Biofilm formation and antimicrobial resistance of Pseudomonas aeruginosa in cheese production systems.

The emergence of drug-resistant Pseudomonas aeruginosa is an increasing global concern affecting human and animal health, food production systems, and environmental safety. This study investigated its occurrence, antimicrobial resistance, and biofilm-forming ability using phenotypic assays, and identify the biofilm-associated genetic markers in 120 cheese samples including 30 samples each of (Kariesh, Tallaga, Processed, and Romy) collected from various retail sources in Cairo and Giza, Egypt. Pseudomonas aeruginosa isolates were identified using both biochemical tests and molecular confirmation using 16 S rRNA gene. Antimicrobial susceptibility was evaluated using the disk diffusion method. Biofilm formation was assessed phenotypically through the microtiter plate and tube assays, while the biofilm-associated genes pelA and pslA were detected using PCR. Pseudomonas aeruginosa was detected in 18 samples (15%), and identification was confirmed through biochemical and molecular methods. Antimicrobial susceptibility testing revealed that 55% of isolates were extensively drug-resistant, while 45% exhibited multidrug resistance, with MAR indices ≥ 0.2 and an average MAR index of 0.68, indicating exposure to high-risk environments with frequent antibiotic use. Phenotypic assays showed strong biofilm-forming capabilities among isolates, with 100% positive by microtiter plate and 95% by tube method. Molecular screening further confirmed the prevalence of biofilm-associated genes, detecting pelA in 72% and pslA in 61% of isolates. Overall, Pseudomonas aeruginosa isolated from cheese samples exhibited substantial antimicrobial resistance and robust biofilm-forming ability, posing significant concerns to cheese quality and consumer health. These findings highlight the urgent need for continuous surveillance, improved dairy hygiene, effective sanitation, responsible antimicrobial practices, and alternative control strategies within the dairy sector to reduce potential public health hazards.