To investigate levels of mitochondrial protein (Smac) and astrocyte-derived protein (S100B) regulated by pathogen infection after craniocerebral injury, and to analyze their relationship with curative effect and prognosis.

From January 2016 to January 2018, a total of 112 cases with infection after brain injury surgery (postoperative infection group), 50 cases without infection after brain injury surgery (uninfected group) and 50 cases of healthy examination (control group) in the Third Medical Center of the PLA General Hospital were selected. The levels of serum Smac and S100B protein were detected by enzyme linked immunosorbent assay. The diagnostic values of serum Smac and S100B on postoperative infection after brain injury surgery were analyzed by receiver operating characteristic curve (ROC). The effect of serum Smac and S100B protein on the prognosis of patients with infection after brain injury surgery was analyzed by Logistic regression analysis.

The levels of serum Smac and S100B of cases in postoperative infection group, uninfected group and control group were significantly different (F = 11.346, P = 0.001; F = 9.524, P = 0.008), among whom, patients in postoperative infection group were significantly lower than those of uninfected group (Smac: t = 5.836, P < 0.001; S100B: t = 7.782, P < 0.001), patients in uninfected group were significantly lower than those of control group (Smac: t = 2.946, P = 0.004; S100B: t = 3.889, P < 0.001). Single test of serum Smac or S100B had certain diagnostic value for infection after brain injury surgery (Smac: AUC = 0.689, 95%CI: 0.624-0.757, P = 0.023; S100B: AUC = 0.718, 95%CI: 0.653-0.749, P = 0.011), and the combination of the two indexes could improve the diagnostic efficacy (AUC = 0.857, 95%CI: 0.811-0.926, P = 0.005). Compared with before treatment, the levels of serum Smac and S100B protein were significantly higher of cases in postoperative infection group after treatment, with significant differences (t = 4.802, 6.499; both P < 0.001). There were significant differences in serum Smac and S100B levels of patients with death, poor prognosis and good prognosis after 6 months follow-up (F = 15.065, P < 0.001; F = 7.194, P = 0.016), among whom, Smac and S100B levels of patients with death were significantly lower than those of cases with poor prognosis (t = 2.06, P = 0.046; t = 2.297, P = 0.028); Smac and S100B levels of patients with poor prognosis were significantly lower than those of cases with good prognosis (t = 4.225, 7.110; P < 0.001), all with significant differences. Logistic regression analysis showed that serum Smac and S100B protein were protective factors for the prognosis of infection after brain injury surgery (P = 0.008, 0.003).

The levels of serum Smac and S100B protein were lowly expressed in patients with infection after brain injury surgery, which had certain diagnostic value on pathogen infection. The combination of the two indexes could significantly improve the diagnostic efficacy and affect the curative effect and prognosis.