Prevalence of microbial contamination and disinfectant-resistant P. aeruginosa in bottled drinking water samples tested at the National Institute for Food Control in 2024-2025

Tóm tắt

Bottled drinking water (BDW) is increasingly consumed in Vietnam; however, the risk of microbial contamination remains a significant public health concern. In particular, Pseudomonas aeruginosa (P. aeruginosa) is not only an opportunistic pathogen but also exhibits resistance to common disinfectants used in production processes. This study aimed to describe the current status of microbial contamination according to QCVN 6-1:2010/BYT and the presence of heterotrophic plate counts (HPC) in 70 BDW samples (19–21 L) tested at the National Institute for Food Control between October 2024 and April 2025. Results showed that 28.57% (20/70) of samples failed at least one microbiological parameter, with P. aeruginosa accounting for the highest contamination rate (25.71%, 18/70). Moreover, 52.86% (37/70) of samples exceeded the 500 CFU/mL limit for heterotrophic bacteria. Antimicrobial susceptibility testing revealed that 83% (15/18) of P. aeruginosa isolates were resistant to benzalkonium chloride (BKC) and 44% (7/18) were resistant to didecyldimethylammonium chloride (DDAC). The presence of qacE and qacEΔ1 genes was strongly associated with the resistance phenotype, particularly in strains harboring both genes. These findings indicate that large-volume BDW poses a high risk of microbial contamination, with P. aeruginosa being both a prevalent contaminant and notably resistant to commonly used disinfectants, suggesting the potential dissemination of resistance mechanisms within production and consumer environments.