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Benahmed F, Wang H, Beaubrun JJG, Gopinath GR, Cheng CM, Hanes DE, Hammack TS, Rasmussen M, Davidson MK. Detection of Salmonella enterica subsp. enterica Serovar Cubana from Naturally Contaminated Chick Feed. J Food Prot 2017; 80:1815-1820. [PMID: 28981377 DOI: 10.4315/0362-028x.jfp-16-344] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Because some significant outbreaks of human salmonellosis have been traced to contaminated animal feed, the rapid and efficient detection of Salmonella in feed is essential. However, the current U.S. Food and Drug Administration Bacteriological Analytical Manual (BAM) culture method that uses lactose broth as a preenrichment medium has not reliably supported the results of real-time PCR assays for certain foods. We evaluated the BAM culture method and a quantitative real-time PCR (qPCR) assay using two preenrichment media, modified buffered peptone water and lactose broth, to detect Salmonella enterica subsp. enterica serovar Cubana in naturally contaminated chick feed. After 24 h of incubation, the qPCR method was as sensitive as the culture method when modified buffered peptone water was used as the preenrichment medium but less sensitive than culture when lactose broth was used. After 48 h of incubation, detection of Salmonella Cubana by qPCR and by culture in either preenrichment medium was equivalent. We also compared the performance of the traditional serotyping method, which uses pure cultures of Salmonella grown on blood agar, to two molecular serotyping methods. The serotyping method based on whole genome sequencing also requires pure cultures, but the PCR-based molecular serotyping method can be done directly with the enriched culture medium. The PCR-based molecular serotyping method provided simple and rapid detection and identification of Salmonella Cubana. However, whole genome sequencing allows accurate identification of many Salmonella serotypes and highlights variations in the genomes, even in tight genomic clusters. We also compared the genome of the chick feed isolate with 58 Salmonella Cubana strains in GenBank and found that the chick feed isolate was very closely related to an isolate from a foodborne outbreak involving alfalfa sprouts.
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Affiliation(s)
- Faiza Benahmed
- 1 U.S. Food and Drug Administration, Center for Veterinary Medicine, Division of Animal and Food Microbiology, Laurel, Maryland 20708
| | - Hua Wang
- 2 U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland 20740
| | - Junia Jean-Gilles Beaubrun
- 3 U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Virulence Assessment, Laurel, Maryland 20708; and
| | - Gopal R Gopinath
- 3 U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Virulence Assessment, Laurel, Maryland 20708; and
| | - Chorng-Ming Cheng
- 4 U.S. Food and Drug Administration, Pacific Regional Laboratory Southwest, Irvine, California 92612, USA (retired)
| | - Darcy E Hanes
- 3 U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Virulence Assessment, Laurel, Maryland 20708; and
| | - Thomas S Hammack
- 2 U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland 20740
| | - Mark Rasmussen
- 1 U.S. Food and Drug Administration, Center for Veterinary Medicine, Division of Animal and Food Microbiology, Laurel, Maryland 20708
| | - Maureen K Davidson
- 1 U.S. Food and Drug Administration, Center for Veterinary Medicine, Division of Animal and Food Microbiology, Laurel, Maryland 20708
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