<Original Papers> Potential of Agricultural Water and Pesticide Solution as Preharvest Sources of Microbial Contamination for Several Fruits

[要旨] 和歌山県産の果実（カキ、ウンシュウミカン、ウメ）の各圃場を対象に, 農業用水, 農薬溶液および収穫果実の微生物汚染度を測定し, これらの栽培環境接触物が微生物汚染源として青果物に及ぼす影響を調査した. 農業用水に使用した水源の微生物汚染度は, 河川水が谷の湧水より1log程度高かった. さらに, 農業用水に農薬を溶解することで, 微生物数が最大で2log程度増加し, 微生物汚染度の増大が確認された. 農薬散布から3日後に収穫されたカキ果実では, 農業用水および農薬溶液から土壌由来あるいは植物病原性の7菌種が移行したと推定され, 農薬散布から8日後のウンシュウミカン果実（2菌種）および31日後のウメ果実（1菌種）よりも多いことが確認された. いずれのサンプルからも食中毒原因菌（verotoxin-producing Escherichia coli, Salmonella, Listeria monocytogenes）は検出されず, 農業用水および農薬溶液を介した微生物的食品安全危害はないことが示された. [Abstract] Microflora of field environments (agricultural water and pesticide solutions diluted with agricultural water) and several fruits (persimmons, satsuma mandarin, and Japanese apricots) were investigated to determine the potential of the field environment as a preharvest source of microbial contamination for the fruits. With agricultural water, the microbial counts in river water were 1 log higher than those counts in mountain spring water. When pesticide products were dissolved in agricultural water, the microbial counts increased by 2 logs. Seven species of soilborne or phytopathogenic bacteria andmolds detected on persimmon fruit harvested 3 days after pesticide application were also found in the agricultural water and pesticide solution, suggesting that the field environment could be a source of preharvest contamination. In comparison there were fewer microbial species found on satsuma mandarin fruit (2 species) and Japanese apricot fruit (1 species) harvested 8days and 31 days after pesticide application, respectively, that appeared to be transferred from the agricultural water and pesticide solutions. Since foodborne pathogens such as Salmonella, verotoxin-producing Escherichia coli, and Listeria monocytogenes were not detected in any of the fruit and environmental samples, it is assumed that there are no microbialfood safety hazards resulting from cross-contamination with the environment