Guardabassi L, Gravesen J, Lund C, Bagge L, Dalsgaard A
Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Water Res. 2002 Nov;36(18):4655-8. doi: 10.1016/s0043-1354(02)00154-9.
The effects of sample storage on enumeration of Escherichia coli in marine bathing water and culturable bacteria in drinking water were evaluated. Results showed that overnight storage at 0-5 degrees C significantly reduced the counts of E. coli in bathing water (p = 0.0001) with a mean reduction of 25%. A similar effect of sample storage was observed for the enumeration of culturable bacteria in drinking water at 22 +/- 2 degrees C for 66 +/- 4 h (p = 0.0074; mean reduction = 25%) or at 36 +/- 2 degrees C for 44 +/- 4h (p = 0.0353; mean reduction = 6%). The use of a delayed incubation method, i.e. overnight storage at 0-5 degrees C of inoculated agar plates prior to incubation, did not significantly affect the counts of culturable bacteria when plates were incubated at 22 + 2 degrees C for 66 +/- 4 h, whereas it resulted in a significant increase of the bacterial numbers when plates were incubated at 36 +/- 2 degrees C for 44 +/- 4 h (p = 0.0002; mean increase = 32%). Based on these results, it is suggested to avoid the use of overnight or longer sample storage for the enumeration of E. coli in bathing water samples, as well as for the enumeration of culturable bacteria in drinking water. The delayed incubation method appears to be a reliable procedure for the enumeration of culturable bacteria and could represent a valid alternative to sample storage in order to overcome problems associated with the performance of bacteriological counts during weekends or statutory holidays. However, a multi-laboratory study is needed to evaluate the reproducibility of the delayed incubation method for the enumeration of culturable bacteria and its possible use for the enumeration of E. coli by membrane filtration.
评估了样品储存对海水浴场水中大肠杆菌计数以及饮用水中可培养细菌计数的影响。结果表明，在0 - 5摄氏度下过夜储存显著降低了浴场水中大肠杆菌的数量（p = 0.0001），平均减少了25%。对于饮用水中可培养细菌的计数，在22±2摄氏度下储存66±4小时（p = 0.0074；平均减少 = 25%）或在36±2摄氏度下储存44±4小时（p = 0.0353；平均减少 = 6%）时，观察到了类似的样品储存效果。采用延迟培养方法，即在培养前将接种的琼脂平板在0 - 5摄氏度下过夜储存，当平板在22 + 2摄氏度下培养66±4小时时，对可培养细菌的计数没有显著影响，而当平板在36±2摄氏度下培养44±4小时时，细菌数量显著增加（p = 0.0002；平均增加 = 32%）。基于这些结果，建议避免对海水浴场水样中的大肠杆菌计数以及饮用水中可培养细菌计数采用过夜或更长时间的样品储存。延迟培养方法似乎是一种可靠的可培养细菌计数程序，并且可以作为样品储存的有效替代方法，以克服周末或法定节假日期间进行细菌学计数所面临的问题。然而，需要进行多实验室研究来评估延迟培养方法对可培养细菌计数的再现性及其通过膜过滤法对大肠杆菌计数的可能用途。
