[Resistance of Acinetobacter baumannii to Tigecycline].

OBJECTIVES: To determine the impact of long-term use of antibiotics and ultraviolet radiation on the resistance of Acinetobacter baumannii to tigecycline and the viability of tigecycline-resistant Acinetobacter baumannii .

METHODS: Three strains of tigecycline sensitive Acinetobacter baumannii were selected. Tigecycline resistance was induced through multi-step method or by ultraviolet radiation. Two strains of tigecycline resistant Acinetobacter baumannii were repeatedly passaged on blank MHA plates, for the purpose of determination of minimum inhibitory concentrations (MICs) of tigecycline using broth microdilution method. The tigecycline sensitive (b38) and homologous resistant Acinetobacter baumannii (b38!d) were cultured separately and conjointly to evaluate its fitness costs of tigecycline resistance.

RESULTS: Tigecycline resistant strains were successfully induced using multi-step method. Ultraviolet radiation did not change the sensitivity of the three strains to tigecycline, but elevated the MICs of tigecycline. The MICs of tigecycline did not change over 40 generations. It took much more time for the resistant strains to reach logarithmic growth phase and plateau phase compared with the tigecycline sensitive strains. With repeated passage, the tigecycline resistant strains decreased rapidly, even vanished in conjointly culture.

CONCLUSION: Acinetobacter baumannii can acquire tigecycline resistance. The resistance may have genetic stability. The resistant strains have less adaptability than the sensitive strains.