This experimental in vitro study aimed to investigate the antibacterial effect of levobupivacaine on Staphylococcus aureus in a patient-controlled analgesia (PCA) model at concentrations commonly used for postoperative pain treatment (0.125%) and painless labour (0.0625%). The antibacterial activity was evaluated using colony count reduction and supported by Scanning Electron Microscope (SEM) imaging.

Study solutions were prepared as 100 mL each. Four groups were designed:

• Group 1: 0.125% levobupivacaine + 4 mL fentanyl (200 mcg)
• Group 2: 0.0625% levobupivacaine + 4 mL fentanyl (200 mcg)
• Group 3: 4 mL fentanyl (200 mcg)
• Group 4: 99 mL saline (control)

Each group received 1 mL of Staphylococcus aureus 0.5 McF (1.5×10⁸ cfu/mL). All samples were infused through a Portex bacterial filter at 4 mL/h for 24 hours using PCA devices. Samples collected from bottles, filter inlets, and outlets were cultivated on Blood Agar. Colony counts were compared statistically using the Kruskal-Wallis and Mann-Whitney U tests (p<0.05).

Inclusion Criteria:

• Laboratory study using Staphylococcus aureus bacterial cultures.
• Samples exposed to different concentrations of levobupivacaine and fentanyl solutions.
• Controlled laboratory environment (Dokuz Eylül University, Microbiology Laboratory).

Exclusion Criteria:

• No human participants included.
• No animal models used.
• Studies outside the defined experimental conditions were excluded.

Individual participant data will not be shared because the study was completed in 2011 and data sharing was not included in the original ethics approval.

No masking was performed. The study was conducted as an open-label in vitro experimental model.