# Genomic diversity and antimicrobial resistance of Staphylococcus aureus in Saudi Arabia: a nationwide study using whole-genome sequencing

## TL;DR

This study uses whole-genome sequencing to analyze Staphylococcus aureus in Saudi Arabia, showing how mass gatherings influence bacterial diversity and resistance.

## Contribution

The study provides the first nationwide genomic surveillance of S. aureus in Saudi Arabia, linking mass gatherings to increased genetic diversity and antimicrobial resistance.

## Key findings

- Pilgrimage cities showed higher genetic diversity and antimicrobial resistance in S. aureus isolates.
- International S. aureus clones from diverse geographic origins were identified in pilgrimage cities.
- Genomic prediction of resistance was accurate for beta-lactams but varied for other antibiotics, underscoring the need for phenotypic testing.

## Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) surveillance in regions with mass gatherings presents unique challenges for public health systems. Saudi Arabia, hosting millions of pilgrims annually, provides a distinctive setting for studying how human mobility shapes bacterial populations, yet comprehensive genomic surveillance data from this region remain limited. Here, we present an integrated analysis of S. aureus isolates collected across seven Saudi Arabian regions, combining whole-genome sequencing with extensive antimicrobial susceptibility testing and standardized metadata following findability, accessibility, interoperability and reusability data principles. Our analysis revealed striking differences between pilgrimage and non-pilgrimage cities. Pilgrimage cities showed significantly higher genetic diversity and antimicrobial resistance rates, harbouring numerous international strains, including recognized clones from diverse geographic origins. Reported lineage dynamics are changing, expanding toward community clones. While genomic prediction of antimicrobial resistance showed high accuracy for some antibiotics, particularly beta-lactams, with varying performance for others, it highlights the necessity for phenotypic testing in clinical settings. Our findings demonstrate how mass gatherings drive bacterial population structures and emphasize the importance of integrated surveillance approaches in regions with significant global connectivity and travel.