an in vitro study Galano, Ralph Dominic C. creator author. Japson, Angela B. author. Lague, Inah Krizia O. author. Makinano, Jyrah Mee T. author. Mondarte, Khylla Gayle author. Mopon, Matt Markel author. Marquianos, Lance author. Mose, Ma. Lucia Beatriz author. Ngo, Timothy Bryan author. Omictin, Jannie Lyka author. Ong, Cathelaine Diane author. Perilla, Isabela Louise author. Quimbo, Miguel Luis author. text Subangdaku, Mandaue City University of Cebu - College of Medicine Foundation, Inc. 2026 monographic eng

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iv, 106 pages : color illustrations ; "The emergence of multidrug-resistant Pseudomonas aeruginosa necessitates alternative antimicrobial strategies, such as quorum sensing (QS) inhibition, which targets virulence without exerting selective survival pressure. This study evaluated the anti-quorum sensing and antibiofilm activity of Psidium quajava L. methanolic leaf extracts against P. aeruginosa in vitro. Leaves collected from Medellin, Cebu, were extracted via methanolic maceration, yielding a 5.493% crude extract. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined using a resazurin-based microplate broth dilution assay. Anti-QS activity was quantitatively assessed by measuring biofilm inhibition at sub-inhibitory concentrations using a crystal violet assay, with cinnamaldehyde as the positive control. The extract exhibited poor direct antimicrobial activity, recording an MIC of 12.5 mg/mL and an MBC of >12.5 mg/mL. However, it demonstrated potent, dose-dependent antibiofilm efficacy. At the baseline MIC (12.5 mg/mL), the extract achieved a 96.93% biofilm inhibition rate, remaining significantly effective at 87.68% (6.25 mg/mL) and 73.20% (3.125 mg/mL). Welch's t-test revealed the extract performs comparably to the commercial standard, cinnamaldehyde ($p = 0.408$). Furthermore, Welch's ANOVA indicated maximum statistical efficacy was achieved at 6.25 mg/mL, with no significant difference in inhibition compared to the maximum dose. These findings establish that while P. guajava methanolic leaf extract possesses weak bactericidal effects, it is a highly capable anti-quorum sensing agent that effectively disrupts biofilm formation, offering a promising alternative therapeutic strategy against antibiotic-resistant infections." --Abstact Adult Ralph Galano, Angela Japson, Inah Krizia Lague, Jyrah Mee Makinano, Khylla Gayle Mondarte, Matt Markel Mopon, Lance Morquianos, Ma. Lucia Beatriz Mose, Timothy Bryan Ngo, Jannie Lyka Omictin, Cathelaine Diane Ong, Isabela Louise Perilla, Miguel Luis Quimbo. Includes bibliographical references. Montoya, Ma. Melfer School of Medicine Microbiology Montoya, Ma. Melfer School of Medicine Microbiology Text in English Bacterial infection Antimicrobial resistance Pseudomonas aeruginosa Multidrug-resistant (MDR) Hospital acquired infection Anti-quorum sensing Psidium guajava L Drug resistant bacteria University of Cebu - School of Medicine 260918 20260921095021.0