A culture-dependent and metagenomic approach of household drinking water from the source to point of use in a developing country

Abstract

Rural households in developing countries rely on communal water supplies and household water frequently becomes contaminated following its collection, transportation and during its storage. Using culture-dependent and -independent techniques, we examined the changes in microbial water quality between communal tap water and household water storage in a rural area of Cameroon, Africa. The culturable fecal indicator bacteria (FIB) were used to assess the potential health risks associated with different household water storage conditions (e.g., type of container and open vs. closed container) and interventions (e.g., water storage days, cleaned on the last day of use, and hygiene practices). Only the amount of days the water was stored significantly differed (p-value < 0.05), which showed that potential health risks increased when water was stored for more than 3 days. The higher abundance of molecular FIB in biofilm than household water suggested that omnipresent biofilm in household water could potential health risk. The high-throughput sequencing revealed that the most abundant phylum was Proteobacteria, followed by Actinobacteria and Bacteroidetes in both the water and the biofilm samples. Bacterial genera seen in biofilm bacteria, such as Pseudomonas, Acinetobacter and Comamonas. Acinetobacter, Chryseobacterium, Stenotrophomonas and Corynebacterium, were relatively more abundant in the biofilm than in the water. Potential bacterial pathogens including Acinetobacter baumannii, Citrobacter freundii, Stenotrophomonas maltophilia and Haemophilus influenza, were detected in household water and biofilm. The microbial quality might be affected by water-storage time and households repeatedly using the same water storage containers without proper sanitization, triggering microbial regrowth and biofilm formation on water containers. Higher bacterial diversity and potentially pathogenic bacteria found in the biofilm samples of a household water supply are unhealthy for the house's inhabitants. It is important to develop interventions aimed at preventing the formation of these dangerous biofilms in a communal water supply.

Keywords: Biofilm; Developing country; Drinking water; Household water; Metagenomics.

Graphical abstract

Fig. 1

The potential health risks associated with household water storage condition and practices such as water cleaned last days (A), opened or closed water containers (B), the type of containers (C), and water storage days (D).

Fig. 2

Enumeration of E.coli and total coliform genes from the source water (SB and TS), the two household water from two families (F 4 and F6) and biofilm collected from buckets and cups in F14 and F6. The two households of F14 (Family #14) and F6 (Family #6) were selected among twenty households. Only F14 was instructed to clean containers before sampling. SB and TS indicates spring box and tap stand, respectively.

Fig. 3

Relative abundance of microbial community obtained from the household water systems and source water. Two sampling events (January(J) and May(M)) were conducted to collect water (F) and biofilm (S) samples in this project. Among twenty families, two households (family #14 (F14) and #16 (F6)) were chosen to collect water and biofilm samples from different containers such as buckets(B) and cup(C). SB and T indicate spring box (SB) and tap stand (T), respectively.

Fig. 4

Relative abundance of microbial communities at the genus level, clustering by the type of containers (A), type of samples (B), locations (C) and season (D).

Fig. 5

Alpha-diversity analyses from types of container (cup, bucket and source water), sample location (Tap stand, Spring box, Family #6 and Family #14), sample type (water and biofilm) and season (January and May).

Fig. 6

A principal coordinates analysis (PCoA) showing similar and dissimilar relation among 31 bacterial community samples using the unweighted and weighted UniFrac distance matrix.

Fig. 7

Relative abundance of potential human pathogenic bacteria using 16s rRNA sequencing analysis against human pathogenic bacterial database. The relative abundances were clustered by the type of containers (A), type of samples (B), locations (C) and season (D).