Penggunaan pGFPuv Mutan Untuk Mempelajari Pengaruh Pengeringan Pada ketahanan hidup Cronobacter sakazakii Dalam Jagung.

Abstract

Cronobacter sakazakii is an emerging Gram-negative foodborne bacterial pathogen regarded as the causative agent of meningitis and necrotizing enterocolitis in certain groups of infants. Several isolates of C C. sakazakii have been obtained from food samples in Indonesia and transformation with a Green Fluorescent Protein (GFP) plasmid has produced C. sakazakii pGFPuv mutants with growth pattern similar to that of the wild-type strains. Therefore, they are potential to be used for studying C. sakazakii behaviour without the need to suppress other microorganisms and the use of diagnostic media. The research activities focused on the following objectives : to study the effect of drying on water content and water activity of maize and to evaluate the survival of C. sakazakii pGFPuv as well as other naturally occurring microorganisms in maize during drying. Maize kernels with moisture content of 40% (d.b) were inoculated with C. sakazakii pGFPuv mutant such that the initial concentration in the maize was CFU/g and drying was performed at temperatures of 42 ºC, 46 ºC and 50 ºC for ten days in a drying chamber. Every day the maize samples were taken and the water content were analyzed using oven method while water activity by Aw meter. Total Plate Count and C. sakazakii surviving in the maize were enumerated by standard plate count. The survival rate of C. sakazakii during drying was determined by the slope of linear regression from C. sakazakii survival curve. The results showed that the fate of decrease of C. sakazakii during the rapid decline of water content and Aw can be divided into three phases, i.e. logarithmic decrement, static growth and the final decline. The critical water activity for these pathogenic bacteria was in the range of 0.85-0.86. Observation by SEM showed that C. sakazakii GFPuv form colonies on the surface of corn and the tip cap. This study showed that of C. sakazakii pGFPuv can be used to study the survival of C. sakazakii during corn drying.