A Comparison of Bacterial Colony-Forming Units in Water Bottles and Hydration Bags Among Outdoor Enthusiasts

Abstract

Transporting clean drinking water in an easily accessible container is a priority for many outdoor enthusiasts. Two basic hydration systems are commonly used to provide water: the water bottle and the hydration bladder. The authors tested the hypothesis that there were different levels of microbiologic contamination between these 2 systems. Sixty-seven water samples were collected using sterile techniques from outdoor enthusiasts at several outdoor recreational locations. These users were then asked to complete a brief survey that reported demographic information and details of water container use. Water samples were then plated on sheep blood agar, and the colony-forming units were counted after 24 hours of growth. The 2 groups were compared using Student's t test. The 2 groups using water bottles or hydration bladders did not show significant differences in container age, duration of outdoor activity, or duration since last cleaning. The groups differed slightly in their composition of hikers/walkers/runners vs cyclists. The water bottle group had a mean colony-forming unit count per 100 mL of 37 (95% CI 26-48), and the hydration bladder had a mean of 27 (95% CI 17-35). There was no statistically significant difference between hydration bladders and water bottles in microbial contamination or colonization. Judging from the available data, outdoor enthusiasts should select their water container based on criteria other than the relative exposure to microbes. Additional study is required to replicate this finding in other locations and with improved sample methodology.