Panton-Valentine Leukocidin Facilitates the Escape of Staphylococcus aureus From Human Keratinocyte Endosomes and Induces Apoptosis

• Published in: The Journal of infectious diseases 2014-01, Vol.209 (2), p.224-235
• Main Authors: Chi, Chia-Yu, Lin, Chia-Chun, Liao, Chuang, Yao, Yi-Chuan, Shen, Fan-Ching, Liu, Ching-Chuan, Lin, Chiou-Feng
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Bacteria; Bacterial Toxins - metabolism; Bacteriology; Biological and medical sciences; Cell Line; Community-Acquired Infections - microbiology; Disease Models, Animal; Endosomes; Endosomes - microbiology; Exotoxins - metabolism; Female; Fundamental and applied biological sciences. Psychology; Gene Deletion; Genetic Complementation Test; Humans; Infections; Infectious diseases; Keratinocytes; Keratinocytes - microbiology; Lagomorpha; Leukocidins; Leukocidins - metabolism; Medical sciences; Methicillin resistant staphylococcus aureus; Methicillin-Resistant Staphylococcus aureus - isolation & purification; Methicillin-Resistant Staphylococcus aureus - pathogenicity; Microbiology; Miscellaneous; Rabbits; Skin; Staphylococcal Skin Infections - microbiology; Staphylococcus; Staphylococcus aureus; Taiwan; Virulence; Virulence Factors - metabolism
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/jit445

Skin and soft-tissue infections (SSTIs) caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) have emerged as major health problems throughout the world. Most SSTI CA-MRSA strains produce Panton-Valentine leukocidin (PVL), but its contribution to CA-MRSA pathogenesis is poorly denned. Here, we used an endemic PVL-positive SSTI-causing CA-MRSA strain from Taiwan, together with an isogenic PVL-knockout mutant (Δpvl) and complemented PVL-positive derivative, to evaluate the role of PVL in the pathogenesis of CA-MRSA in the RHEK-1 human keratinocyte cell line and a rabbit skin infection model. We found that both PVL-positive CA-MRSA and isogenic Δpvl strains attached and were engulfed into endosomes of RHEK-1 cells within 1 hour following infection. However, by 2 hours after infection PVL-positive CA-MRSA more effectively disrupted endosomes, escaped into the cytoplasm, and replicated intracellularly. By 6 hours after infection, the PVL-positive strain caused significantly more caspase-dependent keratinocyte apoptosis than the isogenic Δpvl mutant. In the rabbit infection model, 1 week following infection the wildtype strain produced significantly more widespread lesions and cell apoptosis than the isogenic Δpvl mutant. These findings indicate that PVL is an important virulence factor that enables CA-MRSA to produce necrotizing skin infections by allowing the bacteria to escape from endosomes, replicate intracellularly, and induce apoptosis.