Report: Efficacy of AquaHort water treatment against Listeria innocua

In order to test the efficacy of the Aqua‐Hort‐System against the bacterium Listeria innocua in a range of 0 to 4 ppm Cu at various exposure times (1 to 4 hours), Aqua‐Hort Danmark installed a unit at the trial greenhouse of the Institute of Phytomedicin at the Geisenheim Universtiy. During the trial, after 1 hour exposure a significant reduction of the viable counts could be observed at 2 and 4 ppm Cu resulting in efficiency rates of about 40 and 60% respectively. At an exposure of 2 hours also with 1 ppm Cu the bacteria were significantly reduced (efficiency about 58%) and with the two higher concentrations efficiency rates of 79 and 99.6% were achieved. After 4 hours the efficiency rates were 97.57, 99.81 and 99.96% for 1, 2 and 4 ppm Cu respectively.

Nutrient contents of the complete fertiliser FERTY® 3 MEGA (Planta
Düngemittel GmbH, Regenstauf, Germany)

During the trial, 400 L nutrient solution were prepared by 0.5 g/L of the complete fertiliser FERTY® 3 MEGA (ingredients see table 1). The solution ready for use had an electric conductivity of 1030 μS/cm and a pH of 6.4. Preparation took place one day in advance to achieve an adaptation to the ambient temperature of about 20°C. The nutrient solution was pumped with about 1 m3/h through the Aqua‐Hort®‐unit. The Cu‐concentrations were adjusted to 1, 2 and 4ppm Cu according the various treatments and checked by using the "Kupfer‐Test Aquaquant®" (range 0.3 – 5.0 mg/l; Merck KGaA, Darmstadt).

Means of viable counts (cfu/ml) of Listeria innocua in a fertiliser solution after
treatment at different Cu‐concentrations and exposure times.

After passage through the Aqua‐Hort®‐unit samples of 50 ml each were taken and
contaminated with Listeria innocua. For this purpose from bacterial growth of 24 h
plate cultures (TSA) a suspension with an OD590 of 60% transmission was prepared
and 1ml added to the 50ml nutrient solution of each test tube. The samples were
immediately transferred to the lab and stored there at room temperature. To realise
the various exposure times three sub‐samples each were plated onto TSA plates 1, 2
and 4 hours after the samples were contaminated (spiral plater; Meintrup DWS
Laborgeräte GMBH, Lähden – Holte, Germany). At start and end of each treatment Cuconcentration (Kupfer‐Test Aquaquant®; range 0.3 – 5.0mg/l; Merck KGaA,
Darmstadt), electric conductivity, pH and temperature of the nutrient solution were
determined.

Efficiency rates (per cent of control)

Each treatment was repeated four times. The viable counts (cfu/ml) were statistically analysed by ANOVA and significant differences to the control were determined for each exposure time by the Tukey‐test (STATISTICA for Windows version 8.0).

For more information:
Aqua Hort
Aksel de Lasson
Tell: +45 702 26 611 |
[email protected]
www.aqua-hort.dk