Wang Mengran, Wang Jing, Li Tian, Bao Xue, Li Pengyun, Zhang Xiuling, Huang Qi, Meng Xianrong, Li Shaowen
Key Laboratory of Preventive Veterinary Medicine in Hubei Province, College of Veterinary Medicine, Huazhong Agricultural University, Shizishan Street No.1, Hongshan District, Wuhan city 430070, Hubei province, China.
FEMS Microbiol Lett. 2023 Jan 17;370. doi: 10.1093/femsle/fnad021.
Development of cefotaxime-resistance and biofilm formation increase the difficulty to prevent and control the infection and contamination of Salmonella, one of the most important foodborne and zoonotic bacterial pathogen. Our previous study observed that 1/8 minimum inhibitory concentration (MIC) of cefotaxime induced the enhancement of biofilm formation and filamentous morphological change by a monophasic Salmonella Typhimurium strain SH16SP46. This study was designed to explore the role of three penicillin-binding proteins (PBPs) in mediating the induction effect of cefotaxime. Three deletion mutants of the genes mrcA, mrcB, and ftsI, encoding the proteins PBP1a, PBP1b, and PBP3, respectively, were constructed using the parental Salmonella strain SH16SP46. Gram staining and scanning electron microscopy showed that these mutants showed normal morphology comparable to the parental strain without cefotaxime treatment. However, under the stress of 1/8 MIC of cefotaxime, the strains WT, ΔmrcA, and ΔftsI, rather than ΔmrcB, exhibited filamentous morphological change. Moreover, cefotaxime treatment significantly enhanced biofilm formation by the strains WT, ΔmrcA, and ΔftsI, but not by the ΔmrcB strain. The complement of mrcB gene in the ΔmrcB strain recovered the enhanced biofilm formation and filamentous morphological change induced by cefotaxime. Our results suggest that PBP1b encoded by mrcB gene may be a binding target of cefotaxime for initiating the effect on Salmonella morphology and biofilm formation. The study will contribute to further understanding of the regulatory mechanism of cefotaxime on Salmonella biofilm formation.
头孢噻肟耐药性的产生和生物膜的形成增加了预防和控制沙门氏菌感染与污染的难度，沙门氏菌是最重要的食源性病原体和人畜共患病原体之一。我们之前的研究观察到，头孢噻肟的1/8最低抑菌浓度（MIC）可诱导单相鼠伤寒沙门氏菌菌株SH16SP46增强生物膜形成并发生丝状形态变化。本研究旨在探讨三种青霉素结合蛋白（PBPs）在介导头孢噻肟诱导效应中的作用。分别构建了编码蛋白PBP1a、PBP1b和PBP3的基因mrcA、mrcB和ftsI的三个缺失突变体，亲本菌株为沙门氏菌菌株SH16SP46。革兰氏染色和扫描电子显微镜显示，在未用头孢噻肟处理的情况下，这些突变体的形态与亲本菌株相似，均正常。然而，在头孢噻肟1/8 MIC的压力下，野生型菌株、ΔmrcA和ΔftsI菌株而非ΔmrcB菌株出现了丝状形态变化。此外，头孢噻肟处理显著增强了野生型菌株、ΔmrcA和ΔftsI菌株的生物膜形成，但对ΔmrcB菌株没有影响。在ΔmrcB菌株中补充mrcB基因可恢复由头孢噻肟诱导的生物膜形成增强和丝状形态变化。我们的结果表明，由mrcB基因编码的PBP1b可能是头孢噻肟的结合靶点，从而启动对沙门氏菌形态和生物膜形成的影响。该研究将有助于进一步了解头孢噻肟对沙门氏菌生物膜形成的调控机制。
