Identification of a novel chromosome-encoded fosfomycin resistance gene fosC3 in Aeromonas caviae

In this work, a novel functional fosfomycin thiol transferase, FosC3, which shared the highest protein sequence similarity with FosC2, was identified in <i>A. caviae</i>. The fosfomycin inactivation enzyme FosC3 could effectively inactivate fosfomycin by chemical modification. It is implied that such mechanism facilitates <i>A. caviae</i> to respond to fosfomycin exposure, thereby enhancing survival. However, <i>fosC3</i> was not related with any MGE, which differs from many other fosfomycin thiol transferase genes. As a result, <i>fosC3</i> is not expected to be transmitted to other species through horizontal gene transfer mechanism. Our findings will contribute to the resistance mechanism of the common pathogenic <i>A. caviae</i>.