engleski

Acinetobacter baumannii survives in soil for over a year

The acute community-acquired human infections with Acinetobacter baumannii [1] suggest a source of this pathogen outside hospital settings. Due to limited number of attempts, only two studies reported detection of clinically relevant A. baumannii in soils [2, 3]. This study investigated the long-term survival of A. baumannii in soil, to evaluate the soil as a possible environmental reservoir of A. baumannii, prediction of A. baumannii behaviour in soil, and their potential consequences. Fresh and sterilized red soil of pH 8.43 from Istria, Croatia was chosen for the experiment. Three carbapenem-resistant isolates (two environmental and one clinical) were separately suspended in the autoclaved commercial spring water. These suspensions were used to adjust the moisture of the soil to maximum water holding capacity and simultaneously to supplement the soil with 6.7±0.3 log CFU/g of A. baumannii. Inoculated soils were left to dry in the dark at 22°C naturally, following drying in the desiccator. In both fresh and sterilized soils, A. baumannii isolates slightly multiplied when the water content ranged from 32-16 wt%. A drop of soil moisture from 16-5 wt% was accompanied by a sharp decrease in viable A. baumannii. At a soil moisture below 5 wt%, viable A. baumannii were maintained during a one-year monitoring in fresh (final abundance 2.4±0.4 log CFU/g), as well in sterilized (final abundance 4.4±0.1 log CFU/g) soil. Scanning electron microscopy confirmed the presence of A. baumannii biofilm that developed on the soil particles. Extensively- and pandrug-resistant A. baumannii remain viable in soil for over a year. This suggest the soil as a potential source of clinically relevant isolates that poses a threat to people that come into contact with the soil.

Acinetobacter baumannii, environment, soil

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