Enhancement of immunohistochemical detection of Salmonella in tissues of experimentally infected pigs

Abstract

Salmonella Typhimurium is one of the main pathogens compromising porcine and human health as well as food safety, because it is a prevailing source of foodborne infections due to contaminated pork. A prominent problem in the management of this bacteriosis is the number of subclinically infected carrier pigs. As very little is known concerning the mechanisms allowing Salmonella to persist in pigs, the objective of this study was to develop an immunohistochemical approach for the detection of salmonellae in tissue of pigs experimentally infected with Salmonella Typhimurium. Samples were obtained from a challenge trial in which piglets of the German Landrace were intragastrically infected with Salmonella enterica serovar Typhimurium DT104 (1.4-2.1×1010 CFU). Piglets were sacrificed on days 2 and 28 post infection. Tissue samples of jejunum, ileum, colon, ileocecal mesenteric lymph nodes (Lnn. ileocolici), and tonsils (Tonsilla veli palatini) were fixed in Zamboni’s fixative and paraffin-embedded. Different immunohistochemical staining protocols were evaluated. Salmonella was detected in varying amounts in the tissues. Brown iron-containing pigments in the lymph nodes interfered with the identification of Salmonella if DAB was used as a staining reagent. Detergents like Triton X-100 or Saponin enhanced the sensitivity. It seems advisable not to use a detection system with brown staining for bacteria in an experimental setup involving intestinal damage including haemorrhage. The use of detergents appears to result in a higher sensitivity in the immunohistochemical detection of salmonellae.

Salmonella Typhimurium Infection Along the Porcine Gastrointestinal Tract and Associated Lymphoid Tissues

“…1 The invasion is believed to occur mainly in the ileum. 9 After invasion of ileal epithelium, Salmonella is internalized by resident macrophages, reaches the subepithelial dome of the Peyer’s patches, and rapidly disseminates to mesenteric lymph nodes (MLNs), 34 where a combination of both inflammatory and cellular responses is able to stop the infection. 27,42 It is important to highlight the short period of time (less than 24 hours) required for Salmonella to infect pigs and be shed in high concentrations in feces.…”

S. Typhimurium challenge in juvenile pigs modulates the expression and localization of enteric cholinergic proteins and correlates with mucosal injury and inflammation

“…After crossing the intestinal epithelial barrier, S. Typhimurium enters the lamina propria where the pathogen is phagocytosed by macrophage and dendritic cells of the immune system. The pathogen resides and replicates within these leukocytes, permitting dissemination to other organs such as the mesenteric lymph nodes (Broz et al 2012; Rieger et al 2015). Therefore, the focal pattern of ChAT localization observed in challenged pigs in present study follows the pathway of S. Typhimurium invasion.…”

Epidemiological and pathological aspects of salmonellosis in cattle in southern Brazil

“…tissue colonization. IHC is an important diagnostic tool (NIELSEN, 2003;RIEGER et al, 2015), especially when bacterial isolation is not possible, as some of the cases observed in the current study, and frozen tissues for PCR are no longer available.…”