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Updated: Jun 7, 2026
Epithelial Cell Infection Analyses with Shigella
Published on: February 9, 2024
Subtype prevalence, plasmid profiles and growing fluoroquinolone resistance in Shigella from Kolkata, India
Suman Nandy1, Utpala Mitra, K Rajendran
1Bacteriology Division, National Institute of Cholera and Enteric Diseases, Kolkata, India.
Objectives:
Shigellosis is a major public health problem, and increasing antimicrobial resistance has complicated its treatment. We report isolation frequency, plasmid profiles and antimicrobial resistance of Shigella subtypes in Kolkata, India, from a prospective hospital-based study.
Methods:
Fresh stool or rectal swabs were collected from children (<5 years) attending the Diarrhea Treatment Unit of a governmental paediatric referral hospital in Kolkata. Samples were processed following standard methods over a 7-year period from January 2001 to December 2007.
Results:
Of 4478 samples collected, 516 (11.5%) were positive for Shigella spp. S. flexneri (312; 6.9%) was the most frequently isolated serogroup, ranking before S. sonnei (123, 2.7%), S. dysenteriae (48, 1.1%) and S. boydii (33, 0.7%). Although 10 subtypes of S. flexneri were identified, the common ones circulating locally were S. flexneri 2a (179), S. flexneri 6 (38) and S. flexneri 3a (36). Knowledge of Shigella subtypes is important for vaccine development. The majority of Shigella isolates (81.0%) were multidrug (two or more antimicrobial classes) resistant and showed high minimum inhibitory concentration (MIC) with commonly used drugs like ampicillin, tetracycline, co-trimoxazole and nalidixic acid. Emergence of fluoroquinolone (FQ)-resistant S. dysenteriae type 1 (100.0%) in 2002-2003 was followed by frequent isolation (>25.0%) of FQ-resistant S. flexneri 2a, and S. flexneri 3a in 2004, which restricted use of fluoroquinolones for treatment. A number of smaller plasmids (<20 kb) with distinct patterns have been observed for several years in predominant subtypes.
Conclusion:
Long-term surveillance of Shigellae and their antimicrobial resistance are mandatory in endemic areas to formulate treatment policy until any suitable candidate vaccine is available to control the disease.
Insights
Shigella infections in Kolkata children show high multidrug resistance, with fluoroquinolone-resistant strains emerging. Long-term surveillance is crucial for treatment policy and vaccine development.
Area of Science:
- Microbiology
- Infectious Diseases
- Public Health
Background:
- Shigellosis poses a significant global health challenge, exacerbated by rising antimicrobial resistance.
- Effective treatment strategies are hampered by the increasing resistance of Shigella strains.
Purpose of the Study:
- To investigate the isolation frequency, plasmid profiles, and antimicrobial resistance patterns of Shigella subtypes in children in Kolkata, India.
- To inform treatment policies and vaccine development for shigellosis.
Main Methods:
- Prospective hospital-based study involving stool or rectal swab collection from children under five years old.
- Standard microbiological methods were employed for sample processing over a seven-year period (2001-2007).
Main Results:
- Shigella spp. were identified in 11.5% of 4478 samples, with Shigella flexneri being the most common serogroup.
- A high prevalence of multidrug resistance (81.0%) was observed, including resistance to commonly used antibiotics.
- Emergence of fluoroquinolone-resistant Shigella dysenteriae type 1 and Shigella flexneri subtypes was noted, limiting treatment options.
Conclusions:
- Sustained surveillance of Shigella and its antimicrobial resistance is essential in endemic regions.
- This data is critical for developing effective treatment guidelines and guiding vaccine development efforts.
- Understanding circulating Shigella subtypes and their resistance profiles is vital for disease control.
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