A NOTE: POLYVALENT RADIOVACCINE AGAINST SALMONELLA

Salmonella strains exposed to lethal doses of gamma radiation are detoxified but retain their antigenic properties. Using eight Salmonella strains representative of each of the Salmonella serogroups A to G, a polyvalent radiovaccine has been developed which effectively immunizes mice to several Salmonella serotypes.     

Optimum combined test plans for systems and components

Since mathematical models based on component reliabilities are frequently used for prediction of system reliability, it stands to reason that cost-effective inferences on the reliability of a system could be made on the basis of tests of its constituent components. Prior research in the area of system-based component testing has for the most part addressed the development of plans that test only the components. From a practitioner's point of view, this is an issue of concern since system failures are often caused by imperfect interfaces and other causes that are not directly attributable to component failures. The exclusion of system tests may thus be an erroneous approach. This paper addresses the development of test plans that explicitly consider the possibility of interface failures. The paper analyzes a series system to determine when testing should be performed on the system alone, on the components only, and on both, depending on test costs and interface reliabilities. Optimum test plans are: derived by solving a two-stage mathematical program.     

An extension of Palmer's heuristic for the flow shop scheduling problem

We describe a simple modification of Palmer's heuristic for scheduling jobs in a flow shop. While the additional computation required is relatively small, the performance of the algorithm compares very well with that of the more sophisticated and better algorithm of Campbell, et al. (1970) at a fraction of the effort required by the latter.     

DETECTION OF SALMONELLAE IN CHICKEN AND FISH SAMPLES USING DNA PROBE

The use of DNA probes for rapid identification of foodborne pathogens is an emerging field. We have standardized a method for the detection of Salmonella in food samples by using a specific insertion sequence (IS-200) of Salmonella chromosomal DNA as the probe. The procedure for colony hybridization, and washing conditions for the stringency were established. All the ten Salmonella strains, belonging to various serotypes tested were positive while 18 other bacterial cultures, mainly belonging to the family Enterobacteriaceae such as E. coli Shigella, Proteus etc., were negative in colony hybridization. The sensitivity of the detection was found to be 10⁵ cfu using ³²P-labeled probe. We surveyed 16 chicken and 6 fish samples from local market using IS-200 probe after preenrichment and selective enrichment. All the samples tested were found positive with DNA probe. The major strains of Salmonella isolated from these samples were S. gallinarum, S. typhimurium, S. enteritidis, S. choleraesuis and S. paratyphi A. These results were confirmed by standard Salmonella identification method.     

On scheduling parallel machines with two setup classes

We examine I he problem of scheduling jobs at a bank of parallel identical machines where each job requires either a major or a minor setup depending on the job that was processed immediately before it. Several heuristic procedures are proposed and tested with respect to makespan, average flowtime and time spent on setups.     

Performance of Farmer-managed Irrigation Systems for Rice Production in East Java Province,Indonesia

This paper addresses the importance of an institutional mechanism to allocate and distribute irrigation water properly, to reduce conflicts and to mobilize financial support for sustainable rice production. The study reveals that the contributing factors affecting the performance of farmer-managed irrigation systems for rice production are plot size and the application of seed, fertilizer and pesticides, and the influencing factors are water adequacy during the dry season and a fixed schedule of intermittent flow of water distribution. Water inadequacy and dissatisfaction on the timeliness of water distribution are the potential sources of conflicts, whereas the ability of farmers to pay irrigation fees and the acceptance of a fee system are the major concerns about the financial support for irrigation operation and maintenance. The accountability of a water user's association is the main factor influencing the success of an institutional role in the sustainability of rice production.     

MICROBIOLOGICAL QUALITY OF THE DAIRY PRODUCT PEDHA AND ITS IMPROVEMENT USING GAMMA RADIATION

Eighteen pedha samples procured from A and B grade retail shops were examined for their overall microbiological quality and for the presence of foodborne pathogens viz. Staphylococcus aureus, Salmonella sp., Coliforms , Listeria monocytogenes, Yersinia enterocolitica and Bacillus cereus. The microbiological quality of pedha samples from B grade shops was very poor as compared to pedha from A grade shop as evidenced by the very high total bacterial counts (6 × 10⁷ cfu/g), high counts of S. aureus (as high as 7 × 10⁶ cfu/g) and presence of coliforms and Listeria and Yersinia sp. in 33% of the samples. All the samples from A grade shops were also positive for S. aureus though negative for coliforms , Yersinia, Salmonella, Listeria and B. cereus. Gamma irradiation of pedha at a dose of 3kGy at 0C reduced overall bacterial load by five log cycles and S. aureus and coliforms could be totally eliminated. However, 5 kGy dose was necessary to eliminate S. aureus if the initial number exceed 1 × 10⁵ cfu/g. Inoculated pack studies confirmed that 3 kGy dose was sufficient for the complete elimination of up to 1 × 10⁵ cfu/g of S. aureus. A dose of 3 kGy had minimal effect on the sensory quality of pedha and even pedha samples irradiated at 5 kGy dose were acceptable. Treatment with 3 kGy dose of gamma radiation totally eliminated S. aureus and coliforms in pedha, thereby ensuring their microbial safety.     

RADIATION CONTROL OF VIBRIO PARAHAEMOLYTICUS IN SHRIMP

The effectiveness of a radicidation process using 1 kGy of gamma radiation was evaluated with respect to the destruction of Vibrio parahaemolyticus contamination in shrimp. D₁₀ values of this pathogen ranged from 0.03 kGy in frozen buffer to 0.10 kGy in naturally contaminated frozen shrimp. The efficacy of the process was demonstrated.     

ELIMINATION OF SALMONELLA FROM FROZEN SHRIMP BY GAMMA RADIATION

Shrimp samples were found to be contaminated with Salmonella. The D₁₀ values of S. typhimurium and S. enteritidis were between 0.225 to 0.250 kGy when cells were irradiated in frozen 0.1 M phosphate buffer. The radiation resistance of these Salmonella spp. increased marginally when cells were irradiated in shrimp homogenate. A radiation dose of 4.0 kGy completely eliminate Salmonella from frozen prepackaged shrimp, which was confirmed by inoculated pack studies .