Detection of the iroN virulence gene in multidrug-resistant Escherichia coli isolated from quails in traditional markets of Surabaya, Indonesia

Background and Aim: Escherichia coli is a common intestinal commensal in poultry, but avian pathogenic E. coli (APEC) strains can cause colibacillosis and pose zoonotic risks due to genetic similarities with human extraintestinal pathogenic E. coli (ExPEC). Quails sold in traditional markets may serve as reservoirs for multidrug-resistant (MDR) and virulent strains, yet data from Indonesia are limited. Iron acquisition systems, such as the iroN gene encoding the salmochelin siderophore receptor, are critical virulence determinants in APEC, enabling survival in iron-limited host environments and potentially linking to antimicrobial resistance (AMR). This cross-sectional laboratory-based study aimed to detect MDR E. coli from quail cloacal swabs in Surabaya's traditional markets and screen MDR isolates for the iroN gene, highlighting market level risks within a One Health framework. Materials and Methods: From November to December 2024, 150 cloacal swabs were collected from quails across five traditional markets (Turi, Bratang, Cemara Pabean, Kupang, and Benowo) in Surabaya, Indonesia. Samples were enriched in buffered peptone water, streaked on eosin methylene blue agar and MacConkey agar, and confirmed as E. coli via Gram staining and biochemical tests (Triple Sugar Iron Agar, Simmons Citrate Agar, Sulfide Indole Motility, and Methyl Red–Voges Proskauer). Antibiotic susceptibility was assessed using the Kirby–Bauer disk diffusion method on Mueller–Hinton agar against aztreonam (ATM 30 μg), ciprofloxacin (CIP, 5 μg), tetracycline (TE, 30 μg), kanamycin (K, 30 μg), and chloramphenicol (C, 30 μg), interpreted per Clinical and Laboratory Standards Institute M100 (2023) guidelines. MDR was defined as resistance to ≥3 antibiotic classes. MDR isolates underwent polymerase chain reaction for iroN detection. Results: E. coli was isolated from 148/150 samples (98.7%), with 100% positivity in Turi, Bratang, and Cemara Pabean markets. Resistance rates were highest to C (33.1%), followed by TE (22.3%), ATM (13.5%), K (6.1%), and C (4.7%). Four isolates (2.7%) were MDR, distributed in Turi (1), Cemara Pabean (2), and Kupang (1). MDR patterns included ATM/CIP/TE (two isolates), ATM/CIP/K (one), and ATM/CIP/TE/K/C (one). All four MDR isolates were positive for iroN, indicating a 100% association in this subset. Conclusion: Quails in Surabaya's traditional markets harbor prevalent E. coli with notable AMR, including MDR strains carrying the iroN virulence gene, underscoring their role as potential APEC reservoirs. This convergence of resistance and virulence highlights zoonotic and public health risks, necessitating enhanced AMR surveillance, market hygiene, and antibiotic stewardship under One Health principles. Future studies should explore genomic mechanisms and transmission pathways. Keywords: antimicrobial resistance, avian pathogenic Escherichia coli, E. coli, traditional markets, iroN virulence gene, polymerase chain reaction, public health.