Staphylococcus aureus is a known pathogen causing intoxication by producing
enterotoxins in food.
Staphylococcal enterotoxin A is one of the
enterotoxins commonly implicated in
staphylococcal food poisoning. The ability of crude
alkaloid extract from papaya leaves to inhibit the growth of S. aureus and
staphylococcal enterotoxin A synthesis was investigated.
Staphylococcal enterotoxin A gene-carrying S. aureus was isolated from raw milk and ready-to-eat foods. Crude
alkaloid was extracted from ground, dried papaya leaves using ultrasonic-assisted extraction, and a MIC of the
alkaloid was determined by the broth macrodilution method. Furthermore, S. aureus isolate was exposed to the crude
alkaloid extract at one- and twofold MIC, and the expression of sea was subsequently analyzed using a quantitative reverse transcription real-time PCR. Ten isolates of S. aureus were obtained, and nine of those isolates were sea carriers. The yield of crude
alkaloid extract was 0.48 to 1.82% per dry weight of papaya leaves. A MIC of crude
alkaloid to S. aureus was 0.25 mg/ml. After exposure to the
alkaloid at 0.25 and 0.5 mg/ml for 2 h, a significant increase in cycle threshold values of sea was observed. The sea was expressed 29 and 41 times less when S. aureus was exposed to crude
alkaloid at one- and twofold MIC, respectively. This study revealed that crude
alkaloid of papaya leaves could control
staphylococcal enterotoxin A gene-carrying S. aureus by suppressing the expression of sea, in addition to the ability to inhibit the growth of S. aureus. The expression of sea was successfully quantified.