Identifikasi Bakteri Patogen pada Permukaan Kulit Buah Mentimun (Cucumis sativus) dari Tiga Lokasi di Bogor

Abstract

Buah mentimun merupakan produk pangan yang umum dikonsumsi tanpa pengolahan. Hal ini meningkatkan kemungkinan terdapat kontaminasi bakteri pada buah mentimun, termasuk bakteri patogen. Identifikasi bakteri patogen menjadi langkah penting bagi proses penanggulangan masalah ini. Penelitian bertujuan mengisolasi, menguji aktivitas hemolisis, mengidentifikasi molekular serta mendeteksi keberadaan gen virulensi bakteri patogen yang terdapat pada permukaan kulit buah mentimun. Bakteri diisolasi dari air rendaman buah mentimun yang diencerkan secara serial hingga 10^6. Hasil pengenceran disebar pada blood agar dan dipilih koloni dengan karakter kasat mata yang berbeda. Bakteri patogen dikonfirmasi aktivitas hemolisisnya dan dipilih isolat dengan aktivitas hemolisis sempurna untuk karakterisasi lebih lanjut. Karakterisasi dilakukan secara makroskopis dan mikroskopis. Isolat diidentifikasi secara molekuler dengan gen 16s rRNA dan dideteksi keberadaan gen virulensi plcH, toxA, dan lasB. Terdapat bakteri patogen sebanyak 10^4 CFU/gram yang dideteksi pada setiap permukaan kulit buah mentimun. Sepuluh isolat yang secara kasat mata berbeda diisolasi, dimurnikan, dan dikarakterisasi aktivitas hemolisisnya. Tiga isolat dengan aktivitas hemolisis sempurna diidentifikasi memiliki karakter Gram positif, berbentuk basil dan memiliki endospora. Identifikasi molekular menunjukan ketiga isolat memiliki kemiripan sekuens tertinggi dengan Bacillus altitudinis, Bacillus cereus, dan Bacillus xiamenensis. Seluruh isolat terdeteksi memiliki gen plcH, hanya satu isolat yang memiliki gen toxA dan tidak isolat yang memiliki gen lasB.

Cucumber is a food product that is commonly consumed without processing. This increases the possibility of bacterial contamination of cucumbers, including pathogenic bacteria. Identification of pathogenic bacteria is an important step in the process of overcoming this problem. The research aims to isolate, test hemolysis activity, molecular identification and detect the presence of virulence genes for pathogenic bacteria on the surface of cucumber skin. Bacteria were isolated from cucumber soaking water which serially diluted to 106. The dilution was spread on blood agar and colonies with different visible characteristics were selected. Pathogenic bacteria were re-confirmed for their hemolysis activity and isolates with perfect hemolysis activity were selected for further macroscopic and microscopic characterization. Isolates were identified molecularly using the 16s rRNA gene and detected the presence of the virulence genes plcH, toxA, and lasB. There is pathogenic bacteria around 10^4 CFU/gram detected on each surface of the cucumber skin. Ten isolates that were different isolated, purified, and re-characterized hemolysis activity. Three isolates with perfect hemolysis activity were selected and identified as Gram-positive, basil-shaped and had endospores. Molecular identification showed that three isolates had the highest sequence similarity to Bacillus altitudinis, Bacillus cereus, and Bacillus xiamenensis. All isolates were detected to have the plcH gene, only one isolate had the toxA gene and no isolates had the lasB gene.