عنوان
پدید آورنده
موضوع
رده
کتابخانه
محل استقرار
TLpq2293155069
انگلیسی
Comparative Genomics of Plasmid-Bearing Staphylococcus aureus Strains Isolated from Various Retail Meats
[Thesis]
Neyaz, Leena S.
Fakhr, Mohamed K.
The University of Tulsa
2019
214
Ph.D.
The University of Tulsa
2019
Staphylococcus aureus is rated as one of the top foodborne pathogens responsible for various food poisoning outbreaks around the world. The ability of some S. aureus linages to evolve rapidly and disseminate is greatly aided by plasmids that act as vehicles for circulating a variety of virulence, antimicrobial resistance, and other advantageous genes. Limited studies have investigated plasmids and their relatedness among isolates from different reservoirs including meat and other foods. Indeed, the majority of the 437 S. aureus plasmid sequences deposited in the GenBank to date are from clinical human isolates and those isolated from food are extremely limited. The objectives of this study were to characterize plasmids, including large ones, along with their replicons and host chromosomes in S. aureus strains isolated from various retail meats in order to fill the current knowledge gap, to explore if the genomic structure is source specific, and to determine if plasmid fusion to form large plasmids is a common event in the evolution of S. aureus plasmids. Two hundred and twenty-two S. aureus isolates (55 chicken, 43 beef liver, 42 pork, 29 chicken liver, 24 beef, 22 turkeys, and 7 chicken gizzard) were subjected to initial plasmid screening with alkaline lysis and PFGE. The tested isolates showed a high prevalence of plasmids with variable sizes (1-336 kb). The detected plasmids were screened for the presence of various replicon sequences and a relationship between some rep genes, the isolate meat source, and antimicrobial and virulence genes was detected. The whole genomes of ten plasmid-bearing S. aureus strains carrying different rep genes (3 beef, 4 chicken, 2 turkey, and 1 pork) was subjected to Next Generation Sequencing. The chromosomes of the ten sequenced strains varied in size from 2,654,842 bp-2,807,514 bp. A total of 25 plasmids harbored by these S. aureus strains and varied in size from 1,400 bp-118,000 bp were fully sequenced and annotated. Comparative genomic analysis for the core and pan genomes of the ten sequenced strains showed some similarities between the strains isolated from the same retail meat source proposing an origin specific genomic composition. All genomes showed the presence of several virulence genes known to help in attachment, invasion, and toxin production which are often present in human clinical strains. Most chromosomes showed the presence of several antimicrobial resistance, heavy metal resistance, and stress response genes. While most of the sequenced plasmids in this study harbored genes related to plasmid replication and several hypothetical proteins, some of these plasmids contained genes responsible for antimicrobial resistance and virulence. Finally, we analyzed the distribution and evolution of 331 plasmid sequences of S. aureus retrieved from the NCBI database. A total of 25 rep families were identified with 51% of plasmids carried more than one rep sequence and almost all of multi-rep plasmids were large plasmids. This indicates that plasmids fusion among S. aureus strains is a common event and the genomes of large plasmids are more dynamic. The phylogenetic analysis of the of rep families nucleotide sequences showed several well defined subtypes representing a true phylogenetic groups. Some subtypes belong to the same rep family can be carried on the same plasmid, but have different evolutionary history.
Food science
Microbiology
Fakhr, Mohamed K.
Neyaz, Leena S.
مطالعه متن کتاب p
[Thesis]
276903
a
Y
