Among the patients infected with gram-negative bacteria, there were 4 cases of Klebsiella pneumoniae infection, 3 cases of Acinetobacter baumannii infection, and 2 cases of Escherichia coli infection, and the serum PCT value of gram-negative bacterial infection was greater than that of gram-negative bacterial infection, and the difference was statistically significant (P < 0.05). The gene discussed is CALCA; the disease is gram-negative bacterial infections.