Antimicrobial susceptibility trends of S. Typhi and S. Paratyphi in a post-COVID-19 pandemic India, from a multicenter surveillance network

Abstract

We conducted a multicenter surveillance study to identify changes in antimicrobial susceptibility patterns of Salmonella Typhi and S. Paratyphi in India since the COVID-19 pandemic began. We collected S. Typhi and S. Paratyphi isolates from blood or bone marrow culture-confirmed enteric fever cases at eight sites in seven cities across India between 2021 and 2024. We tested the antibiotic susceptibility of 1150 S. Typhi isolates and 265 S. Paratyphi isolates via disc diffusion and determined their minimum inhibitory concentrations (MICs) of ceftriaxone and azithromycin via broth dilution. 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. Furthermore, we observed yearly increases in the mean, median and 90th percentile of azithromycin MICs for S. Typhi and S. Paratyphi isolates throughout India between 2021 and 2023. Finally, we found that only 0.70% of S. Typhi isolates and 1.13% of S. Paratyphi isolates exhibited susceptibility to ciprofloxacin. Our results indicate the necessity for a shift from ciprofloxacin in the treatment of enteric fever, and the importance of implementing long-term monitoring of resistance to alternative antibiotics such as azithromycin and ceftriaxone.