Macrolide resistance in streptococcus pyogenes in Malta

Abstract

Streptococcus pyogenes is a gram-positive coccus belonging to Lancefield Group A, which tends to cause a wide variety of infections, the most common being throat infections. These infections are mainly treated by penicillin, a Beta-lactam antibiotic, however, in some cases, such infections are treated with macrolide antibiotics. Macrolides tend to inhibit bacterial protein synthesis by acting on the 50S sub-unit of ribosomes. Studies on macrolide resistant Streptococcus pyogenes isolates identified two main resistance mechanisms: target modification, which is expressed by the ermB and the ermTR genes, and efflux pumps expressed by the mefA gene. Global rates of macrolide resistance are typically low to moderate, but there is a notable surge in Asian countries. This prompts inquiry into the prevalence of macrolide resistant Streptococcus pyogenes in Malta over recent years. This study aimed to investigate the prevalence and molecular mechanisms of macrolide resistance in S. pyogenes isolates collected from Malta. A total of 320 clinical isolates were tested phenotypically for resistance to erythromycin and clindamycin, followed by genotypic analysis targeting ermB, ermTR, and mefA. Comparative analysis with other European countries demonstrated that Malta's macrolide resistance rates are comparable to those in Southern Europe, where antibiotic consumption is traditionally high. Furthermore, post-pandemic increases in macrolide resistance suggest an urgent need for enhanced antibiotic stewardship and stricter regulatory policies in outpatient settings. This study underscores the necessity for ongoing surveillance, the exploration of alternative therapeutic options, and the need of implementing Whole-Genome Sequencing (WGS) to uncover unexplored resistance pathways.