|ZHANG, ZENGFENG - Shanghai Jiaotong University|
|CHANG, JIANG - Shanghai Jiaotong University|
|XU, XUEBIN - Shanghai University|
|ZHOU, MIN - Wuhan University|
|SHI, CHUNLEI - Shanghai Jiaotong University|
|SHI, XIANMIN - Shanghai Jiaotong University|
Submitted to: Zoonoses and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2021
Publication Date: 6/4/2021
Citation: Zhang, Z., Chang, J., Xu, X., Zhou, M., Shi, C., Liu, Y., Shi, X. 2021. Dissemination of IncFII plasmids carrying fosA3 and blaCTX-M-55 in clinical isolates of Salmonella Enteritidis. Zoonoses and Public Health. 2021;00:1–9. DOI: 10.1111/zph.12825.
Interpretive Summary: Salmonella is an important foodborne pathogen that causes a disease known as salmonellosis. An antibiotic named fosfomycin is used as a therapeutic agent to treat infections caused by Salmonella. In this study, 14 Salmonella strains that were resistant to fosfomycin were identified through screening of 501 Salmonella strains isolated from patients. The DNA sequence of a plasmid (small circular DNA molecule that co-exists with the bacterial chromosome) was determined, and the gene that confers resistance to fosfomycin known as fosA3 was located on this plasmid. Transposable elements (so called mobile genetic elements) were also found on this plasmid near the location of fosA3 and blaCTX-M-55, another antibiotic resistance gene, indicating that the antimicrobial resistance genes may be transferred among bacteria through a mechanism involving the mobile genetic elements. These findings highlight the importance of surveillance for the prevalence and transmission mechanism of antibiotic resistance genes in Salmonella to better understand the potential threat to public health and to develop control strategies.
Technical Abstract: Multidrug-resistant Salmonella Enteritidis (S. Enteritidis) isolates have become a significant threat to public health, and fosfomycin has been proposed as one of the therapeutic antibiotics for serious infections by resistant pathogens. In this study, a total of 501 clinical S. Enteritidis isolates were screened and 14 (2.8%) isolates exhibited resistance to fosfomycin (MIC = 1024 µg/mL) as well as ceftriaxone (MIC = 128 µg/mL). The fosA3 gene was identified in these 14 isolates. The fosA3 gene that co-transferred with blaCTX-M-55 was observed on the IncFII plasmid with sizes of ~78 (n=7) or ~111 (n=2) kbp in 9 transconjugants. The fosA3-bearing plasmid p12367A is 111,764 bp in length and possessed typical IncFII backbone. A 7.6-kbp multidrug resistance region (MRR) was identified in p12367A, which comprised of fosA3 and blaCTX-M-55 interspersed with 'ISEcp1 and three copies of IS26. Two typical antibiotic resistance determinants (IS26-orf3-orf2-orf1-fosA3-IS26 and IS26-orf477-blaCTX-M-55-'ISEcp1-IS26) shared one IS26 in the MRR. The genetic arrangement of the MRR may have resulted from the stepwise integration of IS26 mobile elements via homologous recombination. Horizontal transfer of IncFII plasmids might contribute to the dissemination of fosA3 and blaCTX-M-55 resistance genes in S. Enteritidis interspecies. These findings underline the further challenges for the prevention and treatment of Enterobacteriaceae infections posed by epidemic IncFII plasmid bearing fosA3-blaCTX-M-55.