A recent study published in Engineering has shed light on its transmission and epidemiological trends tmexCD1-toprJ1-positive Klebsiella pneumoniae in various ecological niches, highlighting the potential threat posed by this antibiotic-resistant bacterium to global public health. The research, conducted by a team of scientists from several institutions in China, used whole genome sequencing (WGS) to analyze strains from humans, animals, food and the environment, revealing important information about the spread and characteristics of these resistant bacteria.
The study found that tmexCD1-toprJ1-positive strains, which confer resistance to the critical antibiotic tigecycline, are found mainly in Klebsiella pneumoniae from chicken droppings in China. However, the presence of these strains has expanded beyond chickens to other ecological niches and countries, such as Japan, Vietnam, Kenya and others. The researchers observed that the majority of these strains showed resistance to almost all antimicrobials, including colistin, another antibiotic of last resort, with a resistance rate of 42.13%.
The phylogenetic analysis revealed that the tmexCD1-toprJ1 the gene cluster is mainly carried by narrow-host-range plasmids specific for Klebsiella species, which may limit its spread to various bacterial species. However, the study also identified instances where the gene cluster had been captured by host-wide plasmids, suggesting a potential for wider dissemination. Notably, the gene cluster has been found in carbapenem-resistant superinfectants K. pneumoniae (hvCRKP) strains, which are known to cause serious infections in healthcare settings.
The research revealed a significant reduction in its prevalence tmexCD1-toprJ1-positive strains in food animals and humans in China following the withdrawal of antibiotics as growth agents in animal feed in 2020. This finding highlights the importance of antimicrobial stewardship policies to control the spread of resistance genes. The study also pointed out that the frequent use of tetracyclines in chicken farming likely contributes to the high detection rate tmexCD1-toprJ1suggesting that targeted interventions in the poultry industry could be effective in mitigating the spread of these resistant strains.
In addition to the epidemiological findings, the study provided detailed genomic insights into the tmexCD1-toprJ1 gene cluster. The researchers identified several genetic environments surrounding the gene cluster, with the type II structure being the most prevalent. This structure is characterized by the presence of insertion sequences such as IS26, which facilitate the mobility and propagation of resistance genes. The study also highlighted the role of specific types of plasmids, such as IncFIB(Mar)-IncHI1B and IncFIB(K)-IncHI1B, in the spread of tmexCD1-toprJ1.
The findings of this study highlight the need for continued monitoring tmexCD1-toprJ1 in different ecological niches and the enforcement of strict antimicrobial policies in animal husbandry. Its global spread tmexCD1-toprJ1-positive Klebsiella pneumoniae represents a major challenge for the treatment of infections caused by multidrug-resistant bacteria, underscoring the importance of a One Health approach to addressing the growing threat of antimicrobial resistance.
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Journal Reference:
Luchao Lv, et al. (2025). Transmission of tmexCD1-toprJ1-Positive Klebsiella pneumoniae in Multiple Ecological Sites: A Global Epidemiologic and Genomic Analysis. Engineering. DOI: 10.1016/j.eng.2025.03.038. https://www.sciencedirect.com/science/article/pii/S2095809925003467?via%3Dihub.
