Tracking antimicrobial resistance in typhoidal Salmonella, 2020-2024: Output from an antimicrobial resistance surveillance network in New Delhi, India.

BACKGROUND

Enteric fever remains a major health problem in India. Continuous monitoring of antimicrobial resistance (AMR) is essential to guide therapy and control emerging threats.

METHODS

This study aims at analysing the data of Salmonella isolates reported in Delhi NCR over past five years (2020-24). The study has data from 24 laboratories participating in the antimicrobial resistance surveillance network of Delhi. The identification of pathogen and antimicrobial susceptibility testing was performed in each lab using standard methods and the data was compiled and collated using WHONET software and shared to the network on a monthly basis.

RESULTS

A total of 10,689 isolates were analysed: 8371 (78.3%) S. Typhi; 2295 (21.5%) S. Paratyphi A; and 23 (0.2%) S. Paratyphi B. Annual isolates rose from 522 (during 2020) to 3679 (during 2024). Children aged 1-12 years accounted for 46% of cases. Over 5 years period, among S. Typhi, resistance declined for ampicillin (9.6% to 4.1%) and trimethoprim-sulfamethoxazole (8.7% to 3.5%).Chloramphenicol resistance remained ≤5.3%, however, ciprofloxacin non-susceptibility persisted (≈48-60%). Ceftriaxone resistance was rare (3 isolates). Multidrug resistance fell to 1% by 2024. S. Paratyphi A showed similar but generally lower resistance to first-line drugs, yet higher fluoroquinolone resistance (88-98%). No isolate was confirmed by nodal centre as being resistant to azithromycin or carbapenems.

CONCLUSION

Susceptibility to traditional first-line agents is improving, and multidrug resistance is low; however, fluoroquinolone resistance remains high. Ongoing AMR surveillance and prudent antibiotic use are essential to sustain treatment efficacy.