Staphylococcus aureus response and adaptation to vancomycin

Staphylococcus aureus: A Review of the Pathogenesis and Virulence Mechanisms

Staphylococcus aureus is a formidable human pathogen responsible for infections ranging from superficial skin lesions to life-threatening systemic diseases. This review synthesizes current knowledge on its pathogenesis, emphasizing colonization dynamics, virulence mechanisms, biofilm formation, and antibiotic resistance. By analyzing studies from PubMed, Scopus, and Web of Science, we highlight the pathogen's adaptability, driven by surface adhesins (e.g., ClfB, SasG), secreted toxins (e.g., PVL, TSST-1), and metabolic flexibility in iron acquisition and amino acid utilization. Nasal, skin, and oropharyngeal colonization are reservoirs for invasive infections, with biofilm persistence and horizontal gene transfer exacerbating antimicrobial resistance, particularly in methicillin-resistant S. aureus (MRSA). The review underscores the clinical challenges of multidrug-resistant strains, including vancomycin resistance and decolonization strategies' failure to target single anatomical sites. Key discussions address host-microbiome interactions, immune evasion tactics, and the limitations of current therapies. Future directions advocate for novel anti-virulence therapies, multi-epitope vaccines, and AI-driven diagnostics to combat evolving resistance. Strengthening global surveillance and interdisciplinary collaboration is critical to mitigating the public health burden of S. aureus.

Combination therapy delays antimicrobial resistance after adaptive laboratory evolution of Staphylococcus aureus

Antibiotic resistance, driven by misuse and overuse of antibiotics, is one of the greatest threats against human health. The antimicrobial pressure during prolonged antibiotic treatment of chronic bacterial infections selects for resistance. While antibiotic combinations may reduce resistance emergence, antibiotic-tolerant persister cells can serve as a reservoir for resistance development. Therefore, targeting these cells with anti-persister drugs might provide a novel strategy for resistance prevention. In this study, we conducted 42 days of adaptive laboratory evolution using Staphylococcus aureus exposed to rifampicin, ciprofloxacin, daptomycin, and vancomycin, alone or in combination with the anti-persister drug mitomycin C. We monitored antibiotic susceptibility daily and assessed phenotypic changes in growth and biofilm formation in evolved strains. Whole-genome sequencing revealed mutations linked to antibiotic resistance and phenotypic shifts. Rifampicin resistance developed within a few days, while ciprofloxacin and daptomycin emerged in approximately 3 weeks. Treatments with vancomycin or mitomycin C resulted in minimal changes in susceptibility. While combination therapy delayed resistance, it did not fully prevent it. Notably, the combination of rifampicin with mitomycin C maintained rifampicin susceptibility throughout the long-term evolution experiment. Sub-inhibitory antibiotic treatments selected for both previously characterized and novel mutations, including unprecedented alterations in the nucleotide excision repair system and azoreductase following mitomycin C exposure. The delayed resistance development observed with combination therapy, particularly mitomycin C's ability to suppress rifampicin resistance, suggests potential therapeutic applications. Future studies should evaluate the clinical efficacy of anti-persister drugs in preventing resistance across different bacterial pathogens and infection models.

Characterization of agr-like Loci in Lactiplantibacillus plantarum and L. paraplantarum and Their Role in Quorum Sensing and Virulence Inhibition of Staphylococcus aureus

The pathogenicity of Staphylococcus aureus is largely regulated by the agr quorum sensing (QS) system encoded by agrBDCA, which coordinates virulence factor production through secretion and sensing of auto-inducing peptides (AIPs). agr-like systems are also present in coagulase-negative staphylococci, and several of these encode AIPs that inhibit S. aureus QS. In lactic acid bacteria, a similar locus was previously identified in Lactiplantibacillus plantarum WCSF1 termed lamBDCA. Here, we characterized the lamBDCA locus in L. plantarum LMG 13556 and L. paraplantarum CIRM-BIA 1870, and explored the effects on S. aureus QS. Notably, we found that co-cultivation with L. paraplantarum significantly inhibits S. aureus QS and hemolysin production, while less so for L. plantarum. The inhibition by L. paraplantarum was lost upon disruption of its lamBDCA locus, suggesting that the L. paraplantarum AIP mediates cross-species interference with S. aureus agr activation. Transcriptomic analysis revealed that lamBDCA in L. paraplantarum controls the expression of genes belonging to various functional categories, including stress response and metabolism. The latter includes genes encoding riboflavin (B2 vitamin) biosynthesis, which enabled the growth of the L. paraplantarum lamB mutant in the presence of roseoflavin, a toxic riboflavin analogue. Collectively, our results show that L. paraplantarum CIRM-BIA 1870 interferes with S. aureus virulence gene expression through QS suppression, and they implicate QS in the probiotic properties of L. paraplantarum.