The investigation of bacteria in the oral of Trichomonas gallinae infected pigeons and the antibiotic resistance analysis of Klebsiella pneumoniae clinical isolates from farm pigeons in Shandong Province of China.

While the global dissemination of extended-spectrum β-lactamases (ESBLs) in clinical isolates from various animals is well-documented, research on Klebsiella pneumoniae in Trichomonas gallinae-infected pigeons, particularly concerning antibiotic resistance genes in China, remains limited. This study aimed to investigate the relationship between oral harmful microbiota in pigeons and T. gallinae infection, as well as to isolate K. pneumoniae from the oral cavities of infected pigeons. Furthermore, we assessed the resistance profiles of K. pneumoniae isolates against quinolones, tetracyclines, and aminoglycosides, and identified the carriers of related resistance genes, including bla genes encoding SHV, TEM, and CTX-M-9 ESBLs.Our results revealed that approximately 30% of pigeons from Laiwu City and Tai'an City in Shandong Province were infected with T. gallinae. Notably, the species diversity and abundance of oral bacteria were significantly higher in infected pigeons compared to their uninfected counterparts, indicating a positive correlation between T. gallinae infection and oral microbial alterations. Among the 14 bacterial species isolated from oral samples of infected pigeons, seven were identified as K. pneumoniae isolates. The majority of these isolates exhibited multidrug resistance to ampicillin, ceftazidime, cefotaxime, and aminoglycosides. PCR analysis confirmed the presence of TEM, SHV, and CTX-M-9 genes in all seven K. pneumoniae isolates. The predominant plasmid-mediated resistance genes included qnrB (for quinolones), tetA (for tetracyclines), and aac(6')-Ⅰb (for aminoglycosides). These findings provide a overview of antibiotic susceptibility patterns and the emergence of resistance genes in K. pneumoniae isolates from farm pigeons in Shandong, China. They underscore the widespread multidrug resistance in these isolates and highlight the potential risk of antibiotic resistance transmission between animals and humans.