Surveillance of CTX-M group 1-producing Enterobacterales at the migratory Little Stint (Calidris minuta)-goat-aquatic interface in the Kenyan Rift Valley: a One Health approach.

The escalation of antimicrobial resistance (AMR) among critical-priority, extended-spectrum β-lactamase (ESBL)-producing pathogens poses a global public health threat. Applying a One Health framework, this study characterized CTX-M Group 1 gene variants alongside co-carried β-lactamase gene families (bla OXA1 - like, bla SHV, and bla TEM) in Enterobacterales across the migratory shorebirds Little Stints (Calidris minuta)-livestock-aquatic interface in the Kenyan Rift Valley. Sampling occurred across two migratory cohorts-arrival from the Arctic and pre-departure from the lakes in a repeated cross-sectional eco-surveillance design across two contrasting environments: Lake Bogoria (low anthropogenic pressure) and Lake Magadi (high pressure). From 389 fecal and water samples (C. minuta, n = 184; free-ranging domestic goats, n = 157; water, n = 48), 507 Gram-negative bacterial isolates were recovered, 479 of which were Enterobacterales. Phenotypic ESBL screening identified 15.7% (75/479) ESBL-positive Enterobacterales from 68 samples (C. minuta, n = 30; goats, n = 30; water, n = 8). Conventional polymerase chain reaction (PCR) of 79 isolates (75 phenotypic ESBL-Enterobacterales producers and four ESBL-negative Klebsiella pneumoniae controls) detected CTX-M Group 1 variants in 14 isolates (13 ESBL-positive strains and one ESBL-negative K. pneumoniae). The CTX-M Group 1 variants were identified in Escherichia coli (n = 6), Enterobacter cloacae (n = 4), Klebsiella pneumoniae (n = 3), and Providencia rettgeri (n = 1), frequently co-harboring bla OXA1 - like, bla SHV, and bla TEM gene families. Detection frequencies exhibited site-specific and temporal trajectories across domains. To our knowledge, this is the first PCR-based detection of CTX-M Group 1 variants in C. minuta within this ecosystem. Rather than a mere passive corridor, the Kenyan Rift Valley serves as a dynamic ecological epicenter where global migratory flyways intersect with local anthropogenic drivers to modulate AMR. Despite the lack of sequencing data, this study provides vital baseline landscape data highlighting the need for sustained One Health-AMR surveillance and environmental stewardship.