Emergence of aztreonam/avibactam and tigecycline-resistant Pseudomonas putida group Co-producing bla, bla and bla with a novel sequence type ST268 in Southwestern China.

Objectives: The emergence of carbapenem-resistant Pseudomonas putida (CRPP) has raised public awareness. This study investigated two strains from the Pseudomonas putida group that were resistant to carbapenem, tigecycline, and aztreonam-avibactam (ATM-AVI), with a focus on their microbial and genomic characteristics.

Methods: We assessed the antibiotic resistance profile using broth dilution, disk diffusion, and E-test methods. Efflux pump phenotype testing and real-time quantitative PCR were employed to evaluate efflux pump activity in tigecycline resistance, while polymerase chain reaction was utilized to detect common carbapenem genes. Additionally, whole-genome sequencing was performed to analyze genomic characteristics. The transferability of bla and bla was assessed through a conjugation experiment. Furthermore, growth kinetics and biofilm formation were examined using growth curves and crystal violet staining.

Results: Both strains demonstrated resistance to carbapenem, tigecycline, and ATM-AVI. Notably, NMP can restore sensitivity to tigecycline. Subsequent analysis revealed that they co-produced bla, bla, tmexCD-toprJ, and bla, belonging to a novel sequence type ST268. Although they were closely related on the phylogenetic tree, they exhibited different levels of virulence. Genetic environment analysis indicated variations compared to prior studies, particularly regarding the bla and bla genes, which showed limited horizontal transferability. Moreover, it was observed that temperature exerted a specific influence on their biological factors.

Conclusion: We initially identified two P. putida ST268 strains co-producing bla, bla, bla, and tmexCD-toprJ. The resistance to tigecycline and ATM-AVI can be attributed to the presence of multiple drug resistance determinants. These findings underscore the significance of P. putida as a reservoir for novel antibiotic resistance genes. Therefore, it is imperative to develop alternative antibiotic therapies and establish effective monitoring of bacterial resistance.