Internalisation of pgfg Escherichia coli into Centella asiatica during growing period using hydroponic system / Khalilah Abdul Khalil, Rohana Mat Nor and Zainuri Mohd Salleh

Most of the recent years, an increase in human foodborne illness has been associated with high consumption of fresh produce. It has been reported that 17 foodborne outbreaks were linked to contamination of lettuce and other salad vegetables, and about 50% of these outbreaks ware attributed to contamination with Escherichia coli 0157:H7. None of the chemical or physical treatments currently use as a disinfectant can be relied on to eliminate all types of human pathogens. Studies have been shown that E.coli 0157:H7 can survive on lettuce leaf surfaces for extended periods when mature plants were exposed to contaminated water. Other human pathogens like Listeria monocytogenes and Salmonella were also found to be internalised into inner tissue of lettuce plants when these pathogens were introduced at high cell densities (107 -109 cfu/ml). Though recent studies have examined the application of several human pathogens on mature lettuce, little is known about the attachment of these pathogens to different types of growing plants. Devising successful intervention steps to reduce population of human pathogens on and in vegetables eaten raw, it is necessary to understand and characterise the nature of bacterial intemalisation and attachment to the plants. As a result, the potential of Esc.coli to become internalised into germinating and hydroponically grown centella asiatica has been studied. With inoculated germinating centella asiatica with 103 cfu/ml and 107 cfu/ml separately with Esc. coli bioluminescence tag could be recovered from external and internal sites of root, stems and leave centella asiatica in 4 days of inoculation. When Esc.coli bioluminescence was introduced with different cell density, 103 cfu/ml and 107 cfu/ml into nutrient solution of hydroponically cultivated centella asiatica, it has been observed that intemalisation of pathogen has relied on cell number of population. Intemalisation into the leave part was only can be detected at day 28 (1.30±0.02) until day 42 (1.60+0.09) post inoculation and was undetected thereafter when it 10 cfu/ml been introduced. Whereas in 10 cfu/ml, the intemalisation of pathogen into the leave part was detected at day 14 (1.97±0.10) and extended until day 63 (0.90±0.08) of cultivation period and disappeared thereafter.