Comparison of genotypes of Salmonella enterica serovar Enteritidis phage type 30 and 9c strains isolated during three outbreaks associated with raw almonds.
In 2000 to 2001, 2003 to 2004, and 2005 to 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 pulsed-field gel electrophoresis (PFGE), multilocus 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 strains in a manner that correlated with PT. The CGI analysis confirmed that the majority of the differences between the S. Enteritidis PT9c and PT30 strains corresponded to bacteriophage-related genes present in the sequenced genomes of S. Enteritidis PT4 and S. enterica serovar Typhimurium LT2. However, PFGE, MLVA, and CGI failed to discriminate between S. Enteritidis PT30 strains related to outbreaks from unrelated clinical strains or between strains separated by up to 5 years. 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.
Parker
Craig T
CT
Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan St., Albany, CA 94710, USA. craig.parker@ars.usda.gov
Huynh
Steven
S
Quiñones
Beatriz
B
Harris
Linda J
LJ
Mandrell
Robert E
RE
D001434:Bacteriophage Typing; D016000:Cluster Analysis; D055028:Comparative Genomic Hybridization; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D055442:Metabolome; D018598:Minisatellite Repeats; D027861:Prunus / Q000382:microbiology*; D012478:Salmonella Food Poisoning / Q000453:epidemiology* / Q000382:microbiology; D012477:Salmonella enteritidis / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
D004269:DNA, Bacterial