Presence of Pseudomonas aeruginosa in coliform-free sachet drinking water in Ghana

• We tested the microbiological quality of 80 sachet water samples in low-income areas.
• Zero samples tested positive for fecal coliforms or E. coli.
• Poor-reputation brands were associated with higher heterotrophic bacteria plate counts.
• 41% of samples contained P. aeruginosa, regardless of brand reputation.
• The results signal an opportunity to revisit packaged water standards in West Africa.

Sachet water is now an important source of drinking water security in West Africa, and the sachet industry continues to mature as market share increasingly shifts from cottage industry players to high-volume corporate producers. Modern sachet production lines are prone to the development of biofilms, and traditional microbiological indicators of fecal water contamination may not capture all the potential risks to human health in such a widely-consumed product. This study tested a sample of 80 sachets purchased along two commercial transects in low-income neighborhoods of Accra, Ghana, for total coliforms (TC), fecal coliforms (FC), Escherichia coli (EC), total heterotrophic bacteria (THB), and Pseudomonas aeruginosa (PA), and examined the relationships between these indicators and brand reputation. Just 5% of samples tested positive for TC, and none tested positive for FC and EC, yet 41% of samples tested positive for PA. After controlling for one popular brand, a negative brand reputation was associated with both THB presence (P = 0.015) and the number of samples with THB > 500 CFU/mL (P = 0.038), but PA was found in brands of both positive and negative reputations, and was only correlated with THB counts. The emergence of PA presents an opportunity for the re-evaluation of packaged water quality standards in a rapidly-globalizing, urban environment.