Date Published: January 23, 2017
Publisher: Public Library of Science
Author(s): Harald Handschuh, Michael P. Ryan, Jean O’Dwyer, Catherine C. Adley, Zhe-Xue Quan.
The aim of this study was to determine and identify bacteria inhabiting the supply chain of an airline’s drinking water using phenotypic and 16S rDNA sequence-based analysis. Water samples (n = 184) were sourced from long-haul and short-haul aircraft, the airline water source and a water service vehicle. In total, 308 isolates were characterised and their identity determined, which produced 82 identified bacterial species belonging to eight classes: γ-Proteobacteria; β-Proteobacteria; α-Proteobacteria; Bacilli; Actinobacteria; Flavobacteria; Sphingobacteria and Cytophaga. Statistical differences in bacterial diversity were found to exist across sampling locations (X2 = 39.220, p = 0.009) and furthermore, differences were observed (X2 = 15.475, p = 0.030) across aircraft type (long- or short-haul). This study demonstrates the diverse nature of microorganisms within the aircraft drinking water supply chain. To the best of our knowledge, this is the most extensive study undertaken to date of microbial diversity in aircraft drinking water.
Water can support and host an array of pathogenic  and non-pathogenic microorganisms, amongst which are bacteria, fungi, viruses, protozoa, helminths and Schistosoma . As such, a fundamental aspect of safeguarding public health is the routine microbiological analysis of drinking water for early detection of microbial contamination and assessing sources of deterioration in quality. Bacteria found in fresh water, including naturally occurring aquatic bacteria, can come from many different habitats, or from soil, human or animal intestinal tracts; the primary taxonomic groups are α-Proteobacteria, β-Proteobacteria, Bacteroidetes [3, 4] and γ-Proteobacteria . Aquatic bacteria are predominantly Gram-negative and are comprised largely of genera such as Pseudomonas, Acinetobacter Flavobacterium, and Cytophaga, along with some types of Gram-positive bacteria such as coryneform bacteria, Micrococcus and Bacillus . Pyrosequencing of drinking water from a US university campus to analyse its microbial ecology revealed that α-Proteobacteria and β-Proteobacteria dominated this bacterial community .
A total of 308 identified bacterial isolates were recovered from routine aircraft water samples collected along the water supply chain from the Water Source, Water Service Vehicle (WSV), and from water taps in the galleys of both short- and long-haul designated aircraft. Bacteria identified belonged to eight classes (Fig 1): γ-Proteobacteria; β-Proteobacteria; α-Proteobacteria; Bacilli; Actinobacteria; Flavobacteria; Sphingobacteria and Cytophaga.
To the best of our knowledge this is the first comprehensive study undertaken on microbial diversity in aircraft drinking water. Bacterial classes identified in this study are typical; representing the bacterial diversity of drinking water found in other studies, notwithstanding that drinking water is collected on occasions from multiple water sources and airports in different countries. It is acknowledged that the bacterial isolates found in this study may cause illness especially in sections of the population with underlying diseases such as immunocompromised individuals. It is important to note that no official reports of illness resulting from the consumption of aircraft drinking water could be identified in literature. However, enforcement of regulations and continued watchfulness by national health authorities, voluntary international structures such as the International Air Transport Association Drinking-Water Quality Pool (IDQP) and airlines themselves, is needed to keep the risk of contactable diseases from aircraft water at bay.