Genomic Insights into Methicillin-Resistant Staphylococci

The emergence and global spread of methicillin-resistant staphylococci pose a critical challenge to human and veterinary medicine. Genome sequencing and comparative phylogenomics have illuminated the origin, evolution and dissemination of resistance determinants across species and environments. Analyses of mobile genetic elements, including diverse staphylococcal cassette chromosome mec (SCCmec) variants and plasmids, have revealed the mechanisms by which mec genes are acquired, maintained and transferred among coagulase-negative staphylococci, Macrococcus and Staphylococcus aureus. These insights underpin efforts to track transmission routes in livestock, wildlife and clinical settings and to develop strategies that limit the expansion of multidrug-resistant lineages.

Research from Nature Portfolio

Recent studies have applied whole-genome sequencing to non-aureus staphylococci and Mammaliicoccus isolated from Hipposideros bats, uncovering novel sequence types and demonstrating that migratory mammals can harbour mecA-positive strains with additional virulence genes. These findings highlight bats as under-recognised reservoirs of methicillin resistance and underscore the need for One Health surveillance that includes wildlife.

Foundational work on methicillin resistance in Macrococcus caseolyticus has identified a novel mecD gene situated within discrete resistance islands integrated at the rpsI locus. The mecD operon confers resistance to all classes of β-lactams and is flanked by recombinase genes, indicating a capacity for horizontal mobilisation across the Staphylococcaceae family and potential emergence of new resistant pathogens.

Genomic Insights into Methicillin-Resistant Staphylococci publication trend

The graph below shows the total number of articles in genomic insights into methicillin-resistant staphylococci across all publications each year (not limited to Nature Index journals).

Technical terms

mecA: A gene encoding the penicillin-binding protein PBP2a, conferring resistance to β-lactam antibiotics.

mecC: A mecA homologue found in SCCmec XI elements, mediating methicillin resistance in livestock and wildlife strains.

mecD: A recently identified mec gene in Macrococcus caseolyticus that confers resistance to all β-lactams.

SCCmec: A mobile chromosomal element that carries mec genes and regulatory components between staphylococcal genomes.

Whole-genome sequencing (WGS): High-throughput determination of the complete DNA sequence of an organism’s genome.

Horizontal gene transfer: Movement of genetic material between organisms by mechanisms other than direct inheritance.

Coagulase-negative staphylococci (CoNS): A group of staphylococcal species that lack the coagulase enzyme and often serve as reservoirs of resistance genes.

References

1. Molecular characterization of non-aureus staphylococci and Mammaliicoccus from Hipposideros bats in Southwest Nigeria. Scientific Reports (2024).
2. Novel methicillin resistance gene mecD in clinical Macrococcus caseolyticus strains from bovine and canine sources. Scientific Reports (2017).
3. Beyond the Wild MRSA: Genetic Features and Phylogenomic Review of mecC-Mediated Methicillin Resistance in Non-aureus Staphylococci and Mammaliicocci. Microorganisms (2023).
4. Bats Are Carriers of Antimicrobial-Resistant Staphylococcaceae in Their Skin. Antibiotics (2023).
5. Evidence of in vitro mecB-mediated β-lactam antibiotic resistance transfer to Staphylococcus aureus from Macrococcus psychrotolerans sp. nov., a psychrophilic bacterium from food-producing animals and human clinical specimens. Applied and Environmental Microbiology (2025).