Infectious bronchitis (IB) is a highly contagious respiratory disease caused by a gammacoronavirus that has been circulating for many years in chickens in Bangladesh, resulting in significant economic losses. The aim of this study was to detect and characterize infectious bronchitis virus (IBV) from clinical outbreaks and surveillance samples. Real-time RT-PCR was used to detect IBV in pooled lung and tracheal tissue samples (n = 78), oropharyngeal swabs (n = 19), and pooled fecal samples (n = 13) from live-bird markets. Both respiratory and nephropathogenic forms of IB were suspected at necropsy (n = 7) from clinical outbreaks. Sequencing of hypervariable regions (HVR1-2 and HVR3) of the region of the spike gene (S) encoding the S1 subunit of five isolates revealed circulation of the Mass-like, QX-like, and 4/91-like genotypes of IBV in Bangladesh. Each genotype was extremely variable, as shown by separate clustering of the viruses in a phylogenetic tree and high nucleotide (nt) sequence divergence (38.8–41.2% and 25.7–37.4% in the HVR1-2 and HVR3 sequence, respectively). The unique mutation G65E was observed in each Mass-like isolate, and Y328S was observed in each 4/91-like Bangladeshi isolate. Three neutralizing epitope sites were predicted within the HVRs that differed significantly among the three genotypes. In addition, one Bangladeshi isolate carried fixed mutations at 294F and 306Y, like other pathogenic QX-like IBVs, which could affect epitopes involved in neutralization, facilitating virus circulation among vaccinated flocks. Therefore, continuous screening and genotype characterization will be necessary to track the epidemiology of IBV and control IB infection in Bangladesh.

传染性支气管炎（IB）是一种由伽马冠状病毒引起的高度传染性呼吸道疾病，该病毒已在孟加拉国的鸡群中传播多年，造成重大经济损失。本研究的目的是从临床暴发和监测样本中检测和表征传染性支气管炎病毒 (IBV)。实时 RT-PCR 用于检测来自活禽市场的合并肺和气管组织样本（n = 78）、口咽拭子（n = 19）和合并粪便样本（n = 13）中的 IBV。临床暴发的尸检（n = 7）怀疑呼吸道和肾病形式的IB。对编码五个分离株的 S1 亚基的刺突基因 (S) 区域的高变区 (HVR1-2 和 HVR3) 进行测序揭示了 Mass 样、QX 样、和 4/91 样基因型的 IBV 在孟加拉国。每个基因型都极其可变，如系统发育树中病毒的单独聚类和高核苷酸 (nt) 序列差异（HVR1-2 和 HVR3 序列分别为 38.8-41.2% 和 25.7-37.4%）所示。在每个类似 Mass 的分离物中观察到独特的突变 G65E，在每个 4/91 样的孟加拉国分离物中观察到 Y328S。在 HVR 中预测了三个中和表位位点，这三个基因型之间存在显着差异。此外，一种孟加拉分离株在 294F 和 306Y 处携带固定突变，与其他致病性 QX 样 IBV 一样，这可能影响参与中和的表位，促进疫苗接种鸡群之间的病毒传播。所以，