Antibiotic Susceptibility and Biofilm Formation of Citrobacter Spp. Isolated from Clinical and Environmental Sites in Hilla Province, Iraq

Background: Citrobacter spp. are opportunistic pathogens associated with nosocomial infections. Their ability to form biofilms and exhibit antimicrobial resistance complicates treatment and highlights significant clinical concerns. Objective: This study aimed to isolate Citrobacter species from clinical and environmental sources in Hilla Province, Iraq, and evaluate their biofilm-forming capacity and antibiotic resistance profiles. Methodology: This cross-sectional study was conducted from October 2024 to April 2025. A total of 150 samples were collected from the clinical specimens (urine, stool, and wounds) and hospital environments. Isolates were identified and antibiotic susceptibility testing was performed using the VITEK 2 system. Biofilm formation was quantitatively assessed using the microtiter plate method. Results: Of the 150 samples,is isolates 15 (10%) were confirmed as Citrobacter species. C. freundii was the most prevalent (53.3%). All isolates formed biofilms, with 60% classified as strong producers. Antibiotic resistance was the highest against Ciprofloxacin and Trimethoprim/ Sulfamethoxazole (46.6% each), while all isolates remained susceptible to carbapenems, aminoglycosides, and colistin. The Multiple Antibiotic Resistance (MAR) index indicated that 40% of the isolates showed no resistance, whereas several others exhibited indices up to 0.3. Conclusion: Citrobacter isolates from Hilla Province demonstrated a significant capacity for biofilm formation and exhibited resistance to first-line antibiotics, underscoring their role as emerging pathogens. These findings emphasize the need for continuous surveillance, robust antimicrobial stewardship, and stringent infection control measures in healthcare settings.