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Published on: January 3, 2020
Inhibitory effect of Eleutherine americana Merr. extract on Staphylococcus aureus isolated from food
B O T Ifesan1, C Hamtasin, W Mahabusarakam
1Dept. of Microbiology, Prince of Songkla Univ., Songkhla, Thailand.
Abstract:
About 106 samples of ready-to-eat foods were purchased over a period of 3 mo out of which 76 (71.69%) were contaminated with Staphylococcus aureus. S. aureus isolated from the food samples were characterized phenotypically using traditional biochemical methods. Ninety-four percent of the isolates were mannitol fermenters, 86% positive for coagulase test, while 80% produced lipase enzyme. Antibiotic susceptibility test revealed that 21% and 63% of the food isolates were resistant to oxacillin and penicillin, respectively. The antibacterial activity of the bulb of Eleutherine americana used in Thai cuisine was investigated by agar disc diffusion using 2.5 mg of the crude extract and produced inhibition zone between 14.5 and 15.7 mm, while the minimum inhibitory concentration (MIC) value ranged from 0.06 to 1.00 mg/mL on both food isolates and reference strains. Growth curve in the presence of the crude ethanol extract at 4 MIC showed bacteriostatic effect by 5 log reduction relative to the control. Partially purified fractions tentatively identified by column chromatography were suspected to be responsible for the antibacterial property. This study suggests that E. americana bulb has potential for application as a natural preservative in foods.
Insights
Ready-to-eat foods frequently harbor Staphylococcus aureus. Eleutherine americana bulb extract demonstrated significant antibacterial activity, suggesting its potential as a natural food preservative.
Area of Science:
- Food Microbiology
- Natural Product Chemistry
- Antimicrobial Agents
Background:
- Ready-to-eat foods are susceptible to contamination by pathogenic bacteria.
- Staphylococcus aureus is a common foodborne pathogen.
- Natural compounds are being explored as alternatives to synthetic food preservatives.
Purpose of the Study:
- To investigate the prevalence of Staphylococcus aureus in ready-to-eat foods.
- To evaluate the antibacterial activity of Eleutherine americana bulb extract against S. aureus.
- To assess the potential of E. americana as a natural food preservative.
Main Methods:
- Phenotypic characterization and biochemical testing of isolated S. aureus.
- Antibiotic susceptibility testing of S. aureus isolates.
- Agar disc diffusion and minimum inhibitory concentration (MIC) assays for E. americana extract.
- Growth curve analysis to determine bacteriostatic/bactericidal effects.
Main Results:
- 71.69% of ready-to-eat food samples were contaminated with S. aureus.
- S. aureus isolates showed resistance to penicillin (63%) and oxacillin (21%).
- E. americana crude extract exhibited significant antibacterial activity with inhibition zones (14.5-15.7 mm) and low MIC values (0.06-1.00 mg/mL).
- The extract displayed a bacteriostatic effect, reducing bacterial growth by 5 log.
Conclusions:
- Staphylococcus aureus is prevalent in ready-to-eat foods, with notable antibiotic resistance.
- Eleutherine americana bulb possesses potent antibacterial properties against S. aureus.
- E. americana shows promise as a natural preservative to enhance food safety.
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