Characterization of endemic strains of Shigella sonnei by use of plasmid DNA analysis and pulsed-field gel electrophoresis to detect patterns of transmission.

Shigellosis is hyperendemic in Utah. Most isolates are Shigella sonnei, making it difficult to identify epidemiologic clustering. To better define transmission, molecular markers and epidemiologic data were examined for 90 cases. Plasmid analysis and pulsed-field gel electrophoresis (PFGE) of the S. sonnei isolates identified 11 and 4 patterns, respectively. Plasmid pattern I infections occurred in 8 day care centers over a 6-month period, suggesting spread between centers. Plasmid pattern III was isolated from children at 3 additional centers and pattern IV was associated with another day care center, suggesting different outbreaks. By PFGE, plasmid groups I and XI appeared identical, as were plasmid groups II and V; plasmid group X had a unique pattern. Plasmid groups III, IV, and VII-IX were closely related PFGE subtypes. Both plasmid analysis and PFGE allow better characterization of S. sonnei transmission patterns of "endemic" strains and could lead to improved control measures.

Effects of fibronectin and group B streptococci on tumour necrosis factor-alpha production by human culture-derived macrophages.

Group B streptococci (GBS) are an important cause of sepsis and shock in the new-born. We have previously reported that GBS induce the production of tumour necrosis factor-alpha (TNF-alpha) by human monocytes and culture-derived macrophages. We have also shown that fibronectin (FN) promotes interaction between GBS and human phagocytes. In the present study, we investigated the effect of FN and GBS on the production of TNF-alpha by adult and neonatal culture-derived macrophages. We report that soluble FN alone was a strong stimulus for the production of TNF-alpha by culture-derived macrophages (FN 50 micrograms/ml = 623.33 +/- 47 pg/ml TNF, versus media alone 3 +/- 1.5 pg/ml; P < 0.0001). While GBS also induce the production of TNF-alpha by macrophages, the addition of FN to GBS had more than an additive effect on TNF-alpha levels. FN-mediated TNF-alpha production by macrophages was inhibited by both soluble arginine-glycine-aspartic acid (RGD) peptide (71%; P < 0.0001) and anti-beta 3-integrin monoclonal antibody 7G2 (54%; P < 0.0001). Neonatal culture-derived macrophages produced significantly more TNF-alpha in response to GBS (356.4 pg/ml +/- 27.7) than adult cells did (222.0 pg/ml +/- 21.0; P = 0.037), and dramatically more in response to FN alone (neonatal 1931.0 pg/ml +/- 23.0 versus adult 463.5 43.5 pg/ml; P < 0.0001). FN may contribute to the high levels of TNF-alpha production implicated in the pathophysiology of GBS sepsis and shock.

Production of tumor necrosis factor by human cells in vitro and in vivo, induced by group B streptococci.

Tumor necrosis factor alpha (TNF alpha) has been implicated as one of the major mediators of the gram-negative septic shock syndrome. In our studies, group B streptococci (GBS) induced the production of TNF alpha by human mononuclear cells in a dose- and time-dependent manner. Human mixed mononuclear cell cultures exposed to an encapsulated (657.6 +/- 71.3 pg/ml; n = 30 preparations) or an unencapsulated transposon mutant of type III GBS (755.8 +/- 54.7 pg/ml; n = 9) produced similar amounts of TNF alpha. Isolated monocytes and culture-derived macrophages produced higher amounts of TNF alpha (1565 +/- 211 and 1790 +/- 928 pg/ml respectively) in response to GBS than did mixed mononuclear cell cultures. In response to GBS, mixed mononuclear cells from neonates produced significantly more TNF alpha (729.1 +/- 45 vs 520.3 +/- 47.2 pg/ml; p = 0.004) than did cells from adults. Examination of specimens from patients with neonatal GBS disease revealed detectable levels of TNF alpha (7 to 424 pg/ml) in the serum of 5 of 10 patients with sepsis, in 5 of 5 urine samples from infants with sepsis, and in the cerebrospinal fluid of 1 patient with meningitis. These results suggest both a major role for TNF alpha in the pathogenesis of human neonatal GBS sepsis and shock and a potential role for immunotherapy directed against this cytokine in this fulminant neonatal bacterial infection.