# Exploring the genetic landscape of the Copper Homeostasis and Silver Resistance Island (CHASRI) in Salmonella enterica

## TL;DR

This study explores how a genetic element called CHASRI, which helps Salmonella tolerate copper and silver, is spread across different strains and food sources.

## Contribution

The study reveals that CHASRI is present in a broader range of Salmonella serovars and food sources than previously known, and identifies new integration patterns of CHASRI.

## Key findings

- CHASRI is found in multiple Salmonella serovars and isolates from various food sources.
- CHASRI can integrate as a standalone element or as part of an SGI-4 variant.
- The genetic landscape of CHASRI is more diverse than previously understood.

## Abstract

Copper is essential for all living organisms, but becomes toxic when present in excess. Biological systems have evolved mechanisms to keep organisms in copper homeostasis. Studies have shown that Salmonella can acquire mobile genetic elements that provide enhanced tolerance to stressed environments, such as the Copper Homeostasis and Silver Resistance Island (CHASRI), which has become more prevalent in certain serovars that are exposed to higher levels of copper. In this study, whole genome sequence data available from NCBI Pathogen Detection was used to determine the incidence of the CHASRI is in Salmonella enterica isolates. The results show that the CHASRI is present in a wider range of serovars than previously known and can be found in isolates from different food sources, including nuts, spices, and produce. Salmonella Genomic Island-4 (SGI-4) was previously described as the primary mobile element through which the CHASRI was transferred to Salmonella; however, results from this comparative study of closed reference genomes identified additional integrations of the CHASRI as both a singular mobile element and as a component of an SGI-4 variant.