Microbiological Profile and Antimicrobial Susceptibility of Bacteria Associated with Clinical Vaginitis in Dairy Cows

Avarseji, Amirali; Dabiri, Seyyed Amirhossein; Bakhtiarynia, Farnia

doi:10.66224/ari.2026.372447.4081

Microbiological Profile and Antimicrobial Susceptibility of Bacteria Associated with Clinical Vaginitis in Dairy Cows

Articles in Press

Document Type : Original Articles

Authors

¹ department of clinical science.university of tehran

² 3. Resident in Large Animal Internal Medicine, Islamic Azad University, Science and Research Branch, Tehran, Iran

³ Doctor of Veterinary Medicine Student, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

10.66224/ari.2026.372447.4081

Abstract

Bovine vaginitis is a significant reproductive disorder impacting the fertility and economic viability of dairy herds. This study aimed to identify the bacterial etiologic agents associated with clinical vaginitis in dairy cows and evaluate their antimicrobial susceptibility profiles. Vaginal discharge samples were collected from 8 dairy cows exhibiting clinical signs of vaginitis, followed by standard bacteriological isolation and antimicrobial susceptibility testing (AST) using the Kirby-Bauer disk diffusion method against a comprehensive panel of 16 antibiotics. Bacterial growth was observed in 62.5%of the samples, while 3 samples remained culture-negative. Streptococcus spp. emerged as the predominant etiologic agent, recovered from 62.5% of the cows, alongside Enterobacter aerogenes which was identified in 12.5% of the cases. The AST revealed high heterogeneity among the Streptococcus spp. isolates. Although all isolates were completely susceptible to amoxicillin, amikacin, enrofloxacin, florfenicol, and ceftiofur, variable resistance dynamics were observed against penicillin, gentamicin, streptomycin, and erythromycin. Notably, while earlier isolates showed intrinsic resistance to sulfonamides (trimethoprim-sulfamethoxazole and Soltrim), the newly recovered multi-drug resistant strain demonstrated susceptibility, shifting the overall resistance rate to 80%. The coexistence of strains with such contrasting susceptibility profiles within the same herd highlights the active circulation of multi-drug resistant (MDR) opportunistic pathogens. These findings strongly emphasize that relying on empirical antibiotic therapy is highly risky, and continuous AST monitoring is strictly required for the effective clinical management of bovine reproductive infections.

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