea Agar, the bottom agar layer, is
added to the tube to differentiate other non-
lactose-fermenters, (such as Proteus species),
from Salmonella and Shigella species.
Technical insert comes with an easy-to-follow
identification algorithm in a flow-chart format
New test means
safe oysters
January 22, 2006
IFT Daily News
Two papers
published recently
in Applied and
Environmental
Microbiology and
co-authored by
UAB biologist Asim
Bej, Ph.D.,
highlight a real-
time test developed
in his laboratory
that can be
completed within a
day and specifically
identifies the
presence of less
than three Vibrio
vulnificus
bacterium per gram
of enriched oyster
meat. “The test
complies with
federal guidelines
requiring that by
2007 post-harvest
treated oysters
must not contain
more 30 Vibrio
vulnificus
bacterium per gram
of oyster meat. By
selecting the
appropriate
primers and probe
for the test, we are
able to not only
detect the
bacterium, but also
help avoid false
positive results,
ensuring a steady
supply of oysters
safe from V.
vulnificus
bacterium for
consumers.”
Ready-to-Use, Diagnostic Slide
Culture System for Identifying
Fungi

The Hardy Diagnostics MycoVue™ System is a
ready-to-use, diagnostic slide culture system
for identifying fungi. It streamlines the
identification of fungi by its microscopic
morphological appearance. Accurate
identification of filamentous fungi is based on
the microscopic examination of sporulating
parts of a colony since each species has a
characteristic morphology in the arrangement
of its spores and fruiting bodies. The
MycoVue™ System provides the laboratorian
with a standardized, comprehensive method
that eliminates time-consuming preparations
and technical difficulties encountered with the
classical slide culture technique. It simplifies
the slide culture method by providing all the
necessary components for this procedure in
one ready-to-use disposable unit.
The system comes complete with a protective
lid and a built-in humidifying chamber. The
device is designed to fit easily onto a
microscope stage, thereby allowing direct
viewing of the developing fungus through the
device, thus eliminating the disruption of the
fungal colony. If desired, the cover slip can be
removed and stained for further evaluation or
preservation.

The MycoVue™ is offered with your choice of
two media formulations: Potato Flake Agar or
SABHI™ Agar with Chloramphenicol - for the
inhibition of contaminating bacteria.
AFNOR Approval of RAPID'Salmonella: 48 hr Full Results for Salmonella
spp. Detection

Bio-Rad has extended its range of culture media to include RAPID'Salmonella. This new chromogenic
detection method for Salmonella spp. has recently been validated by AFNOR, according to the ISO 16140
requirements, for food and animal feed samples (No. BRD 07/11-12/05).
With RAPID'Salmonella, full results can be obtained within 48 hr (the second enrichment can last longer
than 6 hr for more convenience).
Method:
After overnight Buffered Peptone Water pre-enrichment (18 hr +/- 2 hr), followed by selective enrichment
in Rappaport Vassiliadis Soy (RVS) broth with an incubation time between 6 hr and 26 hr, 10 ml of the
RVS broth are inoculated on the RAPID'Salmonella chromogenic plating agar.
An alternative confirmation is also validated in the RAPID'Salmonella protocol and gives results in 1 hr.
The principle of the RAPID'Salmonella medium relies on the demonstration of two enzymatic activities.
Salmonella spp. takes the form of readily identified, typical magenta colonies (due to the detection of C8
esterase). Counter selection is used in RAPID'Salmonella to reveal other bacteria with a different color.
RAPID'Salmonella can detect motile and non-motile Salmonella as well as lactose-positive Salmonella,
including S. typhi and S. paratyphi.

Key benefits:
- Economical, and easy to use: 2 broths, 1 plate
- Fast:
- full results can be obtained within 48 hr
- alternative confirmation in 1 hr
- Highly sensitive: detection of lactose-positive and non-motile S. paratyphi and S. typhi
- Easy to read: magenta colonies are Salmonella spp.
- Good specificity and selectivity
RAPID'Salmonella chromogenic plating agar is also of interest as a second selective medium in the ISO
6579 reference method.
BactiFlow® Real-time Microbial Analysis with Digital Flow Cytometry












BactiFlow® is based on the proven cell labeling, laser excitation and digital data treatment technology
utilized by ScanRDI®, a solid-phase cytometer developed by Chemunex that provides real-time microbial
analysis for filterable samples within two hours.  A variation on the technology allows non-filterable samples
to be analyzed using flow cytometry. The resulting real-time microbial analysis helps pharmaceutical,
cosmetics and personal care companies reduce production times and inventories, minimize in-process
contamination, release products in 24 hours, reduce costs and improve product quality.

