Free Access

Table I.

Expression of virulence of 16 L. monocytogenes strains and their VBNC forms, by formation of plaques in the human adenocarcinoma cell line HT-29. The results are expressed as the number of plaques obtained for 7 log CFU deposited per well.

Strain Source Virulence (mean log + SD) culturable strains Virulence (mean log + SD) VBNC
EGDea (control) Reference strain 5.23 ± 0.40 ND
Scott A Reference strain 6.38 ± 0.03 0
EGDeb Reference strain 5.18 ± 0.11 0
L1069 Patient 5.75 ± 0.34 0
L1371 Patient 5.18 ± 0.27 0
L1372 Patient 6.70 ± 0.13 0
L3365 Patient 6.18 ± 0.47 0
L3368 Patient 5.35 ± 0.23 0
L3371 Patient 5.66 ± 0.14 0
L839 Salmon 5.44 ± 0.37 0
L1272 Salmon 5.81 ± 0.26 0
L1338c Salmon 4.28 ± 0.24 0
L2663 Salmon 4.98 ± 0.16 0
L2735 Salmon 5.56 ± 0.21 0
L1317 Drainpipe 4.88 ± 0.27 0
L2842 Salmon waste 5.61 ± 0.31 0
L1232 Seawater 5.88 ± 0.13 0

ND: Not done.

a

Control used in the plaque cell test.

b

Used in the VBNC experiments.

c

Examined in a immunocompetent mouse assay and shown to be virulent.