Green tea () extract inhibits biofilm formation in acyl homoserine lactone-producing, antibiotic-resistant isolated from Pasig River, Philippines.

The drastic development of urban districts around the world has caused changes in the environment, specifically on metropolitan waterways such as the Pasig River in the Philippines. These significant changes resulted in diversity of microorganisms and their mechanisms employed such as antibiotic resistance and their communication system or quorum sensing (QS). In this study, four bacterial isolates from Pasig River, identified as , sp., , and , were observed to employ short-chain acyl homoserine lactone (AHL) as their signalling molecule based on assays using the biosensor strain CV026. Furthermore, isolate was shown to be resistant to chloramphenicol. This poses a significant threat not just to public health but also to the aquatic life present in the river. Thus, green tea () extract was tested for its capability to inhibit biofilm formation in , as well as the short-chain acyl homoserine lactone QS system using ATCC 12472. Results showed that the extract significantly ( < 0.05) inhibited biofilm formation in at as low as 62.5 μg/mL (31.55%). Increasing the concentration (500 μg/mL) did not significantly ( > 0.05) enhance the activity (41.21%). Furthermore, the extract also inhibited pigmentation in ATCC 12472, suggesting QS inhibition. This study adds into record the production of short-chain AHLs by , sp., , and , as well as the potential of green tea extract as inhibitor of biofilm formation in antibiotic-resistant possibly through QS inhibition.