Article Figures & Data
Figures
- Fig. 1.
Abilities of clinical and nonclinical strains ofY. enterocolitica biotype 1A to adhere to (A) and invade (B) HEp-2 cells and to adhere to (C) and invade (D) CHO cells. Approximately 107 CFU was incubated with epithelial cells for 3 h before nonadherent bacteria were removed by three washes. To determine the number of adhesive bacteria, some epithelial cells were lysed and the cell-associated bacteria were enumerated. To determine the number of intracellular bacteria, other epithelial cells were incubated in fresh tissue culture medium containing 100 μg of gentamicin/ml for 90 min before epithelial cells were lysed and bacteria were enumerated. Data are expressed as percentages of the original inoculum and are means from at least two separate experiments using duplicate wells. In the box-and-whisker plots, the horizontal line within the box is the median value, the limits of the box are the 10th and 90th percentiles, and the whiskers are the 5th and 95th percentiles. The difference in adhesion between the two groups of isolates is not significant (P = 0.3 for HEp-2 cells and P = 0.14 for CHO cells by the Mann-Whitney test). The difference in invasion between the two groups of isolates is significant (P = 0.002 for HEp-2 cells andP < 0.001 for CHO cells).
- Fig. 2.
TEM of CHO cells incubated for 3 h with representative strains of Y. enterocolitica: 937 (biotype 1A, invasive) (A), AM5 (biotype 1A, noninvasive) (B), and W22703c (biotype 2, invasive) (C). Findings similar to those illustrated in panels A and B were observed with eight other strains of Y. enterocolitica biotype 1A, five invasive and three noninvasive. Bar = 1 μm.
- Fig. 3.
CHO cells incubated for 3 h with representative strains of Y. enterocolitica: 937 (biotype 1A, invasive) (A), AM5 (biotype 1A, noninvasive) (B), and W22703c (biotype 2, invasive) (C). Large numbers of strain 937 are associated with groups of five or more CHO cells, whereas only a few bacteria (arrows) of strain AM5 are associated with these cells. Strain W22703c demonstrates a more even pattern of association with the CHO cells. Findings similar to those illustrated in panels A and B were observed with eight other strains of Y. enterocolitica biotype 1A, five invasive and three noninvasive. Giemsa stain was used. Bar = 5 μm.
- Fig. 4.
Colonization of BALB/c mice by strains of Y. enterocolitica. Mice were inoculated by gavage with one of four strains of biotype-1A Y. enterocolitica, namely, clinical isolate 61525 (•) or 937 (▪) or nonclinical isolate IP2222 (○) or AM5 (□). Each point represents the mean CFU obtained from the ilea (A), ceca (B), or colons (C) of three mice at the times indicated after inoculation. The duration of colonization by clinical isolates in all three sites was significantly longer than that for the nonclinical strains (P ≤ 0.01).
Tables
- Table 2.
Effect of prolonged incubation on the number of internalized bacteria recovered from CHO cellsa
Strain Biotype Origin Internalized bacteriab after: Fold increasec 4.5 h 22.5 h Y. enterocolitica W22703c 2 Clinical 22.5 ± 7.4 25.5 ± 2.2 1.1 937 1A Clinical 0.24 ± 0.11 1.0 ± 0.60 4.3 T83 1A Clinical 0.38 ± 0.11 1.33 ± 0.06 3.5 AM5 1A Nonclinical 0.03 ± 0.01 0.11 ± 0.08 4.3 IP2222 1A Nonclinical 0.03 ± 0.02 0.21 ± 0.14 6.1 E. coliHB101 0.01 ± 0.01 0.01 ± 0.02 1.5 ↵a This experiment was performed as described in Materials and Methods, “Bacterial adhesion to and invasion of tissue culture cells.” The counts at 4.5 and 22.5 h measured invasion of and replication in tissue culture cells, respectively.
↵b Percent of original inoculum; mean ± standard deviation from three independent determinations.
↵c Calculated from raw data.
