Purpose. Zika virus infections have recently been reported in many dengue-endemic areas globally. Both dengue (DENV) and Zika (ZIKV) virus are transmitted by Aedes mosquitoes, raising the possibility of mixed infections in both vector and host. We evaluated DENV and ZIKV prevalence in human and vector samples in Kolkata, a DENV-endemic city.
Methodology. Blood samples were collected from 70 patients presenting dengue-like fever symptoms at a hospital in Kolkata during 2015–16. Serum was obtained and tested for DENV infection by DENV NS1-based ELISA. Adult (n=8) and larval stages (n=12) of Aedes were also collected. A RT-PCR-based screening of both viruses supplemented by amplicon sequencing was performed.
Results. Of the 70 samples, 20 DENV NS1-positive serum samples were used for detailed molecular study for DENV infection. Eighteen of these (90 %) were positive by hemi-nested serotype-specific RT-PCR for DENV1/2/3, with four samples showing evidence of DENV2-3 or DENV1-3 mixed infection. None were ZIKV-positive using NS5 or ENV-based PCR, though weak amplification of a DENV1 NS5 sequence was detected in three serum samples indicating cross-reactivity of the primers. All mosquito samples were ZIKV-negative, whereas 5/8 (63 %) of adult mosquitoes and 11/12 (92 %) of larvae were DENV3-positive.
Conclusion. Both host and vector samples showed absence of ZIKV but high prevalence of DENV. The high rate of infection of larvae with DENV is suggestive of trans-ovarial transmission that could contribute to the surge of human infections during each post-monsoon season. It would be important to guard against false positives using the available Zika-reporting primer sets.
Purpose. Enteroviruses (EV) 71 and coxsackievirus A (CVA) 16 are the most prevalent EV serotypes responsible for hand, foot and mouth disease (HFMD). Nevertheless, CVA6 was found to be the leading cause of HFMD in the Nanjing area, of China in 2013. This study aims to provide insights into the occurrence of the emergent recombinant CVA6 through examination of the evolutionary history and the involved recombination events.
Methodology. The viral protein1 (VP1) and non-structural (NS) 2C and 3D of 28 Nanjing CVA6 strains were aligned, among which the full-length sequences of eight strains were further characterized.
Results. We revealed the co-existence of two recombinant forms (RFs), RF-A and RF-J, in the local area. RF-J is a novel RF group, comprising a proportion of local and Shanghai CVA6 strains from 2013. The appearance of RF-J CVA6 strains was most likely the result of two recombination events, with the co-circulating CVA4 and CVA8 providing the regions beyond positions 4001~4045 and 4866~4873, respectively. Evolutionary history analysis showed that the VP1 sequences of RF-J derived from RF-A, which was also probably the ancestor of several other RF groups. The 3D region of RF-J was closely related to CVA8. The point in time of emergence of the most recent common ancestor (tMRCA) of RF-J in China was estimated to be around 2011 in both terms of VP1 and 3D region.
Conclusion. The emerging recombinant CVA6 variants belong to a novel RF-J group which was most likely formed by at least two recombination events. Continued monitoring on the geographical distribution of various CVA6 RFs is essential.
Purpose. Among the pneumococcal proteins, pneumococcal surface protein A (PspA) is considered the most promising candidate for a serotype-independent vaccine. This study aimed to investigate the serotype, genetic diversity of PspA, lineage (genotype) and drug resistance traits of pneumococcal isolates from paediatric patients.
Methodology. A total of 678 non-invasive pneumococcal isolates obtained from June to November 2016 were analysed. All isolates were characterized for PspA families, serotypes and macrolide resistance genes. Seventy-one representative isolates of non-vaccine serotypes (NVTs) were genetically analysed for the clade-defining region (CDR) of PspA, as well as multi-locus sequence typing (MLST).
Results. The detection rate of NVTs was 87.9 % (n=596), including dominant NVTs 15A (14.5 %, n=98), 35B (11.8 %, n=80), 15C (9.3 %, n=63) and 23A (9.0 %, n=61). Most isolates (96.6 %) possessed macrolide resistance genes erm(B) and/or mef(A/E). PspA families 1, 2 and 3 were detected in 42.3, 56.6 and 0.6 % of isolates, respectively. Nucleotide sequences of CDR showed high identity (90–100 %) within the same PspA clade, although the CDR identity among different PspA families ranged from 53 to 69 %. All isolates of NVTs 23A, 10A, 34, 24, 22F/22A, 33F, 23B and 38 were from PspA family 1, while NVTs 35B, 15C, 15B and 11A/11D isolates were from family 2. In contrast, genetically distinct PspAs were found in NVTs 6C and 15A. PspA family 3/clade 6 was detected in only NVT serotype 37 isolates assigned to ST447 and ST7970, showing the mucoid phenotype.
Conclusion. The present study revealed the predominance of PspA families 1 and 2 in NVTs, and the presence of family 3 in serotype 37.