VOLUME 19 NUMBER 1 (January to June 2026)

From vendor to consumer: Evaluating the microbial quality of generic bottled water in Rizal Province, Philippines

Introduction: In Rizal Province, Philippines, generic bottled water is widely distributed through street vendors and small retail outlets and is often presumed by consumers to be safe. However, potential microbial contamination poses public health risks, particularly in areas lacking stringent quality controls. Therefore, this study assessed the microbial and physicochemical quality of these bottled waters and their compliance with national and international safety standards.

Materials and Methods: Seventy-five bottled water samples representing 15 brands were collected from five locations in Rizal Province between May and November 2025. Samples were analyzed for Escherichia coli (E. coli), total coliforms (TC), heterotrophic plate count (HPC) bacteria, and yeast and mold (YM) using Neogen Petrifilm^TM. Biochemical and phenotypic identification of E. coli was performed using the VITEK 2 system. Antimicrobial susceptibility testing was conducted on confirmed E. coli isolates. Physicochemical parameters (pH, turbidity, and chloride) were measured and analyzed for correlation with microbial concentrations.

Results: A total of 56% of samples exceeded at least one microbial safety threshold. E. coli was detected in 2.7% of samples, TC in 16%, HPC in 33%, and YM in 27%. All E. coli isolates were fully susceptible to all 30 antibiotics tested. Brand identity significantly influenced microbial contamination (p < 0.01). Positive correlations were found between E. coli and TC (ρ = 0.447), TC and HPC (ρ = 0.487), and HPC and YM (ρ = 0.422). pH had no significant correlation with microbial load.

Conclusions: A considerable proportion of bottled water sold in Rizal failed to meet microbial safety standards. Although all E. coli isolates were antibiotic-sensitive, their presence indicates inadequate treatment or post-treatment contamination. Enhanced regulation, routine monitoring, and public education are recommended to ensure microbial safety and consumer protection in informal bottled water markets.