Microbial contamination of packaged drinking water in Nigeria.

Objectives: About 18% of urban households in Nigeria depend on packaged sachet water as the primary source of drinking water. This review assessed microbial contamination of these products with an emphasis on total coliforms and the faecal indicator bacteria (FIB) - Escherichia coli (E. coli) and thermotolerant coliforms (TTC).

Methods: PubMed/Medline, African Index Medicus, AfroLib, Global Health Library, Embase and the ISI Web of Science databases were searched to identify original research published up to October 2020. The literature findings were synthesised narratively in line with the review objectives. To assess prevalence of microbial contamination, a random effects meta-analysis, was also conducted using the R metafor package in RStudio. The protocol for this review is registered on PROSPERO with reference number CRD 42019128474.

Results: Fifty-two of 429 studies were identified for inclusion. At 53.27%, contamination prevalence was higher for total coliforms (95% CI: 39.05-66.98, I  = 81%, p < 0.01, 42 studies) than FIB (12.38%, 95% CI: 7.92-18.85, I  = 61%, p < 0.01, 33 studies) suggesting that treatment failure is a major contributor to the poor microbial quality reported in the included studies. Within the FIB group, the prevalence of contamination with E. coli was 13.30% (95% CI: 8.23-20.80, I  = 65%, p < 0.01, 27 studies) versus 6.24% (95% CI: 1.12-28.06, I  = 72%, p < 0.01, six studies) for TTCs. Other microbial contaminants reported were Pseudomonas aeruginosa, Klebsiella and Enterococcus faecalis and these showed multidrug antibiotic resistance.

Conclusions: The findings of this review highlight the need for improved regulatory oversight with more stringent monitoring of the microbial quality of sachet water products in Nigeria.