Occurrence and Molecular Characterization of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli in Broilers in Indonesia.

Extended-spectrum β-lactamase-producing Escherichia coli (ESBL-E. coli) are widespread in the food chain, but nationwide surveillance in Indonesian broiler production is limited. This study investigated the occurrence, antimicrobial resistance, phylogenetic diversity, and molecular characteristics of ESBL-E. coli from broilers in Indonesia. A total of 2182 E. coli isolates from broiler cecal samples across three regions during the period 2018-2020 were analyzed. Antimicrobial susceptibility testing and ESBL phenotyping were performed following the CLSI guidelines. ESBL resistance genes and phylogenetic groups were detected using multiplex/quadruplex PCR. ESBL-E. coli (9.9%) was most frequently observed in the western (15.2%) region, followed by the central (8.0%) and eastern (7.2%) regions. A total of 85 resistance patterns were identified, with 98.5% exhibiting multidrug resistance. The blaCTX-M gene was detected in 97.5% of isolates, predominantly blaCTX-M-1 (97.5%), while blaCTX-M-9 was found in 2.5%. The blaTEM gene was present in 33.0% of ESBL isolates; however, blaSHV and blaOXA-1 were absent. Phylogenetic group A predominated (42.0%), followed by E (22.5%), B1 (20.5%), F (10.5%), C (2.5%), and D (2.0%). This study demonstrates a significant occurrence of ESBL-E. coli in Indonesian broilers with regional variation and blaCTX-M predominance. The high rate of multidrug resistance poses a serious public health concern, emphasizing the urgent need for antimicrobial stewardship and enhanced surveillance programs.