Tigecycline Resistance Mechanisms in Klebsiella pneumoniae

Tigecycline has become a critical last-resort antibiotic against multidrug-resistant Klebsiella pneumoniae, yet resistance to this agent is rising globally. The predominant mechanisms involve up-regulation or mutation of efflux pumps—particularly the AcrAB-TolC and OqxAB systems—leading to active extrusion of tigecycline from the bacterial cell. Mutations in transcriptional regulators such as RamR, MarR and AcrR often derepress their corresponding targets (ramA, marA, acrA) and drive overexpression of efflux components. Plasmid-borne genes encoding variant tetracycline-inactivating enzymes (for example, tet(X) and mutated tet(A)) have also been reported, mediating enzymatic modification of the drug. Additional contributions arise from alterations in outer-membrane permeability and target-protection factors. The convergence of chromosomal mutations and mobile genetic elements accelerates dissemination of resistance across clinical and environmental reservoirs. This poses a critical threat to patient outcomes, since tigecycline is frequently used when other treatments fail. Understanding these mechanisms is essential for guiding stewardship efforts, informing diagnostic assays and designing novel adjuvant therapies to restore antibiotic potency.

Research from Nature Portfolio

Recent studies have characterised tigecycline resistance in extensively drug-resistant, carbapenem- and colistin-resistant K. pneumoniae collected over multiple years in Southeast Asia. A high-risk clone (ST16) bearing co-existing carbapenemase genes was shown to exhibit tigecycline non-susceptibility in over 90 percent of isolates. Genetic analyses revealed frequent mutations in ramR and its binding site upstream of ramA, as well as in marR and acrR, culminating in overexpression of the AcrAB efflux pump and its activator RamA. In a subset of isolates, plasmid-encoded variants of tet(A) contributed further to reduced tigecycline susceptibility. These findings highlight the interplay of chromosomal mutations and mobile resistance determinants in emerging high-risk clones and underscore the need for regional surveillance of last-resort antibiotic efficacy.

Tigecycline Resistance Mechanisms in Klebsiella pneumoniae publication trend

The graph below shows the total number of articles in tigecycline resistance mechanisms in klebsiella pneumoniae across all publications each year (not limited to Nature Index journals).

Technical terms

Efflux pump: A membrane-associated protein complex that exports antimicrobial agents from bacterial cells, reducing intracellular drug concentration. ramR: A transcriptional repressor of ramA; mutations in ramR lead to increased ramA expression and up-regulation of the AcrAB-TolC efflux system. tet(A): A gene encoding a tetracycline efflux pump; mutated versions can broaden substrate specificity to include tigecycline. Plasmid: A mobile, extrachromosomal DNA element that can carry antibiotic resistance genes and transfer them between bacteria. Last-resort antibiotic: An antimicrobial reserved for severe or multidrug-resistant infections when other treatments have failed.

References

1. The investigation of molecular epidemiological characteristics and resistance mechanism of tigecycline resistant Klebsiella pneumoniae from a large teaching hospital in southwest China, Chongqing. Frontiers in Cellular and Infection Microbiology (2025).
2. Occurrence and mechanisms of tigecycline resistance in carbapenem- and colistin-resistant Klebsiella pneumoniae in Thailand. Scientific Reports (2024).
3. A widespread single amino acid mutation in AcrA reduces tigecycline susceptibility in Klebsiella pneumoniae. Microbiology Spectrum (2023).
4. The Rapid Emergence of Tigecycline Resistance in blaKPC–2 Harboring Klebsiella pneumoniae, as Mediated in Vivo by Mutation in tetA During Tigecycline Treatment. Frontiers in Microbiology (2018).
5. First Emergence of acrAB and oqxAB Mediated Tigecycline Resistance in Clinical Isolates of Klebsiella pneumoniae Pre-Dating the Use of Tigecycline in a Chinese Hospital. PLOS ONE (2014).