Date of Completion

2024

Document Type

Thesis

Degree Name

Bachelor of Science in Medical Laboratory Science

Keywords

Antimicrobial, Staphylococcus Epidermidis

Abstract

This study explores the antimicrobial potential of Lactobacillus plantarum cell-free extract (CFE) against Staphylococcus epidermidis, a bacterium commonly linked to hospital-acquired infections and known for its increasing resistance to antibiotics. The research aimed to assess whether L. plantarum CFE could effectively inhibit the growth of S. epidermidis by measuring the zone of inhibition (ZOI) under varying pH and temperature conditions to determine how these factors influence its antimicrobial properties. The extract was obtained by culturing L. plantarum in MRS broth, after which its inhibitory effect was analyzed using the Kirby-Bauer disk diffusion method. Its performance was compared to vancomycin, a commonly used antibiotic, across pH levels of 3, 6, and 9, and temperatures of 60°C, 80°C, and 100°C. The findings showed that untreated CFE

exhibited a mean ZOI of 8.53 mm, suggesting antimicrobial activity. However, its effectiveness was highly dependent on environmental conditions. The strongest inhibition occurred at pH 3 (11.35 mm ZOI), while activity decreased significantly at pH 9 (6.00 mm ZOI). Temperature also played a role, with the highest inhibition observed at 60°C (10.33 mm ZOI), which declined at 100°C (6.00 mm ZOI), indicating that extreme heat may weaken its effects. A lactic acid assay confirmed the presence of 0.713 g/L, which is believed to contribute to the extract’s antimicrobial action. While vancomycin consistently exhibited stronger inhibition, L. plantarum CFE still demonstrates potential as an alternative antimicrobial agent when optimized for acidity and moderate temperatures.

First Advisor

Theo John Segismundo, RMT

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