PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14365/2

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Browsing PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection by Author "Abu-Lail, Nehal I."

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    Phenotypic Characterization of PilA, PilB, and PilD Mutants of Acinetobacter Baumannii 5075: Impacts on Growth, Biofilm Formation, and Tazobactam Response
    (MDPI, 2025) Salinas, Joel H.; Gordesli-Duatepe, Fatma Pinar; Diaz-Sanchez, Angelica; Abu-Lail, Nehal I.
    Background/Objectives: The Type IV pilus assembly system in Acinetobacter baumannii is a major determinant of its pathogenicity, playing a role in surface-associated functions via the biogenesis of Type IV pili (T4P). Tazobactam (TAZ) is a well-characterized beta-lactamase inhibitor, primarily used in combination with beta-lactam antibiotics such as piperacillin (PIP) to counteract bacterial resistance mechanisms. While A. baumannii resistance to beta-lactam antibiotics has been well studied, the influence of T4P on its susceptibility to TAZ remains largely unexplored. For this reason, we investigated how multidrug-resistant A. baumannii 5075 (AB5075) responds to TAZ by assessing the roles of pilA, pilB, and pilD in bacterial growth and biofilm formation under direct TAZ exposure, with a focus on phenotypic characterization rather than molecular mechanisms. Methods: Bacterial growth kinetics were quantified by measuring the optical densities of cell suspensions and the colony forming units per volume (CFUs/mL) at different time intervals. Time-kill assays and microtiter dish biofilm formation assays were used to evaluate how effectively TAZ can inhibit growth and biofilm formation, respectively. Results: Time-kill assays confirmed that 32 mu g/mL of TAZ inhibited growth in both wild-type (WT) and mutant strains, with the pilD mutant showing initial resistance before eventual inhibition. Biofilm assays showed that the pilA mutant had the highest biofilm formation at 8 h, surpassing the WT strain. A prolonged 32 mu g/mL of TAZ exposure (24-36 h) significantly reduced biofilm production across all strains, with inhibition rates reaching 89% for the WT, 82% for the pilA mutant, 91% for the pilB mutant, and 86% for the pilD mutant. Conclusion: These findings deepen our understanding of the strain-specific roles of T4P components in growth and biofilm regulation in AB5075, and highlight the potential of TAZ as a therapeutic strategy against biofilm-associated infections.
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    Citation - WoS: 10
    Citation - Scopus: 12
    Responses of Acinetobacter Baumannii Bound and Loose Extracellular Polymeric Substances To Hyperosmotic Agents Combined With or Without Tobramycin: an Atomic Force Microscopy Study
    (Amer Chemical Soc, 2019) Deliorman, Muhammedin; Gördesli Duatepe, Fatma Pınar; Davenport, Emily K.; Fransson, Boel A.; Call, Douglas R.; Beyenal, Haluk; Abu-Lail, Nehal I.
    In this work, contributions of extracellular polymeric substances (EPS) to the nanoscale mechanisms through which the multidrug-resistant Acinetobacter baumannii responds to antimicrobial and hyperosmotic treatments were investigated by atomic force microscopy. Specifically, the adhesion strengths to a control surface of silicon nitride (Si3N4) and the lengths of bacterial surface biopolymers of bound and loose EPS extracted from A. baumannii biofilms were quantified after individual or synergistic treatments with hyperosmotic agents (NaCl and maltodextrin) and an antibiotic (tobramycin). In the absence of any treatment, the loose EPS were significantly longer in length and higher in adhesion to Si3N4 than the bound EPS. When used individually, the hyperosmotic agents and tobramycin collapsed the A. baumannii bound and loose EPS. The combined treatment of maltodextrin with tobramycin collapsed only the loose EPS and did not alter the adhesion of both bound and loose EPS to Si3N4. In addition, the combined treatment was not as effective in collapsing the EPS molecules as when tobramycin was applied alone. Finally, the effects of treatments were dose-dependent. Altogether, our findings suggest that a sequential treatment could be effective in treating A. baumannii biofilms, in which a hyperosmotic agent is used first to collapse the EPS and limit the diffusion of nutrients into the biofilm, followed by the use of an antibiotic to kill the bacterial cells that escape from the biofilm because of starvation.