Isolation and Molecular Identification of Potentially Pathogenic Free-Living Amoeba in Tap Water Faucets in Quezon...

Free-living amoebae (FLA) are ubiquitous in environmental water and soil, and their presence in water systems for human consumption is a public health concern due to their potential pathogenicity and ability to act as a reservoir for pathogenic bacteria. This study identified potentially pathogenic FLAs in urban water systems, specifically from tap water faucets. A total of 26 faucets were sampled, with 16 (62%) testing positive for FLAs. These included faucets from comfort rooms (n = 6), laboratories (n = 4), households (n = 14), and public parks (n = 2). Initial identification was based on the morphology of trophozoites and cysts, followed by molecular identification using universal 18S rRNA primers and sequencing. A total of 21 FLAs were isolated, including 11 Vermamoeba vermiformis, three Vannella spp., and one each of Ptolemeba bulliensis, Protacanthamoeba bohemica, Stenamoeba polymorpha, Stenamoeba amazonica, and Micriamoeba tesseris, along with two unidentified species. One of the unidentified isolates exhibited branching trophozoites and distinct double-walled cysts. The high detection rate of FLAs in tap water suggests a potential health risk, either through direct infection or by serving as vectors for pathogenic bacteria. These findings highlight the importance of routinely monitoring urban water systems for FLA contamination to safeguard public health.