Department of Microbiology, Aravind Medical Research Foundation, 1 Anna Nagar, Madurai, 625020, Tamil Nadu, India; School of Chemical and Biotechnology, SASTRA University, Thanjavur, Tamil Nadu, India.
Department of Microbiology, Aravind Medical Research Foundation, 1 Anna Nagar, Madurai, 625020, Tamil Nadu, India.
Exp Eye Res. 2021 Nov;212:108764. doi: 10.1016/j.exer.2021.108764. Epub 2021 Sep 9.
Virulence-factor encoding genes (VFGs) and antimicrobial resistance genes (ARGs) of ocular Methicillin-Resistant Staphylococcus aureus (MRSA), are the reason behind the common cause of severe and untreatable ocular infection and are largely unknown. The unavailability of the complete genome sequence of ocular MRSA strains hinders the unambiguous determination of ARGs and VRGs role in disease pathogenesis and their genomic location. To fulfill this critical need, we achieved the high-quality complete genome of four ocular MRSA strains (AMRF3 - AMRF6) by combining MinION nanopore sequencing technology, followed by polishing with Illumina sequence reads. We obtained a single chromosome and a plasmid in each strain. Sequence typing revealed that AMRF3 and AMRF5 strains harbored ST772, whereas AMRF4 and AMRF6 harbored ST 2066. All plasmids carried heavy metal cadmium resistance genes cadC and cadD, while cadA was detected only in the plasmid pSaa6159 of AMRF4 and AMRF6 strains. Further, pSaa6159 contains a complete Tn552 transposon with beta-lactamase genes, blaI, blaR1, and blaZ. Interestingly, pSaa6159 in AMRF6 carried five copies of Tn552 transposon. Several exotoxins and enterotoxins were identified across ocular MRSA strains and ST2066 strains found to be not carried any enterotoxins; this finding suggests that these two strains are exotoxigenic. Besides, ST2066 strains carried serine proteases (splA, splB, splD, splE and spIF) and exotoxin (seb and set 21) for their virulence, while ST772 carried antimicrobial resistance genes (blaZ, dfrG, msrA, mphC and fosB) and enterotoxin sec for virulence, suggesting sequence type-specific resistance and virulence. Also, we identified many VFGs and ARGs, that provided multi-drug resistance, enterotoxigenic, exotoxigenic, biofilm-forming, host tissue adhesion and immune response evasion in ocular MRSA strains. Thus, our study provides a better insight into the genomes of ocular MRSA strains that would provide more effective treatment strategies for ocular MRSA infection.
眼部耐甲氧西林金黄色葡萄球菌 (MRSA) 的毒力因子编码基因 (VFGs) 和抗菌药物耐药基因 (ARGs) 是导致严重且难以治疗的眼部感染的常见原因，但这些基因在很大程度上尚未被了解。眼部 MRSA 菌株的全基因组序列尚不可用，这阻碍了明确确定 ARGs 和 VRGs 在疾病发病机制中的作用及其基因组位置。为了满足这一关键需求，我们通过结合 MinION 纳米孔测序技术，随后使用 Illumina 测序读数进行打磨，成功获得了 4 株眼部 MRSA 菌株 (AMRF3-AMRF6) 的高质量全基因组。我们在每个菌株中都获得了一条染色体和一条质粒。序列分型显示，AMRF3 和 AMRF5 菌株携带 ST772，而 AMRF4 和 AMRF6 菌株携带 ST2066。所有质粒均携带重金属镉耐药基因 cadC 和 cadD，而 cadA 仅在 AMRF4 和 AMRF6 菌株的质粒 pSaa6159 中检测到。此外，pSaa6159 含有完整的 Tn552 转座子，其中包含 bla 基因、blaR1 和 blaZ。有趣的是，pSaa6159 在 AMRF6 中携带了 5 个 Tn552 转座子拷贝。在眼部 MRSA 菌株和 ST2066 菌株中均发现了多种外毒素和肠毒素，但 ST2066 菌株未携带任何肠毒素；这一发现表明这两个菌株是外毒素产生菌。此外，ST2066 菌株携带丝氨酸蛋白酶 (splA、splB、splD、splE 和 spIF) 和外毒素 (seb 和 set21) 以发挥其毒力，而 ST772 则携带抗菌药物耐药基因 (blaZ、dfrG、msrA、mphC 和 fosB) 和肠毒素 sec 以发挥其毒力，这表明序列类型特异性耐药性和毒力。此外，我们还鉴定了许多 VFGs 和 ARGs，这些基因赋予了眼部 MRSA 菌株多药耐药性、肠毒性、外毒性、生物膜形成、宿主组织黏附性和免疫逃避能力。因此，我们的研究深入了解了眼部 MRSA 菌株的基因组，为眼部 MRSA 感染提供了更有效的治疗策略。
