The Establishment of Enterobacteriaceae andSalmonellaLondon in a New Dairy Farm Environment

Abstract

Salmonella spp. are important zoonotic pathogens in humans and animals. A longitudinal study was conducted at the Iowa State University's campus (at the Dairy/Animal Science Education and Discovery Facility) to observe change in Enterobacteriaceae (specifically Salmonella) before and after the placement of dairy livestock. To our knowledge, this is the first study that evaluated environmental changes of Gram-negative organisms in a new dairy farm environment. Environmental samples were taken using drag swabs and immediately processed in the laboratory using phenotypic methods (replica plating, the BBL Crystal Identification System for enteric/nonfermenter organisms™, and plating on specialized media/broths). Genotypic methods were also used (BAX PCR™ and pulsed-field gel electrophoresis). Organisms identified as Salmonella were sent to the National Veterinary Services Laboratory (Ames, IA) for confirmatory serotyping. Resistance to antibiotics (ampicillin, nalidixic acid, and tetracycline) was determined by replica plating of Enterobacteriaceae and Salmonella isolates using the guidelines of the National Antimicrobial Resistance Monitoring System and Clinical and Laboratory Standards Institute. The microflora of Enterobacteriaceae changed as cattle were introduced and as time progressed. Additionally, multidrug-resistant isolates began to appear immediately after cattle were introduced (multidrug-resistant isolates were rare prior to introduction of livestock). Variables such as temperature and humidity did not affect the proliferation of bacterial organisms. Seventeen Salmonella isolates were identified as Salmonella London and three isolates as Salmonella Montevideo. Based on pulsed-field gel electrophoresis-generated dendrograms, it is likely that 17 Salmonella London isolates and 3 Salmonella Montevideo isolates are clonal.

Genomic characterization of Salmonella enterica serovar Kentucky and London recovered from food and human salmonellosis in Zhejiang Province, China (2016–2021)

“…This finding was inconsistent to the situation in Northern America and Europe, where more than half of the ST198 human cases were associated with traveling to the areas of ST198 endemicity (Westrell et al, 2014;Haley et al, 2019). As expected, S. London genomes exhibited remarkable diversity, in line with the increasing understanding of S. London distribution, which was formed by a high degree of horizontal gene transfer (Shipp and Dickson, 2011;Trimoulinard et al, 2017). Close associations between humans and food animals (pork, chicken, beef, and animal-derived food products in the category of miscellaneous food) were previously noted and were reaffirmed by the present survey.…”

A Longitudinal Study of the Establishment and Proliferation ofEnterococcuson a Dairy Farm

“…To our knowledge, this is the second study of the establishment and proliferation of bacteria (and antibiotic resistance) before and after the introduction of production livestock on previously unused farm land. As noted, the first was conducted in our laboratory (Shipp and Dickson, 2011). While there may be an abundance of information regarding treatment of conditions in dairy cattle such as mastitis and post-parturient disease (DeGaris and Lean, 2008;Petersson-Wolfe et al, 2008;Sischo, 2006;Zhao and Lacasse, 2008), the role that non-human sources and reservoirs (other than hospitalized patients) may play in the spread of Enterococcus is controversial and poorly understood (Hershberger et al, 2005).…”

“…There have been numerous studies of the presence of enterococci on cattle farms, such as in manure (Klein et al, 2011), water (Soupir et al, 2010), and feed (Pradhan et al, 2009), as well as in bedding (Godden et al, 2008) and on the animals themselves (e.g., on hides and in mammary glands) (Fluckey et al, 2009;Petersson-Wolfe et al, 2007). However, to our knowledge, prior to 2011 (Shipp and Dickson, 2011), there have been no longitudinal studies published regarding relocating dairy cattle to previously unused farm land. Longitudinal studies are those that collect data from the same sample elements (such as location) on multiple occasions over time (Lynn, 2009).…”