Plasmid-borne resistance drives global expansion of dangerous Klebsiella strains

A recent study published in Engineering has shed light on the transmission and epidemiological trends of tmexCD1-toprJ1-positive Klebsiella pneumoniae across various ecological niches, highlighting the potential threat this antibiotic-resistant bacterium poses to global public health. The research, conducted by a team of scientists from multiple institutions in China, utilized whole-genome sequencing (WGS) to analyze strains from humans, animals, food, and the environment, revealing significant insights into 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 predominantly identified in Klebsiella pneumoniae from chicken feces in China. However, the presence of these strains has expanded beyond chickens to other ecological niches and countries, including Japan, Vietnam, Kenya, and others. The researchers noted that the majority of these strains exhibited resistance to nearly all antimicrobials, including colistin, another last-resort antibiotic, with a resistance rate of 42.13%.

Phylogenetic analysis revealed that the tmexCD1-toprJ1 gene cluster is primarily carried by narrow host-range plasmids specific to Klebsiella species, which may limit its spread across different bacterial species. However, the study also identified instances where the gene cluster had been captured by broad-host-range plasmids, suggesting a potential for wider dissemination. Notably, the gene cluster has been found in hypervirulent carbapenem-resistant K. pneumoniae (hvCRKP) strains, which are known to cause severe infections in healthcare settings.

The research highlighted a significant decline in the prevalence of tmexCD1-toprJ1-positive strains in food animals and humans in China following the withdrawal of antibiotics as growth promoters in animal feed in 2020. This finding underscores the importance of antimicrobial stewardship policies in controlling 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 of tmexCD1-toprJ1, suggesting 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 various 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 dissemination of the resistance genes. The study also highlighted the role of specific plasmid types, such as IncFIB(Mar)-IncHI1B and IncFIB(K)-IncHI1B, in the spread of tmexCD1-toprJ1.

The findings of this study emphasize the need for continuous monitoring of tmexCD1-toprJ1 across different ecological niches and the enforcement of strict antimicrobial policies in animal husbandry. The global spread of tmexCD1-toprJ1-positive Klebsiella pneumoniae poses a significant challenge to the treatment of infections caused by multidrug-resistant bacteria, highlighting the importance of a One Health approach to address the growing threat of antimicrobial resistance.