TABLE 3

Discrepancy analysis of isolates with discordant results based on the culture dependent algorithm

IsolateOriginal identificationResults of culture-dependent algorithm and motivationResults of molecular algorithmPredicted E. coli serotypeaPredicted Shigella O typePresence/absence of genes for deviant resultsb
505/58S. dysenteriae serotype 8EIEC, O untypeable; serologically S. dysenteriae 8, negative indole production againstS. dysenteriae non-O1/S. boydii/S. sonnei phase II/EIECO38: H26S. dysenteriae serotype 8tnaCAB cluster absent
12698S. flexneri serotype 2bEIEC, O untypeable; serological S. flexneri 2b, positive d-mannitol fermentation againstS. flexneriO13:H14S. flexneri 2bcmtlA, mtlD, and mtlR genes (mannitol operon) present
ZS. flexneri serotype 3aEIEC, O135; S. flexneri polyvalent positive, no conclusive serotype; antigenic formula B;6S. flexneriO13/O135:H14S. flexneri 1cdNA
9355S. boydii serotype 9Provisional Shigella; serologically S. boydii 9, negative indole production againstS. dysenteriae non-O1/S. boydii/S. sonnei phase II/EIECNo O-type genes, H14S. boydii serotype 9tnaCAB cluster present, tnaC and rrlB genes contain features essential for induction of tnaCAB cluster
F54157EIEC, O64S. sonnei, phase II; serologically and biochemically fit by repeatS. dysenteriae non-O1/S. boydii/S. sonnei phase II/EIECO149:H45S. boydii, serotype 1; no S. sonnei, S. flexneri, or S. dysenteriae O-antigen genes presentNA
F54197EIEC, O64S. sonnei, phase II; serologically and biochemically fit by repeatS. dysenteriae non-O1/S. boydii/S. sonnei phase II/EIECO149:H45S. boydii, serotype 1; no S. sonnei, S. flexneri or S. dysenteriae O-antigen genes presentNA
H57237EIEC, O+S. flexneri, serotype YvS. flexneriO13:H14S. flexneri YveNA
  • a Using SerotypeFinder, Center for Genomic Epidemiology.

  • b NA, not applicable.

  • c wzx1-5, gtrII, and gtrX present.

  • d wzx1-5, gtrI, gtrIc, and oac present.

  • e wzx1-5 and lpt-O present.