Bacterial diversity in bioaerosols from two petting zoos

Background: There have been reports of disease outbreaks among visitors of animal exhibits associated with close contact to animals. However, limited studies have described the diversity of bacterial aerosols in petting zoos. We described the bacterial diversity of these aerosols using molecular techniques. Methodology: This cross-sectional pilot study used convenience sampling across two petting zoos (one indoor and one outdoor) within 15-miles of Omaha, Nebraska, during fall 2011. Each petting zoo involved a test and control location. We performed fixed-site bioaerosol sampling using impingement at a constant flow rate of 12.5 liters per minute, for 60 minutes. The samples were analyzed by universal 16s rDNA PCR-based Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Temperature and relative humidity were recorded at each sampling location. Information on feeding and cleaning practices, number and types of animals were documented. Fisher's exact test was applied to compare the bacterial diversity. Results: The predominant organisms identified by PCR-DGGE were Bacteroides spp., Staphylococcus spp., Streptococcus spp.,Enterococcus spp., Escherichia coli, Clostridium spp., and Bifidobacterium spp. While Staphylococcus aureus band was relatively intense in all samples, C. difficile was mainly traced in the outdoor setting. Further, C. difficile specific multiplex PCR revealed presence of (Tcd-B) toxin-B gene/s. A total of 20-26 DGGE bands displayed diversity of known and unknown bacterial species. However, the variation in bacterial profiles overall was not statistically significant. The mean temperature (and relative humidity) for the indoor and outdoor sites were 27°C (27%) and 12 °C (16.5%), respectively. Conclusion: Our results suggest that a mixed diversity of pathogenic and non-pathogenic bacteria may be present at animal exhibits. Petting zoo visitors may be at a potential risk of exposure to pathogens. Identification of pathogens such as S. aureus and toxigenic strains of C. difficile in animal exhibits is a public health concern and demands further research.