Increased Occurrence of Antimicrobial Resistance and Virulence Genes in Escherichia coli from Broilers in the Central Highlands of Vietnam
Abstract
Antimicrobial resistance is becoming a major concern for the poultry industry, particularly as Escherichia coli strains are increasingly exhibiting multidrug resistance. This study aims to assess the antimicrobial resistance and virulence genes of E. coli isolated from broilers in the Central Highlands of Vietnam, providing a scientific basis for managing antimicrobial use in poultry production. A total of 370 rectal fecal samples were collected from 25 farms, including 250 samples from healthy broilers (67.6%) and 120 samples from diarrheal broilers (32.4%). E. coli isolates were identified using conventional biochemical methods and confirmed by 16S rRNA gene sequencing. In addition, isolates from diarrheal samples (n=120) were screened for seven virulence genes (hlyE, iss, eaeA, ent, escV, stx1, and stx2) using PCR. Data were statistically analyzed using R (version 4.4.1) to determine the prevalence of antimicrobial resistance, multidrug resistance (MDR), virulence genes, and AMR/MDR profiles. The results showed high resistance rates to most tested antimicrobial agents, particularly tetracycline and erythromycin (>90%), while ciprofloxacin exhibited the lowest resistance rate (31%–32%). The proportions of isolates resistant to at least one antimicrobial agent and those classified as MDR were 97.5% and 90.3%, respectively. Among the isolates from diarrheal samples, 94.2% carried at least one virulence gene. The genes hlyE, iss, and stx2 were the most prevalent, whereas ent, eaeA, and escV were detected at lower frequencies, and stx1 was not detected (p<0.001). The high prevalence of multidrug resistance, together with the frequent detection of hlyE, iss, and stx2 suggests the co-occurrence of resistance and virulence traits, which may facilitate their dissemination within the intestinal microbiota.
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