Effect of negative air ions on Escherichia coli ATCC 25922 inoculated onto mung bean seed and apple fruit.

The effect of negative air ions on the reduction of Escherichia coli ATCC 25922 inoculated onto mung bean sprout seed and whole or fresh-cut apple fruit was studied. Mung bean seeds, whole Gala apples, and Gala apple slices were inoculated with E. coli ATCC 25922 before being exposed to negative air ions for up to 18 h at room temperature (-23 degrees C). Results revealed a less than 0.5-log reduction of E. coli on mung bean seed even after 18 h of exposure. The reduction of E. coli on the surface of whole apples increased with increasing exposure time from 0.5 to 3 h, but the maximum reduction was less than 1 log CFU/g. Increasing exposure time from 3 to 18 h did not lead to increased treatment efficacy. No reduction of E. coli was observed on apple slices after 3 h of treatment. When the negative air ion system was applied with acetic acid vapor, no additive or synergistic effect of negative ions on the reduction of E. coli was found. These results suggest that negative air ions have a very limited effect on the population of E. coli on mung bean seed and apples.

Detection of airborne Salmonella enteritidis in the environment of experimentally infected laying hens by an electrostatic sampling device.

Bacteriologic culturing of environmental samples taken from sources such as manure pits and egg belts has been the principal screening tool in programs for identifying commercial laying flocks that have been exposed to Salmonella enteritidis and are thus at risk to produce contaminated eggs. Because airborne dust and aerosols can carry bacteria, air sampling offers a potentially efficient and inexpensive alternative for detecting S. enteritidis in poultry house environments. In the present study, an electrostatic air sampling device was applied to detect S. enteritidis in a room containing experimentally infected, caged laying hens. After oral inoculation of hens with a phage type 13a S. enteritidis strain, air samples were collected onto agar plates with the electrostatic sampling device, an impaction air sampler, and by passive exposure to the settling of aerosols and dust. Even though the floor of the room was cleaned once per week (removing most manure, dust, and feathers), air samples were positive for S. enteritidis for up to 4 wk postinoculation. On the basis of both the number of S. enteritidis colonies observed on incubated agar plates and the frequency of positive results, the efficiency of the electrostatic device was significantly greater than that of the passive exposure plates (especially at short collection intervals) and was similar to that of the far more expensive impaction sampler. The electrostatic device, used for a 3-hr sampling interval, detected airborne S. enteritidis on 75% of agar plates over the 4 wk of the study.