| Summary: | Hepatitis C virus subtype 1b (HCV1b) is still the most prevalent subtype worldwide, with massive expansion due to poor health care standards, such as blood transfusion and iatrogenic procedures. Despite safe and effective new direct antiviral agents (DAA), treatment success can depend on resistance-associated substitutions (RASs) carried in target genomic regions. Herein we investigated transmission clusters and RASs among isolates from HCV1b positive subjects in the Calabria Region. Forty-one NS5B and twenty-two NS5A sequences were obtained by Sanger sequencing. Phylogenetic analysis was performed using the maximum likelihood method and resistance substitutions were analyzed with the Geno2pheno tool. Phylogenetic analysis showed sixteen statistically supported clusters, with twelve containing Italian sequences mixed with foreign HCV1b isolates and four monophyletic clusters including only sequences from Calabria. Interestingly, HCV1b spread has been maintained by sporadic infections in geographically limited areas and by dental treatment or surgical intervention in the metropolitan area. The L159F NS5B RAS was found in 15 isolates and in particular 8/15 also showed the C316N substitution. The Y93H and L31M NS5A RASs were detected in three and one isolates, respectively. The A92T NS5A RAS was found in one isolate. Overall, frequencies of detected NS5B and NS5A RASs were 36.6% and 22.7%, respectively. For the eradication of infection, improved screening policies should be considered and the prevalence of natural RASs carried on viral strains.
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