[Genotype distribution of human enteroviruses isolated from swage in Shanghai during year 2013-2014]

Objective: To explore the time and genotype distribution of human enterovirus (HEV) isolated from sewage in Shanghai in 2013-2014. Methods: One sewage sample each was collected from two local sewage plants located in Minhang District and Jiading District on the same day at the day 24-28 of every month from 2013 to 2014. Each sample weighed 1 L. The specimens were concentrated by anionic membrane absorption, eluted with beef extract solution, and then used to inoculate RD, HEp-2, and L20B cell lines. A total of 249 enterovirus strains were isolated from sewage samples during the study period, including 185 non-polio enterovirus (NPEV) and 64 poliovirus (PV) strains, which were identified as vaccine strains. RT-PCR and Sanger sequencing were performed to identify HEV genotypes. Homologous analysis of VP1 sequences was conducted using BioEdit (version 7.0.0). Phylogenetic analysis was performed using the neighbor-joining method based on the alignment of VP1 gene sequences using MEGA (version 4.0.2). Results: Among 185 NPEV strains, 178 strains were successfully sequenced and classified into 15 genotypes, including coxsackievirus group B (CVB) 2, 3, and 5; enteric cytopathic human orphan (ECHO) virus 1, 3, 6, 7, 11, 13, 19, 20, 24, 25, and 30; and coxsackievirus group A 4. CVB5 and ECHO6 genotypes accounted for 33.5% (56 strains) and 24.9% (43 strains) of NPEV isolates, respectively. During the study period, HEV isolates were mainly isolated in summer and autumn in Minhang District. ECHO6 strains were frequently isolated from June 2013 to July 2014. Thereafter, the number of ECHO6 strains gradually reduced in the second half of 2014. CVB5 strains demonstrated scattered distribution from 2013 to the first half of 2014 and gradually increased in the second half of 2014. The distribution of ECHO6 and CVB5 strains in Jiading District was similar to that in Minhang District. In 2013-2014, CVB5 strains comprised C6 and C8 subgenotypes, which belong to two transmission chains and show large differences compared with foreign strains isolated during the same period. ECHO6 strains comprised C6, C8, and D9 subgenotypes, which belong to three transmission chains. Moreover, ECHO6 subgenotype D9 was a dominant subgenotype in Shanghai, with broad geographical distribution both at home and abroad. Conclusion: Poliovirus was identified as a vaccine strain in environmental surveillance from June 2013 to April 2014 in Shanghai. Several transmission strains of ECHO6 and CVB5 were identified, which were the dominant serotypes.