Zhang Junxuan, He Xiaolu, Hao Jinzhen, Wang Yefan, Su Jinyang, Chen Xiaoxin, Deng Liying, Zheng Yizhang, Guo Zixing, Wang Mianzhi, Sun Yongxue
College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong 510642, PR China; Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, Guangdong 510642, PR China; National Laboratory of Safety Evaluation (Environmental Assessment) of Veterinary Drugs, South China Agricultural University, Guangzhou, Guangdong 510642, PR China.
College of Veterinary Medicine, Yangzhou University, Yangzhou, PR China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, PR China.
Poult Sci. 2025 May 5;104(8):105268. doi: 10.1016/j.psj.2025.105268.
Riemerella anatipestifer, an important waterfowl pathogen, causes severe economic losses because of limited prevention and control methods. We aimed to characterize the prophages of R. anatipestifer and explore their role in lysogenic conversion and fitness cost to host bacteria based on the interactive infection of 110 wild-type strains and ATCC 11845. The temperate phages PJA1, PJO17, PJR4, PJL1, and PJX6 were isolated from clinical strains and showed various lytic abilities, high similarity between different Riemerella phages, and stable properties in transmission electron microscopy, temperature sensitivity, and one-step growth curve detection. To study the effects of lysogeny, we developed five lysogenic strains by integrating phages into the genome of JW1, a wild-type and prophage-absent strain of R. anatipestifer that is particularly susceptible to phage infection. The spontaneous induction frequency of the lysogen strains reached approximately 4-log, showing resistance to each other. Genomic analysis revealed high similarity to the first characterized Riemerella phage, RAP44, particularly in structural gene modules. Lysogens exhibited resistance to superinfection by prophages, similar to the reference strain ATCC 11845. Compared to JW1, lysogens showed consistent growth curves and colony morphology but were significantly thicker and shorter in scanning electron microscopy images. The lysogenic conversion process reduced the minimum inhibitory concentration of rifampin for lysogen JW1_PJA1 and JW1_PJO17 to 1/4 and 1/8 of that observed in the strain JW1, respectively, and decreased the MIC of florfenicol for lysogen JW1_PJR4 to half of the original value. Genomic comparisons revealed prophage integration and sequence rearrangement in lysogen genomes under the action of integrase. Co-culture experiments demonstrated that sensitive JW1 could be lysogenized by phages that were spontaneously induced from lysogens. Given the high prevalence of prophages in R. anatipestifer and no significant growth defect under laboratory conditions, lysogenic conversion appears to be a natural adaptation of this pathogen. By elucidating how prophages affect R. anatipestifer resistance and fitness, our findings provide a foundation for harnessing these interactions to design effective phage-based control strategies.
鸭疫里默氏菌是一种重要的水禽病原体，由于预防和控制方法有限，会造成严重的经济损失。我们旨在对鸭疫里默氏菌的前噬菌体进行表征，并基于110株野生型菌株和ATCC 11845的交互感染，探索它们在溶原性转化以及对宿主细菌的适应性代价方面所起的作用。从临床菌株中分离出了温和噬菌体PJA1、PJO17、PJR4、PJL1和PJX6，它们表现出不同的裂解能力，不同鸭疫里默氏菌噬菌体之间具有高度相似性，并且在透射电子显微镜观察、温度敏感性和一步生长曲线检测中具有稳定的特性。为了研究溶原性的影响，我们通过将噬菌体整合到JW1的基因组中构建了五株溶原性菌株，JW1是鸭疫里默氏菌的一株野生型且无前噬菌体的菌株，对噬菌体感染特别敏感。溶原性菌株的自发诱导频率达到约4个对数，且相互之间表现出抗性。基因组分析显示与首个被表征的鸭疫里默氏菌噬菌体RAP44高度相似，特别是在结构基因模块方面。溶原性菌株对前噬菌体的超感染表现出抗性，类似于参考菌株ATCC 11845。与JW1相比，溶原性菌株呈现出一致的生长曲线和菌落形态，但在扫描电子显微镜图像中明显更厚且更短。溶原性转化过程分别将溶原性菌株JW1_PJA1和JW1_PJO17对利福平的最低抑菌浓度降低至JW1菌株中观察值的1/4和1/8，并将溶原性菌株JW1_PJR4对氟苯尼考的最低抑菌浓度降低至原始值的一半。基因组比较揭示了在整合酶作用下溶原性基因组中的前噬菌体整合和序列重排。共培养实验表明，敏感的JW1可被溶原性菌株自发诱导产生的噬菌体溶原化。鉴于前噬菌体在鸭疫里默氏菌中普遍存在，且在实验室条件下无明显生长缺陷，溶原性转化似乎是这种病原体的一种自然适应方式。通过阐明前噬菌体如何影响鸭疫里默氏菌的抗性和适应性，我们的研究结果为利用这些相互作用设计有效的基于噬菌体的控制策略奠定了基础。
