Food Protection Trends - February 2010 - 96

Results: seventy-four of the food samples were negative for CPs with BPa. typical colonies were identified from the remaining six samples. these isolates were shown to be coagulase-negative organisms. a single colony of presumptive growth was recorded from one sample with Brilliance staph 24 agar, which was identified as a coagulase-negative organism. Conclusions: Brilliance staph 24 agar proved to be a suitable alternative to BPa for the enumeration of coagulase-positive staphylococci within 24 h. It resulted in significantly fewer presumptive positive isolates compared to BPa, which required confirmation, and accurate results were available within 24 hours. P1-21 ISO16140 Expert Laboratory Evaluation of a Novel Medium for the Enumeration of Coagulasepositive Staphylococci Mieke Uyttendaele, anja DeLoy-Hendrickx, Dirk Berkvens, niko speybroeck and JonatHan M. CLoKe, Oxoid, Wade Road, Basingstoke, RG24 8PW, United Kingdom Introduction: oxoid Brilliance™ staph 24 agar is a new chromogenic medium for the enumeration of coagulasepositive staphylococci (CPs) from foods within 24 hours. traditionally, Baird-Parker agar supplemented with egg yolk and tellurite (BPa) has been used for enumerating CPs. Isolates on BPa are often difficult to interpret because of the presence of both typical and atypical colonies of staphylococci, which both require confirmation. Rational: Brilliance staph 24 agar was evaluated against BPa for the enumeration of CPs from the five identified food categories detailed in Iso16140:2003. testing was performed according to the method detailed in Iso6888-1:1999, with the exception of Brilliance staph 24 agar which was incubated at 37°C for 24 h. the expert laboratory evaluation was conducted in full accordance of the quantitative methods validation section of Iso16140:2003. Results: Brilliance staph 24 agar showed good equivalence to BPa with dairy, meat, sea-food, bakery products and composite/ready to eat food samples. equivalence of the media was not shown with CPs from sugar snap peas. Results for inclusivity, limit of detection and quantification limit (LoD=2, LoQ=4) were equivalent for the reference and alternative method. exclusivity testing of Brilliance staph 24 agar showed it was more specific than BPa, with no false positive results (0/48) compared to BPa, where 13/48 non-CPs gave typical/ atypical colonies. statistical analysis demonstrated that Brilliance staph 24 agar showed excellent linearity and accuracy. linear regression analysis (GMFR and OlS2) demonstrated that the relative accuracy of the reference and alternative method was equivalent (R=0.999) for all food categories, giving an overall regression of (y=0.9918 + 0.0335). Conclusions: Brilliance staph 24 agar proved to be a suitable alternative to Baird-Parker agar with the five food groups analysed during the expert lab phase of the Iso16140 validation. Brilliance staph 24 agar showed greater specificity than Baird-Parker agar and gave results within 24 h. P1-22 Evaluation of a Novel Medium for the Enumeration of Thermotolerant Campylobacter spp. Wilma Jacobs-Reitsma, Wendy van overbeek, el Bouw, Hilko van der Voet, Jonathan Cloke and annette WHIstanCe, oxoid, Wade Road, Basingstoke, RG24 8PW, United Kingdom Introduction: traditional media for the enumeration of thermotolerant Campylobacter spp. often lack specificity and individual colonies are difficult to count, due to the swarming nature of campylobacters and the presence of blood and charcoal in the media. oxoid Brilliance™ CampyCount agar is a novel defined medium for the direct enumeration of Campylobacter spp. which was evaluated as the first part of an Iso16140:2003 validation of the medium. Colonies of Campylobacter spp. grow as distinct dark red colonies against a clear background. Rational: Brilliance CampyCount agar was evaluated against modified Charcoal Cefoperazone Desoxycholate agar (mCCDa) for the enumeration of thermotolerant Campylobacter spp. from poultry samples, according to the method detailed in Iso10272-2:2006. Both media were incubated at 41.5°C for 40–48 h in a microaerobic atmosphere. the evaluation was conducted in accordance with the quantitative methods validation section of Iso16140:2003. In addition to the confirmation requirements of Iso10272-2, presumptive colonies on Brilliance CampyCount agar were confirmed using the oxoid Dryspot Campylobacter Latex kit and o.B.I.s Campy test. Results: Brilliance CampyCount agar was shown to have comparable performance to the reference method (mCCDa) in terms of inclusivity, exclusivity and to limits of detection and quantification (LoD=3.3, so=0.309). statistical analysis of the linearity, in accordance with Iso16140 showed no statistically significant evidence of lack of fit (P = 0.56). linear regression analysis (GMFR) showed that the relative accuracy of the reference and alternative methods was equivalent (R=0.82, y=-0.22+1.09). Conclusions: Brilliance CampyCount agar was shown to be comparable in performance to mCCDa. Colonies of Campylobacter spp. were easier to enumerate as they were distinct dark red colonies on a clear background. the oxoid Dryspot Campylobacter Latex kit and o.B.I.s Campy tests were found to be accurate methods for the confirmation of presumptive growth on Brilliance CampyCount agar. 96 FOOD PROTECTION TRENDS | FEBRUARY 2010

Food Protection Trends - February 2010

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