ARS | Publication request: Comparative genotypes of Salmonella enterica serovar Enteritidis Phage type 30 and 9c strains isolated from three outbreaks associated with raw almonds

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2010
Publication Date: June 1, 2010
Citation: Parker, C., Huynh, S., Quinones, B., Harris, L., Mandrell,2010 R.E. Comparative genotypes of Salmonella enterica serovar Enteritidis Phage type 30 and 9c strains isolated from three outbreaks associated with raw almonds. Applied and Environmental Microbiology. 76: 3723-3731

Interpretive Summary: In 2000-2001, 2003-2004 and 2005-2006, three outbreaks of Salmonella enterica serovar Enteritidis were linked with the consumption of raw almonds. The S. Enteritidis strains from these outbreaks had rare phage types (PT) that helped determine the food association. Clinical and environmental S. Enteritidis strains were subjected to pulse field gel electrophoresis (PFGE), multi-locus variable-number tandem repeat analysis (MLVA) and DNA microarray-based comparative genomic indexing (CGI) to evaluate their genetic relatedness. All three methods differentiated these S. Enteritidis in a manner that correlated with PT. The CGI analysis confirmed that that the majority of the differences between the almond-related S. Enteritidis strains corresponded to virus-related genes. However, PFGE, MLVA and CGI failed to discriminate between S. Enteritidis strains with the same PT related to outbreaks from unrelated clinical strains, nor between strains separated up to 5 years apart. However, metabolic fingerprinting demonstrated that S. Enteritidis PT4, PT8, PT13a and clinical PT30 strains metabolized L-aspartic acid, L-glutamic acid, L-proline, L-alanine, and D-alanine amino acids more efficiently than S. Enteritidis PT30 strains isolated from orchards. These data indicate that S. Enteritidis PT9c and 30 strains are highly related genetically, and that PT30 orchard strains differ from clinical PT30 strains metabolically, possibly due to fitness adaptations.

Technical Abstract: In 2000-2001, 2003-2004 and 2005-2006, three outbreaks of Salmonella enterica serovar Enteritidis were linked with the consumption of raw almonds. The S. Enteritidis strains from these outbreaks had rare phage types (PT), PT30 and PT9c. Clinical and environmental S. Enteritidis strains were subjected to pulse field gel electrophoresis (PFGE), multi-locus variable-number tandem repeat analysis (MLVA) and In 2000-2001, 2003-2004 and 2005-2006, three outbreaks of Salmonella enterica serovar Enteritidis were linked with the consumption of raw almonds. The S. Enteritidis strains from these outbreaks had rare phage types (PT), PT30 and PT9c. Clinical and environmental S. Enteritidis strains were subjected to pulse field gel electrophoresis (PFGE), multi-locus variable-number tandem repeat analysis (MLVA) andDNA microarray-based comparative genomic indexing (CGI) to evaluate their genetic relatedness. All three methods differentiated these S. Enteritidis in a manner that correlated with PT. The CGI analysis confirmed that that the majority of the differences between the S. Enteritidis PT 9c and 30 strains corresponded to bacteriophage-related genes present in the sequenced genomes of S. Enteritidis PT4 and S. Typhimurium LT2. However, PFGE, MLVA and CGI failed to discriminate between S. Enteritidis PT30 strains related to outbreaks from unrelated clinical strains, nor between strains separated up to 5 years apart. However, metabolic fingerprinting demonstrated that S. Enteritidis PT4, PT8, PT13a and clinical PT30 strains metabolized L-aspartic acid, L-glutamic acid, L-proline, L-alanine, and D-alanine amino acids more efficiently than S. Enteritidis PT30 strains isolated from orchards. These data indicate that S. Enteritidis PT9c and 30 strains are highly related genetically, and that PT30 orchard strains differ from clinical PT30 strains metabolically, possibly due to fitness adaptations.that S. Enteritidis PT9c and 30 strains are highly related genetically, and that PT30 orchard strains differ from clinical PT30 strains metabolically, possibly due to fitness adaptations.that S. Enteritidis PT9c and 30 strains are highly related genetically, and that PT30 orchard strains differ from clinical PT30 strains metabolically, possibly due to fitness adaptations.