Virulence and Antimicrobial Resistance Profiles of Enterococcus spp. Isolated from Clinically Mastitic Versus Apparently Healthy Bovine Milk | [Journal of animal health and production • 2025]

Author(s):

1. Nagham Mohammed Al-Gburi: Zoonotic Research Unit, Veterinary Medicine, University of Baghdad, Baghdad, Iraq.

2. Noor A. Al-Taii: Zoonotic Research Unit, Veterinary Medicine, University of Baghdad, Baghdad, Iraq.

Abstract:

Enterococcus spp. is one of the microorganisms responsible for environmental mastitis, a condition that is dificult to eradicate due to its resistance to commonly used antimicrobials. The current study aimed to evaluate the antimicrobial resistance profiles and virulence gene carriage of Enterococcus spp. isolated from clinical mastitic milk (CMM) and apparently healthy milk (AHM) in dairy cows. A total of 50 milk samples were analyzed, including 25 from cows with clinical mastitis and 25 from apparently healthy cows. Identification of Enterococcus spp. was performed using conventional microbiological methods and confirmed with the VITEK 2 Compact system. Antimicrobial susceptibility was assessed using the disc difusion method, while the presence of virulence genes (esp, asa1, and gelE) was determined by PCR. The results showed no statistically significant diference in the isolation rates of Enterococcus spp. between CMM and AHM samples, though the detection rate was slightly higher in CMM (28%) compared to AHM (24%). In CMM, the predominant species identified were E. faecium and E. faecalis, while only E. faecium was detected in AHM samples. Enterococcus isolates from CMM exhibited high resistance rates to tetracycline, followed by erythromycin, ciprofloxacin, and penicillin. In contrast, AHM isolates showed high resistance to ciprofloxacin, erythromycin, penicillin, vancomycin, and tetracycline. Both CMM and AHM isolates demonstrated a high level of multidrug resistance (MDR) and elevated multiple antibiotic resistance (MAR) index values. PCR analysis revealed that esp, asa1, and gelE genes were present in CMM isolates at rates of 14.2%, 28.5%, and 28.5%, respectively. These virulence genes were not detected in AHM isolates. The presence of these virulence genes in mastitic milk isolates suggests a potential role in the pathogenesis of bovine mastitis. Additionally, the antimicrobial resistance observed in Enterococcus from apparently healthy milk raises public health concerns, as it may facilitate the transmission of resistance and virulence genes to humans through the food chain.

Page(s): 803-811

DOI: 10.17582/journal.jahp/2025/13.3.803.811

Published: Journal: Journal of animal health and production, Volume: 13, Issue: 3, Year: 2025

Keywords:

Antibiotic , Mastitis , Enterococcus spp , Mastitis , , asa1 , gelE , esp

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