1. Role of Reference Laboratories in Detecting Laboratory Contamination Niall De Lappe National Salmonella Reference Laboratory, Galway, Ireland

2. Introduction  Why does it occur? Positive Control Other Positive Isolates  Problem Pseudo-Outbreaks Potential Cost to Food Industry

5. Scale of Problem  M.tuberculosis 1.8-3.5% misdiagnosis  Estimating causes and Rate of laboratory contamination Sinnika Pelkolen

6. Incidence of False Positive Salmonella Isolations  20011 (n = 6)  20022 (n =11)  20033 (n = 9)  20045 (n = 9)  20056 (n = 9)  20061 (n = 2)  20071 (n = 1)

8. Lab A  S.Typhimurium DT132 Oct 2003Beef (n=1) Nov 2003Beef (n=4) & Drain swab (n=1) Dec 2003Pork (n=1) Jan 2004Beef (n=1) Feb 2004Pork (n=1) and Powder (n=1) Apr 2004Beef (n=1) Sent Positive Control S.Typhimurium DT132

9. Lab B  Clinical case 78 y.o. patient hospitalised > 30 days Developed diarrhoea Isolated salmonella from selenite broth  Salmonella from other patient same day Primary plate Both typed as Enteritidis PT1, Na resistant  Considered cross-contaminant

10. Lab C  Isolate from Milk Powder S.Typhimurium, Phage Type Untypable, ASSuT  Asked to send all group B isolates from 2007  S.Typhimurium(n = 17)  S.Derby(n = 26)  S.Reading(n = 4)  S.Bredeney(n = 2)  S.Manhattan(n = 1)  S.Agama(n = 1)

11. Phage Typing and Antibiograms Index Isolate Untypable/ ASSuT DT104 / ACSSuT(n = 4) DT193 / ACSuTm (n = 3) / ACSSuTTm (n = 1) DT12 / A(n = 1) DT2 / T (n = 1) DT120 / none (n = 1) U302 / ACSSuTTm (n = 1) RDNC / T(n = 2) Untypable / SSu(n = 1) / ASSuT(n = 1)* from swine

12. S.Typhimurium, ASSuT, Untypable  Literature Review Associated with Swine  NSRL Databases Human isolates (n = 2) Swine (n = 6) Unknown (n = 2) Milk Powder (n = 2)

13. PFGE BlnI XbaI

14. Variable Number Tandem Repeats

15. No.DateLabSourcePFGEVNTR 03-04072003dHumanIndistinguishable 07-02002007fPork2 band difference 07-02012007fUnknownIndistinguishable 07-02042007fUnknownIndistinguishable 05-08022005eHumanIndistinguishable 07-00282007fPorkIndistinguishable 07-00602007fPorkIndistinguishable 05-09002005CMilk Powder Indistinguishable 05-09022005CSwineIndistinguishable 07-01462007CMilk Powder Indistinguishable 07-02372007CSwineIndistinguishable 07-01472007fSwineIndistinguishable 04-03-10-02-02 04-03-11-02-02 04-04-11-00-02 05-02-07-14-02 05-02-07-00-02 04-03-07-02-02 04-04-16-21-02 04-03-10-02-02 Results

16. Lessons Positive ControlS.Nottingham Value of Subtyping strains routinely Value of different subtyping methods Sensitive Products Store Product for Retesting Test in different area/time than other samples

17. Acknowledgements  NSRL staff  EnterNet  All for listening