Etiologic spectrum of hand, foot and mouth disease and molecular epidemiology of coxsackievirus A10 strains in Qingdao from year 2010 to 2012

Objective To analyze the etiologic spectrum of hand, foot and mouth disease （HFMD） and the molecular characteristics of coxsackievirus A10 （CVA10） strains isolated in Qingdao from year 2010 to 2012.Methods Throat swab specimens were collected from patients with HFMD to detect to-tal enteroviruses （ EVs） , EV71 and CVA16 strains by multiplex real time RT-PCR.The EV-positive speci-mens were further detected by a semi-nested RT-PCR to amplify the sequence of viral genes encoding VP1. The serotypes of EVs were identified based on the sequences of genes encoding VP1.The full-length gene se-quences encoding VP1 of CVA10 isolates were amplified and sequenced. The phylogenetic analysis was con-ducted by using MEGA5.0 software package.Results A total of 1919 outpatients with mild HFMD and 1336inpatients with serious HFMD were recruited in this study .CVA16 strains were the predominant patho-gen for outpatients in year 2010 （ prevalence rate of 53%） and 2012 （ prevalence rate of 73%） .EV71 strains were the predominant pathogen for outpatients in year 2011 （ prevalence rate of 78%） and inpatients in year 2010 （ prevalence rate of 70%） and 2011 （ prevalence rate of 86%） . Some serotypes other than CVA16 or EV71 were the predominant pathogens for inpatients in year 2012 （ prevalence rate 44%） . CVA10 strains were identified in 12 patients with HFMD in year 2010and 17 patients with HFMD in 2012. The full-length gene sequences encoding VP1 of 23 CVA10 isolates were successfully amplified and se-quenced.The phylogenetic analysis showed that the 23 CVA10 isolates all belonged to genotype C and could be further divided into six clades.The genes encoding VP1 of the 23 CVA10 strains shared 97.3% to 1000.%homologies in amino acid sequences.The CVA10 isolates were also similar to their counterparts isolated from other regions during the same period.Conclusion CVA16 and EV71 strains were the preva-lent pathogens of HFMD in Qingdao from year 2010 to 2012, co-circulated with some other serotypes of EVs, especially CVA10 strains.The CVA10 strains belonged to genotype C and shared high homologies among them and their counterparts circulated in other regions during the same period. Key words: Hand, foot and mouth disease;  Enterovirus;  Coxsackievims AIO;  Phylogeneticanalysis