Journal of Biotech Research [ISSN: 1944-3285] 2024; 17:180-186 180 RESEARCH ARTICLE The role of biofilm in Proteus mirabilis as antibiotic resistance biomarker in patients with urinary tract infections Salim Shamkhi Jaafar 1 , Manar Radhi Shannon Alyassiry 2 , Russell Issam Al-Daher 3 , Hasanain Khaleel Shareef 3, 4 , Yasir Haider Al-Mawlah 1, * 1 DNA Research Center, University of Babylon, Babylon, Hillah, Iraq. 2 College of Pharmacy, University of Babylon, Babylon, Hillah, Iraq. 3 Department of Biology, College of Science for Women, University of Babylon, Babylon, Hillah, Iraq. 4 Al-Mustaqbal University, College of Science, Department of Medical Biotechnology, Babylon, Hillah, Iraq. Received: February 22, 2024; accepted: April 23, 2024. Proteus mirabilis, a urease-producing bacterium, is a frequent culprit in urinary tract infections (UTIs). Most Gram- negative bacteria are characterized by their ability to produce biofilms outside their bodies, which usually adhere to solid surfaces. Biofilm formation is a significant concern in UTIs as it can hinder the efficacy of antibiotic treatment. The connection between antibiotic susceptibility and biofilm development was examined in this study in P. mirabilis isolates from UTI patients to identify the profiles of antibiotic susceptibility of P. mirabilis, assess biofilm formation ability among these isolates, and explore potential links between antibiotic resistance and biofilm production. The urine samples of 300 UTI patients from August to November 2023 were taken in Hilla city, Iraq. P. mirabilis isolates were identified and subjected to disc diffusion testing for antibiotic susceptibility and microtiter plate assays for biofilm formation. The results showed that all 67 P. mirabilis isolates harbored the urease gene and exhibited the highest resistance rates to trimethoprim (43.28%), chloramphenicol (31.34%), vancomycin (41.79%), and nitrofurantoin (29.85%), while all isolates were imipenem susceptible. Resistance to other antibiotics ranged from 2.9% to 13.43%. Importantly, 21 (31.34%) isolates were multidrug-resistant (MDR). All isolates formed biofilms with 23 (34.3%) demonstrating strong biofilm production, significantly associated with MDR isolates. This study revealed a substantial proportion of P. mirabilis isolates from UTI patients displaying the development of biofilms and carrying antibiotic resistance, especially among MDR isolates. These findings underscored the crucial need for continuous antibiotic resistance surveillance and novel strategies for preventing and treating UTIs caused by P. mirabilis. Keywords: Proteus mirabilis; URer gene; antibiotic susceptibility; urinary tract infections (UTIs); biofilm formation. * Corresponding author: Yasir Haider Al-Mawlah, DNA Research Center, University of Babylon, Babylon, Hillah 51001, Iraq. Phone: +964 770 571 3626. Email: Yasser.almawla@uobabylon.edu.iq. Introduction Proteus mirabilis is a Gram-negative bacterium and responsible for a significant proportion of human urinary tract infections (UTIs), particularly affecting patients with indwelling catheters [1]. P. mirabilis is thought to be the cause of between 10% and 20% of hospital acquired UTIs [2]. This bacterium can cause UTIs due to a number of virulent factors. One key factor is its production of urease, an enzyme that hydrolyzes urea to ammonia, increasing urinary pH and promoting tissue damage and stone formation [3]. Additionally, P. mirabilis is equipped with