Sensitivity of dairy calf Salmonella enterica serotype Cerro isolates to infection-relevant stressors

Abstract

ABSTRACT Salmonella enterica serotype Cerro ( S . Cerro) is an emerging Salmonella serotype isolated from cattle, but the association of S . Cerro with disease is not well understood. While comparative genomic analyses of bovine S . Cerro isolates have indicated mutations in elements associated with virulence, the correlation of S . Cerro fecal shedding with clinical disease in cattle varies between epidemiologic studies. The primary objective of this study was to characterize the infection-relevant phenotypes of S . Cerro fecal isolates obtained from neonatal calves born on a dairy farm in Wisconsin, USA. The S . Cerro isolates varied in biofilm production and sensitivity to the bile salt deoxycholate. All S . Cerro isolates were sensitive to sodium hypochlorite, hydrogen peroxide, and acidic shock. However, S . Cerro isolates were resistant to nitric oxide stress. Two S . Cerro isolates were unable to compete with S . Typhimurium during infection of calf ligated intestinal loops, indicating decreased fitness in vivo . Together, our data suggest that S . Cerro is sensitive to some innate antimicrobial defenses present in the gut, many of which are also used to control Salmonella in the environment. The observed phenotypic variation in S . Cerro isolates from a single farm suggest phenotypic plasticity that could impact infectious potential, transmission, and persistence on a farm. IMPORTANCE Salmonella enterica is a zoonotic pathogen that threatens both human and animal health. Salmonella enterica serotype Cerro is being isolated from cattle at increasing frequency over the past two decades; however, its association with clinical disease is unclear. The goal of this study was to characterize infection-relevant phenotypes of S . Cerro isolates obtained from dairy calves from a single farm. Our work shows that there can be variation among temporally related S . Cerro isolates and that these isolates are sensitive to killing by toxic compounds of the innate immune system and those used for environmental control of Salmonella . This work contributes to our understanding of the pathogenic potential of the emerging pathogen S . Cerro.