Apr 26, 2010 - This paper describes the development, validation, and ap- plication of a new method to enumerate spores of nonproteo- lytic C. botulinum in ...
APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Oct. 2010, p. 6607–6614 0099-2240/10/$12.00 doi:10.1128/AEM.01007-10 Copyright © 2010, American Society for Microbiology. All Rights Reserved.
Vol. 76, No. 19
Development and Application of a New Method for Specific and Sensitive Enumeration of Spores of Nonproteolytic Clostridium botulinum Types B, E, and F in Foods and Food Materials䌤 Michael W. Peck,1* June Plowman,1 Clare F. Aldus,1 Gary M. Wyatt,1 Walter Penaloza Izurieta,2 Sandra C. Stringer,1 and Gary C. Barker1 Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, United Kingdom,1 and Quality and Safety Department, Nestle´ Research Centre, Vers-chez-les-blanc, 1000 Lausanne 26, Switzerland2 Received 26 April 2010/Accepted 1 August 2010
The highly potent botulinum neurotoxins are responsible for botulism, a severe neuroparalytic disease. Strains of nonproteolytic Clostridium botulinum form neurotoxins of types B, E, and F and are the main hazard associated with minimally heated refrigerated foods. Recent developments in quantitative microbiological risk assessment (QMRA) and food safety objectives (FSO) have made food safety more quantitative and include, as inputs, probability distributions for the contamination of food materials and foods. A new method that combines a selective enrichment culture with multiplex PCR has been developed and validated to enumerate specifically the spores of nonproteolytic C. botulinum. Key features of this new method include the following: (i) it is specific for nonproteolytic C. botulinum (and does not detect proteolytic C. botulinum), (ii) the detection limit has been determined for each food tested (using carefully structured control samples), and (iii) a low detection limit has been achieved by the use of selective enrichment and large test samples. The method has been used to enumerate spores of nonproteolytic C. botulinum in 637 samples of 19 food materials included in pasta-based minimally heated refrigerated foods and in 7 complete foods. A total of 32 samples (5 egg pastas and 27 scallops) contained spores of nonproteolytic C. botulinum type B or F. The majority of samples contained
