Simple Summary
Researchers in this study were looking at certain types of Salmonella bacteria from China that are resistant to many drugs, and have found something surprising. They discovered a new type of this bacteria called S1467 that does not have the usual elements that make it resistant. When they studied S1467’s entire genetic makeup, they found that it has 54 genes that help it resist many different drugs. This shows how important it is to understand this bacterium better, especially how it becomes resistant to drugs. Furthermore, inside this S1467 bacterium, they found a unique section of DNA (about 51 kilobytes in size) that helps it resist drugs. This section also contains a special system called YeeVU, which is rare in this type of Salmonella bacteria. This new finding about S1467, a drug-resistant Salmonella type without the usual drug-resistance elements, is a big deal. It helps us understand more about the different types of Salmonella and how they become resistant to drugs. Knowing this helps scientists come up with better ways to fight Salmonella infections.
Abstract
The emergence of multi-drug resistant (MDR) Salmonella enterica serovar Indiana (S. Indiana) strains in China is commonly associated with the presence of one or more resistance plasmids harboring integrons pivotal in acquiring antimicrobial resistance (AMR). This study aims to elucidate the genetic makeup of this plasmid-free, highly drug-resistant S. Indiana S1467 strain. Genomic sequencing was performed using Illumina HiSeq 2500 sequencer and PacBio RS II System. Prodigal software predicted putative protein-coding sequences while BLASTP analysis was conducted. The S1467 genome comprises a circular 4,998,300 bp chromosome with an average GC content of 51.81%, encompassing 4709 open reading frames (ORFs). Fifty-four AMR genes were identified, conferring resistance across 16 AMR categories, aligning closely with the strain’s antibiotic susceptibility profile. Genomic island prediction unveiled an approximately 51 kb genomic island housing a unique YeeVU toxin–antitoxin system (TAS), a rarity in Salmonella species. This suggests that the AMR gene cluster on the S1467 genomic island may stem from the integration of plasmids originating from other Enterobacteriaceae. This study contributes not only to the understanding of the genomic characteristics of a plasmid-free, highly drug-resistant S. Indiana strain but also sheds light on the intricate mechanisms underlying antimicrobial resistance. The implications of our findings extend to the broader context of horizontal gene transfer between bacterial species, emphasizing the need for continued surveillance and research to address the evolving challenges posed by drug-resistant pathogens.