Changes In Infant Oropharynx Microbiota After Enterovirus Infection

Background:Upper respiratory tract infection( URTI) is common to see in children,which is primarily caused by virus and is frequently accompanied by secondary bacterial infections through poorly understood mechanisms.Enterovirus is one of the most common pathogens contributing to URTI,which is prevalent in late spring,summer and early autumn.Enterovirus is responsible for mild to moderate disease including common cold, herpangina as well as hand foot and mouth disease and sever diseases containing acute heart failure,severe pneumonia,acute flaccid myelitis,sepsis and so on.Unfortunately, no vaccine or antiviral drug is currently available for Enterovirus infection except Poliovirus. As viral infections of public health significance, they represent an important financial burden on health systems worldwide.Thus,finding an effective method for prevention and therapy is essential.Respiratory tract is a reservoir for microbiota which coevolves with human resulting in mutualistic symbiosis.They are called normal flora which play an important role in defending infection,obtaining nutrients,immune maturation and neuroregulation. Numerous studys indicate that the influences of microbiota on virus infections could be either protective or detrimental for host.However,little is known on the role of respiratory microbiota when Enterovirus infiltrates the host.The analysis of infant oropharynx(OP) microbiota after Enterovirus infection would help us get further understanding of virus infectious mechanism and offer a novel thought for prevention and therapy for Enterovirus.Methods: 1.The volunteers involved were from Xijing Hospital affiliated to Fourth Military Medical University. Inclusion criteria of the case group were as follows:1) an attending physician’s diagnosis of URTI among out patient children;2) no intake antibiotics and pribiotics during 1 month;3) be healthy at ordinary time and no any infectious disease during 1 month;4) the ability of the parent/guardian to give informed consent.The normal cases were involved according to the inclusion criteria except the first term.The throat swabs were obtained using the Copan ESWAB and the clinical materials were logged into Epidata software.2.We detected the viruses in throat swabs by Luminex x TAG? RVP FAST kit.3.We performed 16 S ribosomal DNA-targeted pyrosequencing by Illumina Miseq platform on throat swabs and analyzed data using bioinformatics methods.We compared overall community diversity,phylogenetic structure of the ecosystem and relative abundancesof the different bacteria.4.Statistical Product and Service Solutions 17.0 was used to analyze the data and Graph Pad Prism 5 was conducted to plot.Results:1.During May to July in 2015,we recruited 96 URTI children and 15 healthy infants.79 samples were positive in viruses from 96 samples and the dectection rate of viruses was 82.29%. Enterovirus, combination of Enterovirus and other viruses,other coninfection except Enterovirus, Parainfluenza virus 2, Parainfluenza virus 3 and Coronavirus OC43 accounted for 37.50%、11.46%、9.38%、6.25%、5.21% and 5.21%, respectively.We took infants infected with Enterovirus who were younger than 3 years as objects of study and enrolled 24 cases aged 19.17 months on average(male:female=14:10) as well as 15 healthy controls aged 19.27 months on average(male:female=10:5). Simultaneously,we analyzed the microbiota constitution of 3 infants coinfected with Enterovirus and other viruses and 3 beyond 3 years children infected with Enterovirus only.2.We acquired 1,120,649 high-quality 16 S r DNA sequences from 45 samples in total and the average number of sequences per sample is 24,903. The dominant phyla were Firmicutes, Proteobacteria, Actinobacteria, Bacteroidetes, and Fusobacteria.1)Compared with normal group,the OP microbiota diversity of the Enterovirus group decreased(p=0.482),the difference without statistical significance.During the infection, strong trends towards increases in the relative abundances of Fusobacteria(p=0.0098,FDR=0.0098) in phylum and Gemella(p=0.0034,FDR=0.0102) and unclassified Leptotrichiace(p =0.0192,FDR=0.0288) were found.Significant decrease in the relative abudance of Pseudomonas(p=0.0293,FDR=0.0293) was also observed. Gestational weeks,delivery mode,feeding patterns, white blood cell count and neutrophilic granulocyte percentage had no significant connection with the constitution of the OP microbiota of the Enterovirus infected infants.2)The OP microbiota alpha diversity of patients without herps reduced comparing with that of patients with herps(p=0.0111) and normal control(p=0.0392).However,the difference between the constitution of two groups was of no statistical significance.3)Compared with the group infected Enterovirus,the microbiota alpha diversity of the coinfection group showed obvious decrease(p=0.0020). The relative abundance of Fusobacteria lessened weakly. The individual difference was significant.4)The OP microbiota alpha diversity of the senior group presented remarkable discrease(p=0.0062) comparing with that of the younger group.And the relative abundance of Streptococcus reduced(p=0.0229).Conclusions:1. During May to July in 2015,the dominant viruses causing URTI among children in Xi’an City were Enterovirus, Parainfluenza virus 2,Parainfluenza virus 3, Coronavirus OC43 and so on.2.After Enterovirus infection,the OP microbiota alpha diversity of infants decreased; the relative abundance of Gemella and unclassified Leptotrichiace increased,while that of Pseudomonas reduced,which might provide evidence for the usage of some kind of probiotics to treat Enterovirus infection.