Research Progress on Macrococcus: From Basic Biology to Clinical Antimicrobial Resistance Challenges.

Macrococcus is a genus of Gram-positive cocci in the Staphylococcaceae family and a close phylogenetic relative of Staphylococcus. It is not a significant human pathogen but is known to widely colonize different environments, including animal skin and food products. Phylogenetically, Macrococcus is distinct from yet closely related to Staphylococcus, particularly the sciuri group. The species is effectively identified through such molecular markers as hsp60 and 16S rDNA. A key biochemical feature is an identified FAD-dependent oleate hydratase in Macrococcus equipercicus (M. equipercicus). Critically, Macrococcus carries various mobile antibiotic-resistance genes, especially against β-lactams (e.g., mecB, mecD) and macrolides (e.g., mef(F), msr(G)); these genes are located on plasmids, SCCmec-like elements, or resistance islands (e.g., McRImecD), which facilitates their horizontal transfer. Surveillance confirms the widespread presence of methicillin-resistant Macrococcus, often with a multidrug-resistant phenotype, in food animals and their products. Although its own pathogenicity is low, Macrococcus acts as a reservoir and transmission platform for resistance genes: through horizontal gene transfer, it can potentially confer resistance to pathogenic Staphylococcus, thereby posing a threat to animal and public health. This review summarizes the basic biological characteristics and drug resistance-related research progress of the genus Macrococcus; it aims to provide a reference for subsequent studies as well as to establish technical support and a theoretical basis for the epidemiological investigation, drug-resistant strain identification, and clinical drug-resistance risk prevention and control of Macrococcus.