Effects of de-escalation and escalation antibiotic therapy on the formation of NETs during sepsis
To evaluate the function of NETs during different sequential antibiotic therapy, we determined the serum level of MPO-DNA, which is a biomarker of NETs, in CLP septic model. Mice were divided into two groups: the early stage of sepsis (the timepoint was set to 72 h after the initial CLP) and the late stage of sepsis (the timepoint was set to 6 days after the initial CLP). In the early stage, the mice were divided into 4 groups: the de-escalation group (imipenem for 3 days), the escalation group (ceftriaxone for 3 days), the de-escalation+ DNaseI group (used to disrupt the NETs) and the control group. The serum MPO-DNA levels in the control mice were much higher than those in the antibiotic-treated mice (P<0.01), and the MPO-DNA levels in the de-escalation group were higher than those in the escalation group (Fig 2A). When DNaseI administration was added, MPO-DNA in the de-escalation group decreased to levels lower than those in the escalation group.
Next, we determined the MPO-DNA levels in the late stage of sepsis. Three groups were established: the de-escalation group (imipenem for the first 3 days and ceftriaxone for the last 3 days), the escalation group (ceftriaxone for the first 3 days and imipenem for the last 3 days) and the sham group. In the late stage, the serum levels of MPO-DNA in the de-escalation group were lower than those in the escalation group with the adaption of de-escalation therapy (Fig 2B). All the data suggested that de-escalation antibiotic therapy increased NET formation during the early stage of sepsis and decreased NET formation during the late stage of sepsis, which was consistent with the in vitro results described above.