Molecular Detection, Virulence Genes, and Antibiotic Resistance of Klebsiella pneumoniae Isolated from Infertile Mares in Isfahan, Iran

Background: Infertility in mares is a multifactorial condition, with infectious agents playing a significant role in reproductive failure. Among bacterial pathogens, Klebsiella pneumoniae (K. pneumoniae) is recognized as a major contributor to endometritis and other reproductive tract infections, particularly due to its potential for antimicrobial resistance, which complicates therapeutic management. This study aimed to investigate the prevalence, antibiotic resistance patterns, resistance gene profiles and virulence genes of K. pneumoniae isolates in infertile mares in Isfahan Province, Iran. Methods: Uterine lavage samples were collected from ۸۰ infertile mares that had not conceived after at least three artificial or natural inseminations in previous reproductive cycles. Sampling was during estrus using sterile catheterization techniques. Standard bacteriological culture methods were employed to isolate K. pneumoniae, and positive isolates were subjected to phenotypic antibiotic susceptibility testing and PCR-based genotypic analysis to identify resistance and virulence genes. Results: K. pneumoniae was isolated from ۲۲ out of ۸۰ uterine samples, indicating a prevalence of ۲۷.۵%. Endometritis was the most common clinical finding, diagnosed in ۶۰% of the mares. No significant associations were found between infection status and variables such as age, breed, or type of insemination. Antimicrobial susceptibility testing revealed complete resistance to tetracycline (۱۰۰%), followed by high resistance to cephalotin (۷۲.۷%). The lowest resistance rates were observed for imipenem and nitrofurantoin (۱۸.۲%). Molecular analysis identified ۱۸ resistance genes among the isolates. The tetA gene, conferring resistance to tetracycline, was the most frequently detected, present in ۷۷.۳% of isolates. In contrast, the cat۱ gene, associated with chloramphenicol resistance, was found in only ۲۲.۷% of samples. In addition, ۱۵ virulence genes were examined. The results indicated that an increase in the number of virulence genes was associated with a higher likelihood of disease. Among these, afadraBC was the most frequent (۸۶.۴%), while ibeA and PAI were the least frequent (۳۱.۸%). Conclusion: These findings highlight the significant role of multidrug-resistant K. pneumoniae in equine infertility and underscore the need for routine microbial screening, resistance gene profiling, and tailored antimicrobial therapy to improve reproductive outcomes in mares.

کلیدواژه ها:

Antibiotic resistance ، Endometritis ، Infertile mares ، Klebsiella pneumoniae ، Uterine infection ، Virulence genes