Biofilm Formation, Multicellular Behavior, and Antimicrobial Susceptibility of Escherichia coli Strains Isolated from Fish in Ajmer, Rajasthan

Foodborne illnesses remain a major global public health concern, with fish often acting as a carrier of pathogenic bacteria such as Escherichia coli (E. coli). The misuse of antibiotics in aquaculture has further increased the risk of antibiotic resistance, making this issue more urgent. In the present study, fish fecal samples were collected from local markets in Ajmer, Rajasthan, to isolate and characterize E. coli. The isolates were identified using EMB agar and confirmed through biochemical (IMViC) tests, followed by molecular confirmation with PCR amplification of the 16s rRNA gene. Biofilm formation was observed among the isolates, with different morphotypes (RDAR, BDAR, SAW, PDAR) detected. Antimicrobial susceptibility testing revealed varied resistance patterns, with several isolates showing resistance to commonly used antibiotics such as ceftazidime and ciprofloxacin, while others remained sensitive to drugs like meropenem and colistin. The findings highlight the presence of biofilm-forming, multidrug-resistant E. coli strains in fish, posing a potential health risk to consumers. This study underscores the need for stricter monitoring of antibiotic use in aquaculture and better food safety practices to prevent the spread of resistant pathogens through the food chain. Keywords: Foodborne illnesses, Biofilm Formation, Multicellular Behavior, Antimicrobial Susceptibility, E. coli.