Maximum likelihood tree of the 228 C. perfringen strains harboring pCP13-like plasmids. The toxin genes are represented by sky blue squares, plc, cpb, etx, cpe, netB, iap/ibp, cloSI, colA, cpb2, pfoA, nagH, nagI, nagJ, nagK, nagL, nanH, nanI, and nanJ in order from the inside to outside. Source and country of the C. perfringens strains were marked by squares with different colors.