The BactiFlow® System
BactiFlow® is a compact, affordable, microbiology analyzer that offers true real-time microbial testing for
non-filterable and filterable samples. Results are delivered in minutes or hours instead of days - a real
competitive advantage.

Direct Labeling, Direct Detection and Enumeration
BactiFlow® uses direct fluorescent labeling of viable microorganisms, coupled with an ultra-sensitive, direct
counting system by digital flow cytometry. BactiFlow® can detect and enumerate microorganisms without
the need for an incubation period or selective enrichment, providing results within 20 minutes. When some
enrichment or incubation is needed, results are still provided days faster than traditional methods. Labeling
reagents use enzymatic cleavage of a non-fluorescent substrate to liberate free fluorochrome into the
cytoplasm . Only metabolically active cells (including spores) can perform this cleavage, even under
conditions of stress. Thus, each microbial cell is directly labeled, one by one. Once labeled, samples pass
through a quartz flow cell , which forms a narrow analysis stream that ensures microorganisms pass
through the laser excitation beam, and are detected and counted one by one. The fluorescent signals of
each cell are collected by sensitive detectors and analyzed by digital data processing.

A Simple Protocol
Samples are labeled using Fluorassure® reagents. The labeling step takes about 10 minutes and can also
be done with a semiautomatic labeling unit. Once labeling is completed, the sample is loaded into BactiFlow
for fully automated analysis. Results are available within 1 minute. Some specific microorganisms can be
identified by varying reagents and protocols (e.g. Salmonella).

Fast & Sensitive Analysis
All microorganisms pass individually through a flow cell at a rate of up to 500 cells per second. Each
labeled cell fluoresces under laser excitation to be detected one by one and enumerated by sensitive
photomultipliers. Sophisticated cell discrimination ensures accurate and consistent differentiation between
labeled microorganisms and any auto-fluorescent particles that may be present. Cell counting takes less
than 1 minute per sample. Data is displayed as direct cell counts per gram or mL and are stored on a PC
for complete traceability. Neither calibration nor operator interpretation is necessary.

Fully Traceable Results in Hours, Not Days
Results are fully traceable. Data output is in the form of a tabulated result sheet, which includes: operator
and sample identification, time and date stamps, control data and a comprehensive result report - all in a
totally secure password-protected format. BactiFlow® provides a range of applications (TVC, Fungi, water
testing, raw materials, bulk product, final-product release, environmental testing, etc.) that can save 6 to 12
days in the production cycle and reduce warehousing costs, production downtimes and product losses.

High sensitivity and large measuring range
The sensitivity, linearity and reproducibility of BactiFlow® have been evaluated. In all cases, good
correlation between BactiFlow® and the traditional plate-count method was proven. The analyzer had a
direct sensitivity with results available within minutes of less than 100 cells per g or mL. With the
presence/absence protocol, the sensitivity is 1 count/g or mL. The system is linear over a wide range of
counts up to 105 counts per g or mL.

A Fully Automated Option
A fully automated version of BactiFlow® is available via the D-Count, which offers automatic sample loading
(a capacity of 64 samples per batch including positive and negative controls) and automatic cell labeling
(controlled incubation temperature and time).

Summary
The availability of real-time ultra-sensitive microbial testing solutions by Chemunex now offers laboratories
an affordable opportunity to switch to a proactive approach to assessing the quality of their manufacturing
systems and process materials. Having results within minutes or hours, instead of days, with a high
sensitivity creates, for the first time, the opportunity for companies to correct contamination problems as
they arise, thus improving overall efficiency and profitability.

This article is taken from the Nov-Dec 2005, Rapid Microbiology Newsletter - A newsletter for the Rapid
Micro User's Group™


Newsletter #2
2/9, 2006