Yu Ting, Huang Jiayuan, Huang Xinyue, Hao Jingchen, Zhang Pengyu, Guo Tingting, Bao Guangyu, Li Guocai
Department of Microbiology, Institute of Translational Medicine, Medical College, Yangzhou University, Yangzhou, China.
Department of Laboratory Medicine, Affiliated Hospital, Yangzhou University, Yangzhou, China.
Front Microbiol. 2024 Jul 1;15:1381749. doi: 10.3389/fmicb.2024.1381749. eCollection 2024.
The escalating prevalence of bacterial resistance, particularly multidrug-resistant bacteria like , has become a significant global public health concern. The CRISPR-Cas system, a crucial defense mechanism in bacteria against foreign genetic elements, provides a competitive advantage. Type I-Fb and Type I-Fa are two subtypes of CRISPR-Cas systems that were found in A. baumannii, and the I-Fb CRISPR-Cas system regulates antibiotic resistance in . However, it is noteworthy that a majority of clinical isolates of lack or have incomplete CRISPR-Cas systems and most of them are multidrug-resistant. In light of this, our study aimed to examine the impact of antibiotic pressure on the fitness cost of the I-Fb CRISPR-Cas system in .
In the study, we conducted in vitro competition experiments to investigate the influence of sub-minimum inhibitory concentration (sub-MIC) on the CRISPR-Cas systems' fitness cost in . We found that the fitness cost of the CRISPR-Cas system was increased under sub-MIC conditions. The expression of CRISPR-Cas-related genes was decreased, while the conjugation frequency was increased in AB43 under sub-MIC conditions. Through metabolomic analysis, we identified that sub-MIC conditions primarily affected energy metabolism pathways. In particular, we observed increased carbon metabolism, nitrogen metabolism, and intracellular ATP. Notably, the CRISPR-Cas system demonstrated resistance to the efflux pump-mediated resistance. Furthermore, the expression of efflux pump-related genes was increased under sub-MIC conditions.
Our findings suggest that the I-Fb CRISPR-Cas system confers a significant competitive advantage in . However, under sub-MIC conditions, its function and the ability to inhibit the energy required for efflux pumps are reduced, resulting in an increased fitness cost and loss of competitive advantage.
细菌耐药性，尤其是像鲍曼不动杆菌这样的多重耐药菌的流行不断加剧，已成为全球重大的公共卫生问题。CRISPR-Cas系统是细菌抵御外来遗传元件的关键防御机制，赋予细菌竞争优势。I-Fb型和I-Fa型是在鲍曼不动杆菌中发现的CRISPR-Cas系统的两个亚型，I-Fb CRISPR-Cas系统调节鲍曼不动杆菌的抗生素耐药性。然而，值得注意的是，大多数鲍曼不动杆菌临床分离株缺乏或具有不完整的CRISPR-Cas系统，且其中大多数是多重耐药的。鉴于此，我们的研究旨在探讨抗生素压力对鲍曼不动杆菌中I-Fb CRISPR-Cas系统适应性代价的影响。
在本研究中，我们进行了体外竞争实验，以研究亚最小抑菌浓度（sub-MIC）对鲍曼不动杆菌中CRISPR-Cas系统适应性代价的影响。我们发现，在亚最小抑菌浓度条件下，CRISPR-Cas系统的适应性代价增加。在亚最小抑菌浓度条件下，AB43中CRISPR-Cas相关基因的表达降低，而接合频率增加。通过代谢组学分析，我们确定亚最小抑菌浓度条件主要影响能量代谢途径。特别是，我们观察到碳代谢、氮代谢和细胞内ATP增加。值得注意的是，CRISPR-Cas系统表现出对流出泵介导的耐药性的抗性。此外，在亚最小抑菌浓度条件下，流出泵相关基因的表达增加。
我们的研究结果表明，I-Fb CRISPR-Cas系统在鲍曼不动杆菌中赋予显著的竞争优势。然而，在亚最小抑菌浓度条件下，其功能以及抑制流出泵所需能量的能力降低，导致适应性代价增加和竞争优势丧失。
