Molecular characterization of infectious bronchitis virus strains isolated from vaccinated flocks in Serbia and their comparison with the isolated strains from neighboring countries

Abstract

© 2018, Veteriner Fakultesi Dergisi. All rights reserved. The aim of this study was to isolate, genetically characterize and determine phylogenetic relationship of strains detected in Serbia in comparison to other strains. A total of 480 samples collected from 13 different commercial layer flocks, obtained from tracheal swabs were included. Samples taken from 2016 to 2017 were molecularly analyzed by real-time RT-PCR, multiplex nested RT-PCR, and by sequencing of the S1 gene. Phylogenetic analyses based on partial S1 sequences revealed that six strains were classified as the D274 genotype, two strains as the QX genotype and two strains as the 4/91 genotype. The difference in nucleotide similarity between the Serbian isolates belonging to the D274 group ranges from 0 to 1.2%. Comparison of the obtained strains and D274 (X15832) showed differences from 0 to 0.9%. The greatest nucleotide similarity of detected QX strains was with Chinese QXIBV (KC795604), ranging from 98.8% to 99.1%. Two Serbian strains belonging to the 4/91 genotype had 99.7% and 98.8% nucleotide similarities with vaccine strain 4/91 (KF377577). This study has shown that viruses belonging to D274, QX, and 4/91 genotypes were circulating in poultry flocks in Serbia during 2016 and 2017.