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

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

Submitted to: United States Animal Health Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/12/2003
Publication Date: 7/12/2003
Citation: Gast, R.K., Mitchell, B.W., Holt, P.S. 2003. Evaluation Of Culture Media For Use In Detecting Airborne Salmonella Enteritidis In The Environment Of Experimentally Infected Laying Hens With An Electrostatic Sampling Device. United States Animal Health Association Proceedings, p.38, 2003.

Interpretive Summary:

Technical Abstract: Detecting Salmonella enteritidis in the environment of commercial laying hens is a critical aspect of efforts to reduce the production of contaminated eggs by infected flocks. Bacteriological culturing of samples taken from environmental sources such as manure pits and egg belts has been the most commonly used method for screening laying houses to determine whether further testing is necessary. Culturing air samples from poultry house environments might offer an efficient alternative approach for detecting the presence of pathogens such as S. enteritidis. In the present study, an inexpensive and portable electrostatic air sampling device (ESD) was applied to detect S. enteritidis in rooms containing experimentally infected laying hens. In each of two replicate trials, 40 hens were housed in individual cages and the floor of the isolation room was not cleaned during the experiment (allowing manure, dust, and feathers to accumulate). After oral inoculation of the hens with a phage type 13a S. enteritidis strain, air samples were collected three times each week with the ESD onto plates of 6 types of culture media (brilliant green-novobiocin agar, modified lysine iron agar, modified semisolid Rappaport-Vassiliadis agar; Rambach agar, XLD-novobiocin agar, and XLT4 agar). Air samples were collected on each plating medium by exposure for periods of one and two hours. Air sampling plates were incubated for 40 hours at 37° C, examined for presumptive identification of typical S. enteritidis colonies, and were then subjected to confirmatory enrichment culturing. Weekly samples of voided feces from each hen were also collected and cultured for S. enteritidis. Both air samples (collected using all six culture media) and fecal samples were positive for S. enteritidis for 3 weeks post-inoculation. Because presumptive 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. Air sampling periods of one and two hours with the ESD did not yield significantly different frequencies of recovery of S. enteritidis. The frequency of positive air sampling results using brilliant green-novobiocin agar (66.7% overall) was significantly greater than was obtained using most other media. A combination of several plating media (such as brilliant green-novobiocin agar, modified lysine iron agar, and XLT4 agar) allowed detection of S. enteritidis at an overall frequency of 83.3% over the three weeks of sampling.