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Updated: Sep 1, 2025
Author Spotlight: Advancements in Understanding and Combatting Shigella Infections
Published on: February 9, 2024
Clonal serotype 1c multidrug-resistant Shigella flexneri detected in multiple institutions by sentinel-site
Karrie K K Ko1,2,3,4,5, Joash Jun Keat Chu3, Kar Mun Lim3
1Department of Microbiology, Singapore General Hospital, Singapore, Singapore.
Abstract:
Shigella flexneri is a major diarrhoeal pathogen, and the emergence of multidrug-resistant S. flexneri is of public health concern. We report the detection of a clonal cluster of multidrug-resistant serotype 1c (7a) S. flexneri in Singapore in April 2022. Long-read whole-genome sequence analysis found five S. flexneri isolates to be clonal and harboring the extended-spectrum β-lactamases bla CTX-M-15 and bla TEM-1. The isolates were phenotypically resistant to ceftriaxone and had intermediate susceptibility to ciprofloxacin. The S. flexneri clonal cluster was first detected in a tertiary hospital diagnostic laboratory (sentinel-site), to which the S. flexneri isolates were sent from other hospitals for routine serogrouping. Long-read whole-genome sequence analysis was performed in the sentinel-site near real-time in view of the unusually high number of S. flexneri isolates received within a short time frame. This study demonstrates that near real-time sentinel-site sequence-based surveillance of convenience samples can detect possible clonal outbreak clusters and may provide alerts useful for public health mitigations at the earliest possible opportunity.
Insights
Multidrug-resistant Shigella flexneri serotype 1c was detected in Singapore. Near real-time genomic surveillance identified a clonal outbreak, enabling rapid public health response.
Area of Science:
- Microbiology
- Genomics
- Public Health
Background:
- Shigella flexneri is a significant cause of diarrhea.
- The rise of multidrug-resistant strains poses a serious public health threat.
- Emerging resistance necessitates enhanced surveillance methods.
Purpose of the Study:
- To report the detection of a multidrug-resistant Shigella flexneri clonal cluster in Singapore.
- To characterize the genetic makeup and resistance profiles of the identified isolates.
- To evaluate the utility of near real-time genomic surveillance for outbreak detection.
Main Methods:
- Long-read whole-genome sequencing was employed to analyze five Shigella flexneri isolates.
- Isolates were collected from a tertiary hospital diagnostic laboratory serving as a sentinel site.
- Phenotypic antimicrobial susceptibility testing was performed.
Main Results:
- A clonal cluster of multidrug-resistant Shigella flexneri serotype 1c (7a) was identified.
- The isolates harbored blaCTX-M-15 and blaTEM-1 genes, conferring resistance to extended-spectrum cephalosporins.
- Resistance to ceftriaxone and intermediate susceptibility to ciprofloxacin were observed.
- Near real-time genomic analysis at the sentinel site facilitated early detection.
Conclusions:
- Near real-time sequence-based surveillance at sentinel sites can effectively detect clonal outbreak clusters.
- This approach provides timely alerts for public health interventions.
- Genomic surveillance is crucial for monitoring and controlling the spread of antimicrobial resistance.
