Judul: Isolation and identification of Enterobacter sakazakii from fresh vegetables and fruits samples from Bogor Indonesia
Abstrak: E.sakazakii is classified as a pathogenic bacterium that causes illness mostly to infants and immunocompromised individuals. This bacterium belongs to the group of Gram negative Enterobacteriaceae species, which was re-classified as Cronobacter spp. based on DNA hybridization and phenotyping. E. sakazakii has been widely implicated in a number of foodborne diseases, which are characterized by illnesses like meningitis and enteritis especially in pre-termed neonates and or with low birth weight infants. The bacterium has been isolated from various foods including fresh vegetables and fruits and also survives refrigeration temperatures. This research aim was to isolate E.sakazakii from a number of fresh vegetables and fruits samples available in local market surrounding Darmaga area, Bogor, Indonesia. The isolation followed FDA (2002) method modified by Iversen and Forsythe (2004). Rapid biochemical kit, API 20E, was used for biochemical characterization and identification. Molecular confirmation consisted of isolation of DNA and PCR to amplify the gene encoding for 16S rRNA using two different pair of primers, ESA-1/16SUNI-(R) and 16SUNI-L/Saka 2b. A total number of 19 samples tested positive to pre-enrichment and enrichment broth, in BPW (buffered peptone water) and EE (Enterobacteriaceae enrichment) broth, respectively. Isolation in VRBG (Violet Red Bile Glucose) agar yielded all positive results for all samples. However test on DFI (Druggan–Forsythe–Iversen) agar showed only four isolates producing typical blue/green colony, i.e. those isolated from cabbage, chaisin, apple “fuji” and apple “manalagi”. The biochemical test kit API 20E (Analytical Profile Index; bioMe´rieux) showed that none of the samples were positive for E.sakazakii. The PCR results showed that only one isolate i.e. from cabbage, successfully produced an amplicon of the 16S rRNA. This study suggests that isolation rate of E.sakazakii in vegetable is low at 5.2 %.
Keyword: Cronobacter spp., PCR, Enterobacter sakazakii, fresh produce, DNA fragments

Judul: Isolasi dan Identifikasi Keragaman Genetika Cronobacter spp. (Enterobacter sakazakii) yang Diperoleh dari Produk Pangan Kering
Abstrak: Cronobacter spp. (formerly Enterobacter sakazakii) is a group of emerging pathogen that has been implicated as the causative agent of meningitis and necrotizing enterocolitis in certain groups of infants. In Indonesia several isolates have been obtained mostly from powder infant formula and weaning foods. This research aimed to obtain Cronobacter spp. isolates from other dried foods i.e. weaning foods, flours, starches and spices and evaluated the biochemical and genotypic characteristics of the isolates. Isolation was conducted according to FDA method (2002) modified with Iversen and Forsythe (2004), biochemical was conducted by API 20E test and genotypic characterization was conducted by PCR amplification of their 16S rRNA gene using 3 primer pairs respectively, 16 SUNIL/ Saka 2b (Segment 1), ESA1/16 SUNI-R (Segment 2) and 16SUNI-L/16SUNI-R (Universal segment). Results of the DNA amplification were sequenced and then analyzed for their relatedness to reference isolates of C.sakazakii from GenBank using BLAST program. In this study 62 samples of weaning foods, flours, starches and spices were screened for the presence of Cronobacter spp. Twelve typical colonies on DFI were obtained from sample of flours, starches and spices samples. Biochemical test using API 20E suggested that 11 of the 12 presumptives isolates were E. sakazakii while one was identified as E. cloacae. Genotypic analysis revealed that eleven isolates including the one identified as E.cloacae by API test were confirmed as C.sakazakii while one isolates was C.muytjensii. Relationships between strains based on segment 1 was depicted in a dendrogram using the neighbor-joining method showed that the twelve isolates can be differentiated into two groups, meanwhile when universal segment was used, the isolates can be differentiated into three groups.
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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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