Table 1

Outbreak versus nonoutbreak classifications of study isolates based on PFGE and MLVA or SNP-based typing methodologies

ExposureNo. of isolates with:
PFGE/MLVAa patternsSNPb set patterns
OutbreakcNonoutbreakOutbreakdNonoutbreak
Claimed8e (9f)1g9f0
Denied12h09i3j
Unsure3k03k0
Unrelated05l05l
  • a PFGE, pulsed-field gel electrophoresis; MLVA, multiple-locus variable-number tandem-repeat analysis.

  • b SNP, single nucleotide polymorphism.

  • c Outbreak patterns defined as PFGE pattern A/C and MLVA pattern A1 (if performed prior to 2 November 2011) for the case-control study and as PFGE pattern A/C or A/D and MLVA pattern A1 for the publication that detailed the outbreak (16).

  • d The outbreak pattern consists of backbone open reading frame SNP sets 1, 5, 6, and 10 (i.e., SNP set 10 was the terminal SNP set).

  • e Isolates from cases M1 to M8 (all from Missouri).

  • f Isolates from cases M1 to M9 (all from Missouri). The isolate from case M9 had PFGE pattern A/D and was designated as a case in the publication that detailed the outbreak (16) but not in the case-control study. The value in the leftmost column is in parentheses to note that the single subject whose isolate had a variant PFGE pattern was included in one analysis (the paper that detailed the outbreak [16]) but not the other (the case-control study).

  • g Isolate from case M9.

  • h Isolates from cases M10 to M19 (all from Missouri) and cases K1 and K2 (both from Kansas).

  • i Isolates from cases M10 to M17 and K1.

  • j Isolates from cases M18, M19, and K2, which possess SNP sets 1, 5, 6, 10, and 11 (from case M18), 1, 5, 6, 10, and 12 (from case K2), and 1, 5, 6, 10, 13 (from case M19).

  • k Isolates from cases M20 to M22 (all from Missouri).

  • l Isolates from cases unrelated to the outbreak. Isolates from cases WC1 and WC2 have SNP sets 1, 2, and 3 or 1, 2, and 4, respectively, and isolates from cases Wa1 and Wa2 have SNP sets 1, 5, 6, 7, and 8 or 1, 5, 6, 7, and 9, respectively. Isolates from cases WC1, Wa1, and Wa2 have nonoutbreak MLVA patterns. All isolates in these groups, except the isolate from case M23, have the PFGE pattern A/C.