Detection of Salmonella on Bird Feces Contaminated Leafy Green Vegetables Using Phage-Based Magnetoelastic Biosensors

The outbreak of foodborne diseases caused by bacteria, such as O157:H7 E. coli and Salmonella has become a great concern in food safety[1]. The consumption of foodborne bacteria contaminated vegetables is one of the causes of foodborne disease. Vegetables can be contaminated by animal manure, for example, bird feces. Bird feces contain Salmonella which is a pathogen that lives in the intestines of the infected birds and is shed through feces. Bird could fly over or land on leafy green vegetables, such as spinach, iceberg lettuce and cabbage, leading to the potential bird feces contamination. Recently, USFDA found that the outbreak of Salmonella in peanut butter may be linked to the exposure of bird feces to the raw, unshelled peanuts that were stored outdoors where birds were observed flying over and landing on the in-shell peanuts[2]. Even though water washing can remove feces and reduce bacterial contamination, it is still difficult to eliminate bacteria at all. Therefore, rapid detection Salmonella in bird feces contaminated leafy green vegetables is required. The phage-based magnetoelastic biosensor has been developed to detect Salmonella on food surface [3, 4]. In the present work, we optimized the current detection procedures to detect Salmonella on bird feces contaminated vegetables using phage-based magenoelastic biosensors. Several parameters influencing the effectiveness of detection were optimized, such as, blocking agent concentration and incubation time. A protocol was developed to visualize Salmonella on biosensor surface to correlate the resonance frequency measurement of biosensors. Our detection protocol could contribute to screening the leafy green vegetables after harvesting to reduce effort and cost. 

Reference:

1. WHO: Food safety and foodborne illness. In Fact sheet no 237; 2007.

2. FDA: Inspectional Observations. Denver, CO; 2012.

3. Chai, Y, Horikawa, S, Wikle, HC, Wang, Z, Chin, BA, Surface-scanning coil detectors for magnetoelastic biosensors: A comparison of planar-spiral and solenoid coils. Applied Physics Letters. 2013. 103:p.173510.

4. Lakshmanan, RS, Guntupalli, R, Hu, J, Kim, D-J, Petrenko, VA, Barbaree, JM, Chin, BA, Phage immobilized magnetoelastic sensor for the detection of Salmonella typhimurium. Journal of Microbiological Methods. 2007. 71:p.55-60.