Background Antibiotics,a common strategy used for neonatal infection,show consistent effect on the gut microbiota of neonates.Supplementation with probiotics has become increasingly popular in mitigating the loss of the gut microbiota.However,no clear consensus recommending the use of probiotics in the infection of neonates currently exists.This study examined the effects of probiotics on the gut microbiota of infectious neonates when used concurrently with or during the recovery period following antibiotic therapy.Methods Fifty-five full-term neonates diagnosed with neonatal infections were divided into the following groups:NI (no intervention,antibiotic therapy only),PCA (probiotics used concurrently with antibiotics),and PAA (probiotics used after antibiotics).The NI group received antibiotic treatment (piperacillin-tazobactam) for 1 week and the PCA group received antibiotic treatment together with probiotics (Bifidobacterium longum,Lactobacillus acidophilus,and Enterococcusfaecalis)for 1 week.The PAA group received antibiotic treatment for 1 week followed by probiotics for 1 week.Fecal samples were collected at four time nodes:newborn,1 week,2 weeks,and 42 days after birth.The composition of the gut microbiota was determined by the high-throughput sequencing of 16S rRNA amplicons.Results Antibiotic exposure was found to dramatically alter gut microbiota,with a significant decrease of Bifidobacterium and Lactobacillus.The use of probiotics did not restore the overall diversity of the gut microbiota.However,using probiot-ics simultaneously with the antibiotics was found to be beneficial for the gut microbiota as compared to delaying the use of probiotics to follow treatment with antibiotics,particularly in promoting the abundance of Bifidobacterium.Conclusions These results suggest that the early use of probiotics may have a potential ability to remodel the gut microbiota during recovery from antibiotic treatment.However,further study is required to fully understand the long-term effects including the clinical benefits.