Occurrence and characterization of biofilm-forming and multidrug-resistant Shigella spp. in retail poultry meat and associated environments in Sylhet, Bangladesh.

Shigella spp. are important foodborne pathogens increasingly associated with antimicrobial resistance (AMR) and contamination within retail poultry-handling environments. This study investigated the prevalence, antimicrobial resistance profiles, extended-spectrum β-lactamase (ESBL) determinants, virulence-associated genes, efflux pump genes, and biofilm-forming ability of Shigella spp. isolated from retail poultry meat and associated environments in Sylhet, Bangladesh. A total of 300 samples, including cloacal swabs, meat, handler hand swabs, utensil swabs, and wastewater samples, were collected and analyzed using culture-based methods, biochemical tests, and species-specific PCR. We also performed antimicrobial susceptibility testing (AST) and molecular characterization. Overall, 50.0% (150/300) of samples were culture-positive for Shigella. Among the 150 culture-positive samples, 144 (96.0%) were confirmed by species-specific PCR, including 98 Shigella flexneri and 46 S. dysenteriae isolates. When calculated against the total number of samples tested, Shigella flexneri and S. dysenteriae were present in 32.67% (98/300) and 15.33% (46/300) of samples, respectively, with the highest prevalence observed in cloacal swabs (46.38% and 21.74%, respectively). AST revealed high resistance to trimethoprim-sulfamethoxazole (92.9% and 84.8%), tetracycline (87.7% and 87.0%), azithromycin (86.7% and 76.1%), and levofloxacin (76.5% and 56.5%) among S. flexneri and S. dysenteriae, respectively. In contrast, cefixime and gentamicin remained the most effective agents, showing susceptibility rates of 82.7% and 80.6% in S. flexneri and 67.4% and 58.7% in S. dysenteriae. The predominant resistance genes were tetA (72.45; 78.26%), qnrS (80.61; 89.13%), sul1 (50.0; 69.57%), and blaTEM (38.78; 45.65%), while efflux pump genes acrAB (60.20; 80.43%) and tolC (77.55; 86.96%) were widely distributed. Biofilm formation was detected in 37.76% and 56.52% of isolates by Congo red agar and in 27.55% and 36.96% by microtiter plate assay for S. flexneri and S. dysenteriae, respectively. All isolates exhibited MAR indices >0.20, while MDR and possible XDR (P-XDR) phenotypes were detected in 38.78% and 61.22% of S. flexneri and 58.70% and 41.30% of S. dysenteriae isolates, respectively. These findings highlight the occurrence of antimicrobial-resistant and biofilm-forming Shigella spp. within the investigated retail poultry-handling environment and underscore the need for strengthened biosecurity, antimicrobial stewardship, and One Health surveillance strategies.