# Changing Trends in the Prevalence, Seasonal Distribution and Antimicrobial Susceptibility Pattern of Salmonella: An 11-Year Retrospective Study at a Tertiary Care Hospital

## TL;DR

This study analyzed Salmonella trends over 11 years in North India, finding high summer prevalence and increasing resistance to certain antibiotics.

## Contribution

The study provides updated insights into Salmonella prevalence, seasonal patterns, and antimicrobial resistance trends in a tertiary hospital setting.

## Key findings

- Salmonella Typhi was the most common species isolated, followed by Paratyphi A.
- Ciprofloxacin and levofloxacin resistance increased significantly over the study period.
- High susceptibility to ceftriaxone and cotrimoxazole was observed in Salmonella isolates.

## Abstract

Objectives

Salmonella causes enteric fever, a major public health issue in India. The emergence of drug-resistant strains is concerning. This study assessed the prevalence, seasonal distribution, and antibiogram of Salmonella from blood cultures at a tertiary care hospital in North India.

Materials and methods

This retrospective descriptive study was conducted in the Department of Microbiology at a tertiary care centre over 11 years. Blood samples received in the laboratory were processed using the BacT/ALERT system. Identification and antimicrobial susceptibility testing were performed with VITEK 2 (bioMérieux, France). Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 were used as control strains.

Results

Of 67,085 blood cultures, 26,796 (39.9%) were positive, yielding 761 Salmonella isolates: S. Typhi (578, 75.9%), S. Paratyphi A (179, 23.5%), and S. Paratyphi B (4, 0.6%). Outpatients contributed 377 (50.5%) isolates. Prevalence peaked in summer. All isolates showed high susceptibility to ceftriaxone (99.1%), cotrimoxazole (99.2%), and ampicillin (91.8%). Ciprofloxacin susceptibility declined from 25% (2014) to 5% (2024), and levofloxacin from 20% to 10%.

Statistical analysis

Data were analyzed using SPSS version 23.0 (IBM Corp., Armonk, NY, USA). Categorical variables were expressed as frequencies and percentages, with appropriate tables for data presentation.

Conclusions

This study revealed that Salmonella Typhi was the most common species isolated, and a high prevalence of salmonellosis was observed during the summer season. Also, an increased resistance among Salmonella isolates to fluoroquinolones was seen, whereas the sensitivity to ceftriaxone was excellent.