The Evolution of Virulence of Carbapenem-Resistant from the Same Source Under the Pressure of Omadacycline Treatment.

Introduction: (KP) is a common Gram-negative bacterium in clinical practice and can cause various infectious diseases, including pneumonia, liver abscess and bloodstream infection. Carbapenem-resistant (CRKP) has become a major threat to global health due to its high incidence and mortality rates, especially the ST11-CRKP strain prevalent in China.

Methods: The age, main clinical diagnosis, previous health and immune status of the two patients with ST11-CRKP-related infections during the same period reported in this study were similar.

Results: The antibiotic treatment regimens for the two patients were the same in terms of the type and dosage of antibiotics, except for omadacycline. Meanwhile, PFGE, multilocus sequence typing (MLST), and K typing confirmed that the two strains had the same genetic background. Through experiments on serum resistance, biofilm formation, the infection model and the hypermucus phenotype, it was found that CRKP1 showed a hypervirulent phenotype, while CRKP15 showed a hopervirulent phenotype. Whole-genome sequencing further revealed the differences in virulence genes between the two strains and further confirmed the virulence phenotypes of the two strains. Single nucleotide polymorphism (SNP) analysis showed that the gene was one of the key genes for the virulence difference of the two strains with the same genetic background under the therapeutic difference of omadacycline. In addition, the effect of omadacycline on the expression of the gene was evaluated by qRT-PCR technology. The interaction between the gene and omadacycline was confirmed through molecular docking.

Conclusion: To sum up, these findings suggest that under the therapeutic stress of omadacycline, CRKP may adjust virulence through adaptive evolution, and the gene may be the key factor for the differences in virulence within this bacterial population.