Intracellular Staphylococcus aureus and antibiotic resistance: implications for treatment of staphylococcal...

Area of Science:

• Microbiology
• Infectious Diseases
• Cell Biology

Background:

• Staphylococcus aureus is the primary cause of human osteomyelitis, often persisting within host osteoblasts.
• Antibiotic resistance in S. aureus complicates effective treatment strategies for osteomyelitis.

Purpose of the Study:

• To investigate whether antibiotic sensitivities of S. aureus change after invasion and persistence within the osteoblast intracellular environment.
• To evaluate the impact of early versus delayed antibiotic administration on intracellular S. aureus burden.

Main Methods:

• Human and mouse osteoblast cultures were infected with S. aureus.
• Intracellular bacteria were enumerated at various time points (0, 12, 24, 48 hours) after treatment with erythromycin, clindamycin, or rifampin at different intervals.
• Transmission electron microscopy was used to observe structural changes in S. aureus.

Main Results:

• Early administration (time 0) of bacteriostatic antibiotics prevented intracellular S. aureus proliferation, while delayed administration (12 hours) did not.
• Early administration of bactericidal rifampin significantly reduced intracellular S. aureus counts in both human and mouse osteoblasts.
• Significant, time-dependent structural alterations in S. aureus were observed within osteoblasts.
• S. aureus established intracellularly for 12 hours exhibited significantly reduced sensitivity to antibiotics capable of eukaryotic cell penetration.

Conclusions:

• The antibiotic sensitivity of S. aureus is altered by its intracellular location within osteoblasts.
• Early antibiotic intervention is critical for successful treatment of intracellular S. aureus infections.
• Observed structural changes in S. aureus may contribute to decreased antibiotic sensitivity intracellularly.