Pandova Maria, Kizheva Yoana, Hristova Petya
Department of General and Industrial Microbiology, Faculty of Biology, Sofia University, 1164 Sofia, Bulgaria.
Antibiotics (Basel). 2025 Feb 2;14(2):145. doi: 10.3390/antibiotics14020145.
Non-clinical enterococci are relatively poorly studied by means of acquired antibiotic resistance to tetracycline and by the distribution, functionality and role of their CRISPR systems. In our study, 72 enterococcal strains, isolated from various non-clinical origins, were investigated for their phenotypic and genotypic ((M), (O), (S), (L), (K), (T) and (W)) tetracycline resistance. The genetic determinants for HGT (MGEs ( and W), inducible pheromones (, and ), aggregation substances (, , and ) and CRISPR-Cas systems were characterized by PCR and whole-genome sequencing. Four genes (, , and ) were detected in 39% (n = 28) of our enterococcal population, with M (31%) being dominant. The gene location was linked to the Tn6009 transposon. All strains that contained genes also had genes for HGT. No genes were found in and . In our study, 79% of all -positive strains correlated with non-functional CRISPR systems. The strain BM15 was the only one containing a combination of a functional CRISPR system (, , and 1/9) and genes. The CRISPR subtype repeats II-A, III-B, IV-A2 and VI-B1 were identified among strains (CM4-II-A, III-B and VI-B1; BM5-IV-A2, II-A and III-B; BM12 and BM15-II-A). The subtype II-A was the most present. These repeats enclosed a great number of spacers (1-10 spacers) with lengths of 31 to 36 bp. One CRISPR locus was identified in plasmid (p.Firmicutes1 in strain BM5). We described the presence of CRISPR loci in the species , and and their lack in , and . Our findings generally describe the acquisition of foreign DNA as a consequence of CRISPR inactivation, and self-targeting spacers as the main cause.
通过四环素获得性抗生素耐药性以及CRISPR系统的分布、功能和作用对非临床肠球菌的研究相对较少。在我们的研究中，对72株从各种非临床来源分离出的肠球菌菌株进行了四环素耐药性的表型和基因型（（M）、（O）、（S）、（L）、（K）、（T）和（W））研究。通过PCR和全基因组测序对水平基因转移（移动遗传元件（和W）、诱导性信息素（、和）、聚集物质（、、和））和CRISPR-Cas系统的遗传决定因素进行了表征。在我们39%（n = 28）的肠球菌群体中检测到四个基因（、、和），其中M（31%）占主导。基因位置与Tn6009转座子相关。所有含有基因的菌株也都有水平基因转移的基因。在和中未发现基因。在我们的研究中，所有阳性菌株中有79%与无功能的CRISPR系统相关。菌株BM15是唯一含有功能性CRISPR系统（、、和1/9）和基因组合的菌株。在菌株（CM4-II-A、III-B和VI-B1；BM5-IV-A2、II-A和III-B；BM12和BM15-II-A）中鉴定出CRISPR亚型重复序列II-A、III-B、IV-A2和VI-B1。亚型II-A最为常见。这些重复序列包含大量长度为31至36 bp的间隔序列（1 - 10个间隔序列）。在质粒（菌株BM5中的p.Firmicutes1）中鉴定出一个CRISPR位点。我们描述了在、和物种中CRISPR位点的存在情况以及在、和中它们的缺失情况。我们的研究结果总体上描述了由于CRISPR失活导致的外源DNA获取情况，以及自我靶向间隔序列是主要原因。
