Environmental surveillance of polioviruses with special reference to L20B cell line.

With the eradication of poliovirus, the focus has now shifted to environmental surveillance of poliovirus to determine the circulating polioviruses in an area. L20B and RD cell lines are used for isolation of polioviruses. It is imperative to study the efficacy of these cell line in isolating polioviruses from environmental samples. The present study was carried out to determine the sensitivity and specificity of L20B cell line for isolation of polioviruses from environmental samples. L20B and RD cell lines are used for isolation of polioviruses. Molecular characterization was done by using real time RT-PCR. A total of 432 sewage samples from Delhi and Punjab were processed for the isolation of polioviruses during Jan-Dec 2015. 96.76% of the samples were positive in either of the cell lines. Non-polio enteroviruses were obtained in 50 samples on primary isolation. On RT-PCR, 347 (94.29%) samples yielded polioviruses and the rest (21) non-polio enteroviruses or non-enteroviruses. A total of 703 isolates were obtained. 635 isolates were found polioviruses by PCR (90.33%), 20 isolates were found to be NPEV (2.84%) and 48 (6.83%) were found to be NEV. Out of the 20 NPEV isolates, 14 were from RLR (RD-L20B-RD) route and six isolates were from LR (L20B-RD) route. All 48 NEV isolates were from LR route. Thus L20B cell line is more sensitive as compared to RD cell line for isolation of polioviruses however it is not absolutely specific for polioviruses.