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Title: Experimental Salmonella contamination and recovery on bermudagrass

item McLaughlin, Michael
item Brooks, John

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/7/2007
Publication Date: 11/7/2007
Citation: Mclaughlin, M.R., Brooks, J.P. 2007. Experimental Salmonella contamination and recovery on bermudagrass [abstract]. Agronomy Abstracts. Abstract 334, CD-ROM.

Interpretive Summary:

Technical Abstract: Confined swine feeding operations in the southeastern US flush manure into lagoons and the effluent is applied to forage crops cut for hay. Bermudagrass, Cynodon dactylon (L.) Pers., is the most widely used of these summer forages. Application is by irrigation using overhead nozzle center pivot systems or traveling gun reel systems. Although swine manure is known to contain Salmonella, little is known of the incidence and significance of Salmonella in effluents applied to bermudagrass. A laboratory method was developed to test the application and recovery of Salmonella on bermudagrass preliminary to examining this problem in the field. EPA (U.S. Environmental Protection Agency) “worst case water” (WCW) was used to simulate lagoon effluent. WCW with high turbidity and organic matter was originally developed to test water filtration devices. In the present application, WCW was loaded with known levels of Salmonella. Salmonella grown in trypticase soy broth was concentrated and washed by three cycles of centrifugation (5K x g, 15 min, 10C) and suspension in phosphate-buffered saline (PBS). Cell suspensions were counted (colony forming units, cfu/ml) by dilution plating on trypticase soy agar (TSA) and stored at 4C. To simulate irrigation, freshly cut leaves were trimmed to 6 cm in length and 3 cm of the leaf tips dipped individually 10X in Salmonella-loaded WCW. Treated leaves were held on sterile filter paper wetted with sterile distilled water inside glass Petri dishes at room temperature. Individual leaves, removed at intervals for Salmonella testing, were placed tip down in sterile 5-ml plastic culture tubes containing 1 ml of sterile PBS. Salmonella were eluted by vigorous swirling in tightly capped tubes using a vortex mixer (15 sec, 2X) and counted on TSA spread plates. Recovery from leaves exposed to 106 cfu/ml, varied widely (0 - 104 cfu/leaf) within and among cultivars.