Analysis of Acinetobacter baumannii survival in liquid media and on solid matrices as well as effect of disinfectants

BACKGROUND:Acinetobacter baumannii is a cause of healthcare-associated infections and has considerable potential to survive on inanimate hospital surfaces under hostile conditions (e.g. disinfection or desiccation). AIM:To learn more about its survival strategy and capacity to persist in liquid media and on surfaces mimicking hospital environments. METHODS:The effect of temperature, nutrient deprivation, permanence on inanimate surfaces, and exposure to disinfectants on the survival of four A. baumannii strains (ATCC 19606T and three clinical isolates) was studied by monitoring the number of total and viable cells using fluorescent microscopy and of culturable cells by standard cultures. FINDINGS:Bacterial survival was differentially affected by temperature (cells maintained at 20°C remained culturable at least within 30 days) and physical environment (desiccation favoured cell resistance to stress at 37°C). Moreover, persistence was associated with two adaptation patterns: one linked to entry into the viable but non-culturable state, whereas the other apparently followed a bust-and-boom model. During a study on the effect of disinfectant (commercial bleach and quaternary ammonium compounds), it was found that treatment with these antibacterial compounds did not eliminate A. baumannii populations and provoked the reduction of culturable populations, although a fraction of cells remained culturable. CONCLUSION:The ability to persist for long periods on different surfaces, mimicking those usually found in hospitals, along with A. baumannii's capacity to survive after a disinfection process may account for the recurrent outbreaks in intensive care units.