Influence of selective media on Campylobacter detection

Transcription

1 Influence of selective media on Campylobacter detection Repérant Elisabeth, Denis Martine Unit of Hygiene and Quality of Poultry and Pork Products, French National Reference Laboratory for Campylobacter 1

2 NRL for Campylobacter for French labs annual Proficiency Test (PT) ISO (2006) SPF chicken skin + 10 vials contaminated or not with Campylobacter strains 2

3 Campylobacter detection (ISO ) 10 g + 4mL suspension w/wo Campylo + 86 ml Bolton Broth Enrichment Micro-aerobic incubation 4-6 h at 37 C h at 41.5 C Isolation mccda second selective plate Micro-aerobic incubation h at 41.5 C 5 characteristic colonies Tests (morphology/motility, Oxidase, Absence of growth ) Campylobacter detected (or not) in sample 3

4 Influence of the second selective media? 1- Why this question? 2- Results from PT Additional comparison in PT Conclusion 4

5 Campylobacter detection in PT 2014 Results expressed as a/b where a = number of positive samples detected b = total number of positive samples False negative results for low and cross-contaminated samples : Influence of the second selective media? 5

6 Influence of the second selective media? Comparison of 4 selective media in PT 2015: - Brilliance Campy count (BCC), - Campyfood agar (CFA), - CASA, - Rapid Campy (RC) And the mandatory mccda 6

7 Campylobacter detection : results obtained in 2015 from 17 labs C. jejuni C. coli C. lari % of detected growth mccda CFA CASA CCB RC mccda CFA CASA CCB RC mccda CFA CASA CCB RC ND CNC CC/CNC CC best results with CASA : >85% detection for all Campylobacter sp. C. lari most difficult to detect whatever the medium 7

8 Campylobacter detection : results obtained in 2015 from 17 labs Blank C. Coli + E. coli % of detected growth mccda CFA CASA CCB RC mccda CFA CASA CCB RC ND CNC CC/CNC CC CASA more selective for blank samples CASA and CFA more selective for C.coli + E. coli samples mccda less efficient to detect Campylobacter in C.coli + E. coli samples 8

9 Comparison of the 5 media Media vs tested samples - All media selective for Campylobacter strains (p value <0.001) - Significant difference between the 5 media to detect Campylobacter (p=0.05) All tested media were efficient for Campylobacter detection Influence of the selective medium confirmed 9

10 What next? In a previous survey (Repérant et al., 2016): Butzler no.2 more efficient for Campylobacter detection vs. mccda, Karmali and CFA Campylobacter detection highest with Butzler Number of Campylobacter positive samples (n=30) vs media Comparison of 2 different media in PT 2016: Butzler no. 2 and CHROMagar for Campylobacter 10

11 Campylobacter detection : results obtained in 2016 from 15 labs C. jejuni C. coli % of detected growth mccda Butzler CHROMagar mccda Butzler CHROMagar ND CNC CC/CNC CC No significant difference observed between media 11

12 Campylobacter detection : results obtained in 2016 from 15 labs Blank E. coli % of detected growth ND CNC CC/CNC CC mccda Butzler CHROMagar mccda Butzler CHROMagar Butzler no.2 more selective for negative samples CHROMagar more discriminating? 12

13 CHROMagar => Campylobacter strains = red vs. other bacteria = blue C.jejuni + E.coli control 13

14 Sum up - CASA and Butzler no.2 more efficient than mccda to detect Campylobacter and more selective for negative samples - mccda less efficient to detect Campylobacter in cross-contaminated samples - CHROMagar colors differently Campylobacter vs. other bacteria. 14

15 All media used were selective for Campylobacter detection These results confirm the need to use a second medium different from mccda as it will be asked for in the future version of ISO Thank you! 15