Genotypic Characterisation and Antimicrobial Resistance of Extended-Spectrum β-Lactamase-Producing in Humans, Animals, and the Environment from Lusaka, Zambia: Public Health Implications and One Health Surveillance.

Background: Extended-spectrum β-lactamases (ESBL) in are a serious concern due to their role in developing multidrug resistance (MDR) and difficult-to-treat infections.

Objective: This study aimed to identify ESBL-carrying strains from both clinical and environmental sources in Lusaka District, Zambia.

Methods: This cross-sectional study included 58 ESBL-producing strains from hospital inpatients, outpatients, and non-hospital environments. Antimicrobial susceptibility was assessed using the Kirby-Bauer disk diffusion method and the VITEK 2 Compact System, while genotypic analyses utilised the Illumina NextSeq 2000 sequencing platform.

Results: Among the strains isolated strains, phylogroup B2 was the most common, with resistant MLST sequence types including ST131, ST167, ST156, and ST69. ESBL genes such as , , , and were identified, with ST131 and ST410 being the most common. ST131 exhibited a high prevalence of and resistance to fluoroquinolones. Clinical and environmental isolates carried (3.4%), with clinical isolates showing a higher risk of carbapenemase resistance genes and the frequent occurrence of and variants, especially in ST131.

Conclusions: This study underscores the public health risks of - and -carrying . The strengthening antimicrobial stewardship programmes and the continuous surveillance of AMR in clinical and environmental settings are recommended to mitigate the spread of resistant pathogens.