Shafipour Maryam, Mohammadzadeh Abdolmajid, Ghaemi Ezzat Allah, Mahmoodi Pezhman, Mosavari Nader
Department of Pathobiology, Faculty of Veterinary Medicine, Bu-Ali Sina University, Hamedan, Iran.
Infectious Diseases Research Center, Golestan University of Medical Sciences, Gorgan, Iran.
BMC Infect Dis. 2025 Jun 3;25(1):791. doi: 10.1186/s12879-025-11168-y.
Small genetic modules, such as toxin-antitoxin (TA) systems, play specific roles in persistence, antibiotic resistance, and virulence in pathogenic bacteria. Given the transmission of M. bovis to humans and the importance of the spread of antibiotic resistance in this bacterium, this study aimed to compare the presence and sequences of the mazEF3, vapBC3, and relJK genes in type II TA systems of both resistant and sensitive M. bovis isolates.
Fifty-nine M. bovis isolates were obtained from the Razi Vaccine and Serum Research Institute in Iran. M. bovis isolates were confirmed using GeneXpert MTB/RIF and by evaluating of the pncA gene. Rifampin- and isoniazid-resistant isolates were identified using Multiplex Allele-Specific Polymerase Chain Reaction (MAS-PCR). The presence and mutations of the mazEF3, relJK, and vapBC3 genes were analyzed by PCR sequencing. Molecular docking was performed to predict the binding affinity of RelJ to RelK.
Of the 59 M. bovis isolates, 13 (22%) and 3 (5.1%) were resistant to rifampin and isoniazid, respectively. The most common mutations in the rifampin-resistant isolates were observed at codons rpoB516 (92.3%) and rpoB531 (84.6%). The nucleotide sequences of mazEF3, vapBC3, and relK were identical to those in the reference strain in all cases. Molecular docking analysis suggests that the mutant RelJ shows improved binding affinity in comparison to the non-mutant protein for the RelK toxin.
These findings suggest that the relJ gene may be associated with antibiotic resistance in M. bovis. Therefore, increasing the sample size is recommended for a more in-depth investigation of relJ. If successful, this biomarker could be utilized for developing new methods to identify resistant isolates.
小的遗传模块，如毒素-抗毒素（TA）系统，在病原菌的持续性、抗生素抗性和毒力方面发挥着特定作用。鉴于牛分枝杆菌可传播给人类以及该细菌中抗生素抗性传播的重要性，本研究旨在比较耐药和敏感牛分枝杆菌分离株II型TA系统中mazEF3、vapBC3和relJK基因的存在情况及序列。
从伊朗拉齐疫苗和血清研究所获得59株牛分枝杆菌分离株。使用GeneXpert MTB/RIF并通过评估pncA基因来确认牛分枝杆菌分离株。使用多重等位基因特异性聚合酶链反应（MAS-PCR）鉴定耐利福平及异烟肼的分离株。通过PCR测序分析mazEF3、relJK和vapBC3基因的存在及突变情况。进行分子对接以预测RelJ与RelK的结合亲和力。
在59株牛分枝杆菌分离株中，分别有13株（22%）和3株（5.1%）对利福平和异烟肼耐药。在耐利福平分离株中，最常见的突变出现在密码子rpoB516（92.3%）和rpoB531（84.6%）处。在所有情况下，mazEF3、vapBC3和relK的核苷酸序列与参考菌株的序列相同。分子对接分析表明，与非突变蛋白相比，突变型RelJ对RelK毒素的结合亲和力有所提高。
这些发现表明relJ基因可能与牛分枝杆菌的抗生素抗性有关。因此，建议增加样本量以更深入地研究relJ。如果成功，这种生物标志物可用于开发鉴定耐药分离株的新方法。
