Mapping Antibiotic Resistance Determinants in Oral Streptococci

Area of Science:

• Genomics
• Microbiology
• Molecular Biology

Background:

• Antibiotic resistance is a critical global health challenge.
• Oral streptococci, comprising commensals and pathogens, are significant reservoirs of resistance determinants.
• Understanding the genetic basis and exchange of resistance is crucial for combating resistance.

Purpose of the Study:

• To identify core antibiotic resistance determinants in oral streptococci.
• To analyze the variability and gene exchange patterns of these determinants, particularly in relation to mobile genetic elements and penicillin-binding proteins.
• To investigate the contribution of oral streptococci to the resistance of *Streptococcus pneumoniae*.

Main Methods:

• Analysis of 2,087 whole-genome sequences from 15 oral streptococcal species.
• Identification of resistance genes using AMRFinderPlus and the Comprehensive Antibiotic Resistance Database.
• Detection of integrative and conjugative elements (ICEs) using ICEscreen and assessment of penicillin-binding protein (PBP) variability using MMseqs2 and fastGEAR.

Main Results:

• Over 3,500 resistance gene hits from 55 unique genes were identified across 11 antibiotic classes.
• *Streptococcus mitis* and *Streptococcus oralis* exhibited the highest number of resistance determinants per genome.
• Nearly 17% of over 1,800 predicted ICEs carried at least one antibiotic resistance gene.
• Significant genetic exchange was observed from oral streptococci to beta-lactam-resistant *Streptococcus pneumoniae*, particularly involving PBP genes.

Conclusions:

• Tetracycline and macrolide resistance are prevalent in oral streptococci and associated with ICEs.
• Oral streptococci act as a significant source of genetic material for *Streptococcus pneumoniae*, contributing to its antibiotic resistance.
• Understanding the dynamics of genetic exchange is essential for developing strategies to mitigate antibiotic resistance.