Herbicide-Contaminated Soils in Dutsin-Ma Katsina State Nigeria: A Hotbed of Multidrug-Resistant Bacteria

Abstract

Agricultural intensification in Nigeria has led to increased herbicide usage, raising concerns over environmental contamination and its potential ecological effects. This study investigated the microbiological and physicochemical properties of herbicide-contaminated soils in Dutsin-Ma, Katsina State, Nigeria, and assessed the antibiotic resistance profiles of the indigenous bacterial isolates. Soil samples were collected from agricultural sites with a documented history of glyphosate or Agri-Force herbicide application. Standard microbiological techniques were used to isolate and identify bacterial species. The isolates were characterized morphologically and biochemically, and their antimicrobial susceptibility to tetracycline, ciprofloxacin, amoxicillin/clavulanic acid (augmentin), and sulfamethoxazole was determined using agar disk diffusion technique. The soils samples exhibited a near-neutral to slightly alkaline pH (6.5–8.3). Bacterial growth was prolific (91.7% of the samples), with counts ranging from 1.60 × 10⁵ to 3.81 × 10⁵ CFU/g. Five genera were identified: Bacillus, Pseudomonas, Actinomyces, Streptomyces, and Escherichia coli. A high prevalence of multidrug-resistant (MDR) isolates was observed, with 95.65% and 75% of the isolates from the two sample sources being resistant to all four antibiotic classes tested. A uniform TET-CIP-AUG-SUL resistance pattern was observed among the MDR isolates. Herbicide-contaminated soils in Dutsin-Ma host robust bacterial communities adapted to herbicide stress. The exceptionally high level of multidrug resistance among these environmental isolates suggests a strong link between herbicide pollution and the co-selection of antibiotic resistance genes. This finding underscores a significant public health and ecological concern, highlighting the urgent need for prudent agrochemical management and further research on the genetic mechanisms underlying this resistance.