Methods to be Reviewed by OMB in 2016

rowley

et al

ournal of

AOAC I

nternational

97, N

. 2, 2014

433

Confirmation of the samples was conducted according to

AOAC

993.12

Test Portion Distribution

All samples were labeled with a randomized, blind-coded

3-digit number affixed to the sample container. Test portions

were shipped on a Thursday via overnight delivery according

to the Category B Dangerous Goods shipment regulations set

forth by the International Air Transportation Association. Upon

receipt, samples were held by the collaborating laboratory at

refrigeration temperature (3–5°C) until the following Monday

when analysis was initiated. All samples were packed with

cold packs to target a temperature of <7°C during shipment.

In addition to each of the test portions and the total plate

count replicate, collaborators also received a test portion for

each matrix labeled as ‘temperature control’. Participants

were instructed to obtain the temperature of this portion upon

receipt of the package, document results on the Sample Receipt

Confirmation form provided, and fax to the study director.

Test Portion Analysis

Collaborators followed the appropriate preparation and

analysis protocol according to the method for each test portion

size. For both test portion sizes, each collaborator received 72 test

portions of each food product (12 high, 12 low, and 12 controls

for each evaluation). For the analysis of the 25 g test portions by

VIDAS LPT, a 25 g sample replicate was enriched with 225 mL

prewarmed (18–25°C) LPT broth and homogenized for 2 min.

Test portions were incubated for 26–30 h at 30±1°C. For the

125 g test portions analyzed by VIDAS LPT, a 125 g sample

replicate was enriched with 375 mL prewarmed (18–25°C) LPT

broth and homogenized for 2 min. Test portions were incubated

for 24–30 h at 30±1°C. For 125 g test portions, a 1.0 mL aliquot

of the primary enrichment was transferred into 10 mL LPT broth

and incubated for an additional 22–26 h at 30±1°C.

Following enrichment, samples were assayed by VIDAS LPT

and confirmed following procedures outlined in the standard

reference method by streaking an aliquot of the primary

enrichment onto OXA and a proprietary chromogenic agar,

ALOA. Presumptive positive samples were streaked for isolation

on TSA yeast extract (TSAYE) and biochemically confirmed

by morphology verification via Gram stain, hemolysis test, and

by AOAC

2012.02

VITEK 2 GP Biochemical Identification

method (VITEK 2 GP) or API

Listeria

(1) biochemical test kits.

Laboratories utilizing API

Listeria

kits were also required to

conduct a catalase test and an oxidase test.

Both test portion sizes analyzed by the VIDAS LPT methods

were compared to samples (25 g) analyzed using the AOAC

993.12

reference method in conjunction with VITEK 2 GP or

API

Listeria

for the confirmation of

Listeria

in an unpaired

study design. Twenty-five gram test portions were enriched in

prewarmed (45°C) selective enrichment broth, homogenized for

2 min, and incubated at 30 ± 2°C for 48 h. Samples were streaked

onto OXA and presumptive positive samples were streaked for

isolation onto TSAYE. Colonies from TSAYE were confirmed

by morphology verification via Gram stain, hemolysis test, and

by VITEK 2 GP or API

Listeria

kits. Laboratories utilizing API

Listeria

kits were also required to conduct a catalase test and an

oxidase test.

Statistical Analysis

Each collaborating laboratory recorded results for the

reference method and VIDAS LPT results. The data sheets were

submitted to the study director for analysis at the end of each

week. The results of each test portion for each sample were

compiled by the study director and the qualitative VIDAS LPT

results were compared to the reference method for statistical

analysis. Data for each test portion size was analyzed using the

POD statistical model (5, 8). For each inoculation level, the

probability of detection (POD) was calculated as the number

of positive outcomes divided by the total number of trials. The

POD was calculated for the candidate presumptive results,

POD

, the candidate confirmatory results, POD

/POD

the reference method, POD

, the difference in the candidate

presumptive and confirmatory results, dLPOD

, and the

difference in the candidate confirmed and reference methods,

dLPOD

. A

confidence interval of a dLPOD not containing the

point zero would indicate a statistically significant difference

between VIDAS LPT and AOAC

993.12

at the 5% probability

level (9).

AOAC Official Method 2013.10

Listeria

species in a Variety of Foods and

Environmental Surfaces

VIDAS

Listeria

(LPT) Method

First Action 2013

[Applicable to detection of

Listeria

in deli ham (25 and

125 g), pepperoni (25 g), beef hot dogs (25 g), chicken nuggets

(25 g), chicken liver pâté (25 g), ground beef (125 g), deli

turkey (125 g), cooked shrimp (25 g), smoked salmon (25 g),

whole cantaloupe melon, bagged mixed salad (25 g), peanut

butter (25 g), black pepper (25 g), vanilla ice cream (25 g),

queso fresco (25 and 125 g), stainless steel, plastic, ceramic and

concrete environmental surfaces.]

See

Tables

2013.10A

and

for a summary of results of the

collaborative study.

See

supplemental data, Tables 2A–D,

for detailed results of the collaborative study on

J. AOAC Int.

website

, http://aoac.publisher.ingentaconnect.com/content/aoac/

jaoac.

Caution

Listeria monocytogenes

is of particular concern for

pregnant women, the aged, and the infirmed. It is

recommended that these concerned groups avoid

handling this organism. Dispose of all reagents

and other contaminated materials by acceptable

procedures for potentially biohazardous materials.

Some reagents in the kit contain 1 g/Lconcentrations

of sodium azide. Check local regulations prior

to disposal. Disposal of these reagents into sinks

with copper or lead plumbing should be followed

immediately with large quantities of water to

prevent potential hazards. This kit contains products

of animal origin. Certified knowledge of the origin

and/or sanitary state of the animals does not totally

guarantee the absence of transmissible pathogenic

agents. It is, therefore, recommended that these

products be treated as potentially infectious and

Candidates for 2016 Method of the Year

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