For infections such as serratia sepsis, Enterococcus bacteremia, Streptococcus bacteremia, perianal abscess, cecitis, neutropenic colitis, and cryptogenic organizing pneumonia, gemtuzumab ozogamicin may increase the risk of opportunistic infections by destroying CD33-positive immune cells (such as monocytes) and further weakening the innate immune response (15). This evidence concerns the gene CD33 and colitis.