Uji aktivitas antibakteri dari bakteri endofit daun mengkudu (Morinda citrifolia L.) terhadap pertumbuhan Staphylococcus aureus

Introduction: Endophytic bacteria from noni (Morinda citrifolia L.) leaves may represent a source of antibacterial metabolites, but their activity against Staphylococcus aureus requires further investigation. This study aimed to characterize culturable leaf endophytes and assess their preliminary inhibitory responses against S. aureus. Methods: In this laboratory experiment, noni leaves collected in Jambi, Indonesia, were surface-disinfected, homogenized, and cultured on nutrient agar. Isolates were characterized by colony morphology, Gram staining, and catalase, motility, citrate utilization, and methyl red tests. Antibacterial screening employed a disc diffusion assay with 20 µL of whole culture per disc and a 30-µg chloramphenicol disc as the positive control. Measurements from three replicates were analyzed descriptively. Results: Three isolates (A, B, and C) were obtained; all were Gram-negative, motile, catalase-negative rods. Isolates A and B were citrate- and methyl red-positive, whereas isolate C was negative in both tests. Mean recorded clear-zone measurements (± standard deviation) were 1.95 ± 1.61, 1.81 ± 0.72, and 2.86 ± 0.31 mm for isolates A, B, and C, respectively. Chloramphenicol yielded 0.76 ± 0.66 mm, including one zero reading. Discussion: Isolate C showed the highest mean recorded reading and the lowest between-replicate variation. However, unavailable raw diameter measurements, nonstandard susceptibility-testing medium, and an inconsistent positive-control response preclude reliable potency comparisons. These findings constitute preliminary screening observations and support prioritizing isolate C for further characterization and repeat testing under standardized conditions.