Desiccation and ethanol resistances of multidrug resistant Acinetobacter baumannii embedded in biofilm: The favorable antiseptic efficacy of combination chlorhexidine gluconate and ethanol.

Background/purpose: Globally, multidrug-resistant Acinetobacter baumannii (MDRAB) has emerged as an important pathogen in nosocomial outbreaks. This study aimed to investigate the correlation between the biofilm formation and survival of MDRABs, and to investigate the antiseptic efficacy of hand sanitizers for the MDRABs, embedded with biofilm (MDRAB-Bs).

Methods: The MDRABs were selected randomly after pulsed-field gel electrophoresis (PFGE), and their biofilm formation was analyzed. Desiccation and ethanol tolerances were assayed to test the bacterial survival. The antiseptic efficacy of combined chlorhexidine gluconate (CHG) and 70% ethanol agents against MDRAB-Bs were compared with the 70% ethanol cleanser.

Results: Eleven MDRABs, which varied in biofilm formation (MRDAB-B) and planktonic type (MDRAB-P), were tested. In desiccation survival, the mean survival time for the MDRAB-Bs was 49.0 days which was significantly higher than that of their planktonic type (17.3 days) (P < 0.005). The MDRAB-Ps could be eliminated after a 10 min contact with a 30% ethanol agent, however, it took 10 min of 70% ethanol to eliminate the MDRAB-Bs. On the other hand, a 2% CHG in 70% ethanol solution completely eliminated all MDRAB-Bs after 1 min contacted time. The 2% CHG in 70% ethanol agent provided a significantly superior efficacy than the 70% ethanol solution at eliminating the MDRAB-Bs (P < 0.005).

Conclusion: MDRAB with biofilm-formation presented significantly higher desiccation and ethanol resistances than their planktonic type. Moreover, the 2% CHG in 70% ethanol agent provided a superior antiseptic efficacy for MDRAB-Bs than that of the 70% ethanol agent.