Food Protection Trends
Abstracts - August 2007
Detection of Nonpathogenic
and Pathogenic Listeria
Species by Use of a Chromogenic
Agar
Removal of Bacteria from
Fingertips and the Residual
Amount Remaining on the
Hand Washing Nailbrush
Survey of Consumer Attitudes
and the Effectiveness of Hand
Cleansers in the Home
Detection of Nonpathogenic and Pathogenic Listeria Species by Use of a Chromogenic Agar
Lawrence Restaino, Elon W. Frampton, Wiliam C. Lionberg, and Anthony L. Restaino
R & F Laboratories, 2725 Curtiss St., Downers Grove, IL 60515, USA
SUMMARY
A selective and differential chromogenic plating medium (R & F Listeria spp./Listeria monocytogenes
Plating Medium [LSPM]) has been developed that simultaneously differentiates presumptive colonies
of both the nonpathogenic Listeria species (L. innocua, L. seeligeri, L. welshimeri, and L. grayi) and the
pathogenic species (L. monocytogenes and L. ivanovii) on a single plate in 42–48 h at 35ºC. Unlike
chromogenic media that produce only a single color in detecting the presence of all Listeria species
on the basis of ß-glucosidase activity, or those that specifically detect the two pathogenic species
by phosphatidylinositol-specific-phospholipase C activities (PI-PLC), LSPM contains a combination
of indoxyl-derivative chromogenic substrates with which colonies of nonpathogenic Listeria species
are pink because of their β-glucosidase activity, and pathogenic species are blue-green to blue-violet,
depending on the strain-specific balance of β-glucosidase and PI-PLC activities on an agar with an
opaque white background. On LSPM, 39 pure culture strains of L. monocytogenes yielded blue-green
to blue-violet colonies 1–2 mm in diameter with or without surrounding precipitates in 42–48 h,
and 4 strains of L. ivanovii yielded dark blue-green colonies with dark precipitates, whereas all of the
nonpathogenic Listeria strains yielded pink colonies 1–2 mm diameter without precipitates. The ability
to differentiate Listeria spp. from L. monocytogenes over a broad range on the same plate of LSPM was
demonstrated at ratios of 1:1 to 100:1 of L. innocua to L. monocytogenes. Additionally, a high level of
selectivity by this plating medium was evidenced by the lack of growth by common species of five
gram-positive genera (Bacillus, Staphylococcus, Lactobacillus, Pediococcus, and Enterococcus), and eight
gram-negative genera (Escherichia, Enterobacter, Citrobacter, Shigella, Morganella, Providencia, Pantoea, and
Klebsiella). Two yeast genera, Zygosaccharomyces and Candida, also failed to grow at 35ºC.
Full Text Article
Removal of Bacteria from
Fingertips and the Residual
Amount Remaining on the
Hand Washing Nailbrush
O. Peter Snyder, Jr.
Hospitality Institute of Technology and Management, 670 Transfer Road, Suite 21A, St. Paul, MN 55114, USA
SUMMARY
The purpose of this study, which utilized 3 volunteer
participants, was to measure the effectiveness of the double
hand-washing procedure for removing non-pathogenic surrogate
Escherichia coli organisms from fingertips and to measure
the residual E. coli remaining on the nailbrush. Data from the
experiment show that use of the nailbrush during hand and
fingertip washing (Wash #1) reduced an inoculum of E. coli on
fingertips by 2.98 log10 CFU/ml, an almost 1,000–fold reduction.
When Wash #1 was followed by a 10-s wash without the nailbrush
(Wash #2), there was an additional reduction of 1.72 log10 CFU/
ml, an approximately 50–fold reduction. Added together, there
was a total average reduction of 4.70 log10 CFU/ml. Thus, the
double hand-wash method was shown to reduce bacteria on
fingers and to offer a validated solution for the foodservice
operation that wishes to use the FDA Food Code provision
of §3-301.11(D)(6) as an alternative to gloving. The average
E. coli population remaining on the nailbrush after use during
Wash #1 was measured, and it was found that retention was
less than 1 in 107 of the initial bacterial inoculum.
Full Text Article
Survey of Consumer Attitudes
and the Effectiveness of Hand
Cleansers in the Home
Janice M. Brown-1*, John S. Avens-2, Patricia A. Kendall-2, Dorene R. Hyatt-3,
and Martha B. Stone-2
1-Dept. of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO
80523-1571, USA
2-Dept. of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO 80523-1571, USA
3-Dept. of Microbiology Immunology & Pathology,
Colorado State University, Fort Collins, CO 80523-1644, USA
SUMMARY
Although frequent hand washing reduces microbial load, the best handcleansing
agents and hand washing methodologies to employ to reduce microbial
load on hands are not obvious. The objectives of this study were to determine
public attitudes about available hand cleansers and to determine the effectiveness
of three hand cleansers in reducing bacteria on hands. A survey was distributed to
ascertain the rationale used to select specific hand cleansers for use in the home.
Most respondents believed that regular hand soaps (no active ingredient) were
not as effective as antibacterial soaps in reducing bacteria on hands. Liquid hand
soap, antibacterial liquid hand soap, and an alcohol gel sanitizer were evaluated to
determine their effectiveness in reducing bacteria on hands. Comparisons made
between pre-wash agar touch plates and post-wash agar touch plates showed that all
three hand cleansers reduced bacteria on hands when a 20 s hand wash procedure
was used. No significant differences (P > 0.05) were detected between relative colony
numbers (RCN), defined as a visible range of bacterial or fungal colonies, obtained
with liquid hand soap with antibacterial ingredients and liquid hand soap without
such ingredients. However, alcohol gel significantly reduced (P ≤ 0.05) RCN on
hands, compared to results with liquid hand soap and antibacterial hand soap.
Full Text Article
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