EVALUATION OF CULTURE MEDIA FOR DETECTING AIRBORNE SALMONELLA ENTERITIDIS COLLECTED WITH AN ELECTROSTATIC SAMPLING DEVICE FROM THE ENVIRONMENT OF EXPERIMENTALLY INFECTED LAYING HENS

Authors: Gast, Richard; Mitchell, Bailey; Holt, Peter

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2004
Publication Date: 7/1/2004
Citation: Gast, R.K., Mitchell, B.W., Holt, P.S. 2004. Evaluation of Culture Media for Detecting Airborne Salmonella Enteritidis Collected With an Electrostatic Sampling Device from the Environment of Experimentally Infected Laying Hens. Poultry Science v.83 p.1106-1111, 2004.

Interpretive Summary: Because contaminated eggs laid by infected hens can transmit Salmonella enteritidis to humans and cause illness, detecting this pathogen in the environment of laying flocks is an important objective for protecting public health. In the present study, an inexpensive and portable new electrostatic sampling device was used to detect S. enteritidis circulating in the air of a room containing experimentally infected hens. After the hens were infected with S. enteritidis, air samples were collected three times each week onto plates of six different types of agar culture media using the electrostatic sampling device. All six media supported the recovery of S. enteritidis from air samples for three weeks after the hens were infected. Accurate determination of the presence of S. enteritidis on air sampling plates could not be achieved simply by visual inspection of incubated plates, but instead required additional enrichment culturing steps. The highest frequency of S. enteritidis isolation was obtained using brilliant green agar, but even better S. enteritidis recovery was attained using a combination of several different types of media at the same time.

Technical Abstract: Detecting Salmonella enteritidis in the environment of commercial laying hens is critical for reducing the production of contaminated eggs by infected flocks. In the present study, an inexpensive and portable electrostatic air sampling device was used to detect S. enteritidis in rooms containing experimentally infected laying hens. After hens were orally inoculated with a phage type 13a S. enteritidis strain and housed in individual cages, air samples were collected three times each week with electrostatic devices onto plates of six types of culture media (brilliant green agar, modified lysine iron agar, modified semisolid Rappaport-Vassiliadis agar; Rambach agar, XLD agar, and XLT4 agar). Air sampling plates were incubated at 37° C, examined visually for presumptive identification of typical S. enteritidis colonies, and then subjected to confirmatory enrichment culturing. Air samples (collected using all six culture media) were positive for S. enteritidis for three weeks post-inoculation. Because visual determination of the presence or absence of typical S. enteritidis colonies on air sampling plates was not consistently confirmed by enrichment culturing, the post-enrichment results were used for comparing sampling strategies. The frequency of positive air sampling results using brilliant green agar (66.7% overall) was significantly greater than was obtained using most other media. A combination of several plating media (brilliant green agar, modified lysine iron agar, and XLT4 agar) allowed detection of airborne S. enteritidis at an overall frequency of 83.3% over the three weeks of sampling.