Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One Health paradigm.
MRSA strains are categorized into healthcare-associated (HA-MRSA), community-associated (CA-MRSA), and livestock-associated (LA-MRSA). These lineages exhibit clonal complex (CC) variation and host specificity. For example, CC398—initially of human origin—has undergone adaptation in livestock, particularly pigs, leading to its reverse zoonotic transmission. Multiple CCs such as CC1, CC5, CC8, and CC97 have been identified across host species, implicating complex interspecies gene flow and environmental adaptation.
MRSA's global prevalence varies widely. For instance, CA-MRSA accounts for 79% of isolates in Japan, while LA-MRSA has been detected in up to 38.6% of Malaysian dairy cattle. LA-MRSA colonization in animals poses a zoonotic risk, especially to those in close contact, such as farmers and veterinarians. Reports have confirmed transmission events between pets and humans, highlighting the necessity for integrated surveillance.
MRSA pathogenicity is driven by a suite of virulence factors, including MSCRAMMs, enterotoxins, and Panton-Valentine leukocidin (PVL). Biofilm formation and phenol-soluble modulins further augment persistence and immune evasion. Pathogenicity islands such as SaPIbov and mobile genetic elements like SCCmec type XI harboring mecC are critical in host adaptation. Moreover, the lukMF’ toxin, highly expressed in bovine-adapted strains, exacerbates mastitis severity in dairy cattle.
Traditional antibiotics, including vancomycin and daptomycin, remain key treatments, though resistance is escalating. Novel antimicrobials such as tedizolid and delafloxacin, alongside non-antibiotic approaches—phytochemicals, probiotics, nanoparticles, and bacteriophages—show promise. Notably, green-synthesized silver nanoparticles and probiotic strains of Lactobacillus and Bifidobacterium demonstrated significant in vitro efficacy against MRSA
Antibiotic resistance is the ability of a microbe to withstand the effects of antibiotics.
A commonly known pathogen, Staphylococcus aureus, has developed resistance to methicillin, resulting in methicillin-resistant Staphylococcus aureus, or MRSA.
MRSA causes serious skin and soft tissue infections in humans, leading to millions of hospitalizations and fatalities globally each year.
Elderly and immunosuppressed patients are at the highest risk due to prolonged and extensive use of broad-spectrum antibiotics.
Strategies to combat MRSA include the use of phytochemicals, phage therapy, nanoparticles, and probiotics.
Phytochemicals — secondary metabolites extracted from plants — are widely used to inhibit the growth of MRSA.
MRSA-specific phages can reduce MRSA populations by inducing cell lysis.
Nanoparticles exert stress by releasing heavy metal ions in the cells. It alters membrane permeability and disrupts essential cellular functions.
Finally, some probiotic strains secrete antimicrobial compounds that inhibit the growth of MRSA.
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