Citaton: Abdelwahab IA, Abozahra RR, Sultan SA, Abd-elaal HM, Abdelhamid SM. Interspecies Interacton between Pseudomonas aeruginosa, Staphylococcus aureus and E. coli in vitro. J Pure Appl Microbiol. Published online 02 March 2023. doi: 10.22207/ JPAM.17.1.39 © The Author(s) 2023. Open Access. This artcle is distributed under the terms of the Creatve Commons Atributon 4.0 Internatonal License which permits unrestricted use, sharing, distributon, and reproducton in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creatve Commons license, and indicate if changes were made. Abdelwahab et al. | Artcle 8326 J Pure Appl Microbiol. 2023. doi: 10.22207/JPAM.17.1.39 Received: 13 December 2022 | Accepted: 11 February 2023 RESEARCH ARTICLE OPEN ACCESS www.microbiologyjournal.org 1 Journal of Pure and Applied Microbiology P-ISSN: 0973-7510; E-ISSN: 2581-690X *Correspondence: ibrahim.abdelwahab@pua.edu.eg Interspecies Interacton between Pseudomonas aeruginosa, Staphylococcus aureus and E. coli in vitro Ibrahim A. Abdelwahab 1 *, Rania R. Abozahra 2 , Shawky A. Sultan 3 , Hala M. Abd-elaal 4 and Sarah M. Abdelhamid 2  1 Department of Microbiology and Immunology, Faculty of Pharmacy, Pharos University in Alexandria, P.O. Box 37 Sidi Gaber, Alexandria, 21311, Egypt. 2 Department of Microbiology and Immunology, Faculty of Pharmacy, Damanhour University, Damanhour 22511, Egypt. 3 Ministry of Health and Populaton, Cairo 11516, Egypt. 4 Hematology Department, Damanhour Medical Natonal Insttute, Damanhour 22511, Egypt. Abstract Microbial interactons are frequently categorized according to how they afect each populaton in a binary system. We aimed to determine the interacton between P . aeruginosa, S . aureus, and E . coli in-vitro. In this experimental hospitalized patents' sputum, urine, and blood samples were used to collect a total of 90 clinical isolates for the study in Damanhour Medical Natonal Insttute, Behira, Egypt, followed by accurate identfcaton and testng for antbiotc sensitvity. To examine the efect of the supernatant of P. aeruginosa on S. aureus and E. coli determined MIC using broth microdiluton method. We also measured the actvity of lasA protease by assessing the S. aureus cell lysis potental of P. aeruginosa culture supernatants. Extracton of pyocyanin was made to determine the change in the cell nature of S. aureus upon exposure to pyocyanin by using a scanning electron microscope and the shape of colonies on the culture media was determined. Finally, we detect lasA, operon phz, phzM, phzS and rhlAB genes for P. aeruginosa. P. aeruginosa showed a great impact on S. aureus isolates resistant to diferent antbiotcs as it facilitates their killing and may drive the normal colonies of S. aureus into SCVs. The ability to form bioflm by S. aureus and E. coli decreased in the presence of Pseudomonas supernatant. Keywords: Bioflm, Microbial Interactons, P. aeruginosa Interactons, E.coli Interactons, S. aureus Interactons, Operon phz