626. Differences in Gene Expression Levels of Methicillin-Resistant Staphylococcus aureus Genes between Persistent and Resolving Bacteremia
Session: Poster Abstract Session: Microbial Pathogenesis
Thursday, October 5, 2017
Room: Poster Hall CD

Differences in Gene Expression Levels of Methicillin-Resistant Staphylococcus aureus Genes between Persistent and Resolving Bacteremia

Background: Persistent MRSA bacteremia (PB) is associated with higher mortality than resolving MRSA bacteremia (RB). We previously described that PB and RB isolates had no significant differences in genotypes and microbiologic characteristics. In other small studies, the presence of specific genes or phenotype characteristics was associated with PB, but the results were inconsistent. Aim of this study was to determine whether differences in the expression of major genes contribute to the development of PB.

Methods: We analyzed expression levels of major regulatory genes (agr, sarA, sigB, graRS, walKR, saeRS, and vraRS) and virulence factors (htrA, prsA, murZ, spa, clfA, clfB, sdrC, sdrD, sdrE, ebps, fib, hla, psma, icaA, seg, and sen) in 40 MRSA strains isolated from 20 patients with PB (>7 days) and 20 patients with RB (< 3 days) who were matched for clinical and epidemiologic characteristics and bacterial genotypes. Relative gene expression level to gyrB was determined using real-time RT-PCR. In the same way, differential expression of the genes between the first and last isolates from 20 patients with PB was analyzed to evaluate changes of gene expression during PB. In addition, RNA-seq was performed on selected MRSA strains to evaluate the overall differential expression of genes.

Results: There was no difference in the expression level of agr between PB and RB isolates. However, significant differences in gene expression levels between PB and RB isolates were observed in the following genes. Gene with increased expression levels in PB was sigB, global regulator. Genes with decreased expression levels in PB included sarA, global regulator; graRS, walKR, and saeRS, two-component regulatory systems; htrA, clfA, sdrD, sdrE, ebps, and fib, surface protein genes; seg and sen, secreted protein genes (Fig. 1). A similar trend was found in RNA-seq. There were no significant differences in expression of specific genes between the first and last isolates of PB.  

Conclusion: Our results suggest that PB may develop due to infection caused by MRSA strain with altered gene expression rather than changes in specific gene expression levels during bacteremia.

 

Byunghan Ryu, MD1, Seung Hyun Lee, MD1, Jeongmin Hong, MD1, Heungsup Sung, MD, PhD2, Mi-Na Kim, MD, PhD2, Min Jae Kim, MD1, Sung-Han Kim, MD, PhD1, Sang-Oh Lee, MD, PhD1, Sang-Ho Choi, MD, PhD1, Jin-Yong Jeong, PhD3, Yang Soo Kim, MD, PhD1, Jun Hee Woo, MD, PhD1 and Yong Pil Chong, MD, PhD1, (1)Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea, Republic of (South), (2)Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea, Republic of (South), (3)Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea, Republic of (South)

Disclosures:

B. Ryu, None

S. H. Lee, None

J. Hong, None

H. Sung, None

M. N. Kim, None

M. J. Kim, None

S. H. Kim, None

S. O. Lee, None

S. H. Choi, None

J. Y. Jeong, None

Y. S. Kim, None

J. H. Woo, None

Y. P. Chong, None

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