Prevalence and antimicrobial susceptibility of Salmonella spp. isolates from US cattle in feedlots in 1999 and 2000

Abstract

Aims: Faecal samples from cattle in US feedlots were evaluated for the presence of Salmonella. When Salmonella isolates were recovered the antimicrobial resistance patterns were determined. Methods and Results: Faecal samples were collected from pen floors in 73 feedlots in 12 states during the period from October 1999 to September 2000. Pens of cattle selected for sampling were those that had been in the feedlot for the shortest period of time, the longest period of time and a randomly selected pen from the remaining pens. Faecal samples were cultured for Salmonella spp. and all Salmonella isolates were categorized by serotype. The susceptibilities of all isolates were determined using a panel of 17 antimicrobials. Overall, 6AE3% (654/10 417) of the samples cultured positive for Salmonella spp. and 22AE2% (94/422) of pens and 50AE7% (37/73) of feedlots had one or more positive samples. There was little difference in the proportion of positive samples from short-fed (6AE1%, 212/ 3482), random (6AE4%, 217/3400) and long-fed (6AE4%, 224/3485) pens of cattle. One of two pens of cattle that could not be attributed to a pen type had a single positive sample (2AE0%, 1/50). Samples collected during the period of April to June (6AE8%, 209/3054) and July to September (11AE4%, 286/2500) were more likely to be positive than those collected during October to December (4AE0%, 73/1838) and January to March (2AE8%, 86/3025). The most common serotypes of Salmonella were dissimilar from those that are typically seen in human illness and cattle illness. The majority of isolates (62AE8%, 441/702) were sensitive to all of the antimicrobials tested. Resistance was most frequently observed to tetracycline (35AE9%, 252/702) followed by streptomycin (11AE1%, 78/702), ampicillin (10AE4%, 73/702) and chloramphenicol (10AE4%, 73/702). Multiple resistance (resistance to ‡2 antimicrobials) was observed for 11AE7% (82/702) of the isolates. Conclusions: Salmonella was isolated at low frequency from faeces of feedlot cattle and the serotypes were not those commonly associated with human illness. In addition most of the Salmonella isolates were sensitive to all the antimicrobials tested. Significance and Impact of the Study: This study contributes to understanding the ecology of Salmonella in cattle feedlots and the prevalence of resistance among potential food-borne pathogens.

Prevalence and Serovars of Salmonella in the Feces of Free-Ranging White-Tailed Deer (Odocoileus virginianus) in Nebraska

“…Salmonella were detected in 2 (8%) of 26 samples that were collected from the rumen of white-tailed deer harvested on a university ranch in Texas, USA (Branham et al, 2005). The prevalence that we found in deer feces is similar to the overall prevalence in feces (1.4%) reported in a national survey of beef cows in the USA (Dargatz et al, 2000).…”

“…The incidence of human foodborne salmonellosis (Centers for Disease Control and Prevention, 2003a) and prevalence in feedlot cattle feces (Dargatz et al, 2003) are higher in the summer months. The shedding of Salmonella in livestock feces also tends to increase during, or following, periods of stress (Sanchez et al, 2002).…”

“…During the year our deer samples were collected (1998), serovars Infantis and Enteritidis were among the top 20 serovars reported to cause disease in both humans and animals (Centers for Disease Control and Prevention, 1998). For comparison, none of the five most frequently detected serovars in a national survey of beef cows in the USA were among the serovars most likely to cause clinical disease in humans or animals (Dargatz et al, 2000). Typhimurium (McAllum et al, 1978;Sato et al, 2000;Foreyt et al, 2001), Bovis-morbificans (McAllum et al, 1978), and Hartford, Weltevreden, and Kralendyl (Nettles et al, 2002) have been reported to cause disease in deer or elk.…”

Salmonella Enterica Subsp. Enterica in Cattle Egret (Bubulcus Ibis) Chicks From Central Texas: Prevalence, Serotypes, Pathogenicity, and Epizootic Potential

“…Serotypes isolated between May 1, 2000, and April 30, 2003, were cataloged and compared to the Salmonella serotypes isolated from the Egrets (Table 3). Salmonella serotypes isolated from the Egrets were also compared to Salmonella isolates from feedlot and dairy cattle from Texas and adjoining states (Dargatz et al, 2003;Edrington et al, 2004;Callaway et al, 2005).…”

“…b Serotype also isolated from feedlot or dairy cattle (Dargatz et al, 2003;Edrington et al, 2004;Callaway et al, 2005).…”