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Volume 13, Number 12—December 2007
Dispatch

Enhanced Subtyping Scheme for Salmonella Enteritidis

Jie Zheng*, Christine E. Keys†, Shaohua Zhao‡, Jianghong Meng*, and Eric W. Brown†Comments to Author 
Author affiliations: *University of Maryland, College Park, Maryland, USA; †US Food and Drug Administration, College Park, Maryland, USA; ‡US Food and Drug Administration, Laurel, Maryland, USA;

Main Article

Table 2

PFGE diversity indices for various combinations of restriction enzymes in Salmonella Enteritidis

Enzyme/combination PFGE patterns* Mean no. strains/ polytomy† % polytomous strains‡ Node:strain ratio§ Simpson diversity index
XbaI 19 9.1 84 0.30 0.83
BlnI 15 16.3 85 0.22 0.76
SpeI 16 9.6 88 0.28 0.80
SfiI 15 13.2 87 0.24 0.67
PacI 20 9.0 83 0.32 0.74
NotI 26 5.2 82 0.47 0.92
XbaI/BlnI 24 9.7 76 0.37 0.84
XbaI/SpeI 26 6.6 78 0.43 0.88
XbaI/SfiI 30 5.2 75 0.51 0.92
XbaI/PacI 30 5.6 74 0.50 0.91
XbaI/NotI 38 4.2 66 0.63 0.95
BlnI/SpeI 22 8.6 79 0.36 0.84
BlnI/SfiI 26 6.6 78 0.43 0.89
BlnI/PacI 28 6.3 75 0.46 0.88
BlnI/NotI 36 4.3 68 0.61 0.94
SpeI/SfiI 27 5.9 78 0.46 0.90
SpeI/PacI 30 6.8 71 0.46 0.89
SpeI/NotI 35 3.9 72 0.61 0.96
SfiI/PacI 30 5.2 75 0.51 0.87
SfiI/NotI 43 4.0 58 0.67 0.96
PacI/NotI 42 3.6 62 0.70 0.96
SpeI/SfiI/NotI 48 3.8 50 0.64 0.97
SpeI/PacI/NotI 47 3.6 53 0.72 0.97
SfiI/PacI/NotI 51 3.3 47 0.79 0.98
6 enzymes 57 3.6 38 0.78 0.98

*PFGE, pulsed-field gel electrophoresis. Absolute tally of unique PFGE fingerprints or fingerprint combinations derived from the corresponding enzyme or group of enzymes.
†Total no. polytomous strains/no. polytomies in the dendrogram.
‡No. polytomous strains/76 (total S. Enteritidis strains in the analysis).
§Total no. nodes in the dendrogram/76 S.Enteritidis strains.
¶Derived from the formula for assessing discriminatory capability of a subtyping method (13).

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