Antimicrobial-Resistant Bacteria in Environmental Samples From a Rural District Focused on Large-Scale Agricultural Production.

Abstract

Antimicrobial resistance is a growing concern, especially in regions with intense agricultural production. This study investigates the presence of antimicrobial-resistant bacteria in Caramuru, Espírito Santo state, a rural district focused on large-scale agricultural production in Brazil. Samples of water, soil, animal faeces and environmental surfaces were analysed using culture-based methods, revealing the presence of multidrug-resistant strains in agricultural and livestock environments, where antimicrobial use is common. Several bacterial species were detected, with a predominance of Escherichia coli, Enterobacter spp. and Acinetobacter spp., with 58.5% of the samples being resistant to at least one antimicrobial tested. The highest resistance rates among Gram-negative bacilli were ampicillin (80%), followed by cefuroxime (70%) and ceftriaxone (55%). In addition, resistance to polymyxin B was found in 14% of the GNB isolates, including Enterobacter asburiae, Enterobacter cloacae, E. coli, Acinetobacter baumannii and Pseudomonas aeruginosa. The production of extended-spectrum β-lactamases was detected in six multidrug-resistant E. coli samples isolated from river water, dog faeces and pigsty floors, while the production of metallo-β-lactamases was observed in E. asburiae from water samples from the river and toilet, as well as E. cloacae from coffee grounds. The bla_TEM-like gene was identified in multidrug-resistant E. coli strains isolated from all the Caramuru River water and the pigsty floor samples, while bla_CTX-M-1/2-like was found in an Enterobacter bugandensis and E. asburiae strains isolated from flies in the toilet, respectively. These findings indicate the presence of extended-spectrum β-lactamase genes in different environmental and animal-associated sources within the study area. The overlap of these detections with agricultural and surface water sites underscores the importance of monitoring antimicrobial resistance in diverse environmental compartments.