Judul: Molecular Identification Local Isolates of Staphylococcus aureus by Polymerase Chain Reaction (PCR) Method
Abstrak: Foodborne disease is a major concern worldwide, and S. aureus is continuously involved in foodborne disease outbreaks. Staphylococcal enterotoxins (SE) are important virulence factor for the bacterial intoxications. This research aimed to identify local isolates of S. aureus based on universal 16S rRNA gene and to identify whether they possess SE A and C1 genes. Bacterial DNA isolation was conducted using Doyle and Doyle extraction method with some modification. Amplification of genes encoding for 16S rRNA, SEA and SEC1 were investigated using primers 63f/1387r, SEA-1/SEA-2 and SEC1-1/SEC1-2, consecutively. The amplification products of 16S rRNA were sequenced and then analyzed for their relatedness to S. aureus. The resulted sequence was analyzed using BLAST (Basic Local Alignment Search Tool) program and it was found that 5 out of 14 isolates were confirmed as S. aureus. The local isolates of NU4, NU5 and NU9 have 87 – 92% similarity, but all of the local isolates do not have similarity with S. aureus ATCC 25923. Based on amplification of the SE genes, 1 local isolates of S. aureus (NU5) was capable of producing both SEA and SEC1 while 1 local isolate (NU1) was only capable of producing SEA.
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Judul: Study of the Characterization and Detection Methods of Staphylococcus aureus in Foods
Abstrak: Keamanan pangan merupakan hal utama dalam menyediakan pangan yang baik bagi manusia. Saat ini beban penyakit bawaan pangan di Indonesia cukup tinggi yang diperkirakan 680 DALYs per 100.000 penduduk. Keracunan pangan Staphylococcus adalah penyakit bawaan pangan yang umum terjadi di seluruh dunia. Staphylococcus dibedakan menjadi 49 spesies dan 14 di antaranya dapat menyebabkan keracunan pangan, seperti Staphylococcus aureus yang dapat diklasifikasikan menjadi enam biotipe. S. aureus menghasilkan enterotoksin Staphylococcus (SE) yang resisten terhadap enzim proteolitik dan memungkinkan untuk transit utuh melalui saluran pencernaan. Tujuan penulisan karya ilmiah ini adalah untuk mengkaji metode-metode berbasis molekuler yang telah dikembangkan untuk mempelajari karakteristik S. aureus dan SE dalam berbagai jenis pangan, diantaranya pada susu dan produk susu, daging dan produk daging, makanan jajanan, produk biji-bijian, dan minuman. Kajian yang dilakukan melalui penelusuran pustaka terpublikasi melalui internet dengan sumber yang dapat dipertanggungjawabkan tersebut menghasilkan 65 publikasi ilmiah antara tahun 1977–2020. Penandaan plasmid (plasmid profiling) merupakan metode molekuler pertama untuk karakterisasi bakteri melalui isolasi serta pembandingan jumlah dan ukuran plasmid dengan gel elektroforesis agarosa. PFGE (pulsed field gel electrophoresis) dan RFLP (restriction fragment length polymorphism) mengkarakterisasi S. aureus dan SE berdasarkan pemecahan kromosom menjadi fragmen kecil menggunakan enzim restriksi dilanjutkan dengan elektroforesis. PFGE memiliki keunggulan dalam daya diskriminasi, kemampuan pemecahan DNA, reproduktifitas, serta merupakan standar emas untuk typing. RFLP tidak memerlukan informasi urutan DNA atau sintesis oligonukleotida sebelum analisis. PCR (polymerase chain restriction) digunakan untuk menggandakan molekul DNA dengan bantuan enzim DNA polymerase dan primer. PCR memiliki kecepatan dan efisiensi yang tinggi dalam mendeteksi S. aureus dan SE.
Keyword: PCR, PFGE, plasmid profiling, RFLP, Staphylococcus aureus

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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