Craig D L, Fallowfield H J, Cromar N J
Dept of Environmental Health, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia.
Water Sci Technol. 2003;47(3):191-8.
Decay rates in coastal water and sediment for the bacterial pathogens Salmonella typhimurium and S. derby were compared in laboratory-based microcosms with results previously obtained for a number of faecal indicators. In general, the decay rates of Salmonella spp. were greater than either enterococci or coliphage in overlying water and sediment. Decay rates of E. coli were similar to Salmonella spp. in overlying water, although greater in sediment. Raised temperature resulted in an increased decay rate for all organisms in the overlying water (and to a lesser extent in the surface sediment layer). It was demonstrated that decay rates for both S. typhimurium and S. derby were greater in overlying water compared with sediment. This suggested that sediments may be acting as a reservoir for pathogenic microorganisms released into the coastal environment during recreational activity and should be considered when estimating environmental exposure. Using measured decay rates and available dose-response data, a quantitative microbial risk assessment (QMRA) utilising Monte Carlo simulation was undertaken to estimate the risk of infection to Salmonella spp. following exposure to recreational coastal water subject to a range of faecal contamination levels. In waters of extremely poor quality, subject to contamination by faecal coliforms (10(6) CFU/100 mL), the maximum probability of infection on the day of an accidental release was above 2.0 x 10(-1) and remained above 1 x 10(-3) for three days following the initial high concentration.
在基于实验室的微观世界中，比较了沿海海水和沉积物中鼠伤寒沙门氏菌和德比沙门氏菌这两种细菌病原体的衰减率，并与先前针对多种粪便指示菌获得的结果进行了比较。总体而言，沙门氏菌属在上覆水和沉积物中的衰减率高于肠球菌或噬菌体。大肠杆菌在上覆水中的衰减率与沙门氏菌属相似，不过在沉积物中的衰减率更高。温度升高导致上覆水中所有生物体的衰减率增加（在表层沉积物中影响较小）。结果表明，鼠伤寒沙门氏菌和德比沙门氏菌在上覆水中的衰减率高于沉积物。这表明沉积物可能是休闲活动期间释放到沿海环境中的致病微生物的储存库，在评估环境暴露时应予以考虑。利用测得的衰减率和可用的剂量反应数据，采用蒙特卡洛模拟进行了定量微生物风险评估（QMRA），以估计接触受一系列粪便污染水平影响的休闲沿海海水后感染沙门氏菌属的风险。在质量极差、受粪大肠菌群污染（10(6) CFU/100 mL）的水域中，意外排放当天的最大感染概率高于2.0×10(-1)，在初始高浓度后的三天内仍高于1×10(-3)。
