|Straus, David - TEXAS TECH|
Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 4, 2003
Publication Date: January 1, 2004
Citation: Purdy, C.W., Straus, D.C., Clark, R.N. 2004. Diversity of Salmonella serovars in feedyard and nonfeedyard playas of the southern high plains in the summer and winter. American Journal of Veterinary Research. 65:40-44. Interpretive Summary: Most feedyards (FY) in the Southern High Plains drain to a playa (shallow lake) which serves as a retention pond. The potential for bovine pathogens moving by runoff from the FY surface to the retention pond exists. This water has not been well studied for the presence of Salmonella serotypes. Playas not near feedyards were used as controls, even though grass surrounding them is frequently grazed by cattle. Seven feedyard playas and three control playas were analyzed for Salmonella species in the summer and winter. The water and muck (bottom sediment) from four sides of each playa were analyzed by culturing them in an enrichment broth for 24 hrs and a bacterial suspension from this was cultured again in enrichment broth for 24 hrs. The bacterial suspension was then isolated on various specialized medium which only grows Gram-negative enteric bacteria and pathogens. The isolates were further subjected to biochemical characterization. All suspected Salmonella isolates were submitted to the National Veterinary Services Laboratory, Ames, Iowa, for serotyping. No Salmonella were found in the control playas. Seven Salmonella serotypes were isolated from 5 of 7 FY playas in the summer and 13 serotypes were isolated from 7 of 7 FY playas in the winter. A total of 47 Salmonella isolations were made in the summer and 171 Salmonella isolations were made in the winter. These results indicate that FY playas are frequently contaminated with many Salmonella serotypes. These pathogens are called zoonotic agents which indicates that they have the potential to infect any mammal, reptile, or avian species. Therefore, before anyone uses untreated FY playa water they should consider the possibility of their spreading this zoonotic infectious agent to other animals or humans.
Technical Abstract: The isolation of Salmonella and serovar identification were compared in 7 feedyard (FY) and 3 control playas (shallow lakes) of the Southern High Plains in the summer and winter. A prospective controlled study was conducted with the approval of FY managers and ranchers with the promise of anonymity. Water and muck (sediment) samples were collected from the four sides of each playa in duplicate. Water samples (100 ml) were mixed with 100 ml of sulfur-brilliant green enrichment broth, which was incubated at 37 C for 24 hr in a shaker-incubator, then 100 ml of the bacterial suspension were mixed with 100 ml of sulfur-brilliant green and incubated for 24 hr. After the second enrichment, a swab was used to spread the bacterial suspension on differential medium plates. Suspected Salmonella isolates were further characterized by biochemical reactions. Muck samples were similarly processed, except 10 g of muck were mixed with 90 ml of the enrichment broth. All suspected Salmonella isolates were submitted to the American National Veterinary Services Laboratory, Ames, Iowa, via the Amarillo Texas A&M Veterinary Diagnostic Laboratory. No Salmonella isolates were collected from the control playas. Seven Salmonella serovars were isolated from 5 of 7 FY playas in the summer and 13 Salmonella serovars were isolated from 7 of 7 FY in the winter. A total of 47 Salmonella isolates were collected in the summer and 171 Salmonella isolates were collected in the winter. The results indicated that FY playa water is frequently contaminated with many Salmonella serovars. Therefore, this water should not be sprayed on cattle to keep them cool or used for dust abatement in the FY because this can potentially spread this infectious pathogen to other animals and humans.