12-05-2025
SEFI study finds drug-resistant typhoid strain in Ahmedabad
Ahmedabad: Typhoid, once seemingly under control, may now be resistant to key antibiotics in Gujarat. A new surveillance study spanning eight major Indian cities spotlighted Ahmedabad as ground zero for antibiotic-resistant
Salmonella Typhi
(S Typhi) — the bacteria that causes typhoid.
The study revealed that in Ahmedabad, these bacteria resist not just ceftriaxone, a critical antibiotic but several frontline drugs, leaving doctors with fewer options. Conducted by the Surveillance for Enteric Fever in India (SEFI) network from 2021 to 2024, the study was published on April 21, 2025, in Nature's Scientific Reports, flagged Ahmedabad as a hotspot in Western India for this new strain.
"We identified 18 S Typhi isolates from Ahmedabad that were resistant to ceftriaxone, indicating a larger emergence of third-generation cephalosporin-resistant S Typhi in Western India with a novel plasmid profile," states the had collected the samples from Ahmedabad between June 1, 2022 and April 30, 2023. These 18 isolates didn't just resist ceftriaxone, they also stood their ground against ampicillin, ciprofloxacin, and the combination of sulfamethoxazole and trimethoprim. Fortunately, they remained vulnerable to azithromycin and the older antibiotic chloramphenicol, stated the research experts warn this is no reassurance. Experts feel there is an urgent need to update treatment guidelines and intensify monitoring efforts participating centres included AIIMS Delhi, Christian Medical College Ludhiana, Chacha Nehru Bal Chikitsalaya Delhi, Christian Medical College Vellore, St John's Medical College Bengaluru, and institutions in Chandigarh, Kolkata, and Ahmedabad. "While sporadic
ceftriaxone resistance
has been documented in the past across North, South, East India and Mumbai, this Ahmedabad cluster is the largest coherent group so far, with its distinct genetic profile indicating local evolution rather than isolated anomalies," the study the study period, a total of 2,70,228 blood and bone marrow cultures were performed across the participating of the drug-resistant S Typhi from Ahmedabad showed they belonged to the H58 lineage, specifically subtype 4.3.1.2.2, known for antibiotic resistance.
These bacteria carried multiple resistance genes, including those for cephalosporins (like ceftriaxone), fluoroquinolones, sulfonamides, and these resistance genes were found on a single plasmid called IncFIB(K). Plasmids are small DNA structures that can easily transfer between bacteria, allowing rapid spread of resistance. Notably, these bacteria also carried two other plasmids (IncFIB(pHCM2) and IncX1) that did not contain resistance genes. The presence of all three plasmids together in these bacteria is a new finding, according to the study.
