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SummaryThe Salmonella enterica serotype Typhimurium ( S. Typhimurium) genome contains 13 putative fimbrial operons termed agf ( csg ), fim , pef , lpf , bcf , saf , stb , stc , std , stf , sth , sti and stj . Evidence for in vitro expression of fimbrial proteins encoded by these operons is currently only available for agf , fim and pef . We raised antisera against putative major fimbrial subunits of S. Typhimurium, including AgfA, FimA, PefA, LpfA, BcfA, StbA, StcA, StdA, StfA, SthA and StiA. Elaboration of StcA on the bacterial surface could be detected by flow cytometry and immunoelectron microscopy after expression of the cloned stcABCD operon from a heterologous T7 promoter in Escherichia coli. To study the expression of fimbrial antigens in S. Typhimurium by flow cytometry, we constructed strains carrying deletions of agfAB , pef-BACDI , lpfABCDE , bcfABCDEFG , stbABCD , stcABC , stdAB , stfACDEFG , sthABCDE or stiABCDE . Using these deletion mutants for gating, expression of fimbrial antigens was measured by flow cytometry in cultures grown in vitro or in samples recovered 8 h after infection of bovine ligated ileal loops with S.

Infection of bovine ligated loops with the Salmonella enterica serotype Typhimurium wild type but not a sipA sopABDE2 mutant resulted in fluid accumulation, polymorphonuclear cell infiltration, and expression of CXC chemokines, particularly GRO␣. None of these sipA sopABDE2-dependent responses was observed in murineligated loops. The majority of GRO␣ transcripts localized to bovine intestinal epithelium. Thus, different disease outcomes between mice (i.e., no diarrhea) and calves (i.e., diarrhea) may be due to differences in sipA sopABDE2-dependent CXC chemokine gene expression in epithelial cells.Salmonella enterica serotype Typhimurium causes enterocolitis in humans, a localized infection characterized by diarrhea and by pathological changes that are most severe in the intestine and mesenteric lymph nodes (24,25). In contrast, S. enterica serotype Typhi causes typhoid fever, a systemic infection characterized by fever, while diarrhea is considered to be an insignificant symptom developing in only one-third of patients (28). A striking difference between the host responses elicited during infections with serotype Typhimurium and serotype Typhi in humans is the type of inflammation observed in the intestine. Analysis of biopsy samples reveals that inflammation in the intestines of patients infected with serotype Typhimurium is characterized by an infiltrate that is composed primarily of polymorphonuclear (PMN) cells (6, 27), while inflammation in typhoid fever patients is caused predominantly by infiltration with monocytes (21, 39). Similarly, the predominant cell type (representing 95% of fecal leucocytes) in stools from typhoid fever patients is mononuclear, whereas PMN cells predominate (representing 75% of fecal leucocytes) in stool samples from enterocolitis patients (13).Serotype Typhimurium induces fluid accumulation and PMN cell influx in bovine, but not murine ligated ileal loops. Experimental infections of calves or mice with serotype Typhimurium are commonly used as animal models to study the pathogenesis of typhoid fever or enterocolitis, respectively. Serotype Typhimurium causes a typhoid fever-like disease without diarrhea in mice, while infection of calves results in a localized infection characterized by diarrhea (49). We compared the host responses to infection with serotype Typhimurium in mice and calves using the ligated-ileal-loop model. Bovine ligated-ileal-loop surgeries were carried out as described previously (34, 50). In mice, anesthesia was induced and maintained with Propofol (Abbot Laboratories, Chicago, Ill.), an approximately 2-cm incision was made in the abdomen, an ileal loop of 5 to 8 cm was ligated and injected with 0.15 ml of sterile Luria-Bertani (LB) broth or 1 ϫ 10 8 CFU. To prevent dehydration, mice were given two doses of 0.5 ml of sterile saline subcutaneously. Fluid accumulation and inflammatory changes elicited by the serotype Typhimurium wild type (IR715) (41) were compared to those elicited by a sipA sopABDE2 mutant (ZA21) (50) and sterile LB broth. The sipA (sspA), s...

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of chronic enteritis in ruminants (Johne's disease) and a possible etiopathologic agent in human Crohn's disease. The host-pathogen interaction in this chronic disease has largely depended on the randomly collected static lesions studied in subclinically or clinically infected animals. We have established and utilized the neonatal calf ligated ileal loop model to study the early temporal host changes during MAP infection. After inoculation of ligated ileal loop with MAP, samples were analyzed for bacterial invasion, histologic and ultrastructural morphologic changes, and gene expression at several times (0.5-12 hours) postinfection. Our results indicate that MAP invades the intestinal mucosa as early as 0.5 hour postinoculation. Distribution and migration of neutrophils, monocytes/macrophages, and goblet cells were confirmed by histopathology, scanning and transmission electron microscopy. Coincident with the morphologic analysis, we measured by real-time polymerase chain reaction gene expression of various cytokines/chemokines that are involved in the recruitment of mononuclear and polymorphonuclear leukocytes to the site of infection. We also detected expression of several other genes, including intestinal-trefoil factor, profilin, lactoferrin, and enteric ss-defensin, which may play significant roles in the early MAP infection. Thus, the calf ligated intestinal loop model may be used as a human disease model to understand the role of MAP in the pathogenesis of Crohn's disease.

The role of neutrophils in the pathogenesis of Salmonella enterica Typhimurium-induced ruminant and human enteritis and diarrhea has yet to be characterized with in vivo models. To address this question, the in vivo bovine ligated ileal loop model of nontyphoidal salmonellosis was used in calves with the naturally occurring bovine leukocyte adhesion deficiency (BLAD) mutation whose neutrophils are unable to extravasate and infiltrate the extravascular matrix. Data obtained from 4 BLAD Holstein calves homozygous for BLAD (CD18-), 1 to 5 weeks of age, were compared with 4 controls, age-matched Holstein calves negative for BLAD (CD18þ). Morphologic studies revealed that infection of CD18-calves with S Typhimurium resulted in no significant tissue infiltration by neutrophils, less tissue damage, reduced luminal fluid accumulation, and increased bacterial invasion, when compared with CD18þ calves. Ultrastructurally, lesions in enterocytes induced by S Typhimurium infection in CD18-calves-including attachment and disruption of the brush border, apical membrane ruffling formation, and cellular degeneration-were similar to the ones reported in the literature for CD18-calves. Study of cytokine gene expression by quantitative real-time polymerase chain reaction revealed that early stages of acute infection (4-8 hours postinfection) were associated with increased interleukin 8 gene expression in the absence of tissue influx of neutrophils in CD18-calves, whereas later stages of infection (12 hours postinfection) were associated with increased expression of growth-related oncogene a in the presence of neutrophil influx in CD18þ calves. In contrast, the proinflammatory cytokines interleukin 1b and tumor necrosis factor a were poorly correlated with the presence or absence of tissue neutrophils.