We claim, the ornamental design for a toothbrush sterilizer, as shown and described.
FIG. 1 is a perspective view of a toothbrush sterilizer, showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view thereof showing a configuration of use wherein a toothbrush is housed in the toothbrush sterilizer.
The broken line showing of a toothbrush in FIG. 8 represents an environment and is for illustrative purposes only. The remaining broken lines show portions of the toothbrush sterilizer that form no part of the claimed design.