It is the first report to reveal the peptidoglycan recognition protein in C. tritonis, and these results suggest that peptidoglycan recognition protein Ct-PGRP-S1 is an important effector of C. tritonis that modulates bacterial infection resistance of V. alginolyticus and S. aureus, and this study may provide crucial basic data for the understanding of an innate immunity system of C. tritonis. Here, PGLYRP1 is linked to bacterial infectious disease.