Methods to be Reviewed by OMB in 2016

820

ird

et al

ournal of

AOAC I

nternational

. 96, N

. 4, 2013

presented in Table

2013.01B

and in appended Table E and

Figure 2C and D.

Alternative Confirmation with IBISA and ASAP

For the high level, 130 of 132 test portions were reported as

positive by the VIDAS SPT method, with all portions confirming

positive. For the low level, 57 of 131 test portions were reported as

positive by the VIDAS SPT method, with 58 confirming positive.

For the uninoculated controls, none of the 132 samples produced

a presumptive positive result by the VIDAS SPT method, and

all samples confirmed negative. For test portions analyzed by the

USDA/FSIS-MLG method, 131 of 132 high and 54 of 132 low

inoculum test portions confirmed positive. For the uninoculated

controls, none of the 132 test portions confirmed positive.

For the low-level inoculum, dLPOD

values of 0.03 (–0.18,

+0.24) were obtained between the USDA/FSIS-MLG method

and the VIDAS SPT method. The confidence intervals obtained

for dLPOD

indicated no significant difference between the two

methods. dLPOD

values of –0.01 (–0.21, +0.23) were obtained

between presumptive and confirmed VIDAS SPT results.

The confidence intervals obtained for dLPOD

indicated no

significant difference between the presumptive and confirmed

results using either confirmation process.

For the high-level inoculum, dLPOD

values of –0.01

(–0.05, +0.03) were obtained between the USDA/FSIS-MLG

method and the VIDAS SPT method. The confidence intervals

obtained for dLPOD

indicated no significant difference between

the two methods. dLPOD

values of 0.00 (–0.04, +0.04)

were obtained between presumptive and confirmed VIDAS

SPT results. The confidence intervals obtained for dLPOD

indicated no significant difference between the presumptive and

confirmed results. Detailed results of the POD statistical analysis

are presented in Table

2013.01B

and in appended Table F and

Figure 2E and F.

IBISA and ASAP Chromogenic Agar

Results obtained from the IBISA and ASAP chromogenic

agars were comparable to the results obtained from the XLT4

and BGS agars specified by the USDA/FSIS-MLG method.

For the samples analyzed by the reference method, there were

412 positive results obtained from ASAP agar plates, compared

to 411 positive results obtained from XLT4 and BGS agar plates.

For samples analyzed by the VIDAS SPT method and confirmed

following traditional procedures using IBISA and ASAP there

were 476 positive results obtained from ASAP agar plates,

compared to 475 positive results obtained from IBISA, XLT4

and BGS agar plates. For samples analyzed by the VIDAS SPT

method and confirmed following the alternative procedure using

IBISA and ASAP, there were 479 positive results obtained from

IBISA and ASAP agar plates, compared to 475 positive results

obtained from XLT4 and BGS agar plates.

Four uninoculated control samples produced positive results

on the IBISA and ASAP chromogenic agar that were not

detected on either the XLT4 or BGSA reference agars or during

analysis with the VIDAS SPT assay. Because the

Salmonella

species was not detected on the two reference agar plates, the

positive results produced by the chromogenic agar plates may

be an artifact of cross-contamination or laboratory error.

Discussion

For this collaborative study, samples were analyzed at both

375 and 25 g test portions as required by the current AOAC

guidelines, which require methods with more than one sample

preparation or enrichment scheme to analyze one matrix per

procedure.

For the analysis of 375 g test portions, no significant difference

was observed using the POD statistical model in the number

of positive results obtained between the two methods being

compared using both the traditional and alternative confirmation

procedures for the VIDAS SPT method. For the analysis of 25 g

test portions, a significant difference was observed using the

POD statistical model between the two methods for both the

low and high levels of inoculation using both the traditional and

alternative confirmation procedures, with more positive results

obtained using the VIDAS SPT method, indicating a high

level of sensitivity in the detection of the target analyte by the

candidate method.

The results of the POD statistical analysis may indicate the

high sensitivity of the VIDAS SPT assay. The VIDAS SPT

showed a higher sensitivity than the reference method when

test portions of the same size (25 g) were analyzed, and similar

sensitivity to the reference method for test portions that were

15x larger (375 g VIDAS SPT test portions, compared to 25 g

USDA/FSIS-MLG test portions).

No negative feedback was reported to the Study Directors

from the collaborating laboratories with regard to the

performance of the VIDAS SPT assay or the IBISA and ASAP

chromogenic agar. Overall, the VIDAS SPT method recovered

Salmonella

in 475 test samples out of 826 samples analyzed,

compared to 411 positive results out of 826 samples for the

USDA/FSIS-MLG method. Only one unconfirmed positive

result and no false-negative results were obtained using the

VIDAS SPT method.

Recommendations

It is recommended that the VIDAS SPT method, with the

optionalASAP and IBISAagar confirmation method, be adopted

as Official First Action status for the detection of

Salmonella

a variety of foods, including raw ground beef (25 and 375 g),

processed American cheese (25 g), deli roast beef (25 g), liquid

egg (25 g), peanut butter (25 g), vanilla ice cream (25 g), cooked

shrimp (25 g), raw cod (25 g), bagged lettuce (25 and 375 g),

dark chocolate (375 g), powdered eggs (25 g), instant nonfat

dry milk (25 and 375 g), ground black pepper (25 g), dry dog

food (375 g), raw ground turkey (375 g), almonds (375 g),

chicken carcass rinsates, and stainless steel, plastic, and ceramic

environmental surfaces.

Acknowledgments

We extend our sincere thanks to the following collaborators

for their dedicated participation in this study:

John Mills, bioMérieux Industry, Hazelwood, MO

JudyNogle, U.S. Food andDrugAdministration, San Francisco

District Office, Alameda, CA

Willis Fedio and Ruben Zapata, New Mexico State University,

Center for Animal Health, Food Safety and Biosecurity, Las

Cruces, NM

Candidates for 2016 Method of the Year

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