Salmonellae can exist in an asymptomatic carrier state in the human gallbladder. Individuals with gallstones are more likely to become typhoid carriers, and antibiotic treatments are often ineffectual against Salmonella enterica serovar Typhi in carriers with gallstones. Therefore, we hypothesized that Salmonella spp. form biofilms on the surfaces of gallstones, where the bacteria are protected from high concentrations of bile and antibiotics. A number of methods were utilized to examine biofilm formation on human gallstones and glass coverslips in vitro, including confocal, light, and scanning electron microscopy. In our assays, salmonellae formed full biofilms on the surfaces of gallstones within 14 days and appeared to excrete an exopolysaccharide layer that bound them to the surfaces and to other bacteria. Efficient biofilm formation on gallstones was dependent upon the presence of bile, as a biofilm did not form on gallstones within 14 days in Luria-Bertani broth alone. The biofilms formed by a Salmonella enterica serovar Typhi Vi antigen mutant, as well as strains with mutations in genes that eliminate production of four different fimbriae, were indistinguishable from the biofilms formed by the parents. Mutants with an incomplete O-antigen, mutants that were nonmotile, and mutants deficient in quorum sensing were unable to develop complete biofilms. In addition, there appeared to be selectivity in salmonella binding to the gallstone surface that did not depend on the topology or surface architecture. These studies should aid in the understanding of the Salmonella carrier state, an important but underresearched area of typhoid fever pathogenesis. If the basis of carrier development can be understood, it may be possible to identify effective strategies to prevent or treat this chronic infection.

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Hypothesis: A selective surgical approach using either a 1-or a 2-stage resection is relatively safe and effective in the management of acute complicated colonic diverticulosis. Design: A consecutive cohort study. Setting: A university hospital. Patients: Eighty-nine consecutive patients who underwent emergency operations for diverticular disease between July 1, 1984, and June 30, 1999. There were 53 male and 36 female patients (mean age, 47 years). The ethnic background was predominantly Mexican American (58 patients [65.2%]). Interventions: Resections of the affected colon (n = 83) plus construction of a Hartmann pouch or mucous fistula (n = 72) or primary anastomosis (n = 11). Main Outcome Measures: Morbidity, mortality, and length of hospital stay. Results: Sixty-eight operations were performed for perforation at an annual rate that has increased greater than 75% in the past 15 years. Another 14 patients underwent operations for obstruction, and 7 underwent operations to control unremitting hemorrhage. Surgical therapy included resection of the affected segment of the bowel in 83 (93%) of the 89 patients, and a Hartmann pouch or mucous fistula was added in 72 (81%). A primary anastomosis was performed in 4 (80%) of 5 rightsided lesions but in only 7 (8%) of 84 left-sided lesions. Morbidity occurred in 38 (43%) of the 89 patients, and the mortality was 4%, with 4 deaths occurring secondary to sepsis in high-risk patients with perforations (n = 3) or obstructions (n = 1). The average length of hospital stay was 19.7 days (range, 5-80 days). Conclusions: Emergency operations for diverticular disease are uncommon but may be associated with substantial morbidity and occasional mortality. Complicated diverticulosis may present at a relatively young age, and perforated forms appear to be increasing rapidly in prevalence. Most diverticular lesions can be satisfactorily managed using a selective approach based on resection with either a primary anastomosis or a temporary colostomy.