Optimizing water sampling in large building premise plumbing for the detection of opportunistic pathogens

Premise Microbial Testing
Oral Presentation

Prepared by , M. Prévost

Contact Information: emilie.bedard@polymtl.ca; 514-340-4711 x5223


Microbial characteristics of drinking water can be altered in hospital distribution systems. Biofilm, periodical stagnation, high surface-to-volume ratios, and favorable temperatures encountered within large buildings are factors that promote bacterial growth. Opportunistic pathogens are present in hospital water distribution and are often amplified in the hot and cold water distribution systems and may represent a health risk at points-of-use (taps, shower head, etc.). Large building distribution systems have a multitude of points of use. Environmental factors such as chlorine, temperature, materials and residence time may vary significantly between various sectors of a large building system and may affect water quality differently in those sectors. However, microbial quality is only measured at a limited number of sites due to the high cost associated. In such context, the optimal selection of sampling sites and of the sampling methodology is essential to detect areas at risk and prioritize corrective measures. In order to maximize the microbial sampling, several questions should be asked and information gathered ahead of time. Through practical examples, the authors illustrate the importance of answering some of those questions ahead of sampling, to better define how sampling should be conducted: understanding the system design and variations between sectors; locating risk areas through historical data, hydraulics, temperatures at point of use, and users complaints; covering areas serving most vulnerable patients; determining the sampling objective; understanding if sampling should be done on 1st draw or flushed samples and using reference culture or molecular methods; documenting the type of devices and how they can impact water quality; determining the volume to maximize recovery. Detection of opportunistic pathogens in drinking water from premise plumbing presents several challenges and building the right sampling plan is the first step to ensure that sampling results are representative of the system and address the initial sampling objectives.