Figure 2. Effect of the codY mutation on the adherence and invasion ability of Streptococcus suis serotype 2.

(a,b) Evaluating the effect of codY mutation on adherence and invasion ability of S. suis 2. The 10⁵ HEp-2 cells maintained in 24-well plate were infected with S. suis 2 (10⁶ CFU) at a MOI (multiplicity of infection) of 10:1 and incubated at 37 °C for 2 h. The infected cells were washed 3 times with PBS and lysised by sterile distilled water followed by plating the lysis on TSA for cultivation in the 37 °C incubators for 24 hours, determining the CFU numbers of bacteria adhered on HEp-2 cells in indicated groups. The adherence experiments were repeated at least three times (a). The S. suis 2 (10⁶ CFU) at a MOI of 10:1 was incubated with 10⁵ HEp-2 cells at 37 °C for 2 h. The infected cells were washed 3 times with PBS before being kept in DMEM culture medium containing gentamicin (100 μg/ml) and penicillin (5 μg/ml) for 2 h to kill the bacteria outside the HEp-2 cells. Then the HEp-2 cells were washed thrice by PBS followed by calculating the CFU by plating the lysis of the cells for thrice in indicated groups. The percentage of the CFU was normalized to WT group designed as 100%. The data was showed as Means ± S.E.M; The statistic was conducted using Student’s t test (unpaired t test, two tailed); **P < 0.01; *P < 0.05 (b).