Antibiotic resistance dynamics of some common probiotic <i>Lactobacillus</i> species and avian pathogenic <i>Escherichia coli</i> in colibacillosis-diseased <i>versus</i> healthy broiler chickens.

This study focuses on understanding how the sensitivity patterns of common probiotic <i>Lactobacillus</i> species differ between healthy and colibacillosis-diseased broiler chickens and explores any correlation between these patterns and avian pathogenic <i>Escherichia coli</i> (APEC). Ileum samples were collected from the healthy (n = 10) and colibacillosis-diseased (n = 10) broiler poultry farms. <i>Lactobacillus</i> and <i>E. coli</i> were identified and incidence rate of six probiotic <i>Lactobacillus</i> species (<i>L. acidophilus</i>, <i>L. brevis</i>, <i>L. casei</i>, <i>L. plantrum</i>, <i>L. delbrueckii</i>, and <i>L. fermenti</i>) was determined, and their susceptibility to different antibiotics (ampicillin, chloramphenicol, erythromycin, kanamycin, tetracycline, and vancomycin) was tested. A total of 120 <i>Lactobacilli</i> were examined. Certain <i>Lactobacillus</i> spp. from healthy birds (<i>L. brevis</i>) and those affected by colibacillosis (<i>L. acidophilus</i>) showed better sensitivity and lower multiple antibiotic resistance to chloramphenicol, erythromycin, and kanamycin. Statistical analysis revealed significant correlations between ampicillin and chloramphenicol, ampicillin and erythromycin, ampicillin and tetracycline, and ampicillin and vancomycin resistance. Also, a significant correlation was observed between erythromycin and tetracycline, and kanamycin and vancomycin. All APEC strains showed multiple antibiotic resistance. A strong positive correlation was found between resistant <i>Lactobacillus</i> spp. and APEC isolates from diseased birds, indicating co-occurrence of antibiotic resistance. The study suggests that antibiotic resistance in APEC and <i>Lactobacillus</i> species may spread through horizontal transfer, highlighting the need for improved anti-microbial management in poultry systems